ADM706RAR Analog Devices Inc, ADM706RAR Datasheet - Page 11

• Manufacturer Part Number: ADM706RAR
• Description: IC SUPERVISOR MPU 2.63V WD 8SOIC
• Manufacturer: Analog Devices Inc
• Type: Simple Reset/Power-On Resetr

Specifications of ADM706RAR

• Rohs Status: RoHS non-compliant
• Number Of Voltages Monitored: 1
• Output: Push-Pull, Totem Pole
• Reset: Active Low
• Reset Timeout: 160 ms Minimum
• Voltage - Threshold: 2.63V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)

POWER-FAIL COMPARATOR
The power-fail comparator is an independent comparator that
can be used to monitor the input power supply. The inverting
input of the comparator is internally connected to a 1.25 V
reference voltage. The noninverting input is available at the PFI
input. This input is used to monitor 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 is used to monitor the preregulator input simply
by choosing an appropriate resistive divider network. The PFO
output is used to interrupt the processor so that a shutdown
procedure is implemented before the power is lost.
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
When
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.
POWER
INPUT
PFO is low, Resistor R3 sinks current from the summing
ADM706P/ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/ADM708T
R1
R2
POWER-FAIL
Figure 17. Power-Fail Comparator
INPUT
PFI
ADM706P/ADM706R/
ADM708R/ADM708S/
ADM706S/ADM706T/
1.25V
ADM708T
PFO
POWER-FAIL
OUTPUT
Figure 18
Rev. C | Page 11 of 16
.
POWER
VALID RESET BELOW 1 V V
The ADM706R/ADM706S/ADM706T, ADM708R/ADM708S/
ADM708T are guaranteed to provide a valid reset level with V
as low as 1 V. Refer to the Typical Performance Characteristics
section. As V
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
be connected externally to hold the line low if it is required.
INPUT
V
V
V
R1
R2
H
MID
L
Figure 18. Adding Hysteresis to the Power-Fail Comparator
3.3V
PFO
=
=
0V
. 1
=
. 1
ADM663A
0V V
. 1
25
25
CC
25
ADM706R/ADM706S/
ADM706T/ADM708R/
+
ADM708S/ADM708T
⎡
⎢
⎢
⎣
L
drops below 1 V, the internal transistor does not
1
⎛
⎜
⎝
R1
V
+
R1
Figure 19. RESET Valid Below 1 V
IN
⎛
⎜
⎜
⎝
⎛
⎜
⎝
PFI
V
3.3V
ADM706P/ADM706R/
ADM708R/ADM708S/
ADM706S/ADM706T/
R2
. 1
H
R2
+
R2
R2
1.25V
25
R2
+
×
ADM708T
−
R3
⎞
⎟
⎠
R3
V
V
CC
CC
+
–
⎞
⎟
⎟
⎠
GND
R1
R3
RESET
R3
−
CC
⎤
⎥
⎥
⎦
. 1
PFO
25
⎞
⎟
⎠
TO MICROPROCESSOR NMI
R1
Figure 19
, can
CC