DS1238A
MicroManager
www.dalsemi.com
FEATURES
PIN ASSIGNMENT
ꢀ Holds microprocessor in check during power
transients
VBAT
VCCO
VCC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
RST
RST
WDS
CEI
CEO
ST
ꢀ Halts and restarts an out-of-control
microprocessor
ꢀ Warns microprocessor of an impending power
failure
ꢀ Converts CMOS SRAM into nonvolatile
memory
ꢀ Unconditionally write protects memory when
power supply is out of tolerance
ꢀ Delays write protection until completion of
the current memory cycle
VBAT
VCCO
VCC
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
RST
RST
WDS
CEI
CEO
ST
GND
PF
GND
RVT
PF
OSCIN
OSCSEL
NMI
IN
RVT
OSCIN
OSCSEL
NMI
IN
16-Pin DIP (300-mil)
16-Pin SOIC (300-mil)
See Mech. Drawings Section
See Mech. Drawings Section
ꢀ Consumes less than 200 nA of battery current
ꢀ Controls external power switch for high
current applications
ꢀ Debounces pushbutton reset
ꢀ Accurate 10% power supply monitoring
ꢀ Optional 5% power supply monitoring
designated DS1238A-5
PIN DESCRIPTION
VBAT
VCCO
VCC
GND
PF
- +3-Volt Battery Input
- Switched SRAM Supply Output
- +5-Volt Power Supply Input
- Ground
ꢀ Provides orderly shutdown in microprocessor
applications
- Power-Fail
RVT
OSCIN
OSCSEL
IN
- Reset Voltage Threshold
- Oscillator In
- Oscillator Select
- Early Warning Input
- Non-Maskable Interrupt
- Strobe Input
ꢀ Pin-for-pin compatible with MAX691
ꢀ Standard 16-pin DIP or space-saving 16-pin
SOIC
ꢀ Optional industrial temperature range -40°C
to +85°C
NMI
ST
CEO
- Chip Enable Output
- Chip Enable Input
- Watchdog Status
- Reset Output (active low)
- Reset Output (active high)
CEI
WDS
RST
RST
DESCRIPTION
The DS1238A MicroManager provides all the necessary functions for power supply monitoring, reset
control, and memory backup in microprocessor-based systems. A precise internal voltage reference and
comparator circuit monitor power supply status. When an out-of-tolerance condition occurs, the
microprocessor reset and power-fail outputs are forced active, and static RAM control unconditionally
write protects external memory. The DS1238A also provides early warning detection of a user-defined
threshold by driving a non-maskable interrupt. External reset control is provided by a pushbutton reset
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