MIC2755YMM Micrel Inc, MIC2755YMM Datasheet - Page 5

• Manufacturer Part Number: MIC2755YMM
• Description: Battery System Supervisor
• Manufacturer: Micrel Inc
• Type: Battery Backup Circuitr

Specifications of MIC2755YMM

• Number Of Voltages Monitored: 1
• Output: Open Drain or Open Collector
• Reset: Active Low
• Reset Timeout: 700 ms Minimum
• Voltage - Threshold: Adjustable/Selectable
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 576-2202; MIC2755YMM

Functional Description
Typically the MIC2755 is used to monitor the battery supply
of intelligent circuits such as microcontrollers and micropro-
cessors. By connecting the reset output of a MIC2755 to the
reset input of a µC or µP, the processor will be properly reset
at power-on and during power-down and low battery condi-
tions. The /NMI output provides low-battery warnings to the
system. In addition, a system whose battery voltage declines
below the PTH threshold is held in reset to prevent spurious
operation. Thus the MIC2755 effectively detects three battery
states: “battery OK,” “low battery,” and “dead battery.”
Reset Output
/RST is an active-low, open-drain digital output. This output
is asserted for a minimum of 700ms at power-on and for a
minimum of 175ms when RTH(/MR) is externally pulled low,
indicating that a manual reset should be initiated. /RST is an
active-low, open-drain digital output and may be wire-ORed
with other open-drain logic signals. Most applications will
require a pull-up resistor on this pin. /RST may be pulled up
to any voltage not exceeding V
is higher than V
Nonmaskable Interrupt Output
/NMI is the output of a comparator that constantly compares
the level on the NTH pin with the internal voltage reference,
V
ing high-power system operation should not occur; that is,
the battery is low but not dead. Effectively, this function is an
uncommitted comparator with its inverting input connected
to the internal reference, V
nected to NTH, and its output on /NMI. This comparator does
not affect any other MIC2755 functions and may be used
independently.
/NMI is an active-low, open-drain digital output and may be
wire-ORed with other open-drain logic signals. Most appli-
cations will require a pull-up resistor on this pin. /NMI may
be pulled up to any voltage not exceeding V
if this voltage is higher than V
istics”).
January 2006
MIC2755
REF2
. This output is asserted when V
DD
(see “Electrical Characteristics”).
REF2
DD
/RST(max)
, its noninverting input con-
(see “Electrical Character-
NTH
even if this voltage
< V
/NMI(max)
REF2
, indicat-
even
5
Power-Off Output
This output and the /RST output are asserted and latched
when V
is held in reset until the battery is replaced or recharged
and a power-on reset cycle occurs; that is, V
The /POF output may be used to control a linear or switch-
ing regulator, shutting down the regulator when the battery
reaches it end-of-life voltage.
/POF is an active-low, open-drain digital output and may
be wire-ORed with other open-drain logic signals. Most ap-
plications will require a pull-up resistor on this output. /POF
may be pulled up to any voltage not exceeding V
even if this voltage is higher than V
acteristics”).
Power-On Reset
The RTH(/MR) and PTH inputs work together to provide
predictable battery monitoring with user-programmable hys-
teresis and without chatter. The /RST output is asserted for a
minimum of 700ms at power-on. Power-on is determined by
RTH(/MR) exceeding V
the internal logic ignores further transitions on the RTH(/
MR) input, instead monitoring for a low voltage on PTH or
the manual reset condition. If V
/POF and /RST outputs are asserted and latched, holding
the system in its reset state.
Manual Reset
An internal circuit monitors RTH(/MR), comparing it to an
internal 310mV reference, V
below V
circuitry initiates a manual reset cycle and asserts /RST for
at least 175ms. A momentary push-button switch is typically
connected such that RTH(/MR) is forced to ground when the
switch contacts close. This switch is internally debounced.
Each closure of the switch longer than t
output pulse of no less than 175ms and no more than 300ms
being generated. (The manual reset pulse is derived from
the same oscillator and counter as t
is always equal to one fourth of t
who may hold the switch closed from keeping the system in
reset for an extended period of time.
PTH
/MRTV,
< V
and V
REF
, indicating a “dead battery.” The system
PTH
REF1
is still above V
/MRTV
. Once this event has occurred,
PTH
/RST
. When RTH(/MR) is pulled
DD
drops below V
/RST
.) This prevents a user
DBNC
(see “Electrical Char-
. The length of t
REF1
results in a single
RTH
, the internal
Micrel, Inc.
MIC2755
REF1
> V
/POF(max)
REF1
, the
/MR
.