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DS1831/A/B Multisupply Micromonitor
www.maxim-ic.com
FEATURES
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 IN5V 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 (DS1831A) Precision temperature-compensated voltage reference and voltage sensor 16 pin DIP and 16 pin 150mil SO available Operating Temperature of -40C to +85C
DS1831A IN5V RST5V TOL5V TD5V PBRST5V IN1 ST GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 IN3.3V RST3.3V TOL3.3V TD3.3V PBRST3.3V NMI1 WDS TDWD
PIN ASSIGNMENT
DS1831 IN5V RST5V TOL5V TD5V PBRST5V IN1 IN2 GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 IN3.3V RST3.3V TOL3.3V TD3.3V PBRST3.3V NMI1 NMI2 MPBRST
16-Pin (300mil) DIP & 16-Pin (150mil) SO
DS1831B IN5V RST5V TOL5V TD5V PBRST5V IN1 IN2 GND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 IN3.3V RST3.3V TOL3.3V TD3.3V PBST NMI1 NMI2 MPBRST
16-Pin (300mil) DIP & 16-Pin (150mil) SO
16-Pin (300mil) DIP & 16-Pin (150mil) SO
DESCRIPTION
The DS1831 multisupply monitor and reset monitors up to four system voltages: 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 5V input. One of these inputs must be greater than 1V for device operation. Pushbutton (manual reset) functionality is provided for the 5V reset, the
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DS1831/A/B
3.3V reset or for all reset outputs by the master pushbutton. The DS1831A replaces one reference comparator and the master pushbutton with watchdog and the DS1831B 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
IN5V RST 5V TOL5V TD5V PBRST 5V IN1 IN2 ST GND 5V Power Supply Input 5V Reset Open Drain Output Selects 5V Input Tolerance Selects 5V Reset Time Delay 5V Reset Pushbutton Sense Input 1 Sense Input 2 (DS1831) Watchdog Strobe Inputs (DS1831A) Ground MPBRST TDWD NMI2 WDS NMI1 PBRST 3.3V PBST TD3.3V TOL3.3V RST 3.3V IN3.3V Master Pushbutton (DS1831) Watchdog Time Delay Select (DS1831A) Non-maskable Interrupt 2 (DS1831) Watchdog Status Output (DS1831A) Non-maskable Interrupt 1 3.3V Reset Pushbutton Pushbutton Status Output (DS1831B) Select 3.3V Reset Time Delay Selects 3.3V Input Tolerance 3.3V Reset Open Drain Output 3.3V Power Supply Input
DS1831 BLOCK DIAGRAM Figure 1
IN5V 100k PBRST5V TD5V TOL5V
TOLERANCE BIAS
VCC
+ TIME DELAY
RST5V
1.25V T.C.
REFERENCE
MPBRST IN3.3V 100k PBRST3.3V TD3.3V TOL3.3V
100k
Level Sense &
TOLERANCE BIAS
VCC
+ -
TIME DELAY
RST3.3V
-
NMI1
IN1
+ NMI2
IN2 GROUND
+
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DS1831/A/B
OPERATION--POWER MONITOR
The DS1831 provides the functions of detecting out-of-tolerance conditions on a 3.3V (or 3V) and 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 IN5V 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 5V supply is tied to the 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 DS1831A watchdog. TD inputs select time delays for the IN5V and IN3.3V resets outputs and the Watchdog on the DS1831A. 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 push-button 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 VCC MIN 10ms 100ms 1000ms RESET TIME-DELAY TYP 16ms 160ms 1600ms MAX 20ms 200ms 2000ms
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DS1831/A/B
PUSHBUTTON RESET SEQUENCING Figure 2
5V Supply 3.3V Supply
IN5V RST5V TOL5V
1 2 3
16 DS1831 15 14 13 12
IN3.3V RST3.3V TOL3.3V TD3.3V PBRST3.3V
TD5V PBRST5V GND
4 5
NOTE: The RST 5V output is connected to the IN3.3V via a 100 kW resistor in the push-button input and therefore does not require a pull-up resistor (an addition pull up can be used to accelerate responses). If an external pull up is used in this example it must be connected to the 3.3V power supply.
OPERATION--PUSHBUTTON RESET
The DS1831 provides three pushbutton inputs for manual reset of the device. Pushbutton inputs for the 3.3V reset, 5V reset, and a master pushbutton reset (DS1831 and DS1831B only) input; provide multiple options for system control. The 3.3V pushbutton reset and 5V pushbutton resets provide a simple manual reset for the associated reset output; while the master pushbutton reset forces all resets and NMI outputs active low. The 5V reset pushbutton input and the 3.3V reset pushbutton input provide manual reset control input for each associated reset output. When the output associated with a pushbutton input is not active, a pushbutton reset can be generated by pulling the associated PBRST pin low for at least 20s. When the pushbutton is held low the reset will be forced active and will remain active for a reset cycle after the pushbutton is released. See Figure 2 for an application example that allows a user to sequence the reset outputs. A master pushbutton reset cycle can be started if at least one voltage input (IN5V, IN3.3V, IN1, or IN2) is in tolerance and at least one output is active. A master pushbutton reset is generated by pulling the MPBRST pin low for at least 20s. When the pushbutton is held low all outputs are forced active and will remain active for a reset or NMI time delay after the pushbutton is released. The Master Pushbutton input is pulled high through an internal 100kW pull up resistor and debounced via internal circuitry. See Figure 3 for an application example. Figures 4 and 5 for the timing diagram. The 5V and 3.3V pushbutton reset inputs are pulled high through an internal 100kW pull up resistor to the voltage input, which is associated with that pushbutton. The master pushbutton is pulled to the greater of the IN5V and IN3.3V inputs.
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DS1831/A/B
PUSHBUTTON RESET Figure 3
5V Supply
IN5V 10 kW RST5V TOL5V
1 2 3
16 DS1831 15 14 13 12
TD5V PBRST5V GND
4 5
TIMING DIAGRAM--MASTER PUSHBUTTON RESET Figure 4
MPBRST tPDLY VIL tRST RST5V and RST3.3V VOH tPB VIH
NMI1 and NMI2
tNMI VOH
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DS1831/A/B
TIMING DIAGRAM--5V OR 3.3V PUSHBUTTON RESET Figure 5
tPB PBRST5V (or PBRST3.3V) tPDLY VIL tRST RST5V (or RST3.3V) VOH VIL VIH
OPERATION--PUSHBUTTON STATUS
The DS1831B provides a master pushbutton status open drain output. The PBST output indicates the status of the most recent reset condition. If the last reset was generated by the master pushbutton input it would maintain a low condition until cleared by another event (except the master pushbutton) generating a reset. Once cleared it will remain high until the master pushbutton is pulled low generating a reset condition. The PBST output is open drain and will require a pull-up resistor on the output to maintain a valid condition. The value of the pull up resistor is not critical in most cases but must be set low enough to pull the output to a high state. A common value used is 10kW (see Figure 6).
DS1831B APPLICATION EXAMPLE Figure 6
5V Supply 3.3V Supply IN3.3V RST3.3V TOL3.3V TD3.3V PBST NMI1 NMI2 MPBRST VCC 10 kW VCC 10kW
IN5V RST5V VSENSE2 VSENSE1 TOL5V TD5V PBRST5V IN1 IN2 GND
1 2 3 4 5 6 7 8
16 15 14 13 12 11 10 9
DS1831B
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DS1831/A/B
OUTPUT VALID CONDITIONS
The DS1831 can maintain valid outputs as long as one input remains above 1.0V. Accurate voltage monitoring additionally requires that either the 3.3V IN or 5V IN input be above 1.5V. If this condition is not met and at least one of the supply inputs are at or above 1.0V all outputs are maintained in the active condition. The DS1831 requires pull-up resistors on the outputs to maintain a valid output. The value of the pull up resistor is not critical in most cases but must be set low enough to pull the output to a high state. A common pull-up resistor value used is 10kW (see Figure 7).
APPLICATION DIAGRAM--OPEN DRAIN OUTPUTS Figure 7
5V Supply 3.3V Supply
IN5V
10 KW
1 2 3 4 5
16 DS1831 15 14 13 12
IN3.3v
10 kW
RST5V TOL5V TD5V PBRST5V GND
RST3.3V TOL3.3V TD3.3V PBRST3.3V
NOTE: If outputs are at different voltages the outputs can not be connected to form a wired AND.
OPERATION--NON-MASKABLE INTERRUPT
The DS1831 has two referenced comparator (DS1831A has only one referenced comparator) that can be used to monitor upstream voltages or other system specific voltages. Each comparator is referenced to the 1.25V internal band gap reference and controls an open-drain output. When a voltage being monitored decays to the voltage sense point, the DS1831 pulses the NMI output to the active state for a minimum 10s. The comparator detection circuitry also has built-in hysteresis of 100V. The supply must be below the voltage sense point for approximately 2s before a low NMI will be generated. In this way, power supply noise is minimized in the monitoring function, reducing false interrupts. See Figure 8 for the nonmaskable timing diagram. Versatile trip voltages can be configured by the use of an external resistor divider to divide the voltage at a sense point to the 1.25V trip levels of the referenced comparators. See Figure 9 for an example circuit diagram and sample equations. The equations demonstrate a design process to determine the resistor values to use. Connecting one or both NMI outputs to one of the reset specific PBRST s allows the non-maskable interrupt to generate an automatic reset for the reset time period when an out-of-tolerance condition occurs in a monitored supply. An example is shown in Figure 9.
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DS1831/A/B
The output associated with the specific input will be held low if the voltage on the input pin is less than 1.25V. If the voltage is above 1.25V the output will not sink current and will be pulled up by the required pull up resistor. The value of the resistors is not critical in most cases but must be set low enough to pull the output to a high state. A common value used is 10kW. If a NMI output is connected to a pushbutton input an additional pull-up resistor can be used (to improve speed of transitions) but is not required. During a power-up, any detected IN pin levels above VTP by the comparator are disabled from generating an inactive (high) interrupt until at least 1 supply on the VIN inputs rises above 1.5 volts. All NMI outputs will be held active (low) until at least one VIN reaches 1.5 volts at which point the NMI outputs will be based on the value of the associated IN input.
TIMING DIAGRAM--NON-MASKABLE INTERRUPT Figure 8
VIN >1.25V VTP(max) VTP VTP(min) VTP(min) VTP VTP(max)
tNMI NMI tIPD VOH
VOL
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DS1831/A/B
NON-MASKABLE INTERRUPT CIRCUIT EXAMPLE Figure 9
VSENSE2 VSENSE1 VCC
R1 PBRST5V R2 IN1 DS1831 IN2 R4 GND
PBRST3.3V
R3
NMI1
10 KW
NMI2
MPBRST
Example: Therefore:
VSENSE1 = 11.50V trip point VSENSE1 = 11.50V =
R1 + 100 k W 100 kW
R1 + R2 R2
X 1.25V
X 1.25V
Resulting In: R1 = 820kW Repeat the same steps to solve for R3 and R4 with VSENSE2.
OPERATION - WATCHDOG TIMER
The watchdog timer function (DS1831A only) forces the WDS signal active (low) when the ST input does not have a transition (high-to-low or low-to-high) within the predetermined time period. The timeout period is determined by the condition of the TDWD pin (see Table 1). If TDWD is connected to ground the minimum watchdog time-out would be 10ms, TD floating would yield a minimum time-out of 100ms, and TDWD connected to VCC would provide a time-out of 1000ms minimum. Time-out of the watchdog starts when at least one of the RST outputs becomes inactive (high). If a transition occurs on the ST input pin prior to time-out, the watchdog timer is reset and begins to time-out again. If the watchdog timer is allowed to time-out, then the WDS output is pulsed active for a minimum of 100s. The WDS output is an open-drain output and must be pulled up externally. In most applications this output would be connected to one of the Pushbutton inputs and would not require an external pull-up resistor. The value of the resistors is not critical in most cases but must be set low enough to pull the output to a high state. A common value used is 10kW. If a WDS output is connected to a pushbutton input an additional pull-up resistor can be used (to improve speed of transitions) but is not required.
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DS1831/A/B
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 time-out. To guarantee that the watchdog timer does not time-out, a transition must occur at or less than the minimum times shown in Table 1. A typical circuit example is shown in Figure 10. The watchdog timing is shown in Figure 11. The DS1831A watchdog function cannot be disabled. The watchdog strobe input must be strobed to avoid a watchdog time-out however the watchdog status output can be disconnected yielding the same result.
WATCHDOG CIRCUIT EXAMPLE Figure 10
VSENSE1 VCC
R1
PBRST5V IN1 DS1831 ST GND
PBRST3.3V NMI1 10kW WDS TDWD
P
R2
TIMING DIAGRAM -- STROBE INPUT Figure 11
INVALID EDGES ST tST WDS tTD VALID EDGES MIN MAX INDETERMINATE EDGES
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DS1831/A/B
RESET TIMING DIAGRAM--POWER UP Figure 12
tR VINTP (MAX) VINTP (MIN) VINTP
IN5V (or IN3.3V) tRPU
VOH
RST5V (or RST3.3V)
RESET TIMING DIAGRAM -- POWER DOWN Figure 13
IN5V (or IN3.3V) VINTP (MAX) tF VINTP
VINTP (MIN)
RST5V (or RST3.3V)
tRPD
VOL
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DS1831/A/B
ABSOLUTE MAXIMUM RATINGS*
Voltage on IN5V or IN3.3V Pins Relative to Ground Voltage on either RST Relative to Ground Voltage on PBRST 3.3V Relative to Ground Voltage on PBRST 5V Relative to Ground Voltage on MPBRST, IN1, IN2 Relative to Ground Operating Temperature Range Storage Temperature Range Soldering Temperature * -0.5V to +6.0V -0.5V to the greater of IN5V + 0.5V or IN3.3V + 0.5V -0.5V to IN3.3V + 0.5V -0.5V to IN5V + 0.5V -0.5V to the greater of IN5V + 0.5V or IN3.3V + 0.5V -40C to +85C -55C to +125C See IPC/JEDEC J-STD-020A specification
This 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
PARAMETER SYMBOL MIN IN5V (Supply Voltage) V IN 1.0 IN3.3V (Supply Voltage) V IN 1.0 PBRST 3.3V, PBRST 5V, MPBRST , ST VIH 0.7 x VINT input High Level PBRST 3.3V, PBRST 5V, MPBRST , ST -0.3 VIL input Low Level * VINT is the greater voltage level of the IN5V or IN3.3V. MAX 5.5 5.5 VINT + 0.3 0.3 x VINT
(-40C to 85C)
UNITS V V V V NOTES 1 1 1* 1*
DC ELECTRICAL CHARACTERISTICS (-40C to 85C; IN3.3V, IN5V = 1.0V to 5.5V)
PARAMETER Input Leakage Output Current @ 2.4V Output Current @ 0.4V Operating Current @ U5.5V Operating Current @ U3.6V IN5V Trip Point (TOL5V = IN5V) IN5V Trip Point (TOL5V = GND) IN5V Trip Point (TOL5V = Float) IN3.3V Trip Point (TOL3.3V = IN3.3V) IN3.3V Trip Point (TOL3.3V = GND) IN3.3V Trip Point (TOL3.3V = Float) IN Input Trip Points SYMBOL IIL IOH IOL ICC ICC VINTP VINTP VINTP VINTP VINTP VINTP VTP MIN -1.0 +10 80 60 4.63 4.38 4.15 3.06 2.88 2.55 1.25 100 85 4.75 4.49 4.24 3.15 2.97 2.64 1.30 TYP MAX +1.0 UNITS A mA A A V V V V V V V NOTES 2 3 4 5 6
4.50 4.25 4.00 2.98 2.80 2.47 1.15
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DS1831/A/B
CAPACITANCE
PARAMETER Input Capacitance Input Capacitance SYMBOL CIN COUT MAX 5 7 UNITS pF pF
(tA = +25C)
NOTES
AC ELECTRICAL CHARACTERISTICS (-40C to 85C; IN3.3V, IN5V = 1.0V to 5.5V)
PARAMETER RESET Active Time (TD=Low) RESET Active Time (TD=Float) RESET Active Time (TD=High) VCC Detect to RST VCC Detect to RST VIN Detect to NMI NMI Active Time PBRST = VIL PBRST Stable Low to Reset Active Watchdog Timeout (TD(WD)=Low) Watchdog Timeout (TDWD=Float) Watchdog Timeout (TDWD=High) ST Pulse Width Vin Slew Rate (V INTP(MAX) to V INTP(MIN)) Vin Slew Rate (V INTP(MAX) to V INTP(MIN)) SYMBOL tRST tRST tRST tRPU tRPD tIPD tNMI tPB tPDLY tTD tTD tTD tST tF tR 10 100 1000 10 300 0 16 160 1600 MIN TYP MAX 10 16 20 100 160 200 1000 1600 2000 See RESET Active Time 2 10 2 10 20 20 50 20 200 2000 UNITS ms ms ms ms ms ms ms ms ms ms ms ms ns ms ns NOTES 5 5 5 5 6 6
NOTES:
1) All voltages are referenced to ground. 2) All Pushbutton inputs are internally pulled to the associated Supply IN input or the greatest Supply IN input for the MPBRST with an internal Impedance of 100kW. 3) Measured with outputs open and IN3.3V or IN5V 5.5V 4) Measured with outputs open and IN3.3V or IN5V 3.6V. 5) Measured using tR = 5s 6) Noise immunity - pulses <2s at a trip level will not cause a RST or NMI .
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DS1831/A/B
ORDERING INFORMATION
Ordering Part Package Type Description Number DS1831 16-Pin DIP 300mil 5V/3.3V Multisupply Monitor DS1831S 16-Pin SO 150mil 5V/3.3V Multisupply Monitor DS1831A 16-Pin DIP 300mil 5V/3.3V Multisupply Monitor w/Watchdog DS1831AS 16-Pin SO 150mil 5V/3.3V Multisupply Monitor w/Watchdog DS1831B 16-Pin DIP 300mil 5V/3.3V Multisupply Monitor w/Pushbutton Status DS1831BS 16-Pin SO 150mil 5V/3.3V Multisupply Monitor w/Pushbutton Status * Add "/T&R" for tape and reeling of surface mount packages.
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