MicroMonitor Chip. DS1232 Datasheet

DS1232 Chip. Datasheet pdf. Equivalent

DS1232 Datasheet
Recommendation DS1232 Datasheet
Part DS1232
Description MicroMonitor Chip
Feature DS1232; www.maxim-ic.com DS1232 MicroMonitor Chip FEATURES ƒ Halts and restarts an out-of-control micropro.
Manufacture Dallas
Datasheet
Download DS1232 Datasheet





Dallas DS1232
www.maxim-ic.com
DS1232
MicroMonitor Chip
FEATURES
ƒ Halts and restarts an out-of-control
microprocessor
ƒ Holds microprocessor in check during power
transients
ƒ Automatically restarts microprocessor after
power failure
ƒ Monitors pushbutton for external override
ƒ Accurate 5% or 10% microprocessor power
supply monitoring
ƒ Eliminates the need for discrete components
ƒ Space-saving, 8-pin mini-DIP
ƒ Optional 16-pin SOIC surface mount package
ƒ Industrial temperature -40°C to +85°C
available, designated N
PIN ASSIGNMENT
PBRST 1
8 VCC
TD 2
TOL 3
7 ST
6 RST
GND 4
5 RST
DS1232 8-Pin DIP (300-mil)
See Mech. Drawings Section
NC
PBRST
NC
TD
NC
TOL
NC
GND
1 16
2 15
3 14
4 13
5 12
6 11
7 10
89
NC
VCC
NC
ST
NC
RST
NC
RST
DS1232S 16-Pin SOIC (300-mil)
See Mech. Drawings Section
PIN DESCRIPTION
PBRST
TD
TOL
GND
RST
- Pushbutton Reset Input
- Time Delay Set
- Selects 5% or 10% VCC Detect
- Ground
- Reset Output (Active High)
RST - Reset Output (Active Low, open
drain)
ST - Strobe Input
VCC - +5 Volt Power
NC - No Connections
DESCRIPTION
The DS1232 MicroMonitor™ Chip monitors three vital conditions for a microprocessor: power supply,
software execution, and external override. First, a precision temperature-compensated reference and
comparator circuit monitors the status of VCC. When an out-of-tolerance condition occurs, an internal
power fail signal is generated which forces reset to the active state. When VCC returns to an in-tolerance
condition, the reset signals are kept in the active state for a minimum of 250 ms to allow the power supply
and processor to stabilize.
MicroMonitor is a trademark of Dallas Semiconductor.
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Dallas DS1232
DS1232/DS1232S
The second function the DS1232 performs is pushbutton reset control. The DS1232 debounces the
pushbutton input and guarantees an active reset pulse width of 250 ms minimum. The third function is a
watchdog timer. The DS1232 has an internal timer that forces the reset signals to the active state if the
strobe input is not driven low prior to timeout. The watchdog timer function can be set to operate on
timeout settings of approximately 150 ms, 600 ms, and 1.2 seconds.
OPERATION - POWER MONITOR
The DS1232 detects out-of-tolerance power supply conditions and warns a processor-based system of
impending power failure. When VCC falls below a preset level as defined by TOL (Pin 3), the VCC
comparator outputs the signals RST (Pin 5) and RST (Pin 6). When TOL is connected to ground, the RST
and RST signals become active as VCC falls below 4.75 volts. When TOL is connected to VCC, the RST
and RST signals become active as VCC falls below 4.5 volts. The RST and RST are excellent control
signals for a microprocessor, as processing is stopped at the last possible moments of valid VCC. On
power-up, RST and RST are kept active for a minimum of 250 ms to allow the power supply and
processor to stabilize.
OPERATION - PUSHBUTTON RESET
The DS1232 provides an input pin for direct connection to a pushbutton (Figure 2). The pushbutton reset
input requires an active low signal. Internally, this input is debounced and timed such that RST and RST
signals of at least 250 ms minimum are generated. The 250 ms delay starts as the pushbutton reset input is
released from low level.
OPERATION - WATCHDOG TIMER
A watchdog timer function forces RST and RST signals to the active state when the ST input is not
stimulated for a predetermined time period. The time period is set by the TD input to be typically 150 ms
with TD connected to ground, 600 ms with TD left unconnected, and 1.2 seconds with TD connected to
VCC. The watchdog timer starts timing out from the set time period as soon as RST and RST are inactive.
If a high-to-low transition occurs on the ST input pin prior to timeout, the watchdog timer is reset and
begins to timeout again. If the watchdog timer is allowed to timeout, then the RST and RST signals are
driven to the active state for 250 ms minimum. The ST input can be derived from microprocessor
address signals, data signals, and/or control signals. When the microprocessor is functioning normally,
these signals would, as a matter of routine, cause the watchdog to be reset prior to timeout. To guarantee
that the watchdog timer does not timeout, a high-to-low transition must occur at or less than the minimum
shown in Table 1. A typical circuit example is shown in Figure 3.
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Dallas DS1232
MICROMONITOR BLOCK DIAGRAM Figure 1
DS1232/DS1232S
PUSHBUTTON RESET Figure 2
WATCHDOG TIMER Figure 3
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