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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 IN
2.5V
input or the IN
3.3V
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
IN
2.5V
RST
2.5V
TOL
2.5V
TD
2.5V
PBRST
2.5V
IN1
ST
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
IN
3.3V
RST
3.3V
TOL
3.3V
TD
3.3V
PBRST
3.3V
NMI1
WDS
TD
WD
PIN ASSIGNMENT
DS1831C
IN
2.5V
RST
2.5V
TOL
2.5V
TD
2.5V
PBRST
2.5V
IN1
IN2
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
IN
3.3V
RST
3.3V
TOL
3.3V
TD
3.3V
PBRST
3.3V
NMI1
NMI2
MPBRST
16-Pin (300mil) DIP
&
16-Pin (150mil) SO
DS1831E
IN
2.5V
RST
2.5V
TOL
2.5V
TD
2.5V
PBRST
2.5V
IN1
IN2
GND
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
IN
3.3V
RST
3.3V
TOL
3.3V
TD
3.3V
PBST
NMI1
NMI2
MPBRST
16-Pin (300mil) DIP
&
16-Pin (150mil) SO
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
1 of 15
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
IN
2.5V
2.5V Power Supply Input
MPBRST
TD
WD
NMI2
WDS
NMI1
PBRST
3.3V
PBST
RST
2.5V
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
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
TOL
2.5V
TD
2.5V
PBRST
2.5V
TD
3.3V
TOL
3.3V
RST
3.3V
IN1
IN2
ST
GND
IN
3.3V
2 of 15
DS1831C/D/E
BLOCK DIAGRAM
Figure 1
IN
2.5V
100 kW
PBRST
2.5V
TD
2.5V
TOL
2.5V
TOLERANCE
BIAS
V
CC
+
TIME
DELAY
-
RST
2.5V
1.25V T.C.
REFERENC
E
MPBRST
IN
3.3V
100 kW
PBRST
3.3V
TD
3.3V
TOL
3.3V
100 kW
Level Sense
&
Debounce
TOLERANCE
BIAS
V
CC
+
TIME
DELAY
RST
3 3V
-
-
NMI1
IN1
+
-
NMI2
IN2
GROUND
+
3 of 15
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 IN
3.3V
or IN
2.5V
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 additional
one for the DS1831D watchdog. TD inputs select time delays for the IN
2.5V
and IN
3.3V
resets outputs and
the Watchdog on the DS1831D. The reset time delays are shown in Table 1. These allow the selection of
minimum delays of 10ms, 100ms, and 1000ms.
Wiring an individual reset output to the pushbutton input of the other voltage reset allows custom reset
timings or allows for the sequencing of the reset outputs. See Figure 2.
These time delays are set at power-up and cannot be changed after the device reaches an in-tolerance
condition.
TD INPUTS/RESET AND WATCHDOG TIME-DELAYS
Table 1
TD
GND
Float
V
CC
MIN
10ms
100ms
1000ms
RESET TIME-DELAY
TYP
16ms
160ms
1600ms
MAX
20ms
200ms
2000ms
4 of 15