3 V, Voltage Monitoring
Microprocessor Supervisory Circuits
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
FUNCTIONAL BLOCK DIAGRAMS
Precision supply voltage monitor
2.63 V (ADM706P, ADM706R, ADM708R)
2.93 V (ADM706S, ADM708S)
3.08 V (ADM706T, ADM708T)
100 µA quiescent current
200 ms reset pulse width
Debounced manual reset input (MR)
Independent watchdog timer
1.6 sec timeout (ADM706P, ADM706R, ADM706S,
ADM706T)
Reset output
Active high (ADM706P)
Active low (ADM706R, ADM706S, ADM706T)
Both active high and active low (ADM708R, ADM708S,
ADM708T)
Voltage monitor for power fail or low battery warning
Guaranteed RESET valid with VCC = 1 V
Superior upgrade for MAX706P/R/S/T, MAX708R/S/T
WATCHDOG
INPUT (WDI)
WATCHDOG
TRANSITION
DETECTOR
VCC
70μA
MR
VREF*
1.25V
RESET,
(P = RESET)
POWER-FAIL
OUTPUT (PFO)
* VOLTAGE REFERENCE = 2.63V (P/R), 2.93V (S), 3.08V (T)
Figure 1. ADM706P/ADM706R/ADM706S/ADM706T
VCC
70μA
MR
POWER-FAIL
INPUT (PFI)
RESET
RESET
GENERATOR
VREF *
Microprocessor systems
Computers
Controllers
Intelligent instruments
Critical microprocessor monitoring
Battery operated systems
Portable instruments
ADM706P/ADM706R/
ADM706S/ADM706T
POWER-FAIL
INPUT (PFI)
WATCHDOG
OUTPUT (WDO)
RESET AND
WATCHDOG
TIMEBASE
RESET
GENERATOR
VCC
VCC
APPLICATIONS
WATCHDOG
TIMER
06435-001
FEATURES
ADM708R/ADM708S/
ADM708T
1.25V
RESET
POWER-FAIL
OUTPUT (PFO)
* VOLTAGE REFERENCE = 2.63V (R), 2.93V (S), 3.08V (T)
06435-002
Data Sheet
Figure 2. ADM708R/ADM708S/ADM708T
GENERAL DESCRIPTION
The ADM706P/ADM706R/ADM706S/ADM706T and the
ADM708R/ADM708S/ADM708T microprocessor supervisory
circuits are suitable for monitoring either 3 V or 3.3 V power
supplies.
The ADM706P/ADM706R/ADM706S/ADM706T provide
power supply monitoring circuitry that generate a reset output
during power-up, power-down, and brownout conditions. The
reset output remains operational with VCC as low as 1 V.
Independent watchdog monitoring circuitry is also provided. This
activates if the watchdog input does not toggle within 1.6 sec.
In addition, there is a 1.25 V threshold detector for a power fail
warning, low battery detection, or to monitor an additional
power supply. An active low debounced MR input is also
included.
Rev. E
The ADM706R, ADM706S, and ADM706T are identical except
for the reset threshold monitor levels, which are 2.63 V, 2.93 V, and
3.08 V, respectively. The ADM706P is identical to the ADM706R
in that the reset threshold is 2.63 V. It differs only in that it has
an active high reset output.
The ADM708R/ADM708S/ADM708T provide similar functionality as the ADM706R/ADM706S/ADM706T and only differ
in that a watchdog timer function is not available. Instead, an
active high reset output (RESET) is provided in addition to the
active low (RESET) output.
All devices are available in narrow 8-lead PDIP and 8-lead
SOIC packages.
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ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
Data Sheet
TABLE OF CONTENTS
Features .............................................................................................. 1
Manual Reset............................................................................... 10
Applications ....................................................................................... 1
Functional Block Diagrams ............................................................. 1
Watchdog Timer (ADM706P/ADM706R/
ADM706S/ADM706T) .............................................................. 10
General Description ......................................................................... 1
Power Fail Comparator.............................................................. 11
Revision History ............................................................................... 2
Adding Hysteresis to the Power Fail Comparator ................. 11
Specifications..................................................................................... 3
Valid RESET Below 1 V VCC ..................................................... 11
Absolute Maximum Ratings............................................................ 5
Applications Information .............................................................. 12
ESD Caution .................................................................................. 5
Monitoring Additional Supply Levels...................................... 12
Pin Configurations and Function Descriptions ........................... 6
Microprocessors with Bidirectional RESET ........................... 12
Typical Performance Characteristics ............................................. 8
Outline Dimensions ....................................................................... 13
Circuit Information ........................................................................ 10
Ordering Guide .......................................................................... 14
Power Fail Reset .......................................................................... 10
REVISION HISTORY
1/16—Rev. D to Rev. E
Changes to Table 3 ............................................................................ 6
Changes to Table 4 ............................................................................ 7
Changes to Power Fail Comparator Section, Figure 17,
and Figure 18 ................................................................................... 10
Changes to Figure 20 and Figure 22 ............................................. 12
Changes to Ordering Guide .......................................................... 14
10/14—Rev. C to Rev. D
Changes to Pin 4 Description; Table 3 ........................................... 6
Changes to Pin 4 Description; Table 4 ........................................... 7
Changes to Ordering Guide .......................................................... 14
5/08—Rev. B to Rev. C
Changes to Applications Section .....................................................1
Changes to Table 2.............................................................................5
Changes to Table 3.............................................................................6
Changes to Figure 8 ...........................................................................7
Changes to Figure 16.........................................................................9
2/07—Rev. A to Rev. B
Updated Format .................................................................. Universal
Changes to Table 1.............................................................................3
Updated Outline Dimensions ....................................................... 12
Changes to Ordering Guide .......................................................... 13
Rev. E | Page 2 of 16
Data Sheet
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
SPECIFICATIONS
VCC = 2.70 V to 5.5 V (ADM706P/ADM706R/ADM708R), VCC = 3.00 V to 5.5 V (ADM70xS), VCC = 3.15 V to 5.5 V (ADM70xT), TA =
TMIN to TMAX unless otherwise noted.
Table 1.
Parameter
POWER SUPPLY
VCC Operating Voltage Range
Supply Current
LOGIC OUTPUT
Reset Threshold (VRST)
Reset Threshold Hysteresis
RESET PULSE WIDTH
Min
Typ
Max
Unit
Test Conditions/Comments
100
150
5.5
200
350
V
μA
μA
VCC < 3.6 V
VCC < 5.5 V
2.70
3.00
3.15
V
V
V
mV
ms
ms
1.0
2.55
2.85
3.00
2.63
2.93
3.08
20
200
200
160
160
280
280
ms
ADM706P/ADM706R/ADM708R, VCC = 3 V
ADM706S/ADM708S/ADM706T/ADM708T,
VCC = 3.3 V
VCC = 5.0 V
V
V
V
V
V
VRST (max) < VCC < 3.6 V, ISOURCE = 500 μA
VRST (max) < VCC < 3.6 V, ISINK = 1.2 mA
4.5 V < VCC < 5.5 V, ISOURCE = 800 μA
4.5 V < VCC < 5.5 V, ISINK = 3.2 mA
VCC = 1 V, ISINK = 100 μA
V
V
V
V
VRST (max) < VCC < 3.6 V, ISOURCE = 215 μA
VRST (max) < VCC < 3.6 V, ISINK = 1.2 mA
4.5 V < VCC < 5.5 V, ISOURCE = 800 μA
4.5 V < VCC < 5.5 V, ISINK = 3.2 mA
0.4
V
V
V
V
VRST (max) < VCC < 3.6 V, ISOURCE = 500 μA
VRST (max) < VCC < 3.6 V, ISINK = 500 μA
4.5 V < VCC < 5.5 V, ISOURCE = 800 μA
4.5 V < VCC < 5.5 V, ISINK = 1.2 mA
2.25
sec
ns
ns
ADM706P/ADM706R: VCC = 3 V;
ADM706S/ADM706T: VCC = 3.3 V;
VIL = 0.4 V, VIH = VCC × 0.8 V
VRST (max) < VCC < 3.6 V
4.5 V < VCC < 5.5 V
V
V
V
V
μA
VRST (max) < VCC < 3.6 V
VRST (max) < VCC < 3.6 V
VCC = 5.0 V
VCC = 5.0 V
WDI = 0 V or VCC
200
RESET OUTPUT VOLTAGE (ADM706R/ADM708R/
ADM706S/ADM708S/ADM706T/ADM708T)
VOH
VOL
VOH
VOL
VOL
RESET OUTPUT VOLTAGE (ADM706P)
VOH
VOL
VOH
VOL
RESET OUTPUT VOLTAGE
(ADM708R/ADM708S/ADM708T)
VOH
VOL
VOH
VOL
WATCHDOG INPUT (ADM706P/ADM706R/
ADM706S/ADM706T)
Watchdog Timeout Period
WDI Pulse Width
WDI Input Threshold
VIL
VIH
VIL
VIH
WDI Input Current
0.8 × VCC
0.3
VCC − 1.5 V
0.4
0.3
VCC − 0.6 V
0.3
VCC − 1.5 V
0.4
0.8 × VCC
0.3
VCC − 1.5 V
1.00
1.60
100
50
0.6
0.7 × VCC
0.8
3.5
−1.0
+0.02
ADM706P/ADM706R/ADM708R
ADM706S/ADM708S
ADM706T/ADM708T
+1.0
Rev. E | Page 3 of 16
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
Parameter
WDO OUTPUT VOLTAGE
VOH
Min
Typ
MANUAL RESET INPUT
MR Pull-Up Current (MR = 0 V)
MR Pulse Width
MR INPUT THRESHOLD
VIL
VIH
VIL
VIH
MR TO RESET OUTPUT DELAY
POWER FAIL INPUT
PFI Input Threshold
PFI Input Current
PFO OUTPUT VOLTAGE
VOH
VOL
VOH
VOL
Max
Unit
Test Conditions/Comments
0.3
0.4
V
V
V
V
VRST (max) < VCC < 3.6 V, ISOURCE = 500 μA
4.5 V < VCC < 5.5 V, ISOURCE = 800 μA
VRST (max) < VCC < 3.6 V, ISINK = 500 μA
4.5 V < VCC < 5.5 V, ISINK = 1.2 mA
250
600
μA
μA
ns
ns
VRST (max) < VCC < 3.6 V
4.5 V < VCC < 5.5 V
VRST (max) < VCC < 3.6 V
4.5 V < VCC < 5.5 V
0.6
750
250
V
V
V
V
ns
ns
VRST (max) < VCC < 3.6 V
VRST (max) < VCC < 3.6 V
4.5 V < VCC < 5.5 V
4.5 V < VCC < 5.5 V
VRST (max) < VCC < 3.6 V
4.5 V < VCC < 5.5 V
ADM706P/ADM706R/ADM708R, VCC = 3 V
ADM706S/ADM708S/ADM706T/ADM708T,
VCC = 3.3 V, PFI falling
0.8 × VCC
VCC − 1.5 V
VOL
25
100
500
150
70
250
Data Sheet
0.7 × VCC
0.8
2.0
1.2
1.25
1.3
V
−25
+0.01
+25
nA
0.8 × VCC
0.3
VCC − 1.5 V
0.4
Rev. E | Page 4 of 16
V
V
V
V
VRST (max) < VCC < 3.6 V, ISOURCE = 500 μA
VRST (max) < VCC < 3.6 V, ISINK = 1.2 mA
4.5 V < VCC < 5.5 V, ISOURCE = 800 μA
4.5 V < VCC < 5.5 V, ISINK = 3.2 mA
Data Sheet
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
ABSOLUTE MAXIMUM RATINGS
TA = 25°C unless otherwise noted.
Table 2.
Parameter
VCC
All Other Inputs
Input Current
VCC
GND
Digital Output Current
Power Dissipation, N-8 (PDIP)
θJA Thermal Impedance
Power Dissipation, R-8 (SOIC)
θJA Thermal Impedance
Operating Temperature Range
Industrial (Version A)
Lead Temperature (Soldering, 10 sec)
Vapor Phase (60 sec)
Infrared (15 sec)
Storage Temperature Range
ESD Rating
Rating
−0.3 V to +6 V
−0.3 V to VCC + 0.3 V
20 mA
20 mA
20 mA
727 mW
135°C/W
470 mW
110°C/W
Stresses at or above those listed under Absolute Maximum
Ratings may cause permanent damage to the product. This is a
stress rating only; functional operation of the product at these
or any other conditions above those indicated in the operational
section of this specification is not implied. Operation beyond
the maximum operating conditions for extended periods may
affect product reliability.
ESD CAUTION
−40°C to +85°C
300°C
215°C
220°C
−65°C to +150°C
>4.5 kV
Rev. E | Page 5 of 16
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
Data Sheet
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
ADM706P
8
WDO
7
RESET
MR 1
VCC 2
GND 3
GND 3
PFI 4
06435-003
6 WDI
TOP VIEW
PFI 4 (Not to Scale) 5 PFO
Figure 3. ADM706P
ADM706R/
ADM706S/
ADM706T
8
WDO
7
RESET
WDI
TOP VIEW
5 PFO
(Not to Scale)
6
06435-004
MR 1
VCC 2
Figure 4. ADM706R/ADM706S/ADM706T
Table 3. Pin Function Descriptions ADM706P/ADM706R/ADM706S/ADM706T
Pin No.
1
Mnemonic
MR
2
3
4
VCC
GND
PFI
5
PFO
6
WDI
7 (ADM706R/ADM706S/
ADM706T Only)
RESET
7 (ADM706P Only)
RESET
8
WDO
Description
Manual Reset Input. When taken below 0.6 V, a RESET/RESET is generated. MR can be driven
from TTL, CMOS logic, or from a manual reset switch because it is internally debounced. An
internal 70 μA pull-up current holds the input high when floating.
Power Supply Input. Place a 0.1 µF decoupling capacitor between the VCC and GND pins.
Ground. Ground reference for all signals (0 V).
Power Fail Input. PFI is the noninverting input to the power fail comparator. When PFI is less
than 1.25 V, PFO goes low. If unused, PFI connects to GND.
Power Fail Output. PFO is the output from the power fail comparator. It goes low when PFI is
less than 1.25 V.
Watchdog Input. If WDI remains either high or low for longer than the watchdog timeout period, the
watchdog output, WDO, goes low. The timer resets with each transition at the WDI input. Either
a high to low or a low to high transition clears the counter. The internal timer is also cleared
whenever reset is asserted.
Logic Output. RESET goes low for 200 ms when triggered. It is triggered either by VCC being
below the reset threshold or by a low signal on the MR input. RESET remains low whenever VCC
is below the reset threshold. It remains low for 200 ms after VCC goes above the reset threshold
or MR goes from low to high. A watchdog timeout does not trigger RESET unless WDO is
connected to MR.
Logic Output. RESET is an active high output suitable for systems that use active high reset logic. It is
the inverse of RESET.
Watchdog Output. WDO goes low if the internal watchdog timer times out as a result of inactivity on
the WDI input. It remains low until the watchdog timer is cleared. WDO also goes low during
low line conditions. Whenever VCC is below the reset threshold, WDO remains low. As soon as VCC
goes above the reset threshold, WDO goes high immediately.
Rev. E | Page 6 of 16
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
MR 1
VCC 2
GND 3
PFI 4
ADM708R/
ADM708S/
ADM708T
8
RESET
7
RESET
6
NC
TOP VIEW
5 PFO
(Not to Scale)
NC = NO CONNECT
06435-005
Data Sheet
Figure 5. ADM708R/ADM708S/ADM708T
Table 4. Pin Function Descriptions ADM708R/ADM708S/ADM708T
Pin No.
1
Mnemonic
MR
2
3
4
VCC
GND
PFI
5
6
7
PFO
NC
RESET
8
RESET
Description
Manual Reset Input. When taken below 0.6 V, a RESET/RESET is generated. MR can be driven from TTL, CMOS
logic, or from a manual reset switch because it is internally debounced. An internal 70 μA pull-up current holds
the input high when floating.
Power Supply Input. Place a 0.1 µF decoupling capacitor between the VCC and GND pins.
Ground. Ground reference for all signals (0 V).
Power Fail Input. PFI is the noninverting input to the power fail comparator. When PFI is less than 1.25 V, PFO
goes low. If unused, PFI must connect to GND.
Power Fail Output. PFO is the output from the power fail comparator. It goes low when PFI is less than 1.25 V.
No Connect.
Logic Output. RESET goes low for 200 ms when triggered. It is triggered either by VCC being below the reset
threshold or by a low signal on the MR input. RESET remains low whenever VCC is below the reset threshold. It
remains low for 200 ms after VCC goes above the reset threshold or MR goes from low to high. A watchdog
timeout does not trigger RESET unless WDO is connected to MR.
Logic Output. RESET is an active high output suitable for systems that use active high reset logic. It is the
inverse of RESET.
Rev. E | Page 7 of 16
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
VCC = 3.3V
TA = 25°C
1.3V
PFI
VCC
1.2V
3V
PFO
RESET
400ms/DIV
06435-016
06435-013
0V
500ns/DIV
Figure 6. ADM706R/ADM706S/ADM706T and the
ADM708R/ADM708S/ADM708T RESET Output Voltage vs. Supply Voltage
Figure 9. PFI Deassertion Response Time
VCC = VRT
TA = 25°C
3V
VCC
RESET
3V
0V
06435-017
0V
06435-014
RESET
RESET
100ns/DIV
400ms/DIV
Figure 10. RESET, RESET Assertion
Figure 7. RESET Output Voltage vs. Supply Voltage
VCC = VRT
TA = 25°C
VCC = 3.3V
TA = 25°C
1.3V
PFI
3V
1.2V
3V
RESET
RESET
3V
PFO
0V
0V
100ns/DIV
Figure 11. RESET, RESET Deassertion
Figure 8. PFI Assertion Response Time
Rev. E | Page 8 of 16
06435-018
500ns/DIV
06435-015
0V
Data Sheet
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
TA = 25°C
3V
VCC
2V
3V
RESET
2µs/DIV
06435-019
0V
Figure 12. ADM706R/ADM706S/ADM706T and the
ADM708R/ADM708S/ADM708T RESET Response Time
Rev. E | Page 9 of 16
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
Data Sheet
CIRCUIT INFORMATION
WATCHDOG
TRANSITION
DETECTOR
VCC
70μA
MR
MANUAL RESET
WATCHDOG
TIMER
RESET AND
WATCHDOG
TIMEBASE
RESET
GENERATOR
VCC
VREF*
ADM706P/ADM706R/
ADM706S/ADM706T
POWER-FAIL
INPUT (PFI)
The MR input allows other reset sources, such as a manual reset
switch, to generate a processor reset. The input is effectively
debounced by the timeout period (200 ms typical). The MR
input is TTL-/CMOS-compatible; it can also be driven by any
logic reset output. If unused, the MR input can be tied high or
left floating.
WATCHDOG
OUTPUT (WDO)
1.25V
RESET,
(P = RESET)
VCC
* VOLTAGE REFERENCE = 2.63V (P/R), 2.93V (S), 3.08V (T)
Figure 13. ADM706P/ADM706R/ADM706S/ADM706T Functional Block
Diagram
tRS
RESET
MR EXTERNALLY
DRIVEN LOW
MR
VCC
VCC
VREF *
ADM708R/ADM708S/
ADM708T
1.25V
NOTES
RESET = COMPLEMENT OF RESET
RESET
Figure 15. RESET, MR, and WDO Timing
WATCHDOG TIMER (ADM706P/ADM706R/
ADM706S/ADM706T)
POWER-FAIL
OUTPUT (PFO)
* VOLTAGE REFERENCE = 2.63V (R), 2.93V (S), 3.08V (T)
Figure 14. ADM708R/ADM708S/ADM708T Functional Block Diagram
POWER FAIL RESET
The reset output provides a reset (RESET or RESET) output
signal to the microprocessor whenever the VCC input is below
the reset threshold. The actual reset threshold voltage is dependent
on whether a P, R, S, or T suffix device is used. An internal timer
holds the reset output active for 200 ms after the voltage on VCC
rises above the threshold. This is intended as a power-on reset
signal for the microprocessor. It allows time for both the power
supply and the microprocessor to stabilize after power-up. If a
power supply brownout or interruption occurs, the reset line is
similarly activated and remains active for 200 ms after the supply
recovers. If another interruption occurs during an active reset
period, the reset timeout period continues for an additional 200 ms.
The reset output is guaranteed to remain valid with VCC as low
as 1 V. This ensures that the microprocessor is held in a stable
shutdown condition as the power supply starts up.
The ADM706P provides an active high RESET signal; the
ADM706R/ADM706S/ADM706T provide an active low RESET
signal; and the ADM708R/ADM706S/ADM706T provide both
RESET and RESET.
The watchdog timer circuit monitors the activity of the
microprocessor to check that it is not stalled in an indefinite loop.
An output line on the processor is used to toggle the watchdog
input (WDI) line. If this line is not toggled within the timeout
period (1.6 sec), the watchdog output (WDO) is driven low. The
WDO output is connected to a nonmaskable interrupt (NMI) on
the processor. Therefore, if the watchdog timer times out, an
interrupt is generated. The interrupt service routine is used to
rectify the problem.
The watchdog timer is cleared either by a high to low or by a
low to high transition on WDI. Pulses as narrow as 50 ns are
detected. The timer is also cleared by RESET/RESET going
active. Therefore, the watchdog timeout period begins after
reset goes inactive.
When VCC falls below the reset threshold, WDO is forced low
whether or not the watchdog timer has timed out. Normally,
this generates an interrupt, but it is overridden by RESET/RESET
going active.
tWP
tWD
tWD
tWD
WDI
WDO
RESET
RESET EXTERNALLY
TRIGGERED BY MR
Figure 16. Watchdog Timing
Rev. E | Page 10 of 16
tRS
06435-009
RESET
GENERATOR
06435-007
MR
RESET
06435-008
WDO
70μA
POWER-FAIL
INPUT (PFI)
VRT
VRT
tRS
POWER-FAIL
OUTPUT (PFO)
06435-006
WATCHDOG
INPUT (WDI)
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
The power fail comparator is an independent comparator that
monitors the input power supply. The inverting input of the
comparator internally connects to a 1.25 V reference voltage.
The noninverting input is available at the PFI input. This input
monitors the input power supply via a resistive divider network.
When the voltage on the PFI input drops below 1.25 V, the
comparator output (PFO) goes low, indicating a power failure.
For early warning of power failure, the comparator monitors the
preregulator input by choosing an appropriate resistive divider
network. The PFO output interrupts the processor to implement a
shutdown procedure before the power is lost.
INPUT
POWER
VCC
1.25V
R1
R2
POWER-FAIL PFI
INPUT
PFO
PFO
RESET
TO µP NMI
TO µP RESET
ADM706R/ADM706S/
ADM706T/ADM708R/
ADM708S/ADM708T
R3
3.3V
PFO
POWER-FAIL
OUTPUT
0V VL
VIN
VH
Figure 18. Adding Hysteresis to the Power Fail Comparator
RESET
R2 + R3
R1
VH = 1.25 1 +
R2 × R3
RESET
OUTPUT
1.25 VCC − 1.25
VL = 1.25 + R1
−
R3
R2
06435-010
ADM706R/ADM706S/
ADM706T/ADM708R/
ADM708S/ADM708T
–
+
PFI
R2
0V
1.25V
3.3V
R1
As the voltage on the PFI pin is limited to VCC + 0.3 V, it is
recommended to connect the PFI pin with a Schottky diode to
the RESET pin, as shown in Figure 17. This helps with clamping
the PFI pin voltage during device power up and operation.
INPUT
POWER
ADM663A
06435-011
POWER FAIL COMPARATOR
Figure 17. Power Fail Comparator
R1 + R2
VMID = 1.25
R2
ADDING HYSTERESIS TO THE POWER FAIL
COMPARATOR
For increased noise immunity, hysteresis can be added to the
power fail comparator. Because the comparator circuit is noninverting, hysteresis is added simply by connecting a resistor
between the PFO output and the PFI input as shown in Figure 18.
When PFO is low, Resistor R3 sinks current from the summing
junction at the PFI pin. When PFO is high, Resistor R3 sources
current into the PFI summing junction. This results in differing
trip levels for the comparator. Further noise immunity is achieved
by connecting a capacitor between PFI and GND.
VALID RESET BELOW 1 V VCC
The ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/
ADM708T are guaranteed to provide a valid reset level with VCC
as low as 1 V. Refer to the Typical Performance Characteristics
section. As VCC drops below 1 V, the internal transistor does not
have sufficient drive to hold it on so the voltage on RESET is no
longer held at 0 V. A pull-down resistor, as shown in Figure 19, can
connect externally to hold the line low if it is required.
ADM706R/ADM706S/
ADM706T/ADM708R/
ADM708S/ADM708T
RESET
GND
R1
Figure 19. RESET Valid Below 1 V
Rev. E | Page 11 of 16
06435-012
Data Sheet
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
Data Sheet
APPLICATIONS INFORMATION
A typical operating circuit is shown in Figure 20. The unregulated
dc input supply is monitored using the PFI input via the resistive
divider network. Resistor R1 and Resistor R2 are to be selected
so that when the supply voltage drops below the desired level
(for example, 5 V), the voltage on PFI drops below the 1.25 V
threshold, thereby generating an interrupt to the microprocessor.
Monitoring the preregulator input gives additional time to execute
an orderly shutdown procedure before power is lost.
It is possible to use the power fail comparator to monitor a second
supply as shown in Figure 22. The two sensing resistors, R1 and
R2, are selected such that the voltage on PFI drops below 1.25 V at
the minimum acceptable input supply. The PFO output can
connect to the MR input so a reset generates when the supply drops
out of tolerance. In this case, if either supply drops out of tolerance,
a reset is generated.
ADM666A
IN
VX
OUT
GND
+3V/+3.3V
3.3V
VCC
VCC
WDI
ADM706R/
ADM706S/
ADM706T
MANUAL
RESET
PFI
PFO
RESET
NMI
MICROPROCESSORS WITH BIDIRECTIONAL RESET
To prevent contention for microprocessors with a bidirectional
reset line, a current limiting resistor is to be inserted between
the ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/
ADM708T RESET output pin and the microprocessor reset pin.
This limits the current to a safe level if there are conflicting output
reset levels. A suitable resistor value is 4.7 kΩ. If the reset output is
required for other uses, it must be buffered as shown in Figure 23.
RESET
VCC
RESET
I/O LINE
GND
MICROPROCESSOR
GND
BUFFERED
RESET
+3V/+3.3V
ADM706R/ADM706S/
ADM706T/ADM708R/
ADM708S/ADM708T
06435-021
MR
WDO
PFO
GND
Figure 22. Monitoring 3 V/3.3 V and an Additional Supply, VX
If, in the event of inactivity on the WDI line, a system reset is
required, the WDO output is to be connected to the input as
shown in Figure 21.
ADM706R/
ADM706S/ WDI
ADM706T
MICROPROCESSOR
GND
Microprocessor activity is monitored using the WDI input. This
is driven using an output line from the processor. The software
routines toggle this line at least once every 1.6 sec. If a problem
occurs and this line is not toggled, WDO goes low and a nonmaskable interrupt is generated. This interrupt routine is to be used
to clear the problem.
PFI
RESET
RESET
Figure 20. Typical Application Circuit
RESET
MR
R2
INTERRUPT
06435-020
GND
ADM706R/ WDI
ADM706S/
PFI ADM706T
I/O LINE
MICROPROCESSOR
WDO
RESET
06435-022
MR
R1
VCC
MICROPROCESSOR
RESET
GND
Figure 23. Bidirectional Input/Output RESET
Figure 21. RESET from WDO
Rev. E | Page 12 of 16
06435-023
UNREGULATED
DC
MONITORING ADDITIONAL SUPPLY LEVELS
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
OUTLINE DIMENSIONS
0.400 (10.16)
0.365 (9.27)
0.355 (9.02)
8
5
1
4
0.280 (7.11)
0.250 (6.35)
0.240 (6.10)
0.100 (2.54)
BSC
0.325 (8.26)
0.310 (7.87)
0.300 (7.62)
0.060 (1.52)
MAX
0.210 (5.33)
MAX
0.015
(0.38)
MIN
0.150 (3.81)
0.130 (3.30)
0.115 (2.92)
SEATING
PLANE
0.022 (0.56)
0.018 (0.46)
0.014 (0.36)
0.195 (4.95)
0.130 (3.30)
0.115 (2.92)
0.015 (0.38)
GAUGE
PLANE
0.430 (10.92)
MAX
0.005 (0.13)
MIN
0.014 (0.36)
0.010 (0.25)
0.008 (0.20)
0.070 (1.78)
0.060 (1.52)
0.045 (1.14)
070606-A
COMPLIANT TO JEDEC STANDARDS MS-001
CONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS.
Figure 24. 8-Lead Plastic Dual In-Line Package [PDIP]
Narrow Body
(N-8)
Dimension shown in inches and (millimeters)
5.00 (0.1968)
4.80 (0.1890)
4.00 (0.1574)
3.80 (0.1497)
8
1
5
6.20 (0.2441)
5.80 (0.2284)
4
1.27 (0.0500)
BSC
0.25 (0.0098)
0.10 (0.0040)
COPLANARITY
0.10
SEATING
PLANE
1.75 (0.0688)
1.35 (0.0532)
0.51 (0.0201)
0.31 (0.0122)
0.50 (0.0196)
0.25 (0.0099)
45°
8°
0°
0.25 (0.0098)
0.17 (0.0067)
1.27 (0.0500)
0.40 (0.0157)
COMPLIANT TO JEDEC STANDARDS MS-012-AA
CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS
(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR
REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 25. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body
(R-8)
Dimensions shown in millimeters and (inches)
Rev. E | Page 13 of 16
012407-A
Data Sheet
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
Data Sheet
ORDERING GUIDE
Model 1
ADM706PANZ
ADM706PARZ
ADM706PARZ-REEL
ADM706RANZ
ADM706RAR
ADM706RARZ
ADM706RARZ-REEL
ADM706RARZ-REEL7
ADM706SANZ
ADM706SAR
ADM706SAR-REEL
ADM706SARZ
ADM706SARZ-REEL
ADM706TANZ
ADM706TAR
ADM706TAR-REEL
ADM706TARZ
ADM706TARZ-REEL
ADM708RANZ
ADM708RAR
ADM708RAR-REEL
ADM708RARZ
ADM708RARZ-REEL
ADM708SANZ
ADM708SAR
ADM708SAR-REEL
ADM708SARZ
ADM708SARZ-REEL
ADM708TANZ
ADM708TAR
ADM708TARZ
ADM708TARZ-REEL
1
Temperature Range
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
−40°C to +85°C
Package Description
8-Lead Plastic Dual In-Line Package [PDIP]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Plastic Dual In-Line Package [PDIP]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Plastic Dual In-Line Package [PDIP]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Plastic Dual In-Line Package [PDIP]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Plastic Dual In-Line Package [PDIP]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Plastic Dual In-Line Package [PDIP]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Plastic Dual In-Line Package [PDIP]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
8-Lead Small Outline Package [SOIC_N]
Z = RoHS Compliant Part.
Rev. E | Page 14 of 16
Package Option
N-8
R-8
R-8
N-8
R-8
R-8
R-8
R-8
N-8
R-8
R-8
R-8
R-8
N-8
R-8
R-8
R-8
R-8
N-8
R-8
R-8
R-8
R-8
N-8
R-8
R-8
R-8
R-8
N-8
R-8
R-8
R-8
Data Sheet
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
NOTES
Rev. E | Page 15 of 16
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
NOTES
©2007–2016 Analog Devices, Inc. All rights reserved. Trademarks and
registered trademarks are the property of their respective owners.
D00089-0-1/16(E)
Rev. E | Page 16 of 16
Data Sheet
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