DS1832 Maxim Integrated Products, DS1832 Datasheet - Page 2

• Manufacturer Part Number: DS1832
• Description: IC MICROMONITOR 3.3V 8-DIP
• Manufacturer: Maxim Integrated Products
• Series: MicroMonitor™r
• Type: Simple Reset/Power-On Resetr

Specifications of DS1832

• Number Of Voltages Monitored: 1
• Output: Push-Pull, Push-Pull
• Reset: Active High/Active Low
• Reset Timeout: 250 ms Minimum
• Voltage - Threshold: 2.55V, 2.88V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Through Hole
• Package / Case: 8-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

DS1832
The second function the DS1832 performs is pushbutton reset control. The DS1832 debounces the
pushbutton input and guarantees an active reset pulse width of 250 ms minimum. The third function is a
watchdog timer. The DS1832 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, or 1.2 seconds.
OPERATION - POWER MONITOR
The DS1832 detects out-of-tolerance power supply conditions and warns a processor-based system of
impending power failure. When V
falls below a preset level as defined by TOL, the V
comparator
CC
CC
outputs the signals RST and
. When TOL is connected to ground, the RST and
signals become
RST
RST
active as V
falls below 2.98 volts. When TOL is connected to V
, the RST and
signals become
RST
CC
CC
active as V
falls below 2.64 volts. The RST and
are excellent control signals for a microprocessor,
RST
CC
as processing is stopped at the last possible moments of valid V
. On power-up, RST and
are kept
RST
CC
active for a minimum of 250 ms to allow the power supply and processor to stabilize.
OPERATION - PUSHBUTTON RESET
The DS1832 provides an input pin for direct connection to a pushbutton reset (see Figure 2). The
pushbutton reset input requires an active low signal. Internally, this input is debounced and timed such
that RST and
signals of at least 250 ms minimum are generated. The 250 ms delay commences as
RST
the pushbutton reset input is released from the low level.
OPERATION - WATCHDOG TIMER
The watchdog timer function forces RST and
signals active when the
input is not clocked within
RST
ST
the predetermined time period. The timeout period is determined by the condition of the TD pin. If TD is
connected to ground the minimum watchdog timeout would be 62.5 ms, TD floating would yield a
minimum timeout of 250 ms, and TD connected to V
would provide a timeout of 500 ms minimum.
CC
Timeout of the watchdog starts when RST and
become inactive. If a high-to-low transition occurs
RST
on the
input pin prior to timeout, the watchdog timer is reset and begins to timeout again. If the
ST
watchdog timer is allowed to timeout, then the RST and
signals are driven active for a minimum of
RST
250 ms. The
input can be derived from many microprocessor outputs. The most typical signals used
ST
are the microprocessor address signals, data signals or control signals. When the microprocessor
functions 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 times shown in Table 1. A typical circuit example is shown in Figure 4.
The DS1832 watchdog function cannot be disabled. The watchdog strobe input must be strobed to avoid
a watchdog timeout and reset.
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