ASM161, ASM162
mP
Supervisory Circuit
Description
The ASM161 and ASM162 are cost effective, low power
supervisory circuits that monitor power supplies in microprocessor,
microcontroller and digital systems. If the power supply drops below
the reset threshold level, a reset is asserted and remains asserted for at
least 800 ms after V
CC
has risen above the reset threshold. An
improved manual reset architecture gives the system designer
additional flexibility.
The debounced manual reset input is negative edge triggered. The
reset pulse period generated by a MR transition is a minimum of
800 ms and a maximum of 2 sec duration. In addition, The MR input
signal is blocked for an additional 49
mS
minimum after the reset pulse
ends. During the MR disable period, the microcontroller is guaranteed
a time period free of additional manual reset signals. During this
period DRAM contents can be refreshed or other critical system tasks
undertaken. Low power consumption makes the ASM161/162 ideal
for use in portable and battery operated equipments. With 3 V
supplies, power consumption is 8
mW
typically and 30
mW
maximum.
The ASM161 has an open−drain, active−LOW RESET output and
requires an external pull−up resistor. The ASM162 has an active
HIGH RESET output.
The ASM161/162 are offered in compact 4−pin SOT−143 packages.
No external components are required to trim threshold voltage for
monitoring different supply voltages. With six different factory set,
reset, threshold ranges from 2.63 V to 4.63 V, the ASM161/162 are
suitable for monitoring 5 V, 3.6 V and 3.0 V supplies. The
ASM161/162 are available in temperature ranges 0°C to 70°C and
−40°C
to +85°C.
Features
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SOT−143
4 LEAD
CASE 527AF
PIN CONFIGURATIONS
1
GND
RESET
ASM161
(Top View)
RESET is open drain
V
CC
1
GND
V
CC
MR RESET
ASM162
(Top View)
MR
RESET THRESHOLD
Part Suffix
L
M
J
T
S
R
Voltage (V)
4.63
4.38
4.00
3.08
2.93
2.63
•
•
•
•
•
•
•
•
•
•
•
•
Edge Triggered Manual Reset Input
Single Pulse Output
49
mS
Minimum MR Disable Period After Reset
CMOS/TTL Logic or Switch Interface
Debounced Input
Low Supply Current Extends Battery Life
6
mA
/ 15
mA
typ/max at 5.5 V
4.5
mA
/ 10
mA
typ/max at 3.6 V
Long Reset Period
0.8 Sec Minimum, 2 Sec Maximum
Two Reset Polarity Options
ASM161: Active LOW, Open−drain
ASM162: Active HIGH
Pinout Matches the ASM811/812
Small 4−Pin SOT−143 Package
Two Temperature Ranges: 0°C to 70°C
and
−40°C
to +85°C
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 6 of this data sheet.
Applications
•
•
•
•
•
•
•
PDAs
Appliances
Computers and Embedded Controllers
Wireless Communication Systems
Battery Operated and Intelligent Instruments
Automotive Systems
Safety Systems
©
Semiconductor Components Industries, LLC, 2011
August, 2011
−
Rev. 3
1
Publication Order Number:
ASM161/D
ASM161, ASM162
Figure 1. Typical Operating Circuit
Figure 2. Block Diagram
Table 1. PIN DESCRIPTION
Pin #
ASM161
1
2
ASM162
1
−
Pin Name
GND
RESET
Ground.
Active−LOW, open−drain reset output. RESET remains LOW while V
CC
is below the
reset threshold and for 800 ms minimum after V
CC
rises above the reset threshold.
An external pull−up resistor is needed.
Active HIGH reset output. RESET remains HIGH while V
CC
is below the reset
threshold and for 800 ms after V
CC
rises above the reset threshold.
Manual reset input. A negative going edge transition on MR asserts reset. Reset
remains asserted for one reset time−out period (800 ms min). This active−LOW input
has an internal pull−up resistor. It can be driven from a TTL or CMOS logic line or
shorted to ground with a switch. Leave open if unused.
Power supply input voltage.
Function
−
3
2
3
RESET
MR
4
4
V
CC
Detailed Description
The reset function ensures the microprocessor is properly
reset and powers up into a known condition after a power
failure.
Reset Timing
A reset is generated whenever the supply voltage is below
the threshold level (V
CC
< V
TH
). The reset duration is at
least 800 ms after V
CC
has risen above the reset threshold
and is guaranteed to be no more than 2 seconds. The rest
signal remains active as long as the monitored supply
voltage is below the internal threshold voltage.
The ASM161 has an open−drain, active LOW RESET
output (which is guaranteed to be in the correct state for V
CC
down to 1.1 V). The ASM161 uses an external pull−up
resistor. Output leakage current is under 1
mA.
A high
resistance value can be used to minimize current drain.
The ASM162 generates an active−HIGH RESET output.
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2
ASM161, ASM162
Part Number
ASM161
ASM162
Reset Polarity
LOW (use external pull−up resistor)
HIGH
Manual Reset
The ASM161/162 have a unique manual reset circuit. A
negative going edge transition on MR initiates the reset. A
manual reset generates a single reset pulse of fixed length.
The output−reset pulse remains asserted for the Reset Active
Time−Out Period t
RP
and then clears. Once the reset pulse
is completed, the MR input remains disabled for at least
49
mS
but not more than 122
mS.
This period is specified as
t
MRD
.
During the MR disabled period, the microcontroller is
guaranteed a time period free of new manual reset signals.
This period can be used to refresh critical DRAM contents
or other system tasks.
The MR pin must be taken HIGH and LOW again after the
t
MRD
period has been completed to initiate another reset
pulse.
The manual reset input has an internal 20 kW pull−up
resistor. MR can be left open if not used.
Figure 3. Manual Reset Timing
Figure 4. RESET Valid with VCC under 1.1 V
Valid Reset with VCC under 1.1 V
Application Information
Glitch Resistance
The ASM161/162 are relatively immune to short duration
negative−going VCC transients/glitches. A VCC transient
that goes 100 mV below the reset threshold and lasts 20s or
less will not typically cause a reset pulse.
Table 2. ABSOLUTE MAXIMUM RATINGS
Parameter
Pin Terminal Voltage with Respect to Ground
V
CC
RESET, RESET and MR
Input Current at VCC and MR
Rate of Rise at VCC
Power Dissipation (TA = 70°C)
Operating Temperature Range
Storage Temperature Range
Lead Temperature (soldering, 10 sec)
ESD rating
HBM
MM
To ensure that logic inputs connected to the ASM162
RESET pin are in a known state when VCC is under 1.1 V,
a 100 kW pull−down resistor at RESET is needed. The value
is not critical.
This scheme does not work with the open−drain outputs
of ASM161.
Min
−0.3
−0.3
Max
6.0
V
CC
+ 0.3
20
100
320
Unit
V
V
mA
V/ms
mW
°C
°C
°C
KV
V
−40
−65
85
160
300
2
200
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
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3
ASM161, ASM162
Table 3. ELECTRICAL CHARACTERISTICS
(Unless otherwise noted, V
CC
is over the full range and T
A
= 0°C to 70°C for ASM161/162 X C and T
A
=
−40°C
to +85°C for ASM161/162
X E devices. Typical values at T
A
= 25°C, V
CC
= 5 V for L/M/J devices, V
CC
= 3.3 V for T/S devices and V
CC
= 3 V for R devices.)
Parameter
Input Voltage (V
CC
)
Range
Supply Current
(Unloaded)
Symbol
V
CC
I
CC
Conditions
T
A
= 0°C to 70°C
T
A
= 0°C to 70°C,
T
A
=
−40°C
to +85°C
T
A
= 0°C to 70°C,
T
A
=
−40°C
to +85°C
Reset Threshold
V
TH
L Devices
M devices
J devices
T devices
S devices
R devices
Reset Threshold
Temp Coefficient
V
CC
to reset delay
Reset Pulse Width
t
RPW
t
MR
T
CVTH
V
CC
= V
TH
to (V
TH
−100
mV)
T
A
= 0°C to 70°C
T
A
=
−40°C
to 85°C
MR Minimum Pulse
Width
MR Glitch Immunity
MR to RESET
Propagation Delay
MR Input Threshold
V
IH
V
IL
V
IH
V
IL
MR Delay to MR
Retrigger
MR pull−up
resistance
Low RESET output
voltage (ASM161)
V
OL
V
CC
= V
TH
min., I
SINK
= 1.2 mA, ASM161 R/S/T
V
CC
= V
TH
min., I
SINK
= 3.2 mA, ASM161L/M/J
V
CC
> 1.1, I
SINK
= 50
mA
RESET Output
Voltage (ASM162)
HIGH RESET Output
Voltage (ASM162)
V
OL
V
OH
V
CC
= V
TH
max., I
SINK
= 1.2 mA, ASM162 R/S/T
V
CC
= V
TH
max., I
SINK
= 3.2 mA, ASM162 L/M/J
1.8 < V
CC
< V
THmin.
, I
SOURCE
= 150
mA
0.8V
CC
t
MRD
T
A
= 0°C to 70°C
T
A
=
−40°C
to 85°C
10
48
85
85
20
30
0.3
0.4
0.3
0.3
0.4
V
V
KW
V
V
CC
> V
TH
(MAX), R/S/T devices
0.7V
CC
0.25V
CC
122
V
CC
> V
TH
(MAX), L/M/J devices
2.3
0.8
800
600
10
100
0.5
V
CC
< 5.5 V L/M/J
V
CC
< 3.6 V R/S/T
T
A
= 25°C
(Note 1)
T
A
= 25°C
(Note 1)
T
A
= 25°C
(Note 1)
T
A
= 25°C
(Note 1)
T
A
= 25°C
(Note 1)
T
A
= 25°C
(Note 1)
4.56
4.50
4.31
4.25
3.93
3.89
3.04
3.00
2.89
2.85
2.59
2.55
Min
1.1
6
4.5
4.63
4.38
4.00
3.08
2.93
2.63
30
20
1400
2000
2240
mS
ns
mS
V
V
V
V
mS
Typ
Max
5.5
15
10
4.70
4.75
4.45
4.50
4.06
4.10
3.11
3.15
2.96
3.00
2.66
2.70
ppm/
°C
mS
ms
V
Unit
V
mA
1. Over operating temperature range.
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4
ASM161, ASM162
PACKAGE DIMENSIONS
SOT−143, 4 Lead
CASE 527AF−01
ISSUE A
SYMBOL
A
D
e
A1
A2
b
4
3
b2
c
D
E1
E
E
E1
1
2
e
e1
e1
b
L
L1
L2
TOP VIEW
0.40
MIN
0.80
0.05
0.75
0.30
0.76
0.08
2.80
2.10
1.20
1.30
1.92 BSC
0.20 BSC
0.50
0.54 REF
0.25
0.60
2.90
0.90
NOM
MAX
1.22
0.15
1.07
0.50
0.89
0.20
3.04
2.64
1.40
θ
0°
8°
A2
A
q
c
L2
b2
A1
L
L1
SIDE VIEW
Notes:
(1) All dimensions are in millimeters. Angles in degrees.
(2) Complies with JEDEC TO-253.
END VIEW
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