DS1832S+ ,3.3 Volt MicroMonitor ChipFEATURES PIN ASSIGNMENT Halts and restarts an out-of-controlVCCPBRST 1 8microprocessor2TD 7 ST Ho ..
DS1832S+T&R ,3.3 Volt MicroMonitor ChipFEATURES PIN ASSIGNMENT Halts and restarts an out-of-controlVCCPBRST 1 8microprocessor2TD 7 ST Ho ..
DS1833 ,5V EconoResetPIN DESCRIPTIONPIN 1 GroundPIN 2 ResetPIN 3 VCCPIN 4 Ground (SOT-223 only)DESCRIPTIONThe DS1833 Eco ..
DS1833-10 ,5V EconoResetPIN DESCRIPTIONPIN 1 GROUNDPIN 2 RESETPIN 3 VCCPIN 4 GROUND (SOT-223 ONLY)DESCRIPTIONThe DS1233D Ec ..
DS1833-10+ ,5V EconoResetDS18335V EconoReset
DS1833-15 ,5V EconoResetPIN DESCRIPTIONPIN 1 GroundPIN 2 ResetPIN 3 VCCPIN 4 Ground (SOT-223 only)DESCRIPTIONThe DS1833 Eco ..
DZ23C10 ,Zener DiodesDZ23C2V7–DZ23C51Vishay Telefunken300 mW Dual Surface Mount Zener Diodes
DZ23C15-7-F , 300mW DUAL SURFACE MOUNT ZENER DIODE
DZ23C16-7-F , 300mW DUAL SURFACE MOUNT ZENER DIODE
DZ23C18 ,Zener DiodesAbsolute Maximum RatingsT = 25
DS1832S-DS1832S+-DS1832S+T&R
3.3 Volt MicroMonitor Chip
FEATURESHalts and restarts an out-of-control
microprocessorHolds microprocessor in check during powertransientsAutomatically restarts microprocessor after
power failureMonitors pushbutton for external overrideAccurate 10% or 20% microprocessor powermonitoringEliminates need for discrete components20% tolerance for use with 3.0-volt systemsPin-compatible with the DS1232Low cost 8-pin DIP, 8-pin SOIC, and space
saving μ-SOP packages availableIndustrial temperature range of -40°C to
+85°C
PIN ASSIGNMENT
PIN DESCRIPTIONPBRST - Pushbutton Reset Input
TD - Time Delay Set
TOL - Selects 10% or 20% VCC Detect
GND - Ground
RST - Active High Reset Output
RST - Active Low Reset Output - Strobe InputVCC - Power Supply
DESCRIPTIONThe DS1832 3.3-Volt MicroMonitor monitors three vital conditions for a microprocessor: power supply,
software execution, and external override. First, a precision temperature-compensated reference and
comparator circuit monitor the status of VCC. When an out-of-tolerance condition occurs, an internal
power-fail signal is generated which forces the resets to an active state. When VCC returns to anin-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.
DS1832
3.3-Volt MicroMonitor ChipDS1832 8-Pin DIP (300-mil)
See Mech. Drawings Section
PBRST
TOL
GND
VCC
RST
RST
PBRST
TOL
GND
VCC
RST
RST
DS1832μ 8-Pin μ-SOP (118-mil)
See Mech. Drawings Section
PBRST
TOL
GND
VCC
RST
RST
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 ontimeout settings of approximately 150 ms, 600 ms, or 1.2 seconds.
OPERATION - POWER MONITORThe DS1832 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, the VCC comparator
outputs the signals RST and RST. When TOL is connected to ground, the RST and RST signals become
active as VCC falls below 2.98 volts. When TOL is connected to VCC, the RST and RST signals become
active as VCC falls below 2.64 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 RESETThe 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 RST signals of at least 250 ms minimum are generated. The 250 ms delay commences as
the pushbutton reset input is released from the low level.
OPERATION - WATCHDOG TIMERThe watchdog timer function forces RST and RST signals active when the ST input is not clocked within
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 aminimum timeout of 250 ms, and TD connected to VCC would provide a timeout of 500 ms minimum.
Timeout of the watchdog starts when RST and RST become 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 active for a minimum of
250 ms. The ST input can be derived from many microprocessor outputs. The most typical signals used
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.
DS1832
MICROMONITOR BLOCK DIAGRAM Figure 1
PUSHBUTTON RESET Figure 2
TIMING DIAGRAM: PUSHBUTTON RESET Figure 3
DS1832
WATCHDOG TIMER Figure 4
WATCHDOG TIMEOUTS Table 1
TIMING DIAGRAM: STROBE INPUT Figure 5
TIMING DIAGRAM: POWER DOWN Figure 6
DS1832
TIMING DIAGRAM: POWER-UP Figure 7
RSTVALID TO 0 VOLTS VCC Figure 8
OUTPUT VALID CONDITIONSThe RST output uses a push-pull output which can maintain a valid output down to 0.8 volts VCC. To sink
current below 0.8 volts a resistor can be connected from RST to Ground (see Figure 8). This arrangement
will maintain a valid value on RST during both power-up and power-down but will draw current when
RST is in the high state. A value of about 100 kΩ=should be adequate in most situations. The output with
a resistor pull-down can maintain a valid reset down to VCC equal to 0 volts.
DS1832
ABSOLUTE MAXIMUM RATINGS*Voltage on any Pin Relative to Ground -0.5V to +7.0V
Voltage on I/O Relative to Ground -0.5V to VCC +0.5V
Operating Temperature -40°C to +85°C
Storage Temperature -55°C to +125°C
Soldering Temperature 260°C for 10 secondsThis is a stress rating only and functional operation of the device at these or any other conditions
above those indicated in the operation sections of this specification is not implied. Exposure to
absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS (-40°C to +85°C)
DC ELECTRICAL CHARACTERISTICS (-40°C to +85°C; VCC=1.2V to 5.5V)
CAPACITANCE (tA=25°C)
