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PDF DS1238 Data sheet ( Hoja de datos )
| Número de pieza | DS1238 | |
| Descripción | MicroManager | |
| Fabricantes | Dallas | |
| Logotipo |  |
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DS1238
MicroManager
FEATURES
Holds microprocessor in check during power
transients
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
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 DS1238-5
Provides orderly shutdown in microprocessor
applications
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
PIN ASSIGNMENT
VBAT 1 16 RST
VCCO
VCC
GND
PF
RVT
OSCIN
OSCSEL
2
3
4
5
6
7
8
15 RST
14 WDS
13 CEI
VBAT
VCCO
12 CEO
VCC
11 ST
GND
PF
10 NMI
RVT
OSCIN
9 IN OSCSEL
1 16
2 15
3 14
4 13
5 12
6 11
7 10
89
RST
RST
WDS
CEI
CEO
ST
NMI
IN
16-Pin DIP (300-mil)
See Mech. Drawings Section
16-Pin SOIC (300-mil)
See Mech. Drawings Section
PIN DESCRIPTION
VBAT
VCCO
VCC
GND
- +3-Volt Battery Input
- Switched SRAM Supply Output
- +5-Volt Power Supply Input
- Ground
PF - Power-Fail
RVT - Reset Voltage Threshold
OSCIN
- Oscillator In
OSCSEL - Oscillator Select
IN - Early Warning Input
NMI - Non-Maskable Interrupt
ST - Strobe Input
CEO - Chip Enable Output
CEI - Chip Enable Input
WDS - Watchdog Status
RST - Reset Output (active low)
RST - Reset Output (active high)
DESCRIPTION
The DS1238 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 DS1238 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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1 page  
OSCILLATOR CONTROLS Table 1
Watchdog Timeout Period (typ)
OSCIN OSCSEL
First Period
Following a Reset
Other Timeout
External Ext Clk
Low
20480 Clks
5120 Clocks
Ext Cap Low
≅
2.2 sec
47 pf
X Cpf
≅
550 ms
47 pf
X Cpf
Internal Low Hi/Open
Hi/Open Hi/Open
2.7 sec
2.7 sec
170 ms
2.7 sec
Note that the OSCIN and OSCSEL pins are tri-stated when VCC is below VBAT.
DS1238
Reset Active
Duration
641 Clks
≅
69 ms
47 pf
X Cpf
85 ms
85 ms
POWER MONITOR, WATCHDOG TIMER, AND PUSHBUTTON RESET Figure 3
PUSHBUTTON RESET TIMING Figure 4
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5 Page 
POWER-UP TIMING Figure 11
DS1238
11 of 14
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet DS1238.PDF ] | |
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