ASM705/706/707/708 and ASM813L
Low Power μP
Supervisor Circuits
©2010 SCILLC. All rights reserved. Publication Order Number:
JANUARY 2010 – Rev. 2 ASM705/D
General Description
The ASM705 / 706 / 707 / 708 and ASM813L are cost
effective CMOS supervisor circuits that monitor power-
supply and battery voltage level, and μP/μC operation.
The family offers several functional options. Each device
generates a reset signal during power-up, power-down and
during brownout conditions. A reset is generated when the
supply drops below 4.65V (ASM705/707/813L) or 4.40V
(ASM706/708). For 3V power supply applications, refer to
the ASM705P/R/S/T data sheet. In addition, the
ASM705/706/813L feature a 1.6 second watchdog timer.
The ASM707/708 have both active-HIGH and active-LOW
reset outputs but no watchdog function. The ASM813L has
the same pin-out and functions as the ASM705 but has an
active-HIGH reset output. A versatile power-fail circuit has
a 1.25V threshold, useful in low battery detection and for
monitoring non-5V supplies. All devices have a manual
reset (MR) input. The watchdog timer output will trigger a
reset if connected to MR.
All devices are available in 8-pin DIP, SO and MicroSO
packages.
Features
Precision power supply monitor
4.65V threshold (ASM705/707/813L)
4.40V threshold (ASM706/708)
Debounced manual reset input
Voltage monitor
1.25V threshold
Battery monitor / Auxiliary supply monitor
Watchdog timer (ASM705/706/813L)
200ms reset pulse width
Active HIGH reset output (ASM707/708/813L)
MicroSO package
Application
Computers and embedded controllers
Portable/Battery-operated systems
Intelligent instruments
Wireless communication systems
PDAs and hend-held equipment
Automative Systems
Safety Systems
Typical Operating Circuit
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 2 of 14 | www.onsemi.com
Block Diagram
Pin Configuration
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 3 of 14 | www.onsemi.com
Pin Description
Pin Number
Function
ASM705/706
ASM707/708
ASM813L
DIP/
SO
MicroSO
DIP/
SO
MicroSO
DIP/
SO
MicroSO
1
3
1
3
1
3
Manual reset input. The active LOW input
triggers a reset pulse. A 250 μA pull-up
current allows the pin to be driven by
TTL/CMOS logic or shorted to ground with a
switch.
2
4
2
4
2
4
+5V power supply input.
3
5
3
5
3
5
Ground reference for all signals.
4
6
4
6
4
6
Power-fail input voltage monitor. With PFI
less than 1.25V, PFO goes LOW. Connect
PFI to Ground or VCC when not in use.
5
7
5
7
5
7
Power-fail output. The output is active LOW
and sinks current when PFI is less than
1.25V.
6
8
-
-
6
8
Watchdog input. WDI controls the internal
watchdog timer. A HIGH or LOW signal for
1.6sec at WDI allows the internal timer to
run-out, setting WDO LOW. The watchdog
function is disabled by floating WDI or by
connecting WDI to a high impedance three-
state buffer. The internal watchdog timer
clears when: RESET is asserted; WDI is
three-stated; or WDI sees a rising or falling
edge.
-
-
6
8
-
-
Not Connected.
7
1
7
1
-
-
Active LOW reset output. Pulses LOW for
200ms when triggered, and stays LOW
whenever VCC is below the reset threshold.
RESET remains LOW for 200ms after VCC
rises above the reset threshold or MR goes
from LOW to HIGH. A watchdog timeout will
not trigger RESET unless WDO is
connected to MR.
8
2
-
-
8
2
Watchdog output. WDO goes LOW when
the 1.6 second internal watchdog timer
times-out and does not go HIGH until the
watchdog is cleared. In addition, when VCC
falls below the reset threshold, WDO goes
LOW. Unlike RESET, WDO does not have a
minimum pulse width and as soon as VCC
exceeds the reset threshold, WDO goes
HIGH with no delay.
-
-
8
2
7
1
Active HIGH reset output. The inverse of
RESET. The ASM813L only has a RESET
output.
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 4 of 14 | www.onsemi.com
Detailed Description
A proper reset input enables a microprocessor /
microcontroller to start in a known state. ASM70X and
ASM813L assert reset to prevent code execution errors
during power-up, power-down and brown-out conditions.
RESET/RESET Timing
The RESET/RESET signals are designed to start a
μP/μC in a known state or return the system to a known
state.
The ASM707/708 have two reset outputs, one active-
HIGH RESET and one active-LOW RESET output. The
ASM813L has only an active-HIGH output. RESET is
simply the complement of RESET.
RESET is guaranteed to be LOW with VCC above 1.2V.
During a power-up sequence, RESET remains low until
the supply rises above the threshold level, either 4.65V or
4.40V. RESET goes high approximately 200ms after
crossing the threshold.
During power-down, RESET goes LOW as VCC falls
below the threshold level and is guaranteed to be under
0.4V with VCC above 1.2V.
In a brownout situation where VCC falls below the
threshold level, RESET pulses low. If a brown-out occurs
during an already initiated reset, the pulse will continue
for a minimum of 140ms.
Power Failure Detection With Auxiliary Comparator
All devices have an auxiliary comparator with 1.25V trip
point and uncommitted output (PFO) and noninverting
input (PFI). This comparator can be used as a supply
voltage monitor with an external resistor voltage divider.
The attenuated voltage at PFI should be set just below
the 1.25 threshold. As the supply level falls, PFI is
reduced causing the PFO output to transit LOW. Normally
PFO interrupts the processor so the system can be shut
down in a controlled manner.
Manual Reset (MR)
The active-LOW manual reset input is pulled high by a
250μA pull-up current and can be driven low by
CMOS/TTL logic or a mechanical switch to ground. An
external debounce circuit is unnecessary since the
140ms minimum reset time will debounce mechanical
pushbutton switches.
By connecting the watchdog output (WDO) and MR, a
watchdog timeout forces RESET to be generated. The
ASM813L should be used when an active-HIGH RESET
is required.
Watchdog Timer
The watchdog timer available on the ASM705/706/813L
monitors μP/μC activity. An output line on the processor
is used to toggle the WDI line. If this line is not toggled
within 1.6 seconds, the internal timer puts the watchdog
output, WDO, into a LOW state. WDO will remain LOW
until a toggle is detected at WDI.
If WDI is floated or connected to a three-stated circuit, the
watchdog function is disabled, meaning, it is cleared and
not counting. The watchdog timer is also disabled if
RESET is asserted. When RESET becomes inactive and
the WDI input sees a high or low transition as short as
50ns, the watchdog timer will begin a 1.6 second
countdown. Additional transitions at WDI will reset the
watchdog timer and initiate a new countdown sequence.
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 5 of 14 | www.onsemi.com
WDO will also become LOW and remain so, whenever
the supply voltage, VCC , falls below the device threshold
level. WDO goes HIGH as soon as VCC transitions above
the threshold. There is no minimum pulse width for WDO
as there is for the RESET outputs. If WDI is floated, WDO
essentially acts as a low-power output indicator.
Application Information
Ensuring That RESET is Valid Down to VCC = 0V
When VCC falls below 1.1V, the ASM705-708 RESET
output no longer pulls down; it becomes indeterminate.
To avoid the possibility that stray charges build up and
force RESET to the wrong state, a pull-down resistor
should be connected to the RESET pin, thus draining
such charges to ground and holding RESET low. The
resistor value is not critical. A 100kΩ resistor will pull
RESET to ground without loading it.
Bi-directional Reset Pin Interfacing
The ASM705/6/7/8 can interface with μP/μC bi-directional
reset pins by connecting a 4.7kΩ resistor in series with
the RESET output and the μP/μC bi-directional RESET
pin.
Monitoring Voltages Other Than VCC
The ASM705-708 can monitor voltages other than VCC
using the Power Fail circuitry. If a resistive divider is
connected from the voltage to be monitored to the Power
Fail input (PFI), the PFO will go LOW if the voltage at PFI
goes below 1.25V reference. Should hysteresis be
desired, connect a resistor (equal to approximately 10
times the sum of the two resistors in the divider) between
the PFI and PFO pins. A capacitor between PFI and GND
will reduce circuit sensitivity to input high-frequency
noise. If it is desired to assert a RESET for voltages other
than VCC then the PFO output is to be connected to the
MR.
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 6 of 14 | www.onsemi.com
Monitoring a Negative Voltage
The Power-Fail circuitry can also monitor a negative
supply rail. When the negative rail is OK, PFO will be
LOW, and when the negative rail is failing (not negative
enough), PFO goes HIGH (the opposite of when positive
voltages are monitored). To trigger a reset, these outputs
need to be inverted: adding the resistors and transistor as
shown achieves this. The RESET output will then have
the same sense as for positive voltages: good = HIGH,
bad = LOW. It should be noted that this circuit’s accuracy
depends on the VCC line, the PFI threshold tolerance, and
the resistors.
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 7 of 14 | www.onsemi.com
Absolute Maximum Ratings1
Parameter
Min
Max
Unit
Pin Terminal Voltage with Respect to Ground
VCC
-0.3
6.0
V
All other inputs2
-0.3
VCC + 0.3
V
Input Current at VCC and GND
20
mA
Output Current: All outputs
20
mA
Rate of Rise at VCC
100
V/μs
Plastic DIP Power Dissipation
(Derate 9mW/°C above 70°C)
700
mV
SO Power Dissipation
(Derate 5.9mW/°C above 70°C)
470
mW
MicroSO Power Dissipation
(Derate 4.1mW/°C above 70°C)
330
mW
Operating Temperature Range
ASM705E/706E/707E/708E/813LE
-40
+85
°C
ASM705C/706C/707C/708C/813LC
0
70
°C
Storage Temperature Range
-65
160
°C
Lead Temperature (Soldering 10sec)
300
°C
ESD rating HBM
MM
2
200
KV
V
Note: 1. These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may
affect device reliability.
2. The input voltage limits of PFI and MR can be exceeded if the input current is less than 10mA.
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 8 of 14 | www.onsemi.com
Electrical Characteristics
Unless otherwise noted, specifications are over the operating temperature range and VCC supply voltages are 2.7V to 5.5V
(ASM706P,ASM708R), 3.0 V to 5.5V (ASM706/708S), 3.15V to 5.5V (ASM706/708T) and 4.1V to 5.5.V (ASM706/708J).
Parameter
SYMBOL
Test Conditions
Min
TYP
Max
Unit
Operating Voltage Range
VCC
ASM705/6/7/8C
1.2
1.1
1.2
5.5
5.5
5.5
V
ASM813L
ASM705/6/7/8E, ASM813E
Supply Current
ICC
ASM705/706C/813LC
75
75
50
50
140
140
140
140
μA
ASM705E/706E/813LE
ASM707C/708C
ASM707E/708E
RESET Threshold
VRT
ASM705/707/813L1
4.50
4.25
4.65
4.40
4.75
4.50
V
ASM706/7081
RESET Threshold
Hysteresis
1
40
mV
RESET Pulse Width
tRS
1
140
200
280
ms
MR Pulse Width
tMR
0.15
μs
MR to RESET Out Delay
tMD
1
0.25
μs
MR Input Threshold
VIH
2.0
0.8
V
VIL
MR Pullup current
MR = 0V
100
250
600
μA
RESET Output Voltage
ISOURCE = 800μA
VCC - 1.5
0.4
0.3
V
ISINK = 3.2mA
ASM705/6/7/8, VCC = 1.2V,
ISINK = 100μA
RESET Output Voltage
ASM707/8/813L, ISOURCE =
800μA
VCC - 1.5
0.9
0.4
0.4
V
ASM707/8, ISINK = 1.2mA
ASM813L, ISINK =3.2mA
ASM813L, VCC = 1.2V,
ISOURCE = 4μA
Watchdog Timeout
Period
tWD
ASM705/6/813L
1.00
1.60
2.25
S
WDI Pulse Width
tWP
VIL = 0.4V, VIH=0.8VCC,
50
ns
WDI Input Threshold
VIH
ASM705/706/813L, VCC = 5V
3.5
0.8
V
VIL
WDI Input Current
ASM705/6/813L, WDI = VCC
-150
50
-50
150
μA
ASM705/6/813L, WDI = 0V
WDO Output Voltage
VOH
ASM705/6/813L, ISOURCE =
800μA
VCC - 1.5
0.4
V
VOL
ASM705/6/813L, ISINK =
1.2mA
PFI Input Threshold
VCC = 5V
1.2
1.25
1.3
V
PFI Input Current
-25
0.01
25
nA
PFO Output Voltage
VOH
ISOURCE = 800μA
VCC - 1.5
0.4
V
VOL
ISINK = 3.2mA
Note: 1. RESET (ASM705/6/7/8), RESET(ASM707/8, ASM813L)
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 9 of 14 | www.onsemi.com
Package Dimensions 8-Pin MicroSO
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 10 of 14 | www.onsemi.com
Package Dimensions (contd) Plastic DIP (8-Pin)
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 11 of 14 | www.onsemi.com
Package Dimensions (contd) SO (8-Pin)
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 12 of 14 | www.onsemi.com
Ordering Codes
Part Number
Reset Threshold
Temperature
Pins-Package
Package Marking
TIN - LEAD DEVICES
ASM705 Active LOW Reset, Watchdog Output And Manual RESET
ASM705CPA
4.65
0°C to +70 °C
8-Plastic DIP
ASM705CPA
ASM705CSA
4.65
0°C to +70 °C
8-SO
ASM705CSA
ASM705CUA
4.65
0°C to +70 °C
8-MicroSO
ASM705CUA
ASM705EPA
4.65
-40°C to +85°C
8-Plastic DIP
ASM705EPA
ASM705ESA
4.65
-40°C to +85°C
8-SO
ASM705ESA
ASM705EUA
4.65
-40°C to +85°C
8-MicroSO
ASM705EUA
ASM706 Active LOW Reset, Watchdog Output And Manual RESET
ASM706CPA
4.40
0°C to +70 °C
8-Plastic DIP
ASM706CPA
ASM706CSA
4.40
0°C to +70 °C
8-SO
ASM706CSA
ASM706CUA
4.40
0°C to +70 °C
8-MicroSO
ASM706CUA
ASM706EPA
4.40
-40°C to +85°C
8-Plastic DIP
ASM706EPA
ASM706ESA
4.40
-40°C to +85°C
8-SO
ASM706ESA
ASM707 Active LOW & HIGH Reset with Manual RESET
ASM707CPA
4.65
0°C to +70 °C
8-Plastic DIP
ASM707CPA
ASM707CSA
4.65
0°C to +70 °C
8-SO
ASM707CSA
ASM707CUA
4.65
0°C to +70 °C
8-MicroSO
ASM707CUA
ASM707EPA
4.65
-40°C to +85°C
8-Plastic DIP
ASM707EPA
ASM707ESA
4.65
-40°C to +85°C
8-SO
ASM707ESA
ASM708Active LOW & HIGH Reset with Manual RESET
ASM708CPA
4.40
0°C to +70 °C
8-Plastic DIP
ASM708CPA
ASM708CSA
4.40
0°C to +70 °C
8-SO
ASM708CSA
ASM708CUA
4.40
0°C to +70 °C
8-MicroSO
ASM708CUA
ASM708EPA
4.40
-40°C to +85°C
8-Plastic DIP
ASM708EPA
ASM708ESA
4.40
-40°C to +85°C
8-SO
ASM708ESA
ASM813L Active HIGH Reset, Watchdog Output And Manual RESET
ASM813LCPA
4.65
0°C to +70 °C
8-Plastic DIP
ASM813LCPA
ASM813LCSA
4.65
0°C to +70 °C
8-SO
ASM813LCSA
ASM813LCUA
4.65
0°C to +70 °C
8-MicroSO
ASM813LCUA
ASM813LEPA
4.65
-40°C to +85°C
8-Plastic DIP
ASM813LEPA
ASM813LESA
4.65
-40°C to +85°C
8-SO
ASM813LESA
Note: For parts to be packed in Tape and Reel, add “-T” at the end of the part number.
ASM705/706/707/708 and ASM813L
Rev. 2 | Page 13 of 14 | www.onsemi.com
Ordering Codes
Part Number
Reset Threshold
Temperature
Pins-Package
Package Marking
LEAD FREE DEVICES
ASM705 Active LOW Reset, Watchdog Output And Manual RESET
ASM705CPAF
4.65
0°C to +70 °C
8-Plastic DIP
ASM705CPAF
ASM705CSAF
4.65
0°C to +70 °C
8-SO
ASM705CSAF
ASM705CUAF
4.65
0°C to +70 °C
8-MicroSO
ASM705CUAF
ASM705EPAF
4.65
-40°C to +85°C
8-Plastic DIP
ASM705EPAF
ASM705ESAF
4.65
-40°C to +85°C
8-SO
ASM705ESAF
ASM705EUAF
4.65
-40°C to +85°C
8-MicroSO
ASM705EUAF
ASM706 Active LOW Reset, Watchdog Output And Manual RESET
ASM706CPAF
4.40
0°C to +70 °C
8-Plastic DIP
ASM706CPAF
ASM706CSAF
4.40
0°C to +70 °C
8-SO
ASM706CSAF
ASM706CUAF
4.40
0°C to +70 °C
8-MicroSO
ASM706CUAF
ASM706EPAF
4.40
-40°C to +85°C
8-Plastic DIP
ASM706EPAF
ASM706ESAF
4.40
-40°C to +85°C
8-SO
ASM706ESAF
ASM707 Active LOW & HIGH Reset with Manual RESET
ASM707CPAF
4.65
0°C to +70 °C
8-Plastic DIP
ASM707CPAF
ASM707CSAF
4.65
0°C to +70 °C
8-SO
ASM707CSAF
ASM707CUAF
4.65
0°C to +70 °C
8-MicroSO
ASM707CUAF
ASM707EPAF
4.65
-40°C to +85°C
8-Plastic DIP
ASM707EPAF
ASM707ESAF
4.65
-40°C to +85°C
8-SO
ASM707ESAF
ASM708Active LOW & HIGH Reset with Manual RESET
ASM708CPAF
4.40
0°C to +70 °C
8-Plastic DIP
ASM708CPAF
ASM708CSAF
4.40
0°C to +70 °C
8-SO
ASM708CSAF
ASM708CUAF
4.40
0°C to +70 °C
8-MicroSO
ASM708CUAF
ASM708EPAF
4.40
-40°C to +85°C
8-Plastic DIP
ASM708EPAF
ASM708ESAF
4.40
-40°C to +85°C
8-SO
ASM708ESAF
ASM813L Active HIGH Reset, Watchdog Output And Manual RESET
ASM813LCPAF
4.65
0°C to +70 °C
8-Plastic DIP
ASM813LCPAF
ASM813LCSAF
4.65
0°C to +70 °C
8-SO
ASM813LCSAF
ASM813LCUAF
4.65
0°C to +70 °C
8-MicroSO
ASM813LCUAF
ASM813LEPAF
4.65
-40°C to +85°C
8-Plastic DIP
ASM813LEPAF
ASM813LESAF
4.65
-40°C to +85°C
8-SO
ASM813LESAF
Note: For parts to be packed in Tape and Reel, add “-T” at the end of the part number.
ASM705/706/707/708 and ASM813L
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notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC
assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special,
consequential or incidental damages. “Typical” parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and
actual performance may vary over time. All operating parameters, including “Typicals” must be validated for each customer application by customer's technical experts.
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Feature Summary
ASM705
ASM706
ASM707
ASM708
ASM813L
Power fail detector
♦
♦
♦
♦
♦
Brownout detection
♦
♦
♦
♦
♦
Manual RESET input
♦
♦
♦
♦
♦
Power-up/down RESET
♦
♦
♦
♦
♦
Watchdog Timer
♦
♦
♦
Active HIGH RESET output
♦
♦
♦
Active LOW RESET output
♦
♦
♦
♦
RESET Threshold (V)
4.65
4.40
4.65
4.40
4.65