Datasheet MIC2754-TBM5UET, MIC2753-TBM5UDT, MIC2754-LBM5UEL, MIC2754-MBM5UEM, MIC2754-RBM5UER Datasheet (MICREL)

June 1999 1 MIC2753/2754

MIC2753/2754 Micrel

MIC2753/2754

Power Supply Supervisors

Preliminary Information

General Description

The MIC2753 and MIC2754 are ultraminiature, full-featured,
power supply supervisors featuring active-high and active­low reset outputs, respectively.

The MIC2753/4 includes an undervoltage detector with a
power-on reset generator and reset output, an overvoltage
detector with a separate output for activating crowbar circuits,
and a debounced manual reset input. Typical supply current
is a low 30µA.

These devices provide a 140ms minimum reset output at
power-on and assert their reset outputs any time the input
voltage deviates beyond preset overvoltage or undervoltage
thresholds. Reset outputs remain asserted for 140ms (mini­mum) after the input returns to normal or after releasing the
manual reset. When an overvoltage condition is detected, the
overvoltage output is immediately activated. Hysteresis on
both thresholds prevents erratic operation due to noise.

Typical Application

Microcontroller

Manual

Reset

MIC2754

VCC

HVMR

RST

V

CC

VIN

RST IN

GND

GND

Fuse

SCR
Crowbar

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

Features

• Undervoltage and overvoltage monitor

• Separate overvoltage flag output

• Generates 140ms (minimum) power-on reset pulse

• Debounced manual reset input

• Choice of active-high (MIC2753) or
active-low (MIC2754) reset outputs

• Low 30µA typical supply current

• No external components needed

• IttyBitty™ SOT-23-5 package

Applications

• Computer systems

• Embedded controllers

• Power supplies

• Telecommunications systems

MIC2753/2754 Micrel

MIC2753/2754 2 June 1999

Pin Configuration

Part

Identification

RST

MRGND

VIN

UDx

13

45

2

HV HV

MRRST

VIN

UEx

13

45

2

GND

MIC2753

MIC2754

Voltage

Code

Pin Description

Pin No. Pin No. Pin Name Pin Function

MIC2753 MIC2754

1 RST Reset (Digital Output): Active-high output. Asserted when V

IN

falls below

V

THU

(undervoltage threshold), or rises above V

THO

(overvoltage threshold).

Deasserted no less than 140ms after VIN returns within threshold limits.

2 1 /HV High-Voltage Flag (Open-Drain Output): /HV is asserted (active low) when

the input voltage exceeds the V

THO

(overvoltage threshold). It indicates
power supply overvoltage and is intended for connection to a protection
device such as a “crowbar” circuit.

3 3 VIN Analog Input: Voltage monitor input and power supply input to the IC.

4 /RST Reset (Digital Output): Active-low digital output. This output will be asserted

whenever V

IN

falls below V

THU

(undervoltage threshold), or rises above

V

THO

(overvoltage threshold). It will be deasserted no less than 140ms after

VIN returns within the threshold limits.

4 2 GND Ground: Ground return for all IC functions.
5 5 /MR Manual Reset (Digital Input): Logic low initiates immediate, unconditional

reset. If VIN is within tolerance thresholds, when /MR is released (returns
high), the reset output(s) will be deasserted no less than 140ms later. /MR
may be driven by a CMOS or TTL logic signal or a mechanical switch.
(Switch debouncing is performed internally.) /MR has an internal pull-up to
VIN and may remain open if unused.

Ordering Information

Part Number Mark Lower Threshold Monitored Upper Threshold Reset Temperature Package

Voltage Voltage* Voltage Range

MIC2753-RBM5 UDR 2.63V 2.85V±5% 3.08V Active High –40°C to +85°C SOT-23-5
MIC2753-SBM5 UDS 2.93V 3.3V±10% 3.83V Active High –40°C to +85°C SOT-23-5
MIC2753-TBM5 UDT 3.08V 3.3V±5% 3.53V Active High –40°C to +85°C SOT-23-5
MIC2753-MBM5 UDM 4.38V 5.0V±10% 5.81V Active High –40°C to +85°C SOT-23-5
MIC2753-LBM5 UDL 4.63V 5.0V±5% 5.38V Active High –40°C to +85°C SOT-23-5
MIC2754-RBM5 UER 2.63V 2.85V±5% 3.08V Active Low –40°C to +85°C SOT-23-5
MIC2754-SBM5 UES 2.93V 3.3V±10% 3.83V Active Low –40°C to +85°C SOT-23-5
MIC2754-TBM5 UET 3.08V 3.3V±5% 3.53V Active Low –40°C to +85°C SOT-23-5
MIC2754-MBM5 UEM 4.38V 5.0V±10% 5.81V Active Low –40°C to +85°C SOT-23-5
MIC2754-LBM5 UEL 4.63V 5.0V±5% 5.38V Active Low –40°C to +85°C SOT-23-5

* Contact factory for voltages not listed.

June 1999 3 MIC2753/2754

MIC2753/2754 Micrel

Absolute Maximum Ratings (Note 1)

Supply Voltage (VIN) ...................................... –0.3V to 10V

Reset Voltage (V

RST

) ...........................–0.3V to VIN + 0.3V

Manual Reset Voltage (VMR) ............... –0.3V to VIN + 0.3V

Reset Current (I

RST

)...................................................10mA

Continuous Power Dissipation

(PD at TA = +85°C) ..............................................200mW

Storage Temperature (TS) ....................... –65°C to +150°C

ESD Rating, Note 3

Operating Ratings (Note 2)

Supply Voltage (VIN) .......................................... 1.5V to 7V

Ambient Temperature (TA).........................–40°C to +85°C

Junction Temperature (TJ) ........................................ 150°C

Manual Reset (VMR)............................................. 0V to V

IN

Thermal Resistance

(θJA)...................................................................325°C/W

Electrical Characteristics

VIN = 5.0V (L, M voltage code), VIN = 3.3V (T, S voltage code), VIN = 2.85 (R voltage code) TA = 25°C;

bold values indicate 1.5V ≤ VIN ≤ 7.0V, –40°C ≤ TA ≤ +85°C Note 4; unless noted
Symbol Parameter Condition Min Typ Max Units

V

IN

Input Supply Voltage 1.0 7.0 V

I

DD

Operating Supply Current manual reset not asserted 30 100 µA

V

THO

Overvoltage Threshold L voltage code 5.28 5.38 6.00 V

M voltage code 5.62 5.81 6.00 V
T voltage code 3.459 3.53 3.96 V
S voltage code 3.67 3.83 3.96 V
R voltage code 3.018 3.08 3.28 V

V

THU

Undervoltage Threshold L voltage code 4.50 4.63 4.75 V

M voltage code 4.25 4.38 4.50 V
T voltage code 3.00 3.08 3.15 V
S voltage code 2.85 2.93 3.00 V
R voltage code 2.55 2.63 2.70 V

V

HYST

+ Overvoltage Threshold Hysteresis –15 mV

V

HYST

– Undervoltage Threshold Hysteresis +15 mV

t

PROP(RST)

Propagation Delay VIN = V

THO (min)

– 100mV to V

THO (max)

+ 100mV 12 30 µs

VIN = V

THU (max)

+ 100mV to V

THU (min)

– 100mV 12 30 µs

t

RST

Reset Pulse Width 140 240 560 ms

MIC2753/2754 Micrel

MIC2753/2754 4 June 1999

Symbol Parameter Condition Min Typ Max Units

V

OL(RST)

Reset Output Voltage Low R/S/T voltage codes, 0.5 V
MIC2753 VIN = V

THU(max)

+ 100mV, I

SINK

= 50µA

L/M voltage codes, 0.5 V
VIN = V

THU(max)

+ 100mV, I

SINK

= 50µA

V

OH(RST)

Reset Output Voltage High R/S/T voltage codes, V

IN

–0.5 V

MIC2753 VIN = V

THU(min)

– 100mV, I

SOURCE

= 0.5mA

L/M voltage codes, V

IN

–0.8 V

VIN = V

THU(min)

– 100mV, I

SOURCE

= 1.0mA

V

OL(RST)

/Reset Output Voltage Low R/S/T voltage codes, 0.5 V
MIC2754 VIN = V

THU(min)

– 100mV, I

SINK

= 0.5mA

L/M voltage codes, 0.8 V
VIN = V

THU(min)

– 100mV, I

SINK

= 1.0mA

VIN ≥ 1.5V, IOL = 50µA 0.5 V

V

OH(RST)

/Reset Output Voltage High R/S/T voltage codes, V

IN

–0.5 V

MIC2754 VIN = V

THU(max)

+ 100mV, I

SOURCE

= 35µA

L/M voltage codes, V

IN

–0.5 V

VIN = V

THU(max)

+ 100mV, I

SOURCE

= 35µA

V

IH(/MR)

/MR Input Voltage, High 0.8 V

IN

V

V

IL(/MR)

/MR Input Voltage, Low 0.2 V

IN

V

t

PROP(/MR)

Propagation Delay V

/MR

≤ V

IL

to V

RST

≥ V

OH

1 2 µs

MIC2753
Propagation Delay V

/MR

≤ V

IL

to V

/RST

≤ V

OL

1 2 µs

MIC2754

t

/MR(min)

/MR Minimum Input Pulse Width 2.5 µs

I

PU

Pull-Up Current, /MR V

/MR

= 0V 0.2 2 µA

I

IH

Input Current, /MR V

/MR

= V

IN

0.01 µA

V

OL(/HV)

/HV Output Voltage Low VIN > V

THO(max)

, 0.5 V

I

SINK

= 0.5mA, R/S/T voltage codes V

V

IN

> V

THO(max)

, 0.8 V

I

SINK

= 1.0mA, L/M voltage codes V

t

PROP(/HV)

/HV Propagation Delay VIN = V

THO (min)

– 100mV to V

THO (max)

+ 100mV 12 30 µs

I

/HV

/HV Leakage Current VIN = V

THO (min)

– 100mV –2 +2 µA

Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Devices are ESD sensitive. Handling precautions recommended.
Note 4. Final test on outgoing product is performed at TA = 25°C. Device performance over –40°C ≤ TA ≤ +85°C is guaranteed by design.

June 1999 5 MIC2753/2754

MIC2753/2754 Micrel

Typical Characteristics

0

20

40

60

80

100

-40 -20 0 20 40 60 80 100

SUPPLY CURRENT (µA)

TEMPERATURE (°C)

Supply Current

vs. Temperature

1V

3V 4V 5V2V

VIN = 6V

No Load; L, M
volta

g

e codes

0

1

2

3

4

5

6

7

8

9

10

-40 -20 0 20 40 60 80 100

RESET DELAY (µs)

TEMPERATURE (°C)

Power-Down Reset Delay

vs. Temperature

L, M voltage codes

150

200

250

300

-40 -20 0 20 40 60 80 100

RESET PULSE WIDTH (ms)

TEMPERATURE (°C)

Power-Up Reset Timeout

vs. Temperature

0.990

0.995

1.000

1.005

1.010

-40 -20 0 20 40 60 80 100

NORMALIZED THRESHOLD

TEMPERATURE (°C)

Normalized Reset Threshold

vs. Temperature

20

25

30

35

40

45

50

-40 -20 0 20 40 60 80 100

RESET DELAY (ns)

TEMPERATURE (°C)

Manual Reset Delay

vs. Temperature

L, M voltage codes

0

10

20

30

40

-40 -20 0 20 40 60 80 100

OVERVOLTAGE DELAY (µs)

TEMPERATURE (°C)

Overvoltage Delay

vs. Temperature

10mV

20mV

100mV

Overdrive = 200mV

L, M voltage codes

0

10

20

30

40

50

-40 -20 0 20 40 60 80 100

UNDERVOLTAGE DELAY (µs)

TEMPERATURE (°C)

Undervoltage Delay

vs. Temperature

20mV

Overdrive = 10mV

L, M voltage codes

0.990

0.995

1.000

1.005

1.010

-40 -20 0 20 40 60 80 100

THRESHOLD

TEMPERATURE (°C)

Normalized Overvoltage

Threshold vs. Temperature

20

60

100

140

180

220

260

300

-40 -20 0 20 40 60 80 100

PULL-UP CURRENT (nA)

TEMPERATURE (˚C)

MR Pull-up Current

vs. Temperature

2.85V

3.3V

5.0V

MIC2753/2754 Micrel

MIC2753/2754 6 June 1999

Functional Diagram

GND

MR

VIN

RST (MIC2753 only)

RST (MIC2754 only)

HV

1.2V
Bandgap
Reference

Low-Voltage

Detect

High-Voltage

Detect

S

R

Q

Q

350ms typ.

Delay

Line

June 1999 7 MIC2753/2754

MIC2753/2754 Micrel

Timing Diagram

V

IN(nominal)

V

HYST–

V

OH

t

RESET

t

PROP

V

OL

V

OL

V

OH

1.5V

V

THU

A

t

RESET

A. Very short transients will be ignored by the
MIC275x. See “Applications Information.”

B. Without external pull-down or pull-up resistors, the
output is not guaranteed to be valid when V

IN

< 1.5V.

V

RST

V

RST

V

IN

V

HYST+

V

THO

t

PROP

t

RESET

V

OL

V

OH

HV

A

0V

B

B

B

(MIC2753)

(MIC2754)

V

MR

V

IH

V

IL

V

RST

V

OH

V

OL

t

RESET

t

PROP(MR)

(MIC2754)

V

RST

V

OH

V

OL

(MIC2753)

Manual Reset Timing

MIC2753/2754 Micrel

MIC2753/2754 8 June 1999

Functional Description

The MIC275x family of devices are typically used to monitor
power supplies of intelligent circuits such as microcontrollers
and microprocessors. By connecting the appropriate reset
output of an MIC275x to the reset input of a microcontroller or
microprocessor, the processor will be properly reset at power­on, and during power-down and brownout conditions. In
addition, asserting /MR (manual reset input) activates the
reset function.

Reset Outputs

The /RST and/or RST output is asserted any time /MR is
asserted or if VIN deviates beyond the preset threshold
voltages, V

THU

and V

THO

. Reset output(s) remain asserted
for 140ms minimum after VIN returns within the threshold
boundaries and/or /MR is released. A minimum 140ms reset
pulse is also generated at power-on. Hysteresis is included in
the overvoltage and undervoltage comparators to prevent
chattering of the outputs due to noise.

The MIC275x family offers a choice of two reset output
options: the MIC2753 has an active-high RST output, and the
MIC2754 has an active-low /RST output.

Manual Reset Input

The ability to initiate a reset from external logic or a manual
switch is provided in addition to the MIC275x’s automatic
supervisory functions. Driving the /MR input low causes an
immediate and unconditional reset to occur. Assuming VIN is
within the tolerance thresholds when /MR is released (inter­nally pulled to logic high), the reset output will be deasserted

no less than 140ms later. /MR may be driven by a CMOS or
TTL logic signal or a mechanical switch. Typically, a momen­tary push-button switch is connected such that /MR is shorted
to ground when the contacts close. Switch debouncing is
performed internally; the switch may be connected directly
between /MR and GND. /MR has an internal pull-up to V

IN

and may be left open if unused.

Overvoltage Output

The /HV and reset outputs are immediately and uncondition­ally asserted any time VIN exceeds V

THO

(overvoltage thresh­old). /HV is an active-low, open-drain logic output. Overvolt­age on a system power supply rail is generally considered to
be a catastrophic condition which may cause permanent
system damage. If and when an overvoltage condition occurs
using a MIC275x, the system is immediately driven into reset
mode and /HV (overvoltage flag), is driven active.

Typically, an overvoltage signal, such as /HV, is connected to
a “crowbar circuit” using a latching power device such as an
SCR. See “Typical Application”. The crowbar circuit will
clamp the power rail to some low voltage by shunting power
supply current to ground. This should cause some upstream
power supply protection device to be activated, such as fold­back current limiting, a fuse, or circuit breaker. In this way, the
system is most likely to be protected against damage and
spurious operation until the condition can be remedied. /HV
is an open-drain output and may be wire-ORed with other
open-drain logic signals. Some systems may require a pull­up resistor.

System Block Diagram

Reset

Switch

Voltage Monitor

and

Reset Generator

Microprocessor

System

Circuitry

Reset(s)

Crowbar

Circuit

HV

June 1999 9 MIC2753/2754

MIC2753/2754 Micrel

Application Information

Supply Transients

The MIC2753/4 are inherently immune to very short “glitches”
on VIN. In the case of

very brief

transients, VIN may drop
below the reset threshold or exceed the overvoltage thresh­old without activating the RST, /RST or /HV output. As shown
in the graphs of Figure 1, the narrower the transient, the
deeper the threshold overdrive that will be ignored by the
MIC2753/4. The lines on the graph represent the typical
allowable transient duration for a given amount of threshold
overdrive that will not generate a reset or overvoltage indica­tion. The data from which Figure 1 is derived was taken by
adding negative-going square-wave pulses to a dc VIN set at

0.5V above or below the actual measured threshold for the
part being characterized.

In the case of the MIC2754L/M for example (refer to Figure 1),
a transient on VIN which goes below the reset threshold by
100mV and lasts no more than 8.4µs will typically not cause
a reset to occur. Bypass capacitance placed as close as
physically possible to the device’s VIN and GND pins will
increase the transient immunity (0.1µF, for example).

Ensuring Proper Operation at Low Supply

At levels of VIN below 1.5V, the MIC2754’s /RST output driver
cannot turn on sufficiently to sink current and produce a valid
logic-low on the /RST output. In this situation, other CMOS
circuits driven by /RST could be allowed to float, causing

undesired operation. (In most cases, however, it is expected
that the circuits driven by the MIC2754 will be similarly
inoperative at VCC ≤ 1.5V.)

If a given application requires that /RST be valid below VIN =

1.5V, this can be accomplished by adding a pull-down resis­tor to the /RST output. A value of 100kΩ is recommended as
this is usually an acceptable compromise of leakage current
and pull-down current. The resistor’s value is not critical,
however.

The statements above also apply to the MIC2753’s RST
output. That is, to ensure valid RST signal levels at VIN < 1.5V,
a pull-up resistor (as opposed to a pull-down) should be
added to the RST output. A value of 100kΩ is typical for this
application as well. See Figure 2.

Interfacing to Processors with Bidirectional Reset Pins

Some microcontrollers and microprocessors utilize reset
signal pins that are bidirectional in nature, rather than simply
being input only. The Motorola 68HC11 family is one ex­ample. To use the MIC2753/4 with these processors, it is
necessary to insert a resistor into the signal path between the
MIC2753/4’s reset output and the microprocessor’s reset
input. This prevents excessive current from flowing due to
contention between the two drivers. The signal present at the
processor’s reset pin will now be of limited drive capability, so
it is necessary to buffer it in order to drive other circuits. This
technique is shown in Figure 3.

0

10

20

30

40

1 10 100 1000

DURATION (µs)

OVERDRIVE (mV)

Reset Comparator Overdrive

vs. Duration

TA = 25°C

A. Reset

0

1

2

3

4

5

6

7

8

1 10 100 1000

DURATION (µs)

OVERDRIVE (mV)

Overvoltage Comparator

Overdrive vs. Duration

TA = 25°C

B. Overvoltage

Figure 1. MIC2753/2754 Transient Immunity Behavior

MIC2753/2754 Micrel

MIC2753/2754 10 June 1999

Microcontroller

Manual

Reset

MIC2754

VCC

HVMR

RST

V

CC

IN

RST IN

GND

Fuse

R

PULL-DOWN

100k

MCR708A
SCR

2200pF

10k

MIC94030

1k

22Ω

GND

Figure 2a. MIC2754 Valid Reset Below 1.5V

Microcontroller

Manual

Reset

MIC2753

VCC

HVMR

RST

V

CC

IN

RST IN

GND

Fuse R

PULL-UP

100k

MCR708A
SCR

2200pF

10k

MIC94030

1k

22Ω

GND

Figure 2b. MIC2753 Valid Reset Below 1.5V

Microcontroller

Manual

Reset

MIC2754

VCC

HVMR

RST

V

CC

IN

RST IN

GND

GND

Fuse

MCR708A
SCR

R

SERIES

4.7k

BUFFER

/RST signal to
other circuits

2200pF

10k

MIC94030

1k

22Ω

Figure 3. MIC2754 With Processors Using Bidirectional Reset Inputs.

Crowbar Applications

The following MIC275x applications diagrams show an SCR
crowbar circuit. The function of this circuit is to protect system
components from damage caused by excessive supply volt­age, as might be generated by a runaway power supply. The
low R

DS(on)

of the MIC94030 P-channel MOSFET (<1Ω at
VGS = 4.5V) and the 22Ω resistor assure adequate gate
current to trigger the SCR.

The crowbar circuit is designed to be functional over all
operating ranges of the MIC275x. Since the lowest upper­threshold voltage of the MIC275x family is only 3.08V, and
since the SCR-gate forward voltage is about 1V, there is
about 90mA of gate-drive current available: 2.08V ÷ 23Ω =

0.09A. The highest upper-threshold voltage is 5.38V, so
available gate-drive current is about 190mA: 4.38V ÷ 23Ω =

0.190A. The maximum forward gate current of the SCR is

200mA. The SCR trigger characteristics and the gate-drive
capability provide a workable solution for the power-supply
voltage range in question.

The 10kΩ resistor is the pull-up for the open-drain /HV output
of the MIC275x, and the 2200pF capacitor avoids inadvertent
premature triggering of the SCR, which might be caused by
a very narrow spike on the /HV line. Similarly, the 1kΩ resistor
from the SCR-gate to ground keeps the SCR-gate biased off.

The fuse shown in the diagrams, which ultimately protects
both the system components and the crowbar SCR, should
be a fast-blow type. The SCR is rated at 4A(rms), but it can
withstand a brief 25A surge. The crowbar circuit shown
should, conservatively, be capable of blowing a 5A or 6A
fuse.

June 1999 11 MIC2753/2754

MIC2753/2754 Micrel

Package Information

0.20 (0.008)

0.09 (0.004)

0.60 (0.024)

0.10 (0.004)

3.02 (0.119)

2.80 (0.110)
10°

0°

3.00 (0.118)

2.60 (0.102)

1.75 (0.069)

1.50 (0.059)

0.95 (0.037) REF

1.30 (0.051)

0.90 (0.035)

0.15 (0.006)

0.00 (0.000)

DIMENSIONS:

MM (INCH)

0.50 (0.020)

0.35 (0.014)

1.90 (0.075) REF

SOT-23-5 (M5)

MIC2753/2754 Micrel

MIC2753/2754 12 June 1999

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

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

This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or

other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.

© 1999 Micrel Incorporated