MICREL MIC2755BMM Datasheet

MIC2755 Micrel

MIC2755

Battery System Supervisor

Preliminary Information

General Description

The MIC2755 is composed of multiple comparators, a reset
pulse generator, and logic. It is designed for monitoring the
battery supply of portable digital systems, including PDAs
and pagers.

The MIC2755 detects three different battery states: battery
OK, low battery, and dead battery. The reset (/RST) output is
asserted for at least 700ms when a fresh battery is inserted.
The nonmaskable interrupt output (/NMI) is asserted when
the battery voltage is below the NTH threshold, indicating that
high-power system operations should not occur. If and when
battery voltage falls below the power-off threshold (PTH), the
reset output is asserted and latched, inhibiting system opera­tion until the battery is replaced or recharged.

All three voltage thresholds are set using external resistors.
A manual reset function can be implemented by connecting
a switch directly to the power on reset/manual reset [RTH(/MR)]
input. Internal circuitry detects switch activation and gener­ates a minimum 175ms debounced reset signal. The
MIC2755’s power supply input is separate from the detector
inputs to allow it to be powered from a down-stream voltage,
such as the output of a boost converter.

Inputs and outputs can be pulled above V
absolute maximum) without adverse effects or excessive
current draw.

Supply current is typically a low 2µA. Hysteresis is included
on all voltage detectors to prevent chattering due to noise.
The MIC2755 is available in the tiny 8-lead micro-small­outline package.

(up to 7V

DD

Features

• Optimized for PDAs, pagers and
other hand-held devices.

• Detects multiple battery states:

- battery OK

- low battery

- dead battery

• Adjustable voltage thresholds

• High accuracy ±2% voltage thresholds

• Reset generation at power-on (700ms min.)

• Debounced manual reset function

• Internal logic prevents chatter if battery voltage

fluctuates

• Extremely low 2µA typical supply current

• I/Os can be pulled above VDD (7V absolute maximum)

• Immune to brief power supply transients

• Low cost

• 8-lead MSOP

Applications

• PDAs

• Pagers

• Consumer electronics

• Embedded controllers

• Portable instruments

• Data loggers

Ordering Information

Part Number Junction Temp. Range Package

MIC2755BMM –40°C to +85°C 8-pin MSOP

Typical Application

Boost or Buck

Converter

IN OUT
EN

V

BAT(OK)

V

BAT(low)

V

BAT(dead)

= 3.6V
= 3.1V

= 2.9V

SW

RESET

V

656k

344k

BAT

576k

26.7k

400k

MIC2755

VDD /POF
PTH
NTH
RTH(/MR)

/NMI
/RST
GND

100k 100k 100k

Supervised Boost Converter and Microcontroller or Microprocessor

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

February 2000 1 MIC2755

µController or

µProcessor

SUPPLY

/NMI
/RST

GND

MIC2755 Micrel

Pin Configuration

NTH
PTH

GND

Pin Description

Pin Number Pin Name Pin Function

1 RTH(/MR) Power-On Reset Threshold (Analog Input): Comparator input assigned to

2 NTH Nonmaskable Interrupt Threshold (Analog Input): Voltage monitor input

3 PTH Power-Off Threshold (Analog Input): Voltage monitor input assigned to

4 GND Ground: Power and signal return for all IC functions.
5 /POF Power-off (Output): Active-low, open-drain output. Asserted and latched

6 /NMI Nonmaskable Interrupt (Output): Active-low, open-drain output. Asserted

7 /RST Reset (Output): Active-low, open-drain output. Asserted for a minimum of

8 VDD (Analog Input): Power supply input.

1RTH(/MR)
2
3
4

8 VDD

/RST

7

/NMI

6

/POF

5

8-Lead MSOP (MM)

battery-OK condition detection. When the level on this pin first exceeds

, the reset generator cycles. The /RST output is held low for a minimum

V

REF

of 700ms and the /POF threshold output is deasserted.

assigned to “low battery” condition detection. When the level on this pin falls
below V

“dead battery” condition detection. When the level on this pin falls below
V

REF

a reset cycle occurs (V

when V
in reset until the battery is replaced and a power-on reset cycle occurs.

when V
power system operation should not be allowed.

700ms at power-on or anytime V
175ms minimum when RTH (/MR) is externally pulled low (manual reset).

, the /NMI output is asserted.

REF

, the /RST and /POF outputs are asserted. The condition is latched until

PTH

NTH

< V

< V

> V

RTH

, which is a “dead battery” condition. The system is held

REF

, which is a “low battery” condition. This indicates high-

REF

).

REF

drops below V

PTH

. Also asserted for

REF

MIC2755 2 February 2000

MIC2755 Micrel

Absolute Maximum Ratings (Note 1)

Supply Voltage (V
Input Voltage (V
Output Voltage (V
/RST Output Current (I
Storage Temperature (T

ESD Rating, Note 3 ......................................................2kV

) ..................................... –0.3V to +7V

DD

RTH

/RST

), (V

), (V

NTH

), (V

/NMI

) .......................................20mA

/RST

) ....................... –65°C to +150°C

S

) ............. –0.3V to +7V

PTH

), (V

) ........ –0.3V to +7V

/POF

Operating Ratings (Note 2)

Supply Voltage (V
Input Voltage (V
Output Voltage (V

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

Package Thermal Resistance

1-layer PCB (θ

) .................................. +1.5V to +5.5V

DD

), (V

RTH

/RST

) ..............................................206°C/W

JA

NTH

), (V

), (V

/NMI

) ............. –0.3V to +6V

PTH

), (V

) ........ –0.3V to +6V

/POF

4-layer PCB (θJA) ..............................................113°C/W

Electrical Characteristics

VDD = 3.3V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Symbol Parameter Condition Min Typ Max Units

I

DD

I

RTH(/MR)

, I

I

NTH

PTH

I

/RST, I/NMI

I

/POF

V

REF1

V

REF2

V

HYST

Reset Output (/RST)

t

/RST

t

/MR

V

/RST

Reset Input [RTH(/MR)]

V

/MRTV

t

DBNC

t

PROP

Nonmaskable Interrupt Output (/NMI)

t

PROP

V

/NMI

Power-Off Output (/POF)

t

PROP

V

/POF

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. Human body model, 100pF in series with 1.5k .
Note 4. VDD operating range is 1.5V to 5.5V. Output is guaranteed to be held low down to VDD = 1.2V.

Note 5.

Operating Supply Current outputs open, V

outputs open, V

RTH
RTH

, V
, V

NTH
NTH

, V

> 1.24V 2.0 4.0 µA

PTH

, V

< 1.24V 1.7 µA

PTH

, Leakage Current 5pA

, 10 nA

,

Threshold Voltage for RTH(/MR) and PTH inputs 1.215 1.240 1.265 V
Threshold Voltage for NTH inputs 1.215 1.240 1.265 V
Hysteresis Voltage on NTH 20 mV

Comparator

Reset Pulse Width 700 1200 ms
Manual Reset Pulse Width 175 300 ms
/RST Output Voltage Low, Note 4 /RST asserted, I

/RST asserted, I

= 1.6mA, VDD ≥ 1.6V 0.3 V

SINK

= 100µA, VDD ≥ 1.2V 0.4 V

SINK

Manual Reset Trip Voltage 275 310 345 mV
Debounce Time V

/MRTV(min)

Propogation Delay from (V

to RST Asserted

Propagation Delay (V

REF(max)

< V

RTH

< V

/MR

RTH(/MR)(min)

+ 100mV) < V

< V

/MRTV(max)

, Note 5 22 38 ms

– 100mV) 9 µs

NTH

< (V

REF(min)

9 µs

– 100mV)

/NMI Output Voltage Low /NMI asserted, I

/NMI asserted, I

Propagation Delay (V

– 100mV)

/POF Output Voltage Low /POF asserted, I

/POF asserted, I

t

t

t

DBNC

/RST /MR

==

32

8

. These relationships are guaranteed by design.

REF(max)

+ 100mV) < V

= 1.6mA, VDD ≥ 1.6V 0.3 V

SINK

= 100µA, VDD ≥ 1.2V 0.4 V

SINK

< (V

PTH

= 1.6mA, VDD ≥ 1.6V 0.3 V

SINK

= 100µA, VDD ≥ 1.2V 0.4 V

SINK

REF(min)

9 µs

February 2000 3 MIC2755

MIC2755 Micrel

Timing Diagram

V
V

V

BAT

V

V

/MR

/RST

/NMI

/POF

V

V

V
V

V
V
V

/MRH

/MRL

/RSTH

/RSTL
/NMIH

/NMIL

/POFH

/POFL

V

V

V

V

Block Diagram

PTH

0V

RTH

NTH

t

RST

Propagation delays not shown for clarity.
The MIC2755 ignores very brief transients. See “Application

Information” for details.

t

RST

<t

DBNC

>t

DBNC

t

/MR

NOT TO SCALE.

20mV

V

EXPANDED

BAT

VERTICALLY TO

SHOW DETAIL.

NTH

PTH

RTH(/MR)

1.24V
Ref1

1.24V
Ref2

20mV

Hysteresis

310mV

VDD

Machine

Logic-State

/NMI

/RST

/POF

GND

Oscillator

MIC2755 4 February 2000