Document
DS1831C/D/E
3.3V/2.5V Multisupply MicroMonitor
www.maxim-ic.com
FEATURES
§ 2.5V power-on reset § 3.3V power-on reset § Two referenced comparators with separate
outputs for monitoring additional supplies
§ Internal power is drawn from higher of either the IN2.5V input or the IN3.3V input
§ Excellent for systems designed to operate with multiple power supplies
§ Asserts resets during power transients § Pushbutton reset input for system override § Maintains reset for user configurable times
of 10ms, 100ms, or 1s
§ Watchdog timer for software monitoring (DS1831D)
§ Precision temperature-compensated voltage reference and voltage sensor
§ 16-pin DIP and 16-pin 150mil SO available § Operating Temperature of -40°C to +85°C
DS1831D
PIN ASSIGNMENT
DS1831C
IN2.5V RST2.5V TOL2.5V TD2.5V PBRST2.5V
IN1
1 2 3 4 5 6
16 IN3.3V 15 RST3.3V 14 TOL3.3V 13 TD3.3V 12 PBRST3.3V 11 NMI1
IN2 7
10 NMI2
GND 8
9 MPBRST
16-Pin (300mil) DIP &
16-Pin (150mil) SO
DS1831E
IN2.5V RST2.5V TOL2.5V TD2.5V PBRST2.5V
IN1
1 2 3 4 5 6
16 IN3.3V 15 RST3.3V 14 TOL3.3V 13 TD3.3V 12 PBRST3.3V 11 NMI1
IN2.5V RST2.5V TOL2.5V TD2.5V PBRST2.5V
IN1
1 2 3 4 5 6
16 IN3.3V 15 RST3.3V 14 TOL3.3V 13 TD3.3V 12 PBST 11 NMI1
ST 7
10 WDS
IN2 7
10 NMI2
GND 8
9 TDWD
16-Pin (300mil) DIP &
16-Pin (150mil) SO
GND 8
9 MPBRST
16-Pin (300mil) DIP &
16-Pin (150mil) SO
DESCRIPTION
The DS1831C multisupply monitor and reset monitors up to four system voltages: 2.5V supply, 3.3V (or 3V) supply, and two additional user configurable voltage monitors. DS1831 power for internal operation comes from the higher voltage level of the 3.3V input or the 2.5V input. One of these inputs must be greater than 1V for device operation. Pushbutton (manual reset) functionality is provided for the 2.5V
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060303
DS1831C/D/E
reset, the 3.3V reset or for all reset outputs by the master pushbutton. The DS1831D replaces one reference comparator and the master pushbutton with watchdog and the DS1831E replaces the 3.3V
PBRST with a last reset status output.
TOL and TD inputs allow user configuration of the DS1831 for multiple applications. The TOL inputs configure the tolerance for the specified output and the TD inputs configure the reset time delays.
PIN DESCRIPTION
IN2.5V
2.5V Power Supply Input
RST 2.5V
TOL2.5V
TD2.5V
PBRST 2.5V
IN1 IN2 ST GND
2.5V Reset Open Drain Output
Selects 2.5V Input Tolerance
Selects 2.5V Reset Time Delay
2.5V Reset Pushbutton
Sense Input 1
Sense Input 2 (DS1831C/E) Watchdog Strobe Inputs (DS1831D) Ground
MPBRST TDWD
NMI2 WDS NMI1
PBRST 3.3V PBST
TD3.3V TOL3.3V
RST 3.3V
IN3.3V
Master Pushbutton (DS1831C/E) Watchdog Time Delay Select (DS1831D) Non-maskable Interrupt 2 (DS1831C/E) Watchdog Status Output (DS1831D)
Non-maskable Interrupt 1
3.3V Reset Pushbutton (DS1831C/E) Pushbutton Status Output (DS1831E) Select 3.3V Reset Time Delay Selects 3.3V Input Tolerance 3.3V Reset Open Drain Output
3.3V Power Supply Input
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BLOCK DIAGRAM Figure 1
IN2.5V 100 kW
PBRST2.5V TD2.5V
TOL2.5V
VCC TOLERANCE
BIAS
+
MPBRST IN3.3V
PBRST3.3V TD3.3V
TOL3.3V
1.25V T.C. REFERENCE
100 kW
100 kW
-
Level Sense &
Debounce
VCC TOLERANCE
BIAS
+
-
IN1 +
-
IN2 GROUND
+
TIME DELAY
TIME DELAY
DS1831C/D/E
RST2.5V
RST3 3V NMI1 NMI2
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DS1831C/D/E
OPERATION—POWER MONITOR
The DS1831 provides the functions of detecting out-of-tolerance conditions on a 3.3V (or 3V) and 2.5V power supply and warning a processor based system of impending power failure. When an input is detected as out-of-tolerance on either voltage input the RST for that supply will be forced active low. When that input returns to a valid state the associated RST will remain active for the time delay selected with the associated TD input and then return to an inactive state until the next input out-of-tolerance condition.
On power-up both resets are kept active for the selected reset time after the associated power supply input has reached the selected tolerance. This allows the power supply and system power to stabilize before
RST is released.
All internal operating current for the DS1831 will be supplied by either the IN3.3V or IN2.5V input which ever has the highest voltage level.
OPERATION—TOLERANCE SELECT
The DS1831 provides two TOL inputs for individual customization of the DS1831 to specific application requirements. If the TOL for the 2.5V supply is tied to the 2.5V input a 5% tolerance is selected. If the TOL is connected to ground a 10% tolerance is selected or if it is left unconnected a 15% tolerance is selected. If the TOL for the 3.3V supply is tied to the 3.3V input a 5% tolerance is selected, a 10% tolerance is selected if it is connected to ground, and a 20% tolerance is selected if the input is left unconnected. These tolerance conditions are set at power up and can only be changed by power cycling the device.
OPERATION—RESET TIME-DELAY SELECT
The DS1831 provides two TD inputs for individual customization of reset time delays and an additio.