AS1920, AS1922
Tr i 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
Supervi s ory Ci rcuits
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
Output Type
Push/Pull
Open-Drain
Supervisory Voltages
3V, 1.8V, Adjustable
3V, 1.8V, Adjustable
2 Key Features
!
Simultaneous Triple-Voltage Monitoring
Very-Low Supply Current: 6.2µA
±1.5% Accuracy Over Temperature
Reset Time Delay: 200ms
Power Supply Transient Immunity
Guaranteed Reset for V
CC3
≥
1V or V
CC18
≥
1V
Active-Low Push/Pull Reset Output (AS1920)
Active-Low Open-Drain Reset Output (AS1922)
5-pin SOT23 Package
!
!
!
!
!
!
All devices monitor primary and secondary factory-
trimmed voltages. Additionally, a third monitoring voltage
can be selected via an external resistor divider.
The AS1920 has an active-low push/pull reset output,
whereas the AS1922 has an active-low open-drain reset
output.
The AS1920 and AS1922 are available in a 5-pin
SOT23 package.
!
!
3 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
3V
1.8V
2.5V
5
V
CC3
4
R
1
130kΩ
1%
0.1µF
R
2
100kΩ
1%
V
CC18
3
V
CCA
System
Logic
AS1920/
AS1922
1
RESETN
2
GND
0.1µF
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