Datasheet LTC4223-1, LTC4223-2 Datasheet (LINEAR TECHNOLOGY)

LTC4223-1/LTC4223-2

Dual Supply Hot Swap

Controller for Advanced

Mezzanine Card

FEATURES

■

Allows Safe Insertion into Live AMC or MicroTCA

Backplane

■

Controls 12V Main and 3.3V Auxiliary Supplies

■

Limits Peak Fault Current in ≤1μs

■

Adjustable Current Limit with Circuit Breaker

■

Integrated 0.3Ω AUX Switch

■

High Side Current Sense

■

Gate Drive for External N-Channel MOSFET

■

Adjustable Response Time for Overcurrent Protection

■

Adjustable Supply Voltage Power-Up Rate

■

Thermal Shutdown Protection

■

LTC4223-1: Latch Off After Fault

■

LTC4223-2: Automatic Retry After Fault

■

16-Lead SSOP and 5mm × 4mm DFN Packages

APPLICATIONS

■

Advanced Mezzanine Card, MicroTCA Systems

■

Workstations and Server I/O

■

Telecom Networks

DESCRIPTION

The LTC®4223 positive voltage Hot SwapTM controller
allows a board to be safely inserted and removed from
a live AMC or MicroTCA backplane. It controls the main
12V supply with an external N-channel MOSFET and the

3.3V auxiliary supply with an integrated switch. The 12V
output ramp rate is adjustable and includes inrush current
limiting. The 12V output is also protected against short
circuit faults with a fast acting current limit and a 5%
accurate timed circuit breaker. The 3.3V output includes
both soft start and overcurrent protection.

The LTC4223 features a current monitor output for the
12V supply, and reports fault and power-good status for
both supplies. It also detects card presence and allows
independent control of the 12V and auxiliary 3.3V sup­ply outputs. The LTC4223-1 features a latch-off circuit
breaker, while the LTC4223-2 provides automatic retry
after a fault.

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

TYPICAL APPLICATION

Advanced Mezzanine Card Application

6mΩ Si7336ADP

12V

12V

SENSE

IN

AUXIN

V

CC

AUXON
12ON
AUXPGOOD
12PGOOD
FAULT

12IMON

GND

10Ω

47Ω

12V

GATE

LTC4223-1/LTC4223-2

TIMER

0.1μF

IPMC

12V

3.3V

51Ω

330nF

ADC

15nF

12V

OUT

AUXOUT

422312 TA01a

EN

CARRIER

CONNECTOR

12V

7.4A

3.3V
150mA

MODULE
CONNECTOR

EN

5V/DIV

AUXOUT

5V/DIV

12V

OUT

5V/DIV

AUXPGOOD

5V/DIV

12PGOOD

5V/DIV

Normal Power-Up Waveform

20ms/DIV

422312 TA01b

422312f

1

LTC4223-1/LTC4223-2

ABSOLUTE MAXIMUM RATINGS

(Note 1)

Supply Voltages
12V

..................................................... –0.3V to 20V

IN

AUXIN .................................................... –0.3V to 10V

........................................................... –0.3V to 7V

V

CC

Input Voltages

⎯E⎯

12ON, AUXON,

TIMER ..........................................–0.3V to V

12V

............................................... –0.3V to 20V

SENSE

N ................................... –0.3V to 7V

+ 0.3V

CC

Output Voltages

⎯F⎯A⎯U⎯L⎯

T, ⎯1⎯2⎯P⎯G⎯O⎯O⎯D, ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D,

12IMON ................................................... –0.3V to 7V

PIN CONFIGURATION

12V
12V

................................................. –0.3V to 25V

GATE
OUT

- 12V

(Note 3) ................... –4.5V to 0.3V

GATE

AUXOUT ................................................. –0.3V to 10V

Operating Temperature Range

LTC4223-1C/ LTC4223-2C ....................... 0°C to 70°C

LTC4223-1I/ LTC4223-2I ..................... –40°C to 85°C

Storage Temperature Range

GN Package .......................................–65°C to 150°C

DHD Package ..................................... –65°C to 125°C

Lead Temperature (Soldering, 10sec)

GN Package ......................................................300°C

12V

12IMON

AUXON

SENSE

12V

12ON

AUXIN

V

GND

IN

CC

T

JMAX

TOP VIEW

1

2

3

4

5

6

7

8

GN PACKAGE

16-LEAD PLASTIC SSOP

= 125°C, θJA = 110°C/W

16

15

14

13

12

11

10

9

12V

GATE

12V

OUT

12PGOOD

FAULT

AUXOUT

AUXPGOOD

EN

TIMER

12V

SENSE

12V

12IMON

12ON

AUXIN

AUXON

GND

16-LEAD (5mm × 4mm) PLASTIC DFN

EXPOSED PAD (PIN 17) PCB GND CONNECTION OPTIONAL

MUST BE SOLDERED TO PCB TO OBTAIN

= 43°C/W, OTHERWISE θJA = 140°C/W, T

θ

JA

IN

V

CC

TOP VIEW

1

2

3

4

5

6

7

8

DHD PACKAGE

16

12V

GATE

15

12V

OUT

14

12PGOOD

13

12

11

10

9

FAULT

AUXOUT

AUXPGOOD

EN

TIMER

JMAX

= 125°C

17

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE

LTC4223CDHD-1#PBF LTC4223CDHD-1#TRPBF 42231 16-Lead (5mm × 4mm) Plastic DFN 0°C to 70°C

LTC4223CDHD-2#PBF LTC4223CDHD-2#TRPBF 42232 16-Lead (5mm × 4mm) Plastic DFN 0°C to 70°C

LTC4223IDHD-1#PBF LTC4223IDHD-1#TRPBF 42231 16-Lead (5mm × 4mm) Plastic DFN –40°C to 85°C

LTC4223IDHD-2#PBF LTC4223IDHD-2#TRPBF 42232 16-Lead (5mm × 4mm) Plastic DFN –40°C to 85°C

LTC4223CGN-1#PBF LTC4223CGN-1#TRPBF 42231 16-Lead Plastic SSOP 0°C to 70°C

LTC4223CGN-2#PBF LTC4223CGN-2#TRPBF 42232 16-Lead Plastic SSOP 0°C to 70°C

LTC4223IGN-1#PBF LTC4223IGN-1#TRPBF 4223I1 16-Lead Plastic SSOP –40°C to 85°C

LTC4223IGN-2#PBF LTC4223IGN-2#TRPBF 4223I2 16-Lead Plastic SSOP –40°C to 85°C

Consult LTC Marketing for parts specifi ed with wider operating temperature ranges. *The temperature grade is identifi ed by a label on the shipping container.
Consult LTC Marketing for information on non-standard lead based fi nish parts.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifi cations, go to: http://www.linear.com/tapeandreel/

2

422312f

LTC4223-1/LTC4223-2

ELECTRICAL CHARACTERISTICS

The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are T

= 25°C, VCC = 3.3V, V

A

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Supplies

V

DD

Input Supply Range V

CC

AUXIN
12V

IN

I

DD

Input Supply Current V

CC

AUXIN
12V

IN

V

DD(UVLO)

ΔV

DD(UVLO,

HYST)

Input Supply Undervoltage Lockout VCC Rising

V

Rising

AUXIN

V

Rising

12VIN

Input Supply Undervoltage Lockout
Hysteresis

V

CC

AUXIN
12V

IN

Current Limit

ΔV

SENSE(CB)

ΔV

SENSE(ACL)

I

AUX(ACL)

Circuit Breaker Trip Sense Voltage,
(V

12VIN

– V

12VSENSE

)

Active Current Limit Sense Voltage,
(V

12VIN

– V

12VSENSE

)

AUXOUT Active Current Limit V

AUXOUT

= 0V

Integrated Switch

R

DS(ON)

Switch Resistance
(V

– V

AUXIN

AUXOUT

)/I

AUXOUT

I

= 150mA (Note 4)

AUXOUT

Gate Drive

ΔV

GATE

I

GATE(UP)

I

GATE(DN)

I

GATE(FPD)

External N-Channel Gate Drive
(V

12VGATE

– V

12VOUT

)

(Note 3)

External N-Channel Gate Pull-Up Current Gate Drive On, V

External N-Channel Gate Pull-Down Current Gate Drive Off

V

= 17V, V

12VGATE

External N-Channel Gate Fast Pull-Down
Current

Fast Turn Off
V

= 17V, V

12VGATE

Current Sense

G

12IMON

V

12IMON

ΔV

SENSE(MAX)

V

12IMON(CLP)

R

12IMON

V

12IMON(MIN)

12IMON Pin Gain Ratio
ΔV

12IMON

/Δ(V

12VIN

– V

12VSENSE

)

(V

12IMON Pin Output Voltage (V

12IMON Pin Maximum Input Sense Voltage

12IMON Pin Clamp Voltage (V

12IMON Pin Output Resistance (V

12IMON Pin Minimum Output Voltage (V

12VIN

12VIN

12VIN

12VIN

12VIN

– V

– V

– V

– V

– V

12VSENSE

12VSENSE

12VSENSE

12VSENSE

12VSENSE

Comparator Inputs

V

PG(TH)

V

PG(HYST)

V

TMR(TH)

Power Good Threshold Voltage V

Power Good Hysteresis V

TIMER Pin Threshold Voltage V

12VOUT

V

AUXOUT

12VOUT

V

AUXOUT

TIMER

V

TIMER

Falling

Falling

Rising
Falling

= 3.3V, V

AUXIN

= 0V

12VGATE

= 12V

12VOUT

= 12V

12VOUT

) = (75mV, 25mV)

) = 75mV, VCC = 2.7V

) = 150mV, VCC = 2.7V

) = 0V

) = 0V

=12V, unless otherwise specifi ed. (Note 2)

12VIN

●

2.7

●

2.7

●

10

●

●

●

●

2.3

●

2.4

●

9.4

●

40

●

70

●

70

●

47.5 50 52.5 mV

●

54 60 66 mV

●

165 240 330 mA

●

●

4.5 6.2 7.9 V

●

–7 –10 –14 μA

●

0.5 1 2 mA

●

90 160 250 mA

●

30 33 36 V/V

●

2.25 2.475 2.7 V

●

82.5 mV

●

2.9 3.2 3.5 V

●

115 165 215 kΩ

●

●

10

●

2.8

●

20

●

5

●

1.198

●

0.15

0.8

0.4

0.6

2.45

2.5

9.7

110
110
110

0.3 0.5

0 130 mV

10.3

2.885

60
16

1.235

0.2

6
6

14

2
1
1

2.6

2.6
10

180
150
150

10.6

2.97

110

30

1.272

0.25

mA
mA
mA

mV
mV
mV

mV
mV

V
V
V

V
V
V

Ω

V
V

V
V

422312f

3

LTC4223-1/LTC4223-2

ELECTRICAL CHARACTERISTICS

The ● denotes the specifi cations which apply over the full operating
temperature range, otherwise specifi cations are TA = 25°C, VCC = 3.3V, V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

I

TMR(UP)

I

TMR(DN)

TIMER Pull-Up Current V

TIMER Pull-Down Current V

Open Drain Outputs

V

OL

V

OH

I

PU

Output Low Voltage (⎯F⎯A⎯U⎯L⎯T, ⎯1⎯2⎯P⎯G⎯O⎯O⎯D,

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

D)

Output High Voltage (⎯F⎯A⎯U⎯L⎯T, ⎯1⎯2⎯P⎯G⎯O⎯O⎯D,

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

D)

Output Pin Pull-Up Current (⎯F⎯A⎯U⎯L⎯T,

⎯1⎯2⎯P⎯G⎯O⎯O⎯

D, ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D)

Logic Inputs

V

IN(TH)

I

IN(LEAK)

R

PU

Logic Input Threshold (12ON, AUXON, ⎯E⎯N)

Input Leakage Current (12ON, AUXON) VIN = V

⎯E⎯

N Pin Pull-Up Resistance

Other Pin Functions

I

12VSENSE

I

12VOUT

R

OUT(DIS)

12V

12V

OUT Pin Discharge Resistance
12V

Pin Input Current V

SENSE

Pin Input Current Gate Drive On, V

OUT

OUT

AUXOUT

Propagation Delays

t

CB

t

PHL(SENSE)

t

PHH(AUXON)

t

PHH(12ON)

t

RST(ON)

t

RST(VCC)

t

PLL(UVLO)

t

PHL(GATE)

t

PLH(PG)

t

P(12IMON)

AUX Circuit Breaker Trip Delay After Power Up

Sense Voltage, (12VIN – 12V
High to 12V

GATE

Low

SENSE

)

AUXON High to AUXOUT High

12ON High to 12V

GATE

High

Input Low (12ON, AUXON) to ⎯F⎯A⎯U⎯L⎯T High

VCC Low to ⎯F⎯A⎯U⎯L⎯T High

12VIN Low to 12V

AUXIN Low to

⎯E⎯

N High to 12V

12V

Low to ⎯1⎯2⎯P⎯G⎯O⎯O⎯D High

OUT

AUXOUT Low to

Low

GATE

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

Low

GATE

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

D High

D High

Input Sense Voltage Step to 12IMON
Propagation Delay

Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.

Note 2: All currents into device pins are positive; all currents out of
the device pins are negative. All voltages are referenced to GND unless
otherwise specifi ed.

= 1V, Initial Timing Cycle

TIMER

V

= 0V, In AUX Fault Mode

TIMER

V

= 0V, In 12V Fault Mode

TIMER

= 2V, No Faults

TIMER

V

= 2V, In Reset Mode

TIMER

= 3mA

I

OL

(Note 5)

= 1.5V

V

PU

CC

= 12V

12VSENSE

Gate Drive Off

= 6V

V

12VOUT

V

ΔV
ΔV

ΔV

AUXVOUT

SENSE
SENSE

SENSE

= 2V

= 300mV, C
= 100mV, C

= 100mV

= 3.3V, V

AUXIN

= 12V

12VOUT

= 10nF

12VGATE

= 10nF

12VGATE

Note 3: An internal clamp limits the 12V
above 12V

. Driving this pin to voltages beyond the clamp may damage

OUT

=12V, unless otherwise specifi ed. (Note 2)

12VIN

●

–7

●

–7

●

–140

●

1.3

●

2

●

●

VCC – 1 V

●

–6 –10 –14 μA

●

0.8 2 V

●

●

60 100 140 kΩ

●

10 50 100 μA

●

20 50 100 μA

●

400

●

375

●

12 25 50 μs

●

●

●

●

●

●

●

61218 μs

●

61218 μs

●

●

●

●

–10
–10

–200

2
8

–13
–13

–260

2.6
16

0.15 0.4 V

±1 μA

800
750

0.5

1600
1500

1

5

12

15 30 μs

30 60 μs

20 40 μs

80 150 μs

20 40 μs

20 40 μs

20 40 μs

26 μs

pin to a minimum of 4.5V

GATE

the device.
Note 4: For the DFN package, the AUX switch on resistance, R

DS(ON)

is guaranteed by correlation to wafer test measurements.
Note 5: The output pins

pull-up to V

of 10μA. However, an external pull-up resistor may be used

CC

when faster rise time is required or for V

⎯F⎯A⎯U⎯L⎯

T, ⎯1⎯2⎯P⎯G⎯O⎯O⎯D and ⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯D have an internal

voltages greater than VCC.

OH

μA
μA
μA

μA

mA

limit

422312f

Ω
Ω

μs
μs

4

LTC4223-1/LTC4223-2

TYPICAL PERFORMANCE CHARACTERISTICS

Specifi cations are T

3.3V, V

=12V, unless otherwise specifi ed.

12VIN

ICC vs V

1.6

CC

Supply Current vs Temperature

1.0

12IMON Gain Ratio vs
Temperature

35

= 25°C, VCC = 3.3V, V

A

AUXIN

=

1.2

0.8

(mA)

CC

I

0.4

0

3.0 3.5 4.0 4.5

2.5
VCC (V)

5.0 5.5 6.0

12IMON Output Voltage vs Sense
Voltage

4

3

2

1

12IMON OUTPUT VOLTAGE (V)

0

20 40 60 80

0

SENSE VOLTAGE (mV)

100 120 140

422312 G01

422312 G04

0.8

0.6

0.4

SUPPLY CURRENT (mA)

0.2

0

–50

–25

TEMPERATURE (°C)

Power-Good Threshold vs

12V

OUT

Temperature

10.4

10.3

10.2

10.1

POWER-GOOD THRESHOLD (V)

OUT

12V

10.0
–50

–25 0 25 50 75 100

TEMPERATURE (°C)

V

CC

12V

IN

AUXIN

02550

RISING

FALLING

75 100

422312 G02

422312 G05

34

33

32

12IMON GAIN RATIO (V/V)

31

–50

–25 0 25 50 70 100

TEMPERATURE (°C)

AUXOUT Power-Good Threshold
vs Temperature

2.92

2.90

2.88

2.86

AUXOUT POWER-GOOD THRESHOLD (V)

2.84
–50

–25 0 25 50 75 100

RISING

FALLING

TEMPERATURE (°C)

422312 G03

422312 G06

Circuit Breaker Trip Voltage vs
Temperature

52

51

50

49

CIRCUIT BREAKER TRIP VOLTAGE (mV)

48

–50

–25 0 25 50 75 100

TEMPERATURE (°C)

422312 G07

Active Current Limit Sense
Voltage vs Temperature

62

61

60

59

ACTIVE CURRENT LIMIT SENSE VOLTAGE (mV)

58

–50

–25 0 25 50 75 100

TEMPERATURE (°C)

422312 G08

AUX Active Current Limit vs
Temperature

250

240

230

220

210

AUX ACTIVE CURRENT LIMIT (mA)

200

–50

02550

–25

TEMPERATURE (°C)

75 100

422312 G09

422312f

5

LTC4223-1/LTC4223-2

TYPICAL PERFORMANCE CHARACTERISTICS

Specifi cations are TA = 25°C, VCC = 3.3V, V

3.3V, V

0.5

0.4

0.3

=12V, unless otherwise specifi ed.

12VIN

AUX Switch On Resistance vs
Temperature Gate Drive vs Temperature Gate Drive vs I

) (V)

GATE

6.3

6.2

6.1

) (V)

GATE

7

6

5

4

3

GATE

AUXIN

=

0.2

AUX SWITCH-ON RESISTANCE (Ω)

0.1
–50

–25 0 25 50 75 100

TEMPERATURE (°C)

Gate Pull-Up Current vs
Temperature

–11.0

–10.5

–10.0

–9.5

GATE PULL-UP CURRENT (µA)

–9.0

–50

–25 0 25 50 75 100

TEMPERATURE (°C)

422312 G10

422312 G13

6.0

GATE DRIVE (ΔV

5.9
–50

–25 0 25 50 75 100

TEMPERATURE (°C)

AUX Circuit Breaker Trip Delay vs
Temperature

30

25

20

AUX CIRCUIT BREAKER TRIP DELAY (µs)

15

–50

02550

–25

TEMPERATURE (°C)

422312 G11

75 100

422312 G14

2

GATE DRIVE (ΔV

1

0

0

–2 –4

–6 –10

I

(μA)

GATE

Active Current Limit Delay vs
Sense Voltage

100

10

1

0.1

ACTIVE CURRENT LIMIT DELAY (µs)

0.01
50 150 200 250

100

SENSE VOLTAGE (mV)

–8 –12

422312 G12

300

422312 G15

Gate Fast Pull-Down Current vs
Temperature

250

200

150

100

GATE FAST PULL-DOWN CURRENT (mA)

50

–50

–25 0 25 50 75 100

TEMPERATURE (°C)

6

422312 G16

Output Discharge Resistance vs
Temperature Logic Input Threshold vs V

OUTPUT DISCHARGE RESISTANCE (Ω)

1200

1000

800

600

400

200

–50

02550

–25

TEMPERATURE (°C)

12V

OUT

AUXOUT

75 100

422312 G17

3.0

2.5

2.0

1.5

1.0

LOGIC INPUT THRESHOLD (V)

0.5

0

2.5

3.0 3.5

4.0 5.0
VCC (V)

CC

HIGH

LOW

4.5 5.5 6.0

422312 G18

422312f

PIN FUNCTIONS

LTC4223-1/LTC4223-2

12V

(Pin 1): 12V Current Sense Input. Connect this

SENSE

pin to the output of the current sense resistor. The electronic
circuit breaker trips if the voltage across the sense resistor
exceeds 50mV for more than a fault fi lter delay.

(Pin 2): 12V Supply Input. Undervoltage lockout

12V

IN

disables the 12V supply until the input at 12V

exceeds

IN

9.7V.

12IMON (Pin 3): 12V Current Sense Monitoring Output.
This pin monitors the sense voltage between 12V
12V

. The gain ratio between this pin’s voltage and

SENSE

IN

and

the sense voltage is 33.

12ON (Pin 4): 12V Supply On Control Digital Input. A ris-

⎯E⎯

ing edge turns on the external N-channel MOSFET if

N
is pulled low and a falling edge turns it off. A high-to-low
transition on this pin will clear the 12V supply faults.

AUXIN (Pin 5): Auxiliary Supply Input. An internal 0.3Ω
switch is connected between AUXIN and AUXOUT pins.
Undervoltage lockout holds the switch off until the input
at AUXIN exceeds 2.5V.

(Pin 6): Bias Supply Input. This pin provides power

V

CC

to the device’s internal circuitry and operates from 2.7V to
6V. Undervoltage lockout circuit disables the device until
the input at V

exceeds 2.45V. Bypass with 330nF.

CC

AUXON (Pin 7): Auxiliary Supply On Control Digital Input.

⎯E⎯

A rising edge turns on the internal switch if

N is pulled
low and a falling edge turns it off. A high-to-low transi­tion on both this pin and 12ON pin will clear the auxiliary
supply faults.

GND (Pin 8): Device Ground.

TIMER (Pin 9): Timer Capacitor Terminal. Connect a

capacitor between this pin and ground to set a 741ms/μF
duration for initial timing cycle, 123ms/μF for AUX current
limit during power-up and 6ms/μF duration for 12V current
limit before the external MOSFET is turned off.

⎯E⎯

N (Pin 10): Enable Input Intended for Card Presence

Detect. Ground this pin to enable the external N-channel
MOSFET and internal switch to turn on. If this pin is pulled
high, the switches are not allowed to turn on. An internal
100k resistor pulls up this pin. A high-to-low transition
will clear faults.

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

D (Pin 11): Auxiliary Supply Power Status

Output. Open drain output that is normally pulled high
by an internal 10μA current source or an external pull-up
resistor to V

. It pulls low when the AUXOUT pin voltage

CC

exceeds the power-good threshold of 2.901V.

AUXOUT (Pin 12): Auxiliary Supply Output. This pin is
the output from the internal switch connected between
AUXIN and AUXOUT pins. It signals

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

D low when

it exceeds 2.901V. A 750Ω active pull-down discharges
AUXOUT to ground when the internal switch is turned
off.

⎯F⎯A⎯U⎯L⎯

T (Pin 13): Auxiliary and 12V Supply Fault Status

Output. Open drain output that is normally pulled high by an
internal 10μA current source or an external pull-up resistor

. It pulls low when the circuit breaker is tripped due

to V

CC

to an overcurrent fault on auxiliary or 12V supply.

⎯1⎯2⎯P⎯G⎯O⎯O⎯

D (Pin 14): 12V Supply Power Status Output.

Open drain output that is normally pulled high by an in­ternal 10μA current source or an external pull-up resistor

. It pulls low when the 12V

to V

CC

pin voltage exceeds

OUT

the power-good threshold of 10.36V.

12V

(Pin 15): 12V Gate Drive Return and Power-Good

OUT

Input. Connect this pin to the source of the external N­channel MOSFET for gate drive return. This pin signals

⎯1⎯2⎯P⎯G⎯O⎯O⎯

MOSFET is turned off, 12V

D low when it exceeds 10.36V. When the external

is discharged to ground

OUT

through a 800Ω active pull-down.

12V

(Pin 16): Gate Drive for 12V Supply External N-

GATE

Channel MOSFET. An internal 10μA current source charges
the gate of the external N-channel MOSFET. An internal
clamp limits the gate voltage to 6.2V above 12V

OUT

. A
resistor and capacitor network from this pin to ground
sets the turn-on rate and compensates the active current
limit. During turn-off, a 1mA pull-down current discharges
12V
lockout, a 160mA pull-down current between 12V
12V

to ground. During short circuit or undervoltage

GATE

is activated.

OUT

GATE

and

Exposed Pad (Pin 17, DHD Package): Exposed pad may
be left open or connected to device ground.

422312f

7

LTC4223-1/LTC4223-2

FUNCTIONAL DIAGRAM

CHARGE

PUMP

12V

IN

12V

SENSE

12ON 12V FET ON

60mV

+

50mV

+

–

–

R

IN

5k

10μA

ACL

+
–

ECB

+

1mA

A1

+
–

R

OUT

165k

6.2V

GATE

DRIVER

12IMON

12V

GATE

12V

OUT

–

10μA

PG2

+

10.3V

–

12PGOOD

12V SUPPLY

CONTROL

12V PWRGD

V

CC

V

CC

2μA

R2

UVLO3

+

12V

IN

9.7V

–

UVLO2

+

2.45V

VCCV

CC

10μA

AUXIN

2.5V

0.2V

–

+
–

+

UVLO1

CP2

–

CP1

+

1.235V

–

EN CARD PRESENCE

V

CC

200μA

TIMER

AUXON AUX FET ON

GND

SYSTEM

CONTROL

AUX SUPPLY

CONTROL

12V FAULT

AUX FAULT

V

CC

10μA

FAULT

V

CC

10μA

AUXPGOOD

8

AUXIN

THERMAL

SHUTDOWN

MFETRSNS

AUX PWRGD

10μA

PG1

CHARGE

PUMP

+

2.885V

–

AUXOUT

422312 FD

422312f

OPERATION

LTC4223-1/LTC4223-2

The LTC4223 is designed to control the power on an Ad­vanced Mezzanine Card (AMC) or MicroTCA backplane,
allowing boards to be safely inserted and removed. It
controls the 12V main and 3.3V auxiliary power through an
external N-channel MOSFET and integrated pass transistor.
These two supplies can be turned on and off independently
by their respective ON control pins.

If either AUXON or 12ON is pulled high, an initial tim­ing cycle set by the TIMER capacitor value is initiated
once all these conditions are met: input supplies out of

⎯E⎯

undervoltage lockout; TIMER < 0.2V and
end of the initial timing cycle, if the AUXON pin is high, the
internal pass transistor turns on. It enters into an active
current limit loop if the inrush current charging the load
capacitor exceeds 240mA. When the load is in current
limit, a 10μA pull-up charges the TIMER pin capacitor. If
the load capacitor is fully charged and the switch is no
longer in current limit before the TIMER reaches 1.235V,

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

Otherwise the internal switch turns off and
low when TIMER reaches 1.235V.

If 12ON pin is high at the end of the initial timing cycle,
an internal charge pump charges the gate of the external
MOSFET with 10μA pull-up. Connecting an external gate
capacitor limits the inrush current charging the load ca­pacitor. If the inrush current exceeds its limited current

D pulls low indicating that power is good.

N low. At the

⎯F⎯A⎯U⎯L⎯

T pulls

value, an internal analog current limit (ACL) amplifi er
servos the gate to force 60mV across the external sense
resistor connected between 12VIN and 12V
During this period, TIMER pin capacitor is charged by a
200μA pull-up. If the load is fully charged and no longer in
current limit before the TIMER reaches 1.235V,
pulls low. Otherwise 12V shuts off and
when TIMER reaches 1.235V.

If an overcurrent fault occurs on the auxiliary supply after
power-up, the current is limited to 240mA and after a 25μs
delay, the circuit breaker trips and
mal shutdown protects the internal pass transistor from
overheating by shutting it off at 150°C. If an overcurrent
fault occurs on the 12V supply, the current is limited to
60mV/R
charging the TIMER capacitor, the circuit breaker trips

⎯F⎯A⎯U⎯L⎯

and
supply shuts off 12V; a fault on the 12V supply does not
affect the auxiliary supply.

The LTC4223 provides high side current sensing informa­tion for the 12V supply at the 12IMON pin. The 12IMON
output voltage is 33 times the sense voltage, allowing it
to be used with an external ADC.

In the off condition, 12V
to ground by internal N-channel pull downs.

. After a timing cycle delay set by 200μA

SENSE

T pulls low. An overcurrent fault on the auxiliary

and AUXOUT are discharged

OUT

⎯F⎯A⎯U⎯L⎯

⎯F⎯A⎯U⎯L⎯

T pulls low. Ther-

pins.

SENSE

⎯1⎯2⎯P⎯G⎯O⎯O⎯

T pulls low

D

422312f

9

LTC4223-1/LTC4223-2

APPLICATIONS INFORMATION

INTELLIGENT

PLATFORM

MANAGEMENT

CONTROLLER

MP ENABLE
PWR ENABLE

MP GOOD
PWR GOOD
FAULT

3

3.3V

2.2k
PRESENCE

12V

BULK SUPPLY

BYPASS CAPACITOR

3.3V

BULK SUPPLY

BYPASS CAPACITOR

3.3V 3.3V 3.3V

V

7

CLK

6

D

OUT

1

CS

R5*

R6*

10k

10k

58

V

REF

CC

LTC1197L

GND

4

+IN

–IN

1μF

R2
51Ω

R4*
10k

2

3

C2
330nF

3.3V

R

S

6mΩ

21 16

12V

5

6

7
4

11
14
13

3

12V

AUXIN

V

CC

AUXON
12ON

AUXPGOOD
12PGOOD
FAULT

12IMON

SENSE

IN

GND

89

Q1

Si7336ADP

R3

10Ω

12V

GATE

LTC4223-1

TIMER

R

47Ω

C

T

0.1μF

G

C

G

15nF

12V

AUXOUT

422312 F01

OUT

EN

CARRIER AMC

CONNECTOR

PWR

15

12

MP

10

PS1

PS0

MODULE AMC

CONNECTOR

12V

7.4A

3.3V
150mA

3.3V

RESET

*OPTIONAL

Figure 1. Advanced Mezzanine Card/MicroTCA Application

The typical LTC4223 application is in a Carrier board
for Advanced Mezzanine Cards (AMC), delivering 3.3V
auxiliary and 12V power to the AMC module. A control­ler on the Carrier board sequences the turn-on of power
supplies and manages the fault and power-good reports
from the LTC4223.

The LTC4223 detects board presence during insertion and
extraction, allowing power to be delivered in a controlled
manner without damaging the connector. The typical
LTC4223 application circuit is shown in Figure 1. External
component selection is discussed in detail in the Design
Example section.

10

ENABLE

10k

Turn-On Sequence

The power supplies delivered to an AMC module are
controlled by the external N-channel pass transistor, Q1 in
the 12V power path and an internal pass transistor in the

3.3V auxiliary power path. Sense resistor R

monitors the

S

12V load current for fault detection and current sensing
information. GATE capacitor C
control to limit the inrush current. Resistor R

provides gate slew rate

G

with CG

G

compensates the current control loop while R3 prevents
parasitic oscillations in Q1.

422312f

APPLICATIONS INFORMATION

LTC4223-1/LTC4223-2

Several conditions must be met before the external and
internal switches are allowed to turn on. First V
the input supplies (12V

, AUXIN) must exceed their

IN

CC

and

undervoltage lockout thresholds. Next TIMER must be

⎯E⎯

<0.2V and

N must be pulled low.

Once these conditions are met, a debounce timing cycle is
initiated when AUXON or 12ON pin is toggled from low to
high. These two control pins turn on/off the 3.3V auxiliary
and 12V supplies. At the end of the debounce cycle, the
ON pins and fault status are checked. If both ON pins are
high and fault is cleared, the 3.3V auxiliary supply starts
up fi rst followed by the 12V supply. Note that the turn-on
delay for the AUXON and 12ON pins is 15μs and 30μs.
Figure 2 shows the two supplies turning on in sequence

⎯E⎯

N goes low.

after

By default, the internal pass transistor turns on fi rst if
both ON pins are high and start-up conditions met. The
output is current limited at 240mA by its internal ACL
amplifi er as the load current charging the output capaci­tor increases. This causes the TIMER to ramp up with a
10μA pull-up. Normally the AUXOUT voltage exceeds its
power-good threshold before TIMER time-out and then

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

D pulls low.

EN

5V/DIV

TIMER

2V/DIV

AUXOUT

5V/DIV

12V

OUT

5V/DIV

AUXPGOOD

5V/DIV

12PGOOD

5V/DIV

20ms/DIV

Figure 2. Normal Power-Up Sequence

422312 F02

Once AUXOUT signals power is good and the TIMER pin
returns to <0.2V, the external MOSFET is then allowed to
turn on by charging up the GATE with a 10μA current source
(Figure 2). The voltage at the GATE pin rises with a slope
equal to 10μA/C
into the load capacitor C

I

INRUSH

=

and the supply inrush current fl owing

G

(see Figure 14) is limited to:

L1

C

1

L

µA

10•

C

G

The 12V output follows the GATE voltage when the MOSFET
turns on. If the voltage across the current sense resistor

becomes too high, the inrush current is limited by the

R

S

internal current limit circuitry. Once the output, 12V
exceeds its power-good threshold,

⎯1⎯2⎯P⎯G⎯O⎯O⎯

D also pulls

OUT

low.

If only the 12ON pin is high at the end of debounce cycle,
the external MOSFET turns on fi rst. After that, if AUXON
pulls high, the internal switch turns on only after the 12V
output signals power is good and TIMER <0.2V.

Table 1. 12V and Auxiliary Supply Turn-Off Conditions

CONDITION RESULT CLEARED BY

AUX 12V

AUXON Goes
Low

12ON Goes Low No Effect Turns Off 12ON High

⎯E⎯

N Goes High Turns Off Turns Off⎯E⎯N Low

UVLO on V

UVLO on AUXIN Turns Off No Effect AUXIN > UVLO

UVLO on 12V

AUX Overcurrent
Fault

12V Overcurrent
Fault

Thermal
Shutdown

CC

Turns Off No Effect AUXON High

Turns Off Turns Off VCC > UVLO

No Effect Turns Off 12VIN > UVLO

IN

Turns Off Turns Off AUXON and 12ON Low,

No Effect Turns Off 12ON Low, ⎯E⎯N High-to-

Turns Off Turns Off AUXON and 12ON Low,

⎯E⎯

N High-to-Low, UVLO

on V

CC

Low, UVLO on V

⎯E⎯

N High-to-Low, UVLO

on V

CC

120°C

CC

, Temperature <

422312f

11

LTC4223-1/LTC4223-2

APPLICATIONS INFORMATION

Turn-Off Sequence

The switches can be turned off by various conditions and
this is summarized in Table 1.

When the 12ON pin goes low, the external switch is turned
off with the GATE pin pulled to ground by 1mA current
sink. The

⎯1⎯2⎯P⎯G⎯O⎯O⎯

D pin pulls high indicating that power is
no longer good, while an internal N-channel transistor dis­charges the output to ground. Similarly, when the AUXON
pin goes low, the internal switch is turned off,

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

D
pulls high while its output is discharged to ground through
an internal N-channel transistor. Figure 3 shows the two

⎯E⎯

supplies being turned off by

N going high.

Card Presence Detect

⎯P⎯S⎯

In an AMC system,

1 and ⎯P⎯S⎯0 signals are used to

detect the presence of a card upon insertion or removal.

⎯P⎯S⎯

Normally
resistor. If AUXON or 12ON is high when the

1 is connected to the ⎯E⎯N pin with a pull-up

⎯E⎯

N pin goes
low, indicating a board insertion, a timing cycle for contact
debouncing is initiated. Upon insertion, any bounces on the

⎯E⎯

N pin will re-start the timing cycle. When TIMER fi nally

reaches its threshold during ramp up, the fault latches

⎯E⎯

will be cleared. If the

N pin remains low at the end of the

timing cycle, the switches are allowed to turn on.

⎯E⎯

If the

N pin is toggled from low to high, indicating board
removal, all the switches will be turned off after a 20μs delay.
Any latched faults will not be cleared. However, removing

⎯E⎯

the card could cause the

N pin voltage to bounce, clearing

the fault latches undesirably. This is prevented by blanking

the bounces internally with a TIMER ramp up period given

• 123[ms/μF] as shown in Figure 4.

by C

T

Timer Functions

An external capacitor C

connected from the TIMER pin

T

to ground is used to perform several functions.

1. Ignore contact debouncing during card insertion when
the device is enabled. The debounce cycle is given
by ramping up C

with 10μA current to TIMER high

T

threshold (1.235V) and then ramping down with 2μA
current to below TIMER low threshold (0.2V). This gives
an average debounce cycle time of C
After that, if any ON pin is pulled high and

• 741[ms/μF].

T

⎯E⎯

N pin is

low, the switches can be turned on.

⎯E⎯

2. Blanking contact bounce on the

N pin that might
trigger unwanted fault clearing during card removal.
The blanking time is given by C

• 123[ms/μF].

T

3. Fault fi ltering during auxiliary supply power-up in analog
current limit. TIMER pulls up with 10μA and pulls down
with 2μA. The fi lter time is given by C

• 123[ms/μF].

T

4. 12V supply fault fi ltering during and after power-up
in analog current limit. TIMER pulls up with 200μA
and pulls down with 2μA. The fi lter time is given by

• 6[ms/μF].

C

T

5. For cooling off during an auto-retry cycle after
an overcurrent fault on auxiliary or 12V supply
(LTC4223-2). The cool-off time is given by C
[ms/μF] after an auxiliary supply fault and C

• 1482

T

• 1358[ms/

T

μF] after a 12V supply fault.

12

EN

5V/DIV

AUXOUT

5V/DIV

12V

OUT

5V/DIV

AUXPGOOD

5V/DIV

12PGOOD

5V/DIV

100ms/DIV

Figure 3. Normal Power-Down Sequence Figure 4. Debouncing by TIMER during Card Removal

422312 F03

2V/DIV

TIMER

1V/DIV

FAULT

2V/DIV

EN

5ms/DIV

422312 F04

422312f

APPLICATIONS INFORMATION

LTC4223-1/LTC4223-2

As the TIMER capacitor is used for fault fi ltering during
power-up for both the auxiliary and 12V supplies, only
one supply can be started up at any one time. The other
supply waits until the power-good signal is generated by
the powering-up supply and the TIMER pin voltage falls
below 0.2V. By default, the 3.3V auxiliary supply starts up
fi rst if both AUXON and 12ON are high at the end of the
debounce cycle.

Whenever both AUXON and 12ON are pulled low, the de­vice is in reset mode and TIMER capacitor is discharged
to ground by an 8mA current sink.

Thermal Shutdown

The internal 3.3V auxiliary supply switch is protected by
thermal shutdown. If the switch’s temperature reaches

⎯F⎯A⎯U⎯L⎯

150°C, the aux switch will shut off immediately and

T
will pull low. The external 12V supply switch also turns
off. The switches are allowed to turn on again by cycling
both the AUXON and 12ON pins low then high after the
internal switch’s temperature falls below 120°C.

Overcurrent Fault

The LTC4223 features an adjustable current limit with circuit
breaker function that protects the external MOSFET against

FAULT
5V/DIV

I

LOAD

5A/DIV

12V

OUT

5V/DIV

12V

GATE

5V/DIV

0.1ms/DIV

Figure 5. Overcurrent Fault on 12V Output

422312 F05

short circuits or excessive load current on 12V supply. The
voltage across the external sense resistor is monitored by
the analog current limit (ACL) amplifi er and the electronic
circuit breaker (ECB) comparator. If an overcurrent fault
occurs that causes the sense voltage to reach the ACL
threshold (60mV), the ACL amplifi er regulates the MOSFET
to prevent any further increase in current. This overcurrent
condition results in a sense voltage that exceeds the ECB
threshold. As a result, the TIMER capacitor is charged
by a 200μA current. If the condition persists, the TIMER
pin voltage will reach its threshold (1.235V). When this

⎯F⎯A⎯U⎯L⎯

occurs, the

T pin pulls low and a 1mA current pulls
the GATE pin to ground causing the MOSFET to turn off.
The circuit breaker time delay, the time required for the
TIMER pin capacitor to charge from ground to the TIMER
pin threshold, is given by C

• 6[ms/μF].

T

After the MOSFET turns off, the TIMER pin capacitor dis­charges with a 2μA pull-down current. For the auto-retry
version (LTC4223-2), if the TIMER discharges to below

0.2V, a new start-up cycle will begin. The TIMER starts
ramping up and clears faults when it exceeds 1.235V;
thereafter it ramps down (see the section on Auto-Retry
for details). Figure 5 shows an overcurrent fault on the
12V output.

In the event of a severe short-circuit fault on 12V output
as shown in Figure 6, the output current can surge to
tens of amperes. The LTC4223 responds within a very
short time to bring the current under control by pulling
the MOSFET’s GATE-to-SOURCE pin voltage down to zero
volts. Thereafter, the GATE of the MOSFET recovers rapidly
due to the R

compensation network and enters into

G/CG

active current limiting until the TIMER times out. Due to
parasitic supply lead inductance, an input supply without
any bypass capacitor will collapse during the high cur­rent surge and then spike upwards when the current is
interrupted. An input supply transient protection network
comprising of Z1, R1 and C1 shown in Figure 13 is recom­mended if there is no input capacitance.

422312f

13

LTC4223-1/LTC4223-2

APPLICATIONS INFORMATION

There are two different modes of fault time-out for the 3.3V
auxiliary supply: adjustable delay through TIMER capacitor
during power-up when

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

25μs delay after power-up when

D not asserted; fi xed

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

D asserted
low. Under the situation whereby AUXON toggles low then
high for short duration after power-up while

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

D
still pulling low due to output load capacitor, 25μs fault
time-out applies.

When the auxiliary supply is powered up into an output
short, the ACL amplifi er will regulate the gate of the
internal pass transistor to produce 240mA output cur­rent. At this time a 10μA pull-up current starts charging
up the TIMER pin capacitor until it exceeds its threshold
(1.235V). The internal pass transistor then turns off and

⎯F⎯A⎯U⎯L⎯

T pulls low. Thereafter, the TIMER is discharged by

a 2μA pull-down current. The fault fi lter delay is given by

• 123[ms/μF].

C

T

After a successful power-up cycle, the ACL amplifi er pro­tects the auxiliary supply from overcurrent by pulling down
the gate of the internal pass transistor rapidly as shown
in Figure 7. Thereafter, the gate recovers and servos the
output current to about 240mA for 25μs before pulling
down to ground gently, turning the transistor off. At this

⎯F⎯A⎯U⎯L⎯

time,

T pulls low and the 12V external MOSFET is

also turned off by the 1mA GATE pull-down current.

Whenever the 3.3V auxiliary supply trips off due to an
overcurrent fault, the 12V supply also shuts off. The
auxiliary supply is, however, unaffected by faults on the

⎯F⎯A⎯U⎯L⎯

12V supply. In either case
affected channels turn off, and

T latches low when the

⎯F⎯A⎯U⎯L⎯

T is cleared by tog­gling the ON pins. Faults are cleared automatically in the
LTC4223-2 auto-retry version.

If there is signifi cant supply lead inductance, a severe
output short may collapse the input to ground before the
LTC4223 can bring the current under control. In this case
the undervoltage lockout will activate after a 12μs fi lter
delay, and pull the gate down. Then the ACL amplifi er will
take control and regulate the output in active current limit.
Under this situation, the fault time-out is set by TIMER
delay instead of 25μs fi lter delay.

Undervoltage Fault

An undervoltage fault occurs if either AUXIN or 12V

IN

falls
below its undervoltage threshold for longer than 12μs. This
turns off the affected supply’s switch instantly, but does
not clear the fault latches. Further, an undervoltage fault
on one supply does not affect the operation of the other
supply. If the bias supply input, V

falls below its UVLO

CC

threshold for more than 80μs, all supply switches are turned
off and the fault latches are cleared. Operation resumes
from a fresh start-up cycle when V

is restored.

CC

14

ΔV

SENSE

200mV/DIV

12V

OUT

5V/DIV

12V

GATE

5V/DIV

5μs/DIV

422312 F06

FAULT

5V/DIV

I

LOAD

1A/DIV

AUXOUT

5V/DIV

5μs/DIV

Figure 7. Short-Circuit Fault on 3.3V

AUX

422312 F07

OutputFigure 6. Short-Circuit Fault on 12V Output

422312f

APPLICATIONS INFORMATION

LTC4223-1/LTC4223-2

Power-Good Monitor

Internal circuitry monitors the output voltages, AUXOUT
and 12V
respective open drain outputs,
Several conditions must be met before the power-good
outputs assert low.

1. The monitored output should be above its power­good threshold and hysteresis.

2. The input supply is above undervoltage lockout.

⎯E⎯

N is low.

3.

4. The associated ON pin is high.

5. Thermal shutdown is not activated.

If any of the supply outputs falls below its power-good
threshold for more than 20μs, the respective power-good
output will be pulled high by the external pull-up resistor
or internal 10μA pull-up.

Resetting Faults (LTC4223-1)

Any supply faults tripping the circuit breaker are latched
and
(LTC4223-1), to reset a fault latch due to overcurrent or
thermal shutdown on auxiliary supply, pull both AUXON and
12ON pins low together for at least 100μs, after which the

⎯F⎯A⎯U⎯L⎯

again initiates the debounce timing cycle, thereafter the
auxiliary supply starts up fi rst followed by 12V supply. To
skip the debounce timing cycle, fi rst pull only AUXON low
then high for at least 50μs before toggling 12ON low then
high. The fault latch clears on the falling edge of 12ON
and the auxiliary supply powers up. Thereafter, the 12V
supply powers up if 12ON pulls high.

To reset a fault on the 12V supply and re-start the output,
toggle only the 12ON pin low and then high again. Tog­gling the
input, V
will initiate the debounce timing cycle and reset all fault
latches before power-up. Bringing AUXIN or 12V
undervoltage threshold will not reset the fault latches. For
the auto-retry version (LTC4223-2), the latched fault will
be cleared automatically after a cool-off timing cycle.

. The power-good status is reported via their

OUT

⎯A⎯U⎯X⎯P⎯G⎯O⎯O⎯

⎯F⎯A⎯U⎯L⎯

T asserts low. For the latched-off version

T will go high. Toggling both the ON pins high together

⎯E⎯

N pin high then low again or bringing the bias

below its UVLO threshold for more than 100μs

CC

D and ⎯1⎯2⎯P⎯G⎯O⎯O⎯D.

below its

IN

Auto-Retry after a Fault (LTC4223-2)

At time point 1 in Figure 8, if a fault latched-off the 3.3V
auxiliary supply after power-up, a cool-off cycle begins.
The TIMER capacitor charges up to 1.235V with a 10μA
current and then discharges with a 2μA current to 0.2V at
time point 3. This is followed by a debounce timing cycle

⎯F⎯A⎯U⎯L⎯

whereby the fault latch is cleared, and
when TIMER reaches its threshold at time point 4. At the
end of debounce cycle, the internal switch is allowed to
turn on. If the output short persists, the auxiliary supply
powers up into a short with active current limiting. At time
point 7, the fault fi lter delay begins with TIMER ramping
up with a 10μA current. If the TIMER times out at time

⎯F⎯A⎯U⎯L⎯

point 8,
begins with TIMER ramping down with a 2μA current.
The whole process repeats itself until the output-short
is removed.

In Figure 9, a fault latches off the 12V supply at time point
1; a cool-off cycle begins by discharging the TIMER ca­pacitor with 2μA current from 1.235V to 0.2V threshold.
At time point 2 a new debounce timing cycle is initiated
where the fault latch is cleared, and
TIMER reaches its threshold at time point 3. At the end of
the debounce cycle, the 12V GATE is allowed to start up. If
the output short persists, the 12V supply powers up into a
short with active current limiting. At time point 6, the fault
fi lter delay begins with TIMER ramping up with a 200μA
current. The TIMER times out at time point 7,
low and a new cool-off cycle begins with TIMER ramping
down with a 2μA current. The whole process repeats itself
until the output-short is removed.

The auto-retry duty cycle is given by:

DutyCycle

For example, if TIMER capacitor, CT = 0.1μF, the auto-retry
duty cycle for auxiliary and 12V supply is 6.5% and 0.5%
respectively.

T will be pulled low and a new cool-off cycle

⎯F⎯A⎯U⎯L⎯

=

t

tt t

++

COOL DEBOUNCE FILT

FILTER

•%100

T pulls high

T pulls high when

⎯F⎯A⎯U⎯L⎯

T pulls

EER

422312f

15

LTC4223-1/LTC4223-2

APPLICATIONS INFORMATION

GATE Pin Voltage

The gate drive at 12V

is compatible with any logic

GATE

level MOSFET. The guaranteed range of gate drive is 4.5V
to 7.9V, with a typical of 6.2V.

Active Current Loop Compensation

The compensation network consisting of resistor R
gate slew rate control capacitor C
active current limit circuit. The value of C

stabilizes the internal

G

is selected based

G

and

G

on the inrush current allowed. The suggested value for

is 47Ω. The value of CG should be ≤330nF and RG is

R

G

between 10Ω and 100Ω for optimum performance.

High Side Current Sense

The 12V load current is monitored via the voltage across an
external sense resistor. The LTC4223 features a high side
current sense amplifi er that translates the sense voltage
from the positive rail to the negative rail using a resistor
ratio of 33 times. The output voltage at 12IMON pin can

FAULT PULLS LOW DUE TO AUX
OVERCURRENT FAULT AFTER POWER UP
START OF COOL-OFF CYCLE

START OF

DEBOUNCE CYCLE RESET FAULT HIGH

END OF DEBOUNCE CYCLE

START AUX INTERNAL GATE RAMP WHEN STARTUP CONDITIONS ARE MET

then be fed into an LTC1197L ADC as shown in Figure 10
for data conversion. The current sense information can be
used by the system controller to manage the power budget
allocated to the modules on the card. Full scale input to
the current sense amplifi er is 82.5mV, corresponding to
an output of about 2.7V. If the input exceeds 100mV, the
output clamps at 3.2V.

Supply Filtering

V

CC

The internal circuitry of the LTC4223 is powered from the

pin. Bypass VCC with at least 330nF to ground. If VCC

V

CC

is derived from the same supply as is AUXIN, include a
decoupling resistor as shown in Figure 11. This RC net­work allows the V

pin to ride out supply glitches caused

CC

by short circuits on the auxiliary output or on adjacent
boards, thus preventing an undervoltage lockout condi­tion on V

. Since the absolute maximum rating for VCC

CC

is 7V as compared to 10V for AUXIN, select R2 and C2 to
keep the peak voltage seen by V

below 7V during any

CC

voltage spikes.

AUX OUTPUT IN CURRENT LIMIT

FAULT PULLS LOW AND RESTART OF
COOL-OFF CYCLE DURING POWER UP

RESTART OF

DEBOUNCE CYCLE

FAULT

TIMER

I

AUXOUT

12V

12 34 5678 9 10

OUT

10μA

V

TMR

2μA

COOL-OFF CYCLE DEBOUNCE CYCLE

V

TMR

2μA2μA2μA10μA10μA10μA10μA

V

TMR

FILTER DELAY

COOL-OFF CYCLE

AUX INTERNAL GATE REGULATES

V

TMR

Figure 8. Auto-Retry after AUX Overcurrent Fault

422312 F08

422312f

16

APPLICATIONS INFORMATION

LTC4223-1/LTC4223-2

12VIN - 12V

12V

FAULT

TIMER

GATE

SENSE

FAULT PULLS LOW DUE TO
12V OVERCURRENT FAULT
START OF COOL-OFF CYCLE

START OF

DEBOUNCE CYCLE RESET FAULT HIGH

12345678

V

200μA

TMR

2μA

COOL-OFF CYCLE DEBOUNCE CYCLE

60mV 60mV

V

TMR

2μA2μA10μA 200μA10μA

END OF DEBOUNCE CYCLE

START 12V GATE RAMP WHEN STARTUP CONDITIONS ARE MET

12V OUTPUT IN CURRENT LIMIT

FAULT PULLS LOW AND
RESTART OF COOL-OFF CYCLE

V

TMR

FILTER DELAY COOL-OFF CYCLE

12V

REGULATES

GATE

RESTART OF
DEBOUNCE CYCLE

12V

OUT

Figure 9. Auto-Retry after 12V Overcurrent Fault

Supply Transient Protection

The supply inputs, AUXIN and 12V

are fed directly from

IN

the regulated output of the backplane supply, where bulk
bypassing assures a spike-free operating environment.
In other applications where the bulk bypassing is located
far from the LTC4223, spikes generated during output
short circuit events could exceed the absolute maximum
ratings for AUXIN and 12V

. To minimize such spikes,

IN

use wider traces or heavier trace plating to reduce the
power trace inductance. Also, bypass locally with a 10μF
electrolytic and 100nF ceramic, or alternatively clamp
the input with a transient voltage suppressor (Z1, Z2) as
shown in Figure 13. A 10Ω, 100nF snubber damps the
response and eliminates ringing. A recommended layout
of the 12V transient protection devices Z1, R1 and C1
around the LTC4223 is shown in Figure 12.

422312 F08

V

GATE

12V

SENSE

– +Q1

SENSE

+

–

V

OUT

12V

R

IN

5k

12IMON

R

OUT

165k

R

OUT

= • V

R

IN

12V

IN

SENSE

V

= 33 • V

OUT

+IN

–IN

SENSE

V

REF

LTC1197L

V

GND

I

LOAD

LOAD

12V

LTC4223

Figure 10. High Side Current Sense with LTC1197L ADC

CC

CLK

D

OUT

422312 F10

1μF 3.3V

TO SYSTEM
CONTROLLER

CS

422312f

17

LTC4223-1/LTC4223-2

APPLICATIONS INFORMATION

R2

AUXIN

51Ω

C2
330nF

V

CC

422312 F11

Figure 11. RC Network for VCC Filtering

PCB Layout Considerations

For proper operation of the LTC4223’s circuit breaker,
Kelvin-connection to the sense resistor is strongly rec­ommended. The PCB layout should be balanced and
symmetrical to minimize wiring errors. In addition, the
PCB layout for the sense resistor and the power MOSFET
should include good thermal management techniques for
optimal device power dissipation. A recommended PCB
layout for the 12V sense resistor and the power MOSFET
is illustrated in Figure 12.

In applications where load current exceeds 10A, wide
PCB traces are recommended to minimize resistance
and temperature rise. The suggested trace width for 1
oz copper foil is 0.03” for each ampere of DC current to
keep PCB trace resistance, voltage drop and temperature
rise to a minimum. Note that the sheet resistance of 1 oz
copper foil is approximately 0.5mΩ/square, and voltage
drops due to trace resistance add up quickly in high cur­rent applications.

CURRENT FLOW

TO LOAD

12V

IN

W

TRACK WIDTH W:

0.03" PER AMPERE
ON 1OZ Cu FOIL

W

GND

*ADDITIONAL DETAILS OMITTED FOR CLARITY, DRAWING NOT TO SCALE!

SENSE

RESISTOR

R1Z1

C1

LTC4223CGN*

2

8

12V

POWER PAK

R3

GATE

R

161

15

CURRENT FLOW

TO SOURCE

G

SO-8

C

G

CURRENT FLOW

•

•

TO LOAD

W

VIA TO
GND PLANE

VIA TO
GND PLANE

12V

GND

422312 F12

OUT

Figure 12. Recommended Layout for Power MOSFET, Sense

Resistor and GATE Components on 12V Rail

The fi rst step is to select the appropriate value of R
for the 12V supply. Calculating R

value is based on

SENSE

SENSE

the maximum load current and the lower limit for the

mV

AA

.

m= 6 Ω

circuit breaker threshold, ΔV

V

R

SENSE

=

Δ

()( )

SENSE CB MIN

I

()

LOAD MAX

SENSE(CB)(MIN)

..47 5

=

74

In most applications, it will be necessary to use plated­through via to make circuit connections from component
layers to power and ground layers internal to the PCB. For
1 oz copper foil plating, a general rule is 1A of DC current
per via. Consult your PCB fabrication facility for design
rules pertaining to other plating thicknesses.

It is important to place the V
close as possible between V

bypass capacitor C2 as

CC

and GND. The transient

CC

voltage suppressors Z1 and Z2 are also placed between
the supply inputs and ground using short wide traces.

Design Example

As a design example, consider the AMC Hot Swap ap­plication shown earlier in Figure 1 with the power supply
requirements given in Table 2.

18

If a 1% tolerance is assumed for the 6mΩ sense resistor,
the minimum and maximum circuit breaker trip current is
calculated as follows:

Table 2. AMC Power Supply Requirements

SUPPLY VOLTAGE MAXIMUM LOAD

12V 7.4A 800μF

3.3V

AUX

CURRENT

150mA 150μF

Table 3. MicroTCA Power Supply Requirements

SUPPLY VOLTAGE MAXIMUM LOAD

12V 7.6A 1600μF

3.3V

AUX

CURRENT

150mA 150μF

MAXIMUM LOAD

CAPACITANCE

MAXIMUM LOAD

CAPACITANCE

422312f

APPLICATIONS INFORMATION

LTC4223-1/LTC4223-2

Δ

V

SENSE CB MIN

I

TRIP MIN

=

()

Δ

I

TRIP MAX

=

()

For proper operation, I

()( )

R

SENSE MAX

()

V

SENSE CB MAX

()( )

R

S

EENSE MIN

()

TRIP(MIN)

load current with margin, so R

must exceed the maximum

SENSE

.

47 5mmV

=

60678.

52 5

59488Ω

m

Ω

mV

.

m

.

=

A

.

.==

= 6mΩ should suffi ce

A

for the 12V supply.

The second step is to determine the TIMER capacitance
based on the time required to charge up completely the
output load capacitor on auxiliary supply in active current
limit without exceeding the fault fi lter delay. The worst­case start-up time is calculated using the minimum active
current limit value for the auxiliary supply.

t

STUP AUX

()

33

2

LAUX

==

I

AUX ACL MIN

()()

150

µF

165

333

•

mA

.V

3

ms=

CV

•.

For a start-up time of 3ms with a 2x safety margin, the
TIMER capacitance is calculated as:

t

2

•

()

C

T

STUP AUX

=

ms µF

123

[]

=

//

ms

6

ms µF

123

[]

≅

00

.

55µF

Considering the tolerances for the TIMER charging rate
and capacitance, a value of 0.1μF (±10%) for C

should

T

suffi ce.

Since the TIMER charging rate during fault time-out is
20 times faster for the 12V supply as compared to the
auxiliary supply during start-up, this scheme ensures that
the external MOSFET will not overheat under any output­short condition. The fault fi lter delay for the 12V supply
is given by 0.1μF • 6[ms/μF] = 600μs versus 12ms for
the auxiliary supply.

The next step is to verify that the thermal ratings of the
selected external MOSFET for the 12V supply aren’t ex­ceeded during power-up or an output-short.

Assuming the MOSFET dissipates power only due to inrush
current charging the load capacitor, the energy dissipated
in the MOSFET during power-up is the same as that stored
into the load capacitor. The average power dissipated in
the MOSFET is given by:

CV

122•

L OUT

P

AVG

1

=

t

•

CHARGE

2

The inrush current can be limited by using the GATE ca­pacitance (C
is well within its safe operating area (SOA). For I
10μA and C

) so that the power dissipated in the MOSFET

G

=

GATE

= 800μF, we choose CG = 15nF to set the

L1

inrush current to 0.5A.

CI

•

1

I

INRUSH

t

CHARGE

This results in P

LGATE

==

C

G

CV

12

•

1

L OUT

=

I

IINRUSH

= 3W and the MOSFET selected must

AVG

05

.

A

ms=19

be able to tolerate 3W for 19ms. The increase in steady
state junction temperature due to power dissipated in
the MOSFET is ΔT = P

• Zth where Zth is the thermal

AVG

impedance.

Under this condition, the Si7336ADP datasheet’s Tran­sient Thermal Impedance plot indicates that the junction
temperature will increase by 2.4°C using Z

= 0.8°C/W

thJC

(single pulse).

The duration and magnitude of the power pulse that results
during a short-circuit condition on the 12V output are a
function of the TIMER capacitance and LTC4223’s analog
current limit. The short-circuit duration is given as 0.1μF

• 6[ms/μF] = 600μs for C

= 0.1μF. The maximum short-

T

circuit current is calculated using the maximum analog
current limit threshold, ΔV
R

value.

SENSE

I

SHORT MAX

=

()

V

Δ

SENSE ACL MAX

R

SENSE MIN

SENSE(ACL)(MAX)

()( )

()

and minimum

mmV

66

=

m

59411. Ω

A

=

So the maximum power dissipated in the MOSFET is 11A •
12V or 132W for 600μs. The Si7336ADP datasheet’s Tran­sient Thermal Impedance plot indicates that the worse-case
increase in junction temperature during the short-circuit
condition is 13.2°C using Z

= 0.1°C/W (single pulse).

thJC

This will not cause the maximum junction temperature to
be exceeded. The SOA curves of the Si7336ADP are also
checked to be safe under this condition.

422312f

19

LTC4223-1/LTC4223-2

TYPICAL APPLICATION

Card Resident Application with 5V Auxiliary Supply

BD_SEL

12V

PWRFLT

PWREN

BACKPLANE

CONNECTOR

5V

GND

CARD

CONNECTOR

R6
10k

SMAJ13A

SMAJ7.0A

SENSE

Q1

Si7336ADP

R3

10Ω

12V

LTC4223-1

C

T

0.1μF

GATE

R

G

47Ω

AUXPGOOD

GND

C

G

15nF

12V

OUT

12PGOOD

12IMON

12V
10A

+

C

L1

1000μF

5V

AUX

150mA

+

C

L2

150μF

5V

5V

R4

R5

10k

10k

5V

1μF

V

V

CC

REF

GND

CLK

D

OUT

422312 TA02

TO SYSTEM

CS

CONTROLLER

+IN

LTC1197

–IN

R

S

4mΩ

R1

Z1

Z2

10Ω

R7

2.7Ω
C3

100nF

R8
10k

C1
100nF

12V

12V

IN

AUXIN AUXOUT

R2
51Ω

V

CC

C2
330nF

FAULT

AUXON

12ON

EN

TIMER

20

422312f

TYPICAL APPLICATION

Card Resident Application with 12V Power Up First Followed by 3.3V Auxiliary

LTC4223-1/LTC4223-2

PWRFLT

BD_SEL

12V

3.3V

PWREN

BACKPLANE

CONNECTOR

GND

CARD

CONNECTOR

3.3V

SMAJ13A

SMAJ5.0A

R6
10k

Z1

Z2

R8

10k

2N7002K

R

S

4mΩQ1Si7336ADP

R1
10Ω

C1
100nF

12V

IN

AUXIN AUXOUT

R7

2.7Ω
C3

100nF

R9
10k

Q2

R2
51Ω

V

CC

C2
330nF

R5
10k

12ON

AUXON

12PGOOD

FAULT

EN

3.3V3.3V

12V

TIMER

SENSE

R3

10Ω

12V

LTC4223-1

C

T

0.1μF

GATE

R

G

47Ω

AUXPGOOD

GND

C

G

15nF

12V

12IMON

OUT

3.3V

R4
10k

3.3V

1μF

+IN

–IN

+

C
1000μF

+

C
150μF

V

LTC1197L

12V
10A

L1

3.3V

AUX

150mA

L2

V

CC

REF

GND

CLK

D

OUT

CS

422312 TA03

TO SYSTEM
CONTROLLER

422312f

21

LTC4223-1/LTC4223-2

PACKAGE DESCRIPTION

GN Package

16-Lead Plastic SSOP (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1641)

.045 ±.005

.254 MIN

RECOMMENDED SOLDER PAD LAYOUT

.007 – .0098

(0.178 – 0.249)

.016 – .050

NOTE:

1. CONTROLLING DIMENSION: INCHES

2. DIMENSIONS ARE IN

3. DRAWING NOT TO SCALE
*DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH

SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE
**DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD

FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE

(0.406 – 1.270)

INCHES

(MILLIMETERS)

.150 – .165

.0250 BSC.0165 ±.0015

.015 ± .004

(0.38 ± 0.10)

0° – 8° TYP

.189 – .196*

(4.801 – 4.978)

16

15

14

12 11 10

13

.229 – .244

(5.817 – 6.198)

12

×

°

45

.0532 – .0688

(1.35 – 1.75)

.008 – .012

(0.203 – 0.305)

TYP

4

3

5

9

678

(0.102 – 0.249)

.0250

(0.635)

BSC

.009

(0.229)

REF

.150 – .157**
(3.810 – 3.988)

.004 – .0098

GN16 (SSOP) 0204

22

422312f

PACKAGE DESCRIPTION

4.50 ±0.05

3.10 ±0.05

2.44 ±0.05
(2 SIDES)

4.34 ±0.05
(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

LTC4223-1/LTC4223-2

DHD Package

16-Lead Plastic DFN (5mm × 4mm)

(Reference LTC DWG # 05-08-1707)

0.70 ±0.05

PACKAGE
OUTLINE

0.25 ± 0.05

0.50 BSC

PIN 1

TOP MARK

(SEE NOTE 6)

0.200 REF

5.00 ±0.10
(2 SIDES)

R = 0.20

TYP

4.00 ±0.10
(2 SIDES)

0.75 ±0.05

NOTE:

1. DRAWING PROPOSED TO BE MADE VARIATION OF VERSION (WJGD-2) IN JEDEC
PACKAGE OUTLINE MO-229

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE
TOP AND BOTTOM OF PACKAGE

2.44 ± 0.10
(2 SIDES)

0.00 – 0.05
BOTTOM VIEW—EXPOSED PAD

R = 0.115

4.34 ±0.10
(2 SIDES)

TYP

0.25 ± 0.05

0.50 BSC

169

18

0.40 ± 0.10

PIN 1
NOTCH

(DHD16) DFN 0504

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa­tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

422312f

23

LTC4223-1/LTC4223-2

TYPICAL APPLICATION

12V/18A Card Resident Application

BD_SEL

BACKPLANE

CONNECTOR

12V

3.3V

CARD

CONNECTOR

SMAJ5.0A

R

S

2.5mQ1HAT2160H

R1

R2
51Ω

10Ω

C2
330nF

C1
100nF

R8
10k

10k

12V

12V

SENSE

IN

AUXIN AUXOUT

V

CC

R9

AUXON

12ON

EN

TIMER

C

0.1μF

R3

10Ω

12V

GATE

LTC4223-1

T

Z1

SMAJ13A

R7

Z2

2.7Ω
C3

100nF

47Ω

GND

R

G

C

G

15nF

12V

OUT

AUXPGOOD

12PGOOD

FAULT

12IMON

R4
10k

3..3V

1μF

+IN

–IN

+

+

3.3V

R5
10k

LTC1197L

C

L1

1000μF

C

L2

150μF

V

CC

GND

R6
10k

12V
18A

3.3V

AUX

150mA

V

REF

CLK

D

OUT

422312 TA04

CS

TO
CONTROLLER

RELATED PARTS

PART NUMBER DESCRIPTION COMMENTS

LTC1421 Dual Channel, Hot Swap Controller Operates from 3V to 12V, Supports –12V, SSOP-24

LTC1645 Dual Channel, Hot Swap Controller Operates from 3V to 12V, Power Sequencing, SO-8 or SO14

LTC1647-1/LTC1647-2/
LTC1647-3

LTC4210 Single Channel, Hot Swap Controller Operates from 2.7V to 16.5V, Active Current Limiting, SOT23-6

LTC4211 Single Channel, Hot Swap Controller Operates from 2.7V to 16.5V, Multifunction Current Control, MSOP-8 or MSOP-10

LTC4215 Single Channel, Hot Swap Controller Operates from 2.9V to 15V, I

LTC4216 Single Channel, Hot Swap Controller Operates from 0V to 6V, MSOP-10 or DFN-12 (4mm × 3mm)

LTC4221 Dual Channel, Hot Swap Controller Operates from 1V to 13.5V, Multifunction Current Control, SSOP-16

LTC4245 Multiple Channel, Hot Swap Controller 3.3V, 5V, ±12V Supplies, I

LTC4252-1/LTC4252-2/
LTC4252A-1/
LTC4252A-2

Linear Technology Corporation

24

1630 McCarthy Blvd., Milpitas, CA 95035-7417

[phone] ● FAX: [phone]

Dual Channel, Hot Swap Controller Operates from 2.7V to 16.5V, SO-8 or SSOP-16

2

C Compatible Monitoring, SSOP-16 or QFN-24

(4mm × 5mm)

2

C Compatible Monitoring, SSOP-36 or QFN-38

(5mm × 7mm)

–48V Hot Swap Controller Fast Active Current Limiting with Drain Accelerated Response, Supplies from –15V,

MSOP-8 or MSOP-10

LT 0807 • PRINTED IN USA

●

www.linear.com

© LINEAR TECHNOLOGY CORPORATION 2007

422312f