Datasheet MIC2085, MIC2086 Datasheet (Micrel)

MIC2085/2086 Micrel

查询MIC2085供应商

MIC2085/MIC2086

Single Channel Hot Swap Controllers

General Description

The MIC2085 and MIC2086 are single channel positive
voltage hot swap controllers designed to allow the safe
insertion of boards into live system backplanes. The MIC2085
and MIC2086 are available in 16-pin and 20-pin QSOP
packages, respectively. Using a few external components
and by controlling the gate drive of an external N-Channel
MOSFET device, the MIC2085/86 provide inrush current
limiting and output voltage slew rate control in harsh, critical
power supply environments. Additionally, a circuit breaker
function will latch the output MOSFET off if the current limit
threshold is exceeded for a programmed period of time. The
devices’ array of features provide a simplified yet robust
solution for many network applications in meeting the power
supply regulation requirements and affords protection of
critical downstream devices and components.

All support documentation can be found on Micrel’s web
site at www.micrel.com.

Features

• MIC2085: Pin for pin functional equivalent to the
LTC1642

• 2.3V to 16.5V supply voltage operation

• Surge voltage protection to 33V

• Operating temperature range –40°C to 85°C

• Active current regulation limits inrush current

independent of load capacitance

• Programmable inrush current limiting

• Analog foldback current limiting

• Electronic circuit breaker

• Dual-level overcurrent fault sensing

• Fast response to short circuit conditions (< 1µs)

• Programmable output undervoltage detection

• Undervoltage lockout protection

• Power-on reset (MIC2085/86) and

power-good (MIC2086) status outputs

• /FAULT status output

• Driver for SCR crowbar on overvoltage

Applications

• RAID systems

• Cellular base stations

• LAN servers

• WAN servers

• InfiniBand™ Systems

• Industrial high side switching

T ypical Application

(PowerPAK

/POR

FB

283

Q1

Si7884DP

14

11
10

5

7

1

C6

0.01µF

TM

SO-8)

*R6
10Ω

R7
127kΩ
1%

R10

47kΩ

R8

16.2kΩ
1%

C7

0.033µF

µ

s

V

LOGIC

C2

0.022µF

R11
47kΩ

Q2
2N4401

**R9
180Ω

C

LOAD

220µF

Output Signal
(Power Good)

Power-On Reset

Output

Q3
TCR22-4

V

OUT

12V@5A

PWRGD

LOGIC

CONTROLLER

/RESET

34

C1

µ

F

1

16 15

4

ON

6

/FAULT

9

OV

12

COMP—

13

REF

CPOR

C4

µ

F

0.1

R

SENSE

0.007Ω
2%

12

SENSEVCC

MIC2085

GATE

COMP+

COMPOUT

CRWBR

GND

CFILTER

C5

8200pF

POR/START-UP DELAY = 60ms
Circuit-Breaker Response Time = 500
*R6 is an optional component used for noise filtering
**R9 needed when using a sensitive gate SCR

V

12V

/FAULT

GND

IN

Backplane
Connector

PCB Edge
Connector

(or Short)

Long

Pin

Short

Pin

R5

47kΩ

Medium

Pin

Long

Pin

R2

100kΩ

1%

R3

1.82kΩ
1%

R4

10kΩ

1%

Overvoltage (Input) = 13.3V
Undervoltage Lockout = 10.8V
Undervoltage (Output) &
Power-Good (Output) = 11.4V

R1

3.3Ω

C3

µ

F

0.1

InfiniBand is a trademark of InfiniBand Trade Association
PowerPAK is a trademark of Vishay Intertechnology Inc.

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 [phone] • fax + 1 [phone] • http://www.micrel.com

January 2004 1 M0235-121903

MIC2085/2086 Micrel

Ordering Information

Part Number Fast Circuit Breaker Threshold Discharge Output Package

MIC2085-xBQS x = J, 95mV NA 16-pin QSOP

x = K, 150mV*
x = L, 200mV*

x = M, Off

MIC2086-xBQS x = J, 95mV Yes 20-pin QSOP

x = K, 150mV*
x = L, 200mV*

x = M, Off

*Contact factory for availability.

Pin Configuration

CFILTER

CPOR

ON

/POR

/FAULT

FB

GND

1CRWBR

1CRWBR
2
3
4
5
6
7
8

16 VCC

SENSE

15

GATE

14

REF

13

COMP–

12

COMP+

11

COMPOUT

10

OV

9

CFILTER

PWRGD

CPOR

ON

/POR

/FAULT

FB
GND
GND

2
3
4
5
6
7
8
9

10

20 VCC

VCC

19

SENSE

18

GATE

17

REF

16

DIS

15

COMP–

14

COMP+

13

COMPOUT

12

OV

11

MIC2085

16-Pin QSOP (QS)

MIC2086

20-Pin QSOP (QS)

Pin Description

Pin Number Pin Number Pin Name Pin Function

MIC2086 MIC2085

1 1 CRWBR Overvoltage Timer and Crowbar Circuit Trigger: A capacitor connected to

this pin sets the timer duration for which an overvoltage condition will trigger
an external crowbar circuit. This timer begins when the OV input rises above
its threshold as an internal 45µA current source charges the capacitor. Once
the voltage reaches 470mV, the current increases to 1.5mA.

2 2 CFILTER Current Limit Response Timer: A capacitor connected to this pin defines the

period of time (t
fault condition and trip the circuit breaker. If no capacitor is connected, then
t

OCSLOW

OCSLOW

defaults to 5µs.

3 3 CPOR Power-On Reset Timer: A capacitor connected between this pin and ground

sets the start-up delay (t
VCC rises above the UVLO threshold, the capacitor connected to CPOR
begins to charge. When the voltage at CPOR crosses 1.24V, the start-up
threshold (V
C

POR

above V
CPOR rises above the power-on reset delay threshold (VTH), the timer

START

is immediately discharged to ground. When the voltage at FB rises

, capacitor C

FB

resets by pulling CPOR to ground, and /POR is deasserted.
If C

= 0, then t

POR

) in which an overcurrent event must last to signal a

) and the power-on reset interval (t

START

), a start cycle is initiated if ON is asserted while capacitor

begins to charge again. When the voltage at

POR

defaults to 20µs.

START

POR

). When

M0235-121903 2 January 2004

MIC2085/2086 Micrel

Pin Description (Cont.)

Pin Number Pin Number Pin Name Pin Function

MIC2086 MIC2085

4 4 ON ON Input: Active high. The ON pin, an input to a Schmitt-triggered compara-

tor used to enable/disable the controller, is compared to a VTH reference
with 100mV of hysteresis. Once a logic high is applied to the ON pin

> 1.24V), a start-up sequence is initiated as the GATE pin starts

(V

ON

ramping up towards its final operating voltage. When the ON pin receives a
low logic signal (V
high if VCC is above the UVLO threshold. ON must be low for at least 20µs
in order to initiate a start-up sequence. Additionally, toggling the ON pin
LOW to HIGH resets the circuit breaker.

5 5 /POR Power-On Reset Output: Open drain N-Channel device, active low. This pin

remains asserted during start-up until a time period t
voltage rises above the power-good threshold (V
C

determines t

POR

at the FB pin, /POR is asserted for a minimum of one timing cycle, t
/POR pin has a weak pull-up to VCC.

6 N/A PWRGD Power-Good Output: Open drain N-Channel device, active high. When the

voltage at the FB pin is lower than 1.24V, the PWRGD output is held low.
When the voltage at the FB pin is higher than 1.24V, then PWRGD is
asserted. A pull-up resistor connected to this pin and to VCC will pull the
output up to VCC. The PWRGD pin has a weak pull-up to VCC.

7 6 /FAULT Circuit Breaker Fault Status Output: Open drain N-Channel device, active

low. The /FAULT pin is asserted when the circuit breaker trips due to an
overcurrent condition. Also, this pin indicates undervoltage lockout and
overvoltage fault conditions. The /FAULT pin has a weak pull-up to VCC.

8 7 FB Power-Good Threshold Input: This input is internally compared to a 1.24V

reference with 3mV of hysteresis. An external resistive divider may be used
to set the voltage at this pin. If this input momentarily goes below 1.24V,
then /POR is activated for one timing cycle, t
undervoltage condition. The /POR signal de-asserts one timing cycle after
the FB pin exceeds the power-good threshold by 3mV. A 5µs filter on this pin
prevents glitches from inadvertently activating this signal.

9,10 8 GND Ground Connection: Tie to analog ground.

11 9 OV OV Input: When the voltage on OV exceeds its trip threshold, the GATE pin

is pulled low and the CRWBR timer starts. If OV remains above its threshold
long enough for CRWBR to reach its trip threshold, the circuit breaker is
tripped. Otherwise, the GATE pin begins to ramp up one POR timing cycle

after OV drops below its trip threshold.
12 10 COMPOUT Uncommitted Comparator’s Open Drain Output.
13 11 COMP+ Comparator’s Non-Inverting Input.
14 12 COMP- Comparator’s Inverting Input.
15 NA DIS Discharge Output: When the MIC2086 is turned off, a 550Ω internal resistor

at this output allows the discharging of any load capacitance to ground.
16 13 REF Reference Output: 1.24V nominal. Tie a 0.1µF capacitor to ground to ensure

stability.
17 14 GATE Gate Drive Output: Connects to the gate of an external N-Channel

MOSFET. An internal clamp ensures that no more than 13V is applied

between the GATE pin and the source of the external MOSFET. The GATE

pin is immediately brought low when either the circuit breaker trips or an

undervoltage lockout condition occurs.

< 1.14V), the GATE pin is grounded and /FAULT is

ON

after the FB pin

POR

). The timing capacitor

. When an output undervoltage condition is detected

POR

FB

, indicating an output

POR

POR

. The

January 2004 3 M0235-121903

MIC2085/2086 Micrel

Pin Description (Cont.)

Pin Number Pin Number Pin Name Pin Function

MIC2086 MIC2085

18 15 SENSE Circuit Breaker Sense Input: A resistor between this pin and VCC sets the

current limit threshold. Whenever the voltage across the sense resistor
exceeds the slow trip current limit threshold (V
is adjusted to ensure a constant load current. If V
exceeded for longer than time period t

OCSLOW

TRIPSLOW

, then the circuit breaker is
tripped and the GATE pin is immediately pulled low. If the voltage across the
sense resistor exceeds the fast trip circuit breaker threshold, V
any point due to fast, high amplitude power supply faults, then the GATE pin
is immediately brought low without delay. To disable the circuit breaker, the
SENSE and VCC pins can be tied together.

The default V

TRIPFAST

are available: 150mV, 200mV, or OFF(V
factory for availability of other options.

for either device is 95mV. Other fast trip thresholds

TRIPFAST

19,20 16 VCC Positive Supply Input: 2.3V to 16.5V. The GATE pin is held low by an

internal undervoltage lockout circuit until VCC exceeds a threshold of 2.18V.
If VCC exceeds 16.5V, an internal shunt regulator protects the chip from
VCC and SENSE pin voltages up to 33V.

), the GATE voltage

TRIPSLOW

(48mV) is

TRIPFAST

, at

disabled). Please contact

M0235-121903 4 January 2004

MIC2085/2086 Micrel

Absolute Maximum Ratings

(1)

(All voltages are referred to GND)

Supply Voltage (VCC) ..................................... –0.3V to 33V

SENSE Pin..........................................–0.3V to VCC + 0.3V

GATE Pin ....................................................... –0.3V to 22V

ON, DIS, /POR, PWRGD, /FAULT,

COMP+, COMP–, COMPOUT ....................... –0.3V to 20V

CRWBR, FB, OV, REF..................................... –0.3V to 6V

Maximum Currents

Digital Output Pins .....................................................10mA

(/POR, /FAULT, PWRGD, COMPOUT)

DIS Pin .......................................................................30mA

ESD Rating:

Human Body Model...................................................2kV

Machine Model........................................................200V

Operating Ratings

Supply Voltage (VCC) .................................... 2.3V to 16.5V

Operating Temperature Range .................. –40°C to +85°C

Junction Temperature (TJ) ........................................ 125°C

Package Thermal Resistance R

16-pin QSOP.....................................................112°C/W

20-pin QSOP.......................................................91°C/W

(2)

θ(J-A)

Electrical Characteristics

(3)

VCC = 5.0V, TA = 25°C unless otherwise noted. Bold indicates specifications over the full operating temperature range of –40°C to +85°C.
Symbol Parameter Condition Min Typ Max Units

V

CC

I

CC

V

UV

V

UVHYST

V

FB

V

FBHYST

V

OV

∆V

OV

V

OVHYST

I

OV

V

TH

I

CPOR

Supply Voltage 2.3 16.5 V
Supply Current 1.6 2.5 mA
Undervoltage Lockout Threshold VCC rising 2.05 2.18 2.28 V

VCC falling 1.85 2.0 2.10 V
UV Lockout Hysteresis 180 mV
FB (Power-Good) Threshold Voltage FB rising 1.19 1.24 1.29 V
FB Hysteresis 3mV
OV Pin Threshold Voltage OV pin rising 1.19 1.24 1.29 mV
OV Pin Threshold Voltage 2.3V < VCC < 16.5V 5 15 mV

Line Regulation
OV Pin Hysteresis 3mV
OV Pin Current 0.2 µA
POR Delay and Overcurrent (CFILTER) V

Timer Threshold

CPOR

, V

CFILTER

rising 1.19 1.24 1.29 V

Power-On Reset Timer Current Timer on –2.5 –2.0 –1.5 µA

Timer off 5 mA

I

TIMER

Current Limit /Overcurrent Timer on –30 –20 –15 µA
Timer Current (CFILTER) Timer off 2.5 mA

V
∆V

I

CR

V

CR

CR

TRIP

CRWBR Pin Threshold Voltage 2.3V < VCC < 16.5V 445 470 495 mV
CRWBR Pin Threshold Voltage 2.3V < VCC < 16.5V 4 15 mV

Line Regulation
CRWBR Pin Current CRWBR On, V

CRWBR On, V

CRWBR Off, V
Circuit Breaker Trip Voltage V
(Current Limit Threshold) 2.3V ≤ V

TRIP

= VCC –V

≤ 16.5V V

CC

= 0V –60 –45 –30 µA

CRWBR

= 2.1V –1.5 –1.0 mA

CRWBR

= 1.5V 3.3 mA

CRWBR

SENSE

V

TRIPSLOW
TRIPFAST

x = K 150 mV

x = J 80 95 110 mV

40 48 55 mV

x = L 200 mV

V

GS

External Gate Drive V

GATE

– V

CC

VCC < 3V 4 8 9 V
5V < VCC < 9V 11 12 13 V
9V < VCC < 15.0V 4.5 21–V

CC

13 V

January 2004 5 M0235-121903

MIC2085/2086 Micrel

Electrical Characteristics (Cont.)

Symbol Parameter Condition Min Typ Max Units

I

GATE

I

GATEOFF

V

ON

V

ONHYST

I

ON

V

START

V

OL

I

PULLUP

V

REF

∆V

LNR

∆V

LDR

I

RSC

V

COS

V

CHYST

R

DIS

GATE Pin Pull-up Current Start cycle, V

=16.5V –22 –16 –8 µA

V

CC

GATE

= 0V

VCC = 2.3V –20 –14 –8 µA

GATE Pin Sink Current /FAULT = 0, V

V

= 16.5V 25 50 mA

CC

GATE

>1V

VCC = 2.3V 12 20 mA

ON Pin Threshold Voltage ON rising 1.19 1.24 1.29 V

ON falling 1.09 1.14 1.19 V
ON Pin Hysteresis 100 mV
ON Pin Input Current VON = V
Undervoltage Start-up V

Timer Threshold
/FAULT, /POR, PWRGD Output I

Voltage (PWRGD for MIC2086 only)

OUT

CC

rising 1.19 1.24 1.29 V

CPOR

= 1.6mA 0.4 V

0.5 µA

Output Signal Pull-up Current /FAULT, /POR, PWRGD = GND –20 µA
/FAULT, /POR, PWRGD, COMPOUT (PWRGD for MIC2086 only)

Reference Output Voltage I

LOAD

= 0mA; C

= 0.1µF 1.21 1.24 1.27 V

REF

Reference Line Regulation 2.3V < VCC < 16.5V 5 10 mV
Reference Load Regulation I
Reference Short-Circuit Current V
Comparator Offset Voltage VCM = V
Comparator Hysteresis VCM = V

= 1mA 2.5 7.5 mV

OUT

= 0V 3.5 mA

REF

REF
REF

–5 5 mV

3mV

Discharge Pin Resistance ON pin toggles from HI to LOW 100 550 1000 Ω

AC Electrical Characteristics

(4)

Symbol Parameter Condition Min Typ Max Units

t

OCFAST

t

OCSLOW

t

ONDLY

t

FBDLY

Notes:

1. Exceeding the absolute maximum rating may damage the device.

2. The device is not guaranteed to function outside its operating rating.

3. Specification for packaged product only.

4. Specification for packaged product only.

Fast Overcurrent Sense to GATE VCC = 5V 1 µs
Low Trip Time V

C

–V

CC
GATE

= 100mV

SENSE

= 10nF, See Figure 1

Slow Overcurrent Sense to Gate VCC = 5V 5 µs
Low Trip Time V

CC

C

FILTER

–V

= 50mV

SENSE

= 0, See Figure 1
ON Delay Filter 20 µs
FB Delay Filter 20 µs

M0235-121903 6 January 2004

MIC2085/2086 Micrel

1V

48mV

V

GATE

t

OCSLOW

V

TRIPFAST

(VCCÐV

SENSE

)

t

OCFAST

1V

0

CFILTER

0

0

1.24V

Timing Diagrams

Figure 1. Current Limit Response

ON

CPOR

GATE

FB

FB

CPOR

/POR

0

0

0

1.24V
t

POR

Figure 2. Power-On Reset Response

t

ONDLY

1.24V

0

1.24V

0

0

0

Arm Fast Comparator

t

START

1.24V

Arm Slow Comparator

t

POR

1.24V

/POR

0

Figure 3. Power-On Start-Up Delay Timing

50

January 2004 7 M0235-121903

20

Current Limit Threshold (mV)

0

600 800 1000

400200

FB Voltage (mV)

Figure 4. Foldback Current Limit Response

MIC2085/2086 Micrel

g

Typical Characteristics

Supply Current

4.0

vs. Temperature

3.5

3.0
V

= 16.5V

CC

2.5

2.0

VCC= 5V

1.5

1.0

SUPPLY CURRENT (mA)

0.5

0.0

-40 -20 0 20 40 60 80 100

Overcurrent Timer Current

34

VCC= 2.3V

TEMPERATURE (°C)

vs. Temperature

30

26

(µA)

VCC= 16.5V

22

TIMER

I

18

VCC= 5V

14

10

-40 -20 0 20 40 60 80 100

VCC= 2.3V

TEMPERATURE (°C)

Power-On Reset Timer Current

vs. Temperature

2.6

(µA)

CPOR

I

2.4

2.2

2.0

1.8

VCC= 5V

VCC= 2.3V

VCC= 16.5V

1.6

1.4

-40 -20 0 20 40 60 80 100

TEMPERATURE (°C)

Overcurrent Timer (Off) Current

vs. Temperature

5

4

VCC= 16.5V

3

(mA)

2

TIMER

I

VCC= 2.3V

1

0

-40 -20 0 20 40 60 80 100

TEMPERATURE (°C)

VCC= 5V

Power-On Reset Timer (Off) Current

10

vs. Temperature

9

(mA)

I

CPOR

8
7
6
5
4
3
2

VCC= 16.5V

VCC= 5V

VCC= 2.3V

1
0

-40 -20 0 20 40 60 80 100

TEMPERATURE (°C)

Gate Pull-Up Current

vs. Temperature

30

25

20

VCC= 16.5V

(µA)

15

GATE

I

10

VCC= 2.3V

5

0

-40 -20 0 20 40 60 80 100

TEMPERATURE (°C)

VCC= 5V

Gate Pull-Up Current

vs. V

25

20

15

(A)

10

GATE

I

5

0

2 4 6 8 10 12 14 16 18

Gate Sink Current

100

vs. Temperature

CC

(V)

V

CC

90
80

(mA)

70
60

VCC= 16.5V

50

GATEOFF

40

I

VCC= 5V

30

VCC= 2.3V

20
10

-40 -20 0 20 40 60 80 100

TEMPERATURE (°C)

External Gate Drive

vs. Temperature

16

VCC= 5V

14
12
10

8
6
4

VCC= 16.5V

VCC= 2.3V

(V)

GS

V

2
0

-40 -20 0 20 40 60 80 100

TEMPERATURE (°C)

Gate Sink Current

600

vs. Gate Volta

500

400

(mA)

300

GATEOFF

200

I

100

0

02468101214

12V

V

CC

GATE

5V

CC

(V)

External Gate Drive

vs. V

22
20
18
16
14

(V)

12

GS

10

V

8
6
4
2
0

2 4 6 8 10 12 14 16 18

POR Delay/Overcurrent

e

(mV)

V

TH

1.25

1.24

1.23

1.22

1.21

1.20

Timer Threshold
vs. Temperature

VCC= 16.5V

VCC= 5V

-40 -20 0 20 40 60 80 100

TEMPERATURE (°C)

CC

(V)

V

CC

VCC= 2.3V

M0235-121903 8 January 2004

MIC2085/2086 Micrel

1.7

1.8

1.9

2.0

2.1

2.2

2.3

2.4

2.5

-40 -20 0 20 40 60 80 100

UVLO THRESHOLD (V)

TEMPERATURE (°C)

10

14

18

22

26

-40 -20 0 20 40 60 80 100

I

PULLUP

(µA)

TEMPERATURE (°C)

Output Signal Pull-Up Current

vs. Temperature

VCC= 16.5V

VCC= 2.3V

VCC= 5V

Typical Characteristics

Current Limit Threshold

(Fast Trip)

120
115
110
105

(mV)

100

TRIPFAST

V

1.30

1.25

1.20

ON THRESHOLD (V)

1.15

vs. Temperature

VCC= 2.3V

95
90

VCC= 5V

85
80

-40 -20 0 20 40 60 80 100

ON Pin Threshold (Rising)

VCC= 16.5V

VCC= 5V

-40 -20 0 20 40 60 80 100

VCC= 16.5V

TEMPERATURE (°C)

vs. Temperature

VCC= 2.3V

TEMPERATURE (°C)

Current Limit Threshold

(Slow Trip)

vs. Temperature

55

53

(mV)

51

49

TRIPSLOW

V

47

45

-40 -20 0 20 40 60 80 100

1.20

1.15

1.10

ON THRESHOLD (V)

1.05

VCC= 2.3V

VCC= 5V

TEMPERATURE (°C)

ON Pin Threshold (Falling)

vs. Temperature

VCC= 2.3V

VCC= 16.5V

-40 -20 0 20 40 60 80 100

VCC= 16.5V

VCC= 5V

TEMPERATURE (°C)

UVLO Threshold

vs. Temperature

UVLO+

UVLO–

ON Pin Input Current

vs. Temperature

40
35
30
25
20
15
10

5

ON PIN INPUT CURRENT (nA)

0

-40 -20 0 20 40 60 80 100

VCC= 16.5V

VCC= 2.3V

TEMPERATURE (°C)

VCC= 5V

FB (Power-Good) Threshold

1.30

1.25

1.20

FB THRESHOLD (V)

1.15

-40 -20 0 20 40 60 80 100

Comparator Offset Voltage

0.5

0.4

0.3

January 2004 9 M0235-121903

0.2

0.1

0.0

-40 -20 0 20 40 60 80 100

COMPARATOR OFFSET VOLTAGE (V)

vs. Temperature

VCC= 5V

TEMPERATURE (°C)

vs. Temperature

VCC= 5V

VCC= 16.5V

VCC= 2.3V

TEMPERATURE (°C)

VCC= 16.5V

VCC= 2.3V

Overvoltage Pin Threshold

1.30

1.25

1.20

1.15

OVERVOLTAGE PIN THRESHOLD (V)

1000

900
800
700

(Ω)

600

DIS

500

R

400
300
200

vs. Temperature

VCC= 16.5V

VCC= 2.3V

-40 -20 0 20 40 60 80 100

TEMPERATURE (°C)

Discharge Pin Resistance

vs. Temperature

2.3V

5V

16.5V

-40 -20 0 20 40 60 80 100

TEMPERATURE (°C)

MIC2085/2086 Micrel

Test Circuit

V

12V

R

I

IN

IN

C1

0.47mF

R2
154k

W

1%

R3
20k
1%

4

ON

W

SW1

ON/OFF

SENSE

0.01

W

5%

12

34

19,20 18

VCC

SENSE

MIC2086

Si7892DP

(PowerPAK

17

GATE

8

FB

5

/POR

Q1

TM

SO-8)

R1
10

W

C2

0.022mF

Downstream
Signal

R4

97.6k
1%

R5

12.4k
1%

I

OUT

V

OUT

R

LOAD

C

LOAD

W

W

Not all pins shown for clarity.

C3

0.047mF

GNDCPOR CFILTER

9,10 23

DIS

C4

0.047mF

15

SW2

DIS

R6

4.4k

W

C5

0.033mF

R7

1.5k

W

Q2

ZTX788A

R8
330

W

Q3

TCR22-4

M0235-121903 10 January 2004

MIC2085/2086 Micrel

Functional Characteristics

CC

V

ON

C

OUT

I

IN =

I

CC

V

/FAULT

V

POR

OUT

5V/div

1V/div

1V/div

1A/div

5V/div

10V/div

10V/div

12V Hot Insert Response

C

TIME (20ms/div.)

Inrush Current Response

C

R

LOAD =

LOAD =

R

LOAD =

LOAD =

V

IN =

1000µF

V

IN =

5700µF

12V

4.8Ω

12V

3.4Ω

ON

POR

C

OUT

V

/POR

ON

OUT

V

FB

1V/div

1V/div

5V/div

10V/div

1V/div

5V/div

1V/div

12V Turn On Response

TIME (20ms/div.)

Power-Good Response

C

LOAD =

C

R

LOAD =

R

LOAD =

LOAD =

V

IN =

1000µF

V

IN =

1000µF

12V

4.8Ω

12V

4.8Ω

IN

I

ON

GATE

= I
I

V

OUT

IN

OUT

1A/div

1V/div

20V/div

2A/div

5V/div

TIME (10ms/div.)

Turn Off — Normal Discharge

V

(External) = 0

R

DIS

R

LOAD =

C

LOAD =

SW2 = HIGH

TIME (2.5ms/div.)

12V

IN =

4.8Ω

1000µF

PG

ON

GATE

= I
I

V

OUT

IN

OUT

10V/div

1V/div

20V/div

2A/div

5V/div

TIME (10ms/div.)

Turn Off — Crowbar Discharge

V

R

LOAD =

C

LOAD =

SW2 = LOW

TIME (2.5ms/div.)

12V

IN =

4.8Ω

1000µF

January 2004 11 M0235-121903

MIC2085/2086 Micrel

Functional Characteristics (continued)

Turn On Into Short Circuit

ON

1V/div

1V/div

CFILTER

/FAULT

V

OUT

10V/div

5V/div

C

LOAD =

V

IN =

R

LOAD =

1000µF

12V

0

TIME (10ms/div.)

M0235-121903 12 January 2004

MIC2085/2086 Micrel

Functional Block Diagram

MIC2086

SENSE

VCC

CFILTER

GND

FB

CPOR

18 (15)

19,20 (16)

2 (2)

9,10 (8)

8 (7)

3 (3)

20mA

20mA

20mA

17 (14)

16 (13)

12 (10)

13 (11)

14 (12)

7 (6)

5 (5)

15

6

GATE

REF

COMPOUT

COMP+
COMPÐ

DIS*

/FAULT

/POR

PWRGD*

Charge

Pump

48mV

+
Ð

13V

1.24V

+
Ð

95mV

V

REG1

V

CC1

20mA

CC1

UVLO

2.2V

Circuit Breaker 

Response

or

UVLO

REG2

+
Ð

21V

550

W

V

CC1

V

CC1

+

1.24V

1.24V

Ð

+

Glitch

Ð

Filter

Logic

V

CC1

1.5mA

V

CC1

V

CC1

45mA

V

CC1

2.5mA

1.24V

+
Ð

+
Ð

0.45V

1 (1)

CRWBR

ON

4 (4)

1.24V

*DIS and PWRGD are not available on MIC2085.
Pin numbers for MIC2085 are in parenthesis ( ) where applicable.

+

Glitch

Ð

Filter

Glitch

Filter

+
Ð

1.24V

11 (9)

OV

MIC2086 Block Diagram

January 2004 13 M0235-121903

MIC2085/2086 Micrel

Functional Description

Hot Swap Insertion

When circuit boards are inserted into live system backplanes
and supply voltages, high inrush currents can result due to
the charging of bulk capacitance that resides across the
supply pins of the circuit board. This inrush current, although
transient in nature, may be high enough to cause permanent
damage to on-board components or may cause the system’s
supply voltages to go out of regulation during the transient
period which may result in system failures. The MIC2085/86
acts as a controller for external N-Channel MOSFET devices
in which the gate drive is controlled to provide inrush current
limiting and output voltage slew rate control during hot plug
insertions.

Power Supply

VCC is the supply input to the MIC2085/86 controller with a
voltage range of 2.3V to 16.5V. The VCC input can withstand
transient spikes up to 33V. In order to help suppress tran­sients and ensure stability of the supply voltage, a capacitor
of 1.0µF to 10µF from VCC to ground is recommended.
Alternatively, a low pass filter, shown in the typical application
circuit, can be used to eliminate high frequency oscillations as
well as help suppress transient spikes.

Start-Up Cycle

When the voltage on the ON pin rises above its threshold of

1.24V, the MIC2085/86 first checks that its supply (VCC) is
above the UVLO threshold. If so, the device is enabled and
an internal 2µA current source begins charging capacitor
C

to 1.24V to initiate a start-up sequence (i.e., start-up

POR

delay times out). Once the start-up delay (t
CPOR is pulled immediately to ground and a 15µA current
source begins charging the GATE output to drive the external
MOSFET that switches VIN to V

. The programmed start-

OUT

up delay is calculated using the following equation:

V

tC

START POR

=× ≅× µ

TH

I

CPOR

0.62 C ( F)

POR

where VTH, the POR delay threshold, is 1.24V, and I
the POR timer current, is 2µA. As the GATE voltage contin­ues ramping toward its final value (VCC + VGS) at a defined
slew rate (See

nated Start-Up”

“Load Capacitance”/“Gate Capacitance Domi-

sections), a second CPOR timing cycle
begins if: 1)/FAULT is high and 2)CFILTER is low (i.e., not
an overvoltage, undervoltage lockout, or overcurrent state).
This second timing cycle, t

, starts when the voltage at the

POR

FB pin exceeds its threshold (VFB) indicating that the output
voltage is valid. The time period t

is equivalent to t

POR

and sets the interval for the /POR to go Low-to-High after

“power is good” (See Figure 2 of

“Timing Diagrams”

current regulation is employed to limit the inrush current
transient response during start-up by regulating the load
current at the programmed current limit value (See

Limiting and Dual-Level Circuit Breaker”

section). The fol­lowing equation is used to determine the nominal current
limit value:

V

I

LIM

TRIPSLOW

==

R

SENSE SENSE

48mV

R

START

) elapses,

(1)

CPOR

START

). Active

“Current

(2)

where V

TRIPSLOW

in the electrical table and R

is the current limit slow trip threshold found

is the selected value that

SENSE

will set the desired current limit. There are two basic start-up
modes for the MIC2085/86: 1)Start-up dominated by load
capacitance and 2)start-up dominated by total gate capaci­tance. The magnitude of the inrush current delivered to the
load will determine the dominant mode. If the inrush current
is greater than the programmed current limit (I

LIM

capacitance is dominant. Otherwise, gate capacitance is
dominant. The expected inrush current may be calculated
using the following equation:

C

LOAD

C

GATE

GATE

15 A

is the total GATE capacitance

where I

INRUSH I

GATE

≅× ≅µ×

GATE

is the GATE pin pull-up current, C
load capacitance, and C
(C

of the external MOSFET and any external capacitor

ISS

C
C

LOAD
GATE

connected from the MIC2085/86 GATE pin to ground).

Load Capacitance Dominated Start-Up

In this case, the load capacitance, C

, is large enough to

LOAD

cause the inrush current to exceed the programmed current
limit but is less than the fast-trip threshold (or the fast-trip
threshold is disabled, ‘M’ option). During start-up under this
condition, the load current is regulated at the programmed
current limit value (I

) and held constant until the output

LIM

voltage rises to its final value. The output slew rate and
equivalent GATE voltage slew rate is computed by the
following equation:

I

Output Voltage Slew Rate, dV /dt

where I
quently, the value of C

is the programmed current limit value. Conse-

LIM

must be selected to ensure that

FILTER

the overcurrent response time, t

OUT

OCSLOW

LIM

=

C

LOAD

, exceeds the time
needed for the output to reach its final value. For example,
given a MOSFET with an input capacitance C
4700pF, C

is 2200µF, and I

LOAD

is set to 6A with a 12V

LIMIT

ISS

input, then the load capacitance dominates as determined by
the calculated INRUSH > I

,

. Therefore, the output voltage

LIM

slew rate determined from Equation 4 is:

Output Voltage Slew Rate, dV /dt

and the resulting t

OCSLOW

approximately 4.5ms. (See

Overcurrent Timer Delays”

GATE Capacitance Dominated Start-Up

OUT

needed to achieve a 12V output is

“Power-On Reset, Start-Up, and

section to calculate t

=

2200 F

6A

µ

In this case, the value of the load capacitance relative to the
GATE capacitance is small enough such that the load current
during start-up never exceeds the current limit threshold as
determined by Equation 3. The minimum value of C
will ensure that the current limit is never exceeded is given by
the equation below:

I

C (min)

GATE

GATE

=×

I

LIM

C

LOAD

), then load

(3)

is the

LOAD

(4)

= C

GATE

V

2.73

=

ms

GATE

.)

that

OCSLOW

(5)

=

M0235-121903 14 January 2004

MIC2085/2086 Micrel

where C
capacitance (C
connected to the GATE pin of the MOSFET. Once C

is the summation of the MOSFET input

GATE

) and the value of the external capacitor

ISS

GATE

is
determined, use the following equation to determine
the output slew rate for gate capacitance dominated start-up.

I

dV /dt (output)

OUT

Table 1 depicts the output slew rate for various values of C

I

GATE

C

GATE

0.001µF 15V/ms

0.01µF 1.5V/ms

0.1µF 0.150V/ms
1µF 0.015V/ms

GATE

=

C

GATE

= 15µA

dV

OUT

(6)

GATE

/dt

Table 1. Output Slew Rate Selection for GATE

Capacitance Dominated Start-Up

Current Limiting and Dual-Level Circuit Breaker

Many applications will require that the inrush and steady state
supply current be limited at a specific value in order to protect
critical components within the system. Connecting a sense
resistor between the VCC and SENSE pins sets the nominal
current limit value of the MIC2085/86 and the current limit is
calculated using Equation 2. However, the MIC2085/86 ex­hibits foldback current limit response. The foldback feature
allows the nominal current limit threshold to vary from 24mV
up to 48mV as the FB pin voltage increases or decreases.
When FB is at 0V, the current limit threshold is 24mV and for
FB ≥ 0.6V, the current limit threshold is the nominal 48mV.
(See Figure 4 for Foldback Current Limit Response charac­teristic).

The MIC2085/86 also features a dual-level circuit breaker
triggered via 48mV and 95mV current limit thresholds sensed
across the VCC and SENSE pins. The first level of the circuit
breaker functions as follows. Once the voltage sensed across
these two pins exceeds 48mV, the overcurrent timer, its
duration set by capacitor C

, starts to ramp the voltage

FILTER

at CFILTER using a 2µA constant current source. If the
voltage at CFILTER reaches the overcurrent timer threshold
(VTH) of 1.24V, then CFILTER immediately returns to ground
as the circuit breaker trips and the GATE output is immedi­ately shut down. For the second level, if the voltage sensed
across VCC and SENSE exceeds 95mV at any time, the
circuit breaker trips and the GATE shuts down immediately,
bypassing the overcurrent timer period. To disable current
limit and circuit breaker operation, tie the SENSE and VCC
pins together and the CFILTER pin to ground.

Output Undervoltage Detection

The MIC2085/86 employ output undervoltage detection by
monitoring the output voltage through a resistive divider
connected at the FB pin. During turn on, while the voltage at
the FB pin is below the threshold (VFB), the /POR pin is
asserted low. Once the FB pin voltage crosses VFB, a 2µA
current source charges capacitor C
voltage reaches 1.24V, the time period t
CPOR pin is pulled to ground and the /POR pin goes HIGH.

.

If the voltage at FB drops below VFB for more than 10µs, the

. Once the CPOR pin

POR

elapses as the

POR

/POR pin resets for at least one timing cycle defined by t
(see Applications Information for an example).

Input Overvoltage Protection

The MIC2085/86 monitors and detects overvoltage condi­tions in the event of excessive supply transients at the input.
Whenever the overvoltage threshold (VOV) is exceeded at
the OV pin, the GATE is pulled low and the output is shut off.
The GATE will begin ramping one POR timing cycle after the
OV pin voltage drops below its threshold. An external CRWBR
circuit, as shown in the typical application diagram, provides
a time period that an overvoltage condition must exceed in
order to trip the circuit breaker. When the OV pin exceeds the
overvoltage threshold (VOV), the CRWBR timer begins charg­ing the CRWBR capacitor initially with a 45µA current source.
Once the voltage at CRWBR exceeds its threshold (VCR) of

0.47V, the CRWBR current immediately increases to 1.5mA
and the circuit breaker is tripped, necessitating a device reset
by toggling the ON pin LOW to HIGH.

Power-On Reset, Start-Up, and Overcurrent Timer
Delays

The Power-On Reset delay, t

, is the time period for the

POR

/POR pin to go HIGH once the voltage at the FB pin exceeds
the power-good threshold (VTH). A capacitor connected to
CPOR sets the interval, t
start-up delay, t

(see Equation 1).

START

POR

, and t

is equivalent to the

POR

A capacitor connected to CFILTER is used to set the timer
which activates the circuit breaker during overcurrent condi­tions. When the voltage across the sense resistor exceeds
the slow trip current limit threshold of 48mV, the overcurrent
timer begins to charge for a period, t
C
defaults to 5µs. If t

. If no capacitor is used at CFILTER, then t

FILTER

OCSLOW

elapses, then the circuit breaker

OCSLOW

, determined by

is activated and the GATE output is immediately pulled to
ground. The following equation is used to determine the
overcurrent timer period, t

tC

OCSLOW

=×≅×µ

FILTER

OCSLOW

V

I

TIMER

.

TH

0.062 C ( F)

FILTER

where VTH, the CFILTER timer threshold, is 1.24V and
I

, the overcurrent timer current, is 20µA. Tables 2 and

TIMER

3 provide a quick reference for several timer calculations
using select standard value capacitors.

POR

OCSLOW

(7)

January 2004 15 M0235-121903

MIC2085/2086 Micrel

C

POR

t

POR

= t

START

0.01µF 6ms

0.02µF 12ms

0.033µF 18.5ms

0.05µF 30ms

0.1µF 60ms

0.33µF 200ms

Table 2. Selected Power-On Reset and

Start-Up Delays

C

FILTER

t

OCSLOW

1800pF 100µs
4700pF 290µs
8200pF 500µs

0.010µF 620µs

0.020µF 1.2ms

0.033µF 2.0ms

0.050µF 3.0ms

0.1µF 6.2ms

0.33µF 20.75ms

Table 3. Selected Overcurrent Timer Delays

Applications Information

Output Undervoltage Detection

For output undervoltage detection, the first consideration is to
establish the output voltage level that indicates “power is
good.” For this example, the output value for which a 12V
supply will signal “good” is 11V. Next, consider the tolerances
of the input supply and FB threshold (VFB). For this example,
the 12V supply varies ±5%, thus the resulting output voltage
may be as low as 11.4V and as high as 12.6V. Additionally,
the FB threshold has ±50mV tolerance and may be as low as

1.19V and as high as 1.29V. Thus, to determine the values of
the resistive divider network (R5 and R6) at the FB pin, shown
in Figure 5, use the following iterative design procedure.

1) Choose R6 so as to limit the current through the
divider to approximately 100µA or less.

V

FB(MAX)

R6

≥

100 A

µ

R6 is chosen as 13.3kΩ ± 1%.

2) Next, determine R5 using the output “good”
voltage of 11V and the following equation:

VV

OUT(Good)

1.29V

≥

100 A

=

FB

≥Ω

µ



R5 R6

+

()



R6



12.9k






.

(8)

Using some basic algebra and simplifying Equation 8 to
isolate R5, yields:







–1









OUT(Good)

(8.1)

= 11V, and R6 is

R5 R6

where V




=





FB(MAX)



V

OUT(Good)



V



FB(MAX)

= 1.29V, V

13.3kΩ. Substituting these values into Equation 8.1 now
yields R5 = 100.11kΩ. A standard 100kΩ ± 1% is selected.
Now, consider the 11.4V minimum output voltage, the lower
tolerance for R6 and higher tolerance for R5, 13.17kΩ and
101kΩ, respectively. With only 11.4V available, the voltage
sensed at the FB pin exceeds V

FB(MAX)

, thus the /POR and
PWRGD (MIC2086) signals will transition from LOW to
HIGH, indicating “power is good” given the worse case
tolerances of this example.

Input Overvoltage Protection

The external CRWBR circuit shown in Figure 5 consists of
capacitor C4, resistor R7, NPN transistor Q2, and SCR Q3.
The capacitor establishes a time duration for an overvoltage
condition to last before the circuit breaker trips. The CRWBR
timer duration is approximated by the following equation:

t

OVCR

()

≅

I

CR

CR

≅×µ0

.01 C4( F)

(9)

C4 V

×

where VCR, the CRWBR pin threshold, is 0.47V and ICR, the
CRWBR pin current, is 45µA during the timer period (see the
CRWBR timer pin description for further description). A
similar design approach as the previous undervoltage detec­tion example is recommended for the overvoltage protection
circuitry, resistors R2 and R3 in Figure 5. For input overvolt­age protection, the first consideration is to establish the input
voltage level that indicates an overvoltage triggering a sys­tem (output voltage) shut down. For this example, the input
value for which a 12V supply will signal an “output shut down”
is 13.2V (+10%). Similarly, from the previous example:

1) Choose R3 to satisfy 100µA condition.

R3

≥

V

OV(MIN)

100 A

µ

1.19V

≥

100 A

≥Ω

11.9k

µ

.

R3 is chosen as 13.7kΩ ±1%.

2) Thus, following the previous example and
substituting R2 and R3 for R5 and R6, respec­tively, and 13.2V overvoltage for 11V output
“good”, the same formula yields R2 of 138.3kΩ.
The next highest standard 1% value is 140kΩ.

Now, consider the 12.6V maximum input voltage (V

CC

+5%),
the higher tolerance for R3 and lower tolerance for R2, 13.84k
and 138.60kΩ, respectively. With a 12.6V input, the voltage
sensed at the OV pin is below V

OV(MIN)

, and the MIC2085/86
will not indicate an overvoltage condition until VCC exceeds
at least 13.2V.

M0235-121903 16 January 2004

MIC2085/2086 Micrel

V

IN

12V

C1
1µF

4

9

C3

0.05µF

ON

OV

R2

140kΩ

1%

R3

13.7kΩ
1%

R1

100kΩ

Overvoltage (Input) = 13.3V
Undervoltage (Output) = 11.0V
POR/START-UP Delay = 30ms
*R7 needed when using a sensitive gate SCR.
Additional pins omitted for clarity.

R

SENSE

0.012Ω
2%

12

34

16 15

SENSEVCC

MIC2085

CPOR

GND

83

GATE

FB

/POR

/FAULT

CRWBR

IRF7822

14

7

5

6
1

C4

0.01µF

Q1

(SO-8)

0.033µF

R4
10Ω

C2

0.022µF

Downstream
Signals

C5

R5
100kΩ
1%

R6

13.3kΩ
1%

Q2
2N4401

*R7
180Ω

Q3
TCR22-4

C

LOAD

220µF

V

OUT

12V@3A

Figure 5. Undervoltage/Overvoltage Circuit

January 2004 17 M0235-121903

MIC2085/2086 Micrel

/

PCB Connection Sense

There are several configuration options for the MIC2085/86’s
ON pin to detect if the PCB has been fully seated in the
backplane before initiating a start-up cycle. In the typical
applications circuit, the MIC2085/86 is mounted on the PCB
with a resistive divider network connected to the ON pin. R2
is connected to a short pin on the PCB edge connector. Until
the connectors mate, the ON pin is held low which keeps the
GATE output charge pump off. Once the connectors mate,
the resistor network is pulled up to the input supply, 12V in this
example, and the ON pin voltage exceeds its threshold (VON)

of 1.24V and the MIC2085/86 initiates a start-up cycle. In
Figure 6, the connection sense consisting of a logic-level
discrete MOSFET and a few resistors allows for interrupt
control from the processor or other signal controller to shut off
the output of the MIC2085/86. R4 keeps the GATE of Q2 at
VIN until the connectors are fully mated. A logic LOW at the
/ON_OFF signal turns Q2 off and allows the ON pin to pull up
above its threshold and initiate a start-up cycle. Applying a
logic HIGH at the /ON_OFF signal will turn Q2 on and short
the ON pin of the MIC2085/86 to ground which turns off the
GATE output charge pump.

V

IN

12V

ON_OFF

GND

Backplane
Connector

PCB Edge
Connector

Short

Long

Pin

Pin

R4

10kΩ

R1

20kΩ

R3

100Ω

PCB Connection Sense

Long

Pin

Undervoltage (Output) = 11.4V
POR/START-UP DELAY = 30ms
*Q2 is TN0201T (SOT-23)
Additional pins omitted for clarity.

*Q2

R2

20kΩ

C1
1µF

R

SENSE

0.008Ω
2%

12

34

16 15

4

ON

CPOR

C2

0.05µF

SENSEVCC

MIC2085

GND

83

GATE

FB

/POR

/FAULT

Q1

Si7860DP

(PowerPAK

14

7

5

1

TM

SO-8)

R5
10Ω

C2

0.01µF

R6
127kΩ
1%

R7

16.2kΩ
1%

Downstream
Signals

C

LOAD

220µF

V

OUT

12V@5A

Figure 6. PCB Connection Sense with ON/OFF Control

M0235-121903 18 January 2004

MIC2085/2086 Micrel

Higher UVLO Setting

Once a PCB is inserted into a backplane (power supply), the
internal UVLO circuit of the MIC2085/86 holds the GATE
output charge pump off until VCC exceeds 2.18V. If VCC falls
below 2V, the UVLO circuit pulls the GATE output to ground
and clears the overvoltage and/or current limit faults. For a
higher UVLO threshold, the circuit in Figure 7 can be used to
delay the output MOSFET from switching on until the desired
input voltage is achieved. The circuit allows the charge pump

R1

to remain off until VIN exceeds








R2

×

1.24V+





. The GATE

1

drive output will be shut down when VIN falls below

R1








R2

×

1.14V+





. In the example circuit (Figure 7), the rising

1

UVLO threshold is set at approximately 11V and the falling
UVLO threshold is established as 10.1V. The circuit consists
of an external resistor divider at the ON pin that keeps the
GATE output charge pump off until the voltage at the ON pin
exceeds its threshold (VON) and after the start-up timer
elapses.

V

IN

12V

C1
1µF

R1

392kΩ

1%

4

R2

49.9kΩ
1%

C3

0.1µF

Undervoltage Lockout (Rising) = 11.0V
Undervoltage Lockout (Falling) = 10.1V
Undervoltage (Output) = 11.4V
POR/START-UP Delay = 60ms

Additional pins omitted for clarity.

R

SENSE

0.010Ω
2%

12

34

16 15

SENSEVCC

ON

MIC2085

CPOR

GND

83

GATE

/POR

FB

IRF7822

(SO-8)

14

7

5

Q1

R3
10Ω

Downstream
Signal

Figure 7. Higher UVLO Setting

C2

0.01µF

R4
127kΩ
1%

R5

16.2kΩ
1%

C

LOAD

220µF

V

OUT

12V@4A

January 2004 19 M0235-121903

MIC2085/2086 Micrel

Fast Output Discharge for Capacitive Loads

In many applications where a switch controller is turned off by
either removing the PCB from the backplane or the ON pin is
reset, capacitive loading will cause the output to retain
voltage unless a ‘bleed’ (low impedance) path is in place in
order to discharge the capacitance. The MIC2086 is equipped
with an internal MOSFET that allows the discharging of any
load capacitance to ground through a 550Ω path. The dis­charge feature is configured by wiring the DIS pin to the
output (source) of the external MOSFET and becomes active

R

SENSE

0.007

W

V

IN

12V

ON Signal

R1
47k

C1
1mF

W

4

ON

5%

12

34

19,20 18

SENSE

VCC

MIC2086

(DIS pin output is low) once the ON pin is deasserted. Figure
8(a) illustrates the use of the discharge feature with an
optional resistor (R5) that can be used to provide added
resistance in the output discharge path. For an even faster
discharge response of capacitive loads, the configuration of
Figure 8(b) can be utilized to apply a crowbar to ground
through an external SCR (Q3) that is triggered when the DIS
pin goes low which turns on the PNP transistor (Q2). See the
different

“Functional Characteristic”

curves for a comparison

of the discharge response configurations.

Q1

Si7892DP

(PowerPAK

17

GATE

8

FB

15

DIS

TM

SO-8)

R2
10

W

C2

0.022mF

*R5

R3
110k
1%

R4

14.7k
1%

W

W

C

LOAD

1500mF

V

OUT

12V@5A

V

IN

12V

ON Signal

R1
47k

5

C3

0.01mF

PWRGD

GNDCPOR CFILTER

9,10 23

/POR

C4

0.01mF

6

Downstream
Signals

(a)

R

SENSE

0.007

W

5%

12

C1
1mF

W

4

ON

34

19,20 18

SENSE

VCC

MIC2086

Si7892DP

(PowerPAK

17

GATE

8

FB

5

/POR

Q1

TM

SO-8)

R2
10

W

C2

0.022mF

Downstream
Signal

R6

4.4k

W

R3
110k
1%

R4

14.7k
1%

V

OUT

12V@5A

C

LOAD

1500mF

W

W

Q2

ZTX788A

R7
220

W

Q3

TCR22-4

C3

0.01mF

Undervoltage (Output) = 11V
POR/START-UP Delay = 6ms
Circuit Breaker Response Time = 620ms
*R5 of Figure 8(a) is optional to combine in series

with internal 550

Additional pins omitted for clarity.

W.

GNDCPOR CFILTER

9,10 23

(b)

DIS

C4

0.01mF

15

R5

1.5k

W

C5

0.022mF

Figure 8. MIC2086 Fast Discharge of Capacitive Load

M0235-121903 20 January 2004

MIC2085/2086 Micrel

Auto-Retry Upon Overcurrent Faults

The MIC2085/86 can be configured for automatic restart after
a fault condition. Placing a diode between the ON and
/FAULT pins, as shown in Figure 9, will enable the auto­restart capability of the controller. When an application is
configured for auto-retry, the overcurrent timer should be set
to minimize the duty cycle of the overcurrent response to
prevent thermal runaway of the power MOSFET. See

“MOSFET Transient Thermal Issues”

section for further
detail. A limited duty cycle is achieved when the overcurrent
timer duration (t
timer duration (t

OCSLOW

START

) is much less than the start-up delay

) and is calculated using the following

equation:

t

Auto Retry Duty Cycle

−=×

OCSLOW

t

START

100%

(10)

An InfiniBand™ Application Circuit

The circuit in Figure 10 depicts a single 50W InfiniBand™
module using the MIC2085 controller. An InfiniBand™
backplane distributes bulk power to multiple plug-in modules
that employ DC/DC converters for local supply requirements.

The circuit in Figure 10 distributes 12V from the backplane to
the MIC2182 DC/DC converter that steps down +12V to
+3.3V for local bias. The pass transistor, Q1, isolates the
MIC2182’s input capacitance during module plug-in and
allows the backplane to accommodate additional plug-in
modules without affecting the other modules on the backplane.
The two control input signals are VBxEn_L (active LOW) and
a Local Power Enable (active HIGH). The MIC2085 in the
circuit of Figure 10 performs a number of functions. The gate
output of Q1 is enabled by the two bit input signal VBxEn_L,
Local Power Enable = [0,1]. Also, the MIC2085 limits the drain
current of Q1 to 7A, monitors VB_In for an overvoltage
condition greater than 16V, and enables the MIC2182 DC/DC
converter downstream to supply a local voltage rail. The
uncommitted comparator is used to monitor VB_In for an
undervoltage condition of less than 10V, indicated by a logic
LOW at the comparator output (COMPOUT). COMPOUT
may be used to control a downstream device such as another
DC/DC converter. Additionally, the MIC2085 is configured for
auto-retry upon an overcurrent fault condition by placing a
diode (D1) between the /FAULT and ON pins of the controller.

V

IN

5V

R1

47kΩ

R2

ON SIGNAL

/FAULT

OUTPUT

Undervoltage (Output) = 4.27V
POR/START-UP Delay = 12ms
Circuit Breaker Response Time = 290µs
Auto-Retry Duty Cycle = 2.5%
Additional pins omitted for clarity.

33kΩ

D1

1N914

0.02µF

Figure 9. Auto-Retry Configuration

R

SENSE

0.012Ω
5%

12

34

C1
1µF

16 15

4

ON

6

/FAULT

CPOR

C3

SENSEVCC

MIC2085

GND

83

GATE

/POR

CFILTER

2

14

7

FB

5

C4
4700pF

Q1

IRF7822

(SO-8)

R3
10Ω

C2

0.022µF

Downstream
Signal

R4
34kΩ
1%

R5

14.7kΩ
1%

C

LOAD

220µF

V

OUT

5V@2.5A

January 2004 21 M0235-121903

MIC2085/2086 Micrel

InfiniBand™ Application

VB_In

(12V)

VBxEn_L

VB_Ret

InfiniBandª

Backplane

Long

Short

Long

165k

R3

13.3k

W

1%

C1

0.01mF

Local Power

Enable

1%

InfiniBandª

MODULE

R

SENSE

0.007

W

5%

12

34

R2

W

C3

0.1mF

0.022mF

R1
10k

9

11

3

12

13

OV

COMP+

CPOR

COMPÐ

REF

CFILTER

C4

W

16 15

SENSEVCC

MIC2085

GNDONCRWBR

28

GATE

COMPOUT

/POR

/FAULT

78.7k

11k

R4

W

1%

R5

W

1%

C5

0.033mF

Q1

IRF7822

(SO-8)

R7

R6

174k

10

W

14

10

5

7

FB

6

D1
1N914

4

1

Overvoltage (Input) = 16.0V
Undervoltage (Input) = 10.0V
Undervoltage (Output) &
Power-Good (Output) = 10.0V
Circuit Breaker Response Time = 1.2ms
POR/START-UP Delay = 18.5ms
Auto-Retry Duty Cycle = 6.5%

W

1%

C2

0.022mF

Power-On Reset

Output

R8

25.5k

W

1%

MIC2182

DC/DC Converter

V

IN

/UV

RUN/SS

GND

3.3V @ 4A

Figure 10. A 50W InfiniBand™ Application

Sense Resistor Selection

The MIC2085 and MIC2086 use a low-value sense resistor to
measure the current flowing through the MOSFET switch
(and therefore the load). This sense resistor is nominally
valued at 48mV/I

LOAD(CONT)

. To accommodate worst-case
tolerances for both the sense resistor (allow ±3% over time
and temperature for a resistor with ±1% initial tolerance) and
still supply the maximum required steady-state load current,
a slightly more detailed calculation must be used.

The current limit threshold voltage (the “trip point”) for the
MIC2085/86 may be as low as 40mV, which would equate to
a sense resistor value of 40mV/I

LOAD(CONT)

. Carrying the
numbers through for the case where the value of the sense
resistor is 3% high yields:

R

SENSE(MAX)

=

Once the value of R

40mV

1.03 I

()

()

LOAD(CONT)

has been chosen in this manner,

SENSE

it is good practice to check the maximum I

38.8mV

=

I

LOAD(CONT)

LOAD(CONT)

(11)

which
the circuit may let through in the case of tolerance build-up in
the opposite direction. Here, the worst-case maximum cur­rent is found using a 55mV trip voltage and a sense resistor
that is 3% low in value. The resulting equation is:

I

LOAD(CONT,MAX)

=

55mV

0.97 R

()

()

SENSE(NOM)

56.7mV

=

R

SENSE(NOM)

(12)
As an example, if an output must carry a continuous 6A

without nuisance trips occurring, Equation 11 yields:

R

SENSE(MAX)

38.8mV

==Ω

6A

6.5m

.

The next lowest standard value is 6.0mW. At the other set
of tolerance extremes for the output in question:

I

LOAD(CONT,MAX)

56.7mV

=

6.0m

9.45A

=

Ω

,

almost 10A. Knowing this final datum, we can determine
the necessary wattage of the sense resistor, using P = I2R,
where
(0.97)(R

I will be I

SENSE(NOM)

LOAD(CONT, MAX)

).

These numbers yield the following:

P

MAX

, and R will be

= (10A)2 (5.82mΩ)

= 0.582W.

In this example, a 1W sense resistor is sufficient.

MOSFET Selection

Selecting the proper external MOSFET for use with the
MIC2085/86 involves three straightforward tasks:

• Choice of a MOSFET which meets minimum
voltage requirements.

• Selection of a device to handle the maximum
continuous current (steady-state thermal
issues).

• Verify the selected part’s ability to withstand any
peak currents (transient thermal issues).

MOSFET Voltage Requirements

The first voltage requirement for the MOSFET is that the drain­source breakdown voltage of the MOSFET must be greater
than V

. For instance, a 16V input may reasonably be

IN(MAX)

expected to see high-frequency transients as high as 24V.
Therefore, the drain-source breakdown voltage of the MOSFET
must be at least 25V. For ample safety margin and standard
availability, the closest minimum value should be 30V.

M0235-121903 22 January 2004

MIC2085/2086 Micrel

The second breakdown voltage criterion that must be met is
a bit subtler than simple drain-source breakdown voltage. In
MIC2085/86 applications, the gate of the external MOSFET
is driven up to a maximum of 21V by the internal output
MOSFET. At the same time, if the output of the external
MOSFET (its source) is suddenly subjected to a short, the
gate-source voltage will go to (21V – 0V) = 21V. Since most
power MOSFETs generally have a maximum gate-source
breakdown of 20V or less, the use of a Zener clamp is
recommended in applications with VCC ≥ 8V. A Zener diode
with 10V to 12V rating is recommended as shown in Figure

11. At the present time, most power MOSFETs with a 20V
gate-source voltage rating have a 30V drain-source break­down rating or higher. As a general tip, choose surface-mount
devices with a drain-source rating of 30V or more as a starting
point.

Finally, the external gate drive of the MIC2085/86 requires a
low-voltage logic level MOSFET when operating at voltages
lower than 3V. There are 2.5V logic level MOSFETs avail­able. Please see Table 4,

Vendors”

for suggested manufacturers.

“MOSFET and Sense Resistor

MOSFET Steady-State Thermal Issues

The selection of a MOSFET to meet the maximum continuous
current is a fairly straightforward exercise. First, arm yourself
with the following data:

• The value of I
question (see

LOAD(CONT, MAX.)

“Sense Resistor Selection”

for the output in

).

• The manufacturer’s data sheet for the candidate
MOSFET.

• The maximum ambient temperature in which the
device will be required to operate.

• Any knowledge you can get about the heat
sinking available to the device (e.g., can heat be
dissipated into the ground plane or power plane,
if using a surface-mount part? Is any airflow
available?).

The data sheet will almost always give a value of on resis­tance given for the MOSFET at a gate-source voltage of 4.5V,
and another value at a gate-source voltage of 10V. As a first
approximation, add the two values together and divide by two
to get the on-resistance of the part with 8V of enhancement.
Call this value RON. Since a heavily enhanced MOSFET acts
as an ohmic (resistive) device, almost all that’s required to
determine steady-state power dissipation is to calculate I2R.
The one addendum to this is that MOSFETs have a slight
increase in RON with increasing die temperature. A good
approximation for this value is 0.5% increase in RON per °C
rise in junction temperature above the point at which RON was
initially specified by the manufacturer. For instance, if the
selected MOSFET has a calculated RON of 10mΩ at a
TJ = 25°C, and the actual junction temperature ends up
at 110°C, a good first cut at the operating value for R

ON

would be:

RON ≅ 10mΩ[1 + (110 - 25)(0.005)] ≅ 14.3mΩ

The final step is to make sure that the heat sinking available
to the MOSFET is capable of dissipating at least as much
power (rated in °C/W) as that with which the MOSFET’s
performance was specified by the manufacturer. Here are a
few practical tips:

1. The heat from a surface-mount device such as
an SO-8 MOSFET flows almost entirely out of
the drain leads. If the drain leads can be sol­dered down to one square inch or more, the
copper will act as the heat sink for the part. This
copper must be on the same layer of the board
as the MOSFET drain.

Q1

IRF7822

(SO-8)

R3
10Ω

14

C2

0.01µF

7

FB

6

Downstream

5

Signals

Undervoltage (Output) = 11.0V
POR/START-UP Delay = 60ms
*Recommended for MOSFETs with gate-source
breakdown of 20V or less (IRF7822 VGS(MAX) = 12V)
for catastrophic output short circuit protection.
Additional pins omitted for clarity.

*D1
1N5240B
10V

R4
100kΩ
1%

R5

13.3kΩ
1%

C

LOAD

220µF

12V@5A

V

OUT

V

12V

R

SENSE

0.007Ω

IN

C1
1µF

R1

47kΩ

4

R2

33kΩ

0.1µF

2%

12

34

16 15

SENSEVCC

ON

MIC2085

CPOR

C3

GND

GATE

/FAULT

/POR

83

Figure 11. Zener Clamped MOSFET GATE

January 2004 23 M0235-121903

MIC2085/2086 Micrel

2. Airflow works. Even a few LFM (linear feet per
minute) of air will cool a MOSFET down sub­stantially. If you can, position the MOSFET(s)
near the inlet of a power supply’s fan, or the
outlet of a processor’s cooling fan.

3. The best test of a surface-mount MOSFET for
an application (assuming the above tips show it
to be a likely fit) is an empirical one. Check the
MOSFET's temperature in the actual layout of
the expected final circuit, at full operating
current. The use of a thermocouple on the drain
leads, or infrared pyrometer on the package, will
then give a reasonable idea of the device’s
junction temperature.

MOSFET Transient Thermal Issues

Having chosen a MOSFET that will withstand the imposed
voltage stresses, and the worse case continuous I2R power
dissipation which it will see, it remains only to verify the
MOSFET’s ability to handle short-term overload power dissi­pation without overheating. A MOSFET can handle a much
higher pulsed power without damage than its continuous
dissipation ratings would imply. The reason for this is that, like
everything else, thermal devices (silicon die, lead frames,
etc.) have thermal inertia.

In terms related directly to the specification and use of power
MOSFETs, this is known as “transient thermal impedance,”
or Z

. Almost all power MOSFET data sheets give a

θ(J-A)

Transient Thermal Impedance Curve. For example, take the
following case: VIN = 12V, t
I

LOAD(CONT. MAX)

is 2.5A, the slow-trip threshold is 48mV

OCSLOW

has been set to 100msec,

nominal, and the fast-trip threshold is 95mV. If the output is
accidentally connected to a 3Ω load, the output current from
the MOSFET will be regulated to 2.5A for 100ms (t

OCSLOW

before the part trips. During that time, the dissipation in the
MOSFET is given by:

P = E x I E
P

MOSFET

= (4.5V x 2.5A) = 11.25W for 100msec.

MOSFET

= [12V-(2.5A)(3Ω)] = 4.5V

At first glance, it would appear that a really hefty MOSFET is
required to withstand this sort of fault condition. This is where
the transient thermal impedance curves become very useful.
Figure 12 shows the curve for the Vishay (Siliconix) Si4410DY,
a commonly used SO-8 power MOSFET.

Taking the simplest case first, we’ll assume that once a fault
event such as the one in question occurs, it will be a long time
– 10 minutes or more – before the fault is isolated and the
channel is reset. In such a case, we can approximate this as
a “single pulse” event, that is to say, there’s no significant duty
cycle. Then, reading up from the X-axis at the point where
“Square Wave Pulse Duration” is equal to 0.1sec (=100msec),
we see that the Z

of this MOSFET to a highly infrequent

θ(J-A)

event of this duration is only 8% of its continuous R
This particular part is specified as having an R

50°C/W for intervals of 10 seconds or less. Thus:
Assume TA = 55°C maximum, 1 square inch of copper at the

drain leads, no airflow.
Recalling from our previous approximation hint, the part has
an R

of (0.0335/2) = 17mΩ at 25°C.

ON

Assume it has been carrying just about 2.5A for some time.
When performing this calculation, be sure to use the highest

anticipated ambient temperature (T

) in which the

A(MAX)

MOSFET will be operating as the starting temperature, and
find the operating junction temperature increase (∆TJ) from
that point. Then, as shown next, the final junction temperature
is found by adding T

and ∆TJ. Since this is not a closed-

A(MAX)

form equation, getting a close approximation may take one or
two iterations, but it’s not a hard calculation to perform, and
tends to converge quickly.

Then the starting (steady-state)TJ is:

TJ≅ T

≅ T

A(MAX)
A(MAX)

x I2 x R

+ ∆T

J

+ [RON + (T

θ(J-A)

– TA)(0.005/°C)(RON)]

A(MAX)

TJ≅ 55°C + [17mΩ + (55°C-25°C)(0.005)(17mΩ)]

)

x (2.5A)2 x (50°C/W)

TJ≅ (55°C + (0.122W)(50°C/W)

≅ 61.1°C

Iterate the calculation once to see if this value is within a few
percent of the expected final value. For this iteration we will
start with TJ equal to the already calculated value of 61.1°C:

TJ≅ TA + [17mΩ + (61.1°C-25°C)(0.005)(17mΩ)]

x (2.5A)2 x (50°C/W)

TJ ≅ ( 55°C + (0.125W)(50°C/W) ≅ 61.27°C

θ(J-A)

θ(J-A)

.

of

Normalized Thermal Transient Impedance, Junction-to-Ambient

Single Pulse

–3

10

–2

10

Square Wave Pulse Duration (sec)

10

–1

Notes:

P

DM

t

1

t

2

t

– TA = PDMZ

1

t

2

thJA

thJA

= 50°C/W

(t)

30

1. Duty Cycle, D =

2. Per Unit Base = R

3. T

JM

4. Surface Mounted

110

0.1

Thermal Impedance

Normalized Effective Transient

0.01

2

1

Duty Cycle = 0.5

0.2

0.1

0.05

0.02

–4

10

Figure 12. Transient Thermal Impedance

M0235-121903 24 January 2004

MIC2085/2086 Micrel

So our original approximation of 61.1°C was very close to the
correct value. We will use TJ = 61°C.

Finally, add (11.25W)(50°C/W)(0.08) = 45°C to the steady­state TJ to get T

J(TRANSIENT MAX.)

= 106°C. This is an accept-

able maximum junction temperature for this part.

PCB Layout Considerations

Because of the low values of the sense resistors used with the
MIC2085/86 controllers, special attention to the layout must
be used in order for the device’s circuit breaker function to
operate properly. Specifically, the use of a 4-wire Kelvin
connection to measure the voltage across R

SENSE

is highly
recommended. Kelvin sensing is simply a means of making
sure that any voltage drops in the power traces connecting to
the resistors does not get picked up by the traces themselves.
Additionally, these Kelvin connections should be isolated
from all other signal traces to avoid introducing noise onto
these sensitive nodes. Figure 13 illustrates a recommended,

Current Flow
to the Load

W W

*SENSE RESISTOR

(2512)

multi-layer layout for the R

, Power MOSFET, timer(s),

SENSE

overvoltage and feedback network connections. The feed­back and overvoltage resistive networks are selected for a
12V application (from Figure 5). Many hot swap applications
will require load currents of several amperes. Therefore, the
power (VCC and Return) trace widths (W) need to be wide
enough to allow the current to flow while the rise in tempera­ture for a given copper plate (e.g., 1 oz. or 2 oz.) is kept to a
maximum of 10°C ~ 25°C. Also, these traces should be as
short as possible in order to minimize the IR drops between
the input and the load. For a starting point, there are many
trace width calculation tools available on the web such as the
following link:

http://www.aracnet.com/cgi-usr/gpatrick/trace.pl
Finally, plated-through vias are utilized to make circuit con-

nections to the power and ground planes. The trace connec­tions with indicated vias should follow the example shown for
the GND pin connection in Figure 13.

Current Flow

*POWER MOSFET

(SO-8)

D

D

D

D

to the Load

G

S

S

S

**R4

10

W

Via to GND Plane

Via to POWER (VCC)
Plane

16

VCC

15

SENSE

14

GATE

13

REF

**C

12

COMP-

GATE

R3

13.7k
1%

10

11

COMP+

COMPOUT

W

R2
140k

W

1%

9

MIC2085

CRWBR

CFILTER

CPORON/POR

4

3

2

1

**C

FILTER

Current Flow
from the Load

W

**C

POR

Via to GND Plane

/FAULT

FB

5

6

GND OV

7

8

R5
100k

W

1%

R6

13.3k

W

1%

DRAWING IS NOT TO SCALE
*See Table 4 for part numbers and vendors
**Optional components
Trace width (W) guidelines given in "PCB Layout.
Recommendations" section of the datasheet.

Figure 13. Recommended PCB Layout for Sense Resistor, Power MOSFET,

and Feedback/Overvoltage Network

January 2004 25 M0235-121903

MIC2085/2086 Micrel

MOSFET and Sense Resistor Vendors

Device types and manufacturer contact information for power
MOSFETs and sense resistors is provided in Table 4. Some
of the recommended MOSFETs include a metal heat sink on
the bottom side of the package. The recommended trace for

MOSFET Vendors Key MOSFET Type(s) *Applications Contact Information

Vishay (Siliconix) Si4420DY (SO-8 package) I

Si4442DY (SO-8 package) I
Si3442DV (SO-8 package) I
Si7860DP (PowerPAK™ SO-8) I
Si7892DP (PowerPAK™ SO-8) I
Si7884DP (PowerPAK™ SO-8) I
SUB60N06-18 (TO-263) I
SUB70N04-10 (TO-263) I

International Rectifier IRF7413 (SO-8 package) I

IRF7457 (SO-8 package) I
IRF7822 (SO-8 package) I
IRLBA1304 (Super220™)I

Fairchild Semiconductor FDS6680A (SO-8 package) I

FDS6690A (SO-8 package) I
Philips PH3230 (SOT669-LFPAK) I
Hitachi HAT2099H (LFPAK) I

* These devices are not limited to these conditions in many cases, but these conditions are provided as a helpful reference for customer applications.

the MOSFET Gate of Figure 13 must be redirected when
using MOSFETs packaged in this style. Contact the device
manufacturer for package information.

≤ 10A www.siliconix.com

OUT

= 10A-15A, V

OUT

≤ 3A, V

OUT

≤ 12A

OUT

≤ 15A

OUT

≤ 15A

OUT

≥ 20A, V

OUT

≥ 20A, V

OUT

≤ 10A www.irf.com

OUT

≤ 10A [phone]

OUT

= 10A-15A, V

OUT

≥ 20A, V

OUT

≤ 10A www.fairchildsemi.com

OUT

≤ 10A, V

OUT

≥ 20A www.philips.com

OUT

≥ 20A www.halsp.hitachi.com

OUT

CC

CC
CC

CC

CC

≤ 5V [phone]

CC

≤ 5V

≥ 5V
≥ 5V

≤ 5V

CC

≥ 5V

≤ 5V [phone]

[phone]

Resistor Vendors Sense Resistors Contact Information

Vishay (Dale) “WSL” Series www.vishay.com/docswsl_30100.pdf

[phone]

IRC “OARS” Series www.irctt.com/pdf_files/OARS.pdf

“LR” Series www.irctt.com/pdf_files/LRC.pdf
(second source to “WSL”) [phone]

Table 4. MOSFET and Sense Resistor Vendors

M0235-121903 26 January 2004

MIC2085/2086 Micrel

Package Information

PIN 1

0.009 (0.2286)

0.0098 (0.249)

0.0040 (0.102)

SEATING

PLANE

0.025 BSC
(0.635)

0.157 (3.99)

0.150 (3.81)

REF

0.0688 (1.748)

0.0532 (1.351)

0.025 (0.635)
BSC

0.344 (8.74)

0.337 (8.56)

0.012 (0.30)

0.008 (0.20)

0.0098 (0.249)

0.0075 (0.190)

0.196 (4.98)

0.189 (4.80)

16-Pin QSOP (QS)

0.0575 REF

8¡

0.157 (3.99)

0.150 (3.81)

0.012 (0.305)

0.008 (0.203)

0¡

DIMENSIONS:

INCHES (MM)

0.050 (1.27)

0.016 (0.40)

0.244 (6.20)

0.229 (5.82)

0.244 (6.20)

0.229 (5.82)

45¡

8¡
0¡

Rev. 04

0.009 (0.229)

0.007 (0.178)

0.068 (1.73)

0.053 (1.35)

7¡ BSC

0.010 (0.254)

0.004 (0.102)

0.050 (1.27)

0.016 (0.40)

20-Pin QSOP (QS)

Rev. 04

Note:

1. All Dimensions are in Inches (mm) excluding mold flash.

2. Lead coplanarity should be 0.004" max.

3. Max misalignment between top and bottom.

4. The lead width, B to be determined at 0.0075" from lead tip.

January 2004 27 M0235-121903

MIC2085/2086 Micrel

MICREL, INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA

TEL + 1 [phone] FAX + 1 [phone] WEB http://www.micrel.com

The information furnished by Micrel in this data sheet is believed to be accurate and reliable. However, no responsibility is assumed by Micrel for its use.

Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser’s

use or sale of Micrel Products for use in life support appliances, devices or systems is at Purchaser’s own risk and Purchaser agrees to fully indemnify

M0235-121903 28 January 2004

Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.

Micrel for any damages resulting from such use or sale.

© 2003 Micrel, Incorporated.