MIC2755 Datasheet, PDF (1/12 Pages) Micrel Semiconductor – Battery System Supervisor Preliminary Information

MIC2755
MIC2755
Battery System Supervisor
Preliminary Information
Micrel
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 opera-
tion 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 gener-
ates 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_DD (up to 7V
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-small-
outline package.
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 V_DD (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
MIC2755BMM
Junction Temp. Range
–40°C to +85°C
Package
8-pin MSOP
Typical Application
V_BAT
V_BAT(OK) = 3.6V
V_BAT(low) = 3.1V
V_BAT(dead) = 2.9V
656k
576k
344k 26.7k
SW
RESET
400k
100k
MIC2755
VDD
/POF
PTH
/NMI
NTH
/RST
RTH(/MR) GND
Boost or Buck
Converter
IN OUT
EN
100k 100k
µController or
µProcessor
SUPPLY
/NMI
/RST
GND
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
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MIC2755