austriamicrosystems AG
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ams AG
The technical content of this austriamicrosystems datasheet is still valid.
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8141 Unterpremstaetten, Austria
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AS1920, AS1922
Tri p l e - Vo l ta g e , M i c r o - P o w e r M i c r o p r o c e s s o r
S u p e r v i s o r y C i r c u i ts
D a ta S h e e t
1 General Description
The AS1920 and AS1922 microprocessor supervisory
circuits were designed to generate a reset when at least
one of the three monitored supply voltages falls below
its respective trip threshold.
These very-low-current (6.2μA, typ) devices maintain
reset for a minimum timeout period after all supplies
have stabilized. Guaranteed to be in the correct state for
V
CC
> +1.0V, these devices are perfect for multiple-volt-
age systems with low current requirements and strict
monitoring requirements.
The devices are available as the standard products
listed in
Table 1.
Table 1. Standard Products
Model
AS1920-18
AS1922-18
Push/Pull
2 Key Features
Simultaneous Triple-Voltage Monitoring
Very-Low Supply Current: 6.2μA
±1.5% Accuracy Over Temperature
Reset Time Delay: 200ms
c
h
ni
c
a
a
m
lc s
on A
te G
nt
st
il
Output Type
Open-Drain
Supervisory Voltages
3V, 1.8V, Adjustable
e
3V, 1.8V, Adjustable
ble
Guarant
Guarante
Guaranteed Reset for V
CC3
r
5-pin SOT Package
SO
SOT23
Pow
Powe
Power Supply Transient Immunity
t
mmunity
A
Active-Low Push/Pull R
ow
Reset Output (AS1920)
Active-Low Open
ve-Low Ope
Open-Drain Reset Output (AS1922)
All devices monitor primary and secondary factory-
tory-
ry-
trimmed voltages. Additionally, a third monitoring voltage
oring
ring
can be selected via an external resistor divider.
ivider.
vider
The AS1920 has an active-low push/pull reset output,
pull
ou
out
whereas the AS1922 has an active-low open-drain reset
e-low open-dr
-low open-d
et
output.
The AS1920 and AS1922 are available in a 5-pin
le
n
SOT23 package.
3 A
Applications
The devices are ideal for personal computers, note-
books, battery-powered systems, embedded controllers,
intelligent instruments, automotive systems, critical CPU
monitoring, and any multi-supply monitoring application.
Figure 1. Typical Application Diagram
agram
3V
1.8V
8V
System
Logic
2.5V
V
5
V
CC3
4
0.1μF
R
1
130k
1%
0.1μF
R
2
100k
1%
V
CC18
3
V
CCA
AS1920/
AS1922
1
RESETN
2
GND
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Revision 1.00
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1V or V
CC18
V
1V
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AS1920/AS1922
Datasheet - P i n o u t
4 Pinout
Pin Assignments
Figure 2. Pin Assignments (Top View)
RESETN 1
5 V
CC3
GND 2
AS1920/
AS1922
V
CCA
3
4 V
CC18
Pin Descriptions
Pin Number
1
2
3
Table 2. Pin Descriptions
4
5
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Pin Name
RESETN
GND
Description
ption
Ground.
round
ound.
V
CCA
V
CCA
. 1V sense, high-impedance i
s
-impedance
input.
Note:
If this pin is not used it should be tied to V
CC3
or V
CC18
.
I
n
s
V
CC18
V
CC3
Revision 1.00
Reset Logic Output.
This active-low pin serves a the 3V push/pull reset
as
O put.
Th
t.
ow
output. A reset is asserted when any one of the supplies are below its
eset
serte
ert
n
y
th
respective
trip thre
threshold and the reset is held for 200ms after all power supplies
ve
thresh
have stabilized.
V
CC18
. 1.8V sense input and power detect pin (AS1920-18, AS1922-18). This
C
CC
V
se
an
pin provides power to the output reset stage of the device in order to assert a
ides
s
th
valid reset when the voltage on the primary input is down.
set
th
v
Note:
Bypass this pin to GND with a 0.1μF ceramic capacitor.
ote:
ass
V
CC3
. 3V se
sense input and power supply pin (AS1920-18, AS1922-18). This pin
power to the device.
provides po
Bypass this pin to GND with a 0.1μF ceramic capacitor.
Note:
By
B
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AS1920/AS1922
Datasheet - A b s o l u t e M a x i m u m R a t i n g s
5 Absolute Maximum Ratings
Stresses beyond those listed in
Table 3
may cause permanent damage to the device. These are stress ratings only,
and functional operation of the device at these or any other conditions beyond those indicated in
Electrical Character-
istics on page 4
is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
Table 3. Absolute Maximum Ratings
V
CC18
, V
CC3
, V
CCA
to GND
RESETN Open-Drain
RESETN to GND
-0.3V
-0.3
-0.3
+5
+7
V
CC3
+
0.3
V
V
V
Operating Temperature Range
-40
+85
ºC
Storage Temperature Range
Package Body Temperature
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G
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i l
l
-65
+150
ºC
+260
60
ºC
Revision 1.00
Guaranteed to meet specified performance from
p
pe rmance
fr
mance
0 to 70ºC and is designed, characterized and
char
charac rized
an
ed
assured to meet the extended temperature limits
ded temper re
tempe
of -40 to 85ºC but are not tested at these
e
a
temperatures.
peratures.
The r
reflow peak
soldering te
temperature (body
eak
tem
temperature) specified is i accordance with
te
tem
pecified i
in
IPC/JEDEC J-STD-020C “Moisture/Reflow
D
DEC STD-020
Sensitivity Classification for Non-Hermetic Solid
vity Class ation
y Cla
State Surface Mount Devices”.
tate
Sur
The lead finish for Pb-free leaded packages is
he
ead
fo
matte tin (100% Sn).
m
ma
v
a
li
d
3 - 14
Parameter
Min
Max
Units
Comments
AS1920/AS1922
Datasheet - E l e c t r i c a l C h a r a c t e r i s t i c s
6 Electrical Characteristics
V
CC18
= 1.8V, V
CC3
= 3V, V
CCA
= V
CC3
, T
AMB
= -40 to +85ºC (unless otherwise specified).
Table 4. Electrical Characteristics
Symbol
V
RT18
V
RT3
V
RTA
V
CC3
, V
CC18
I
VCC18
I
VCC3
I
VCCA
I
OUT
I
LEAK
t
RST
t
UV
1
Parameter
Reset Threshold V
CC18
Reset Threshold V
CC3
Operating Voltage
Reset Threshold V
CCA
V
CC18
Supply Current
V
CC3
Supply Current
V
CCA
Input Current
Conditions
Min
1.653
2.763
0.982
1
Typ
1.683
2.805
1.00
0.7
Max
1.713
2.847
3.3
2
15
1.018
Unit
V
V
V
Open-Drain RESETN
Output Current
Open-Drain RESETN Output
Leakage Current
Reset Pulse Width
V
CC
Undervoltage
Detect to RESETN
V
OL
Output Voltage Low, RESETN
ow, RESET
V
OH
Output Voltage High, RESETN
ESET
1. Guaranteed by design.
2. Measured from the time (t
1
) when the inpu passes through the input threshold voltage (V
RTX
) to the time (t
2
)
hen
input
when RESETN passes through 1.5V.
s
hrough
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RESETN in Correct Logic State
V
CC18
< V
CC3
, V
CC18
= 1.8V
V
CC18
< V
CC3
, V
CC3
= 3V
V
CCA
= 1V
V
μA
6.2
0
μA
nA
-15
2
15
Reset Not Asserted, Forced to 0V
ed
Reset Not Asserted, RESETN
R
Forced to 5.5V, T
AMB
= 25ºC
RESETN Low,
T
AMB
= 25ºC
ESETN
SETN
AM
C
2
4
13
μA
-0.1
0.1
140
0.1
μA
200
130
280
ms
μs
V
CC18
, V
CC3
, or V
CCA
<
C18
CA
2
Reset Thre
Threshold by > 1%
R et
Th
T
AMB
= 25ºC
I
SINK
= 2.5mA, V
CC3
= 3V,
SIN
mA,
V
CC18
= 0V
C18
0.15
0.05
0.4
0.3
I
SINK
=
100μA,
V
CC3
= 1V,
CC
V
CC18
= 0V
I
SINK
= 100μA, V
CC3
= 0V,
INK
100μA
V
CC18
= 1V
CC1
C
V
0.05
0.05
0.3
0.3
I
SINK
= 1
K
100μA, V
CC3
= 1V,
V
CC18
= 1V
I
SOURCE
= 1μA (AS1922-xx)
S
V
CC3
-
1
V
CC3
-
0.65
V
Revision 1.00
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