AS1920, AS1922
Triple-Voltage, Micro-Power Microprocessor
Supervisory Circuits
austriamicrosystems
Product Brief
www.austriamicrosystems.com Revision 0.65 1 - 2
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 (6.5µA, typ) devices maintain
reset for a minimum timeout period after all supplies
have stabilized. Guaranteed to be in the correct state for
VCC > +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.
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.
Figure 1. Typical Application Diagram
2 Key Features
! Simultaneous Triple-Voltage Monitoring
! Very-Low Supply Current: 6.5µA
! ±1.5% Accuracy Over Temperature
! Reset Time Delay: 200ms
! Power Supply Transient Immunity
! Guaranteed Reset for VCC3 ≥ 1V or VCC18 ≥ 1V
! Active-Low Push/Pull Reset Output (AS1920)
! Active-Low Open-Drain Reset Output (AS1922)
! 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.
Table 1. Standard Products
Model Output Type Supervisory Voltages
AS1920-18 Push/Pull 3V, 1.8V, Adjustable
AS1922-18 Open-Drain 3V, 1.8V, Adjustable
3V
System
Logic
1.8V
2.5V
AS1920/
AS1922
0.1µF
R1
130kΩ
1%
R2
100kΩ
1%
0.1µF
1
RESETN
3
VCCA
2
GND
4
VCC18
5
VCC3