AS1907, AS1908 , AS1909
L o w - Vo l ta g e M i c r o p r o c e s s o r R e s e t C i r c u i ts
D a ta S he e t
1 General Description
The AS1907/AS1908/AS1909 microprocessor supervi-
sory circuits are ideal for monitoring the supply voltage
of digital systems and microprocessors.
The devices are designed to initiate a reset if the supply
voltage goes below a predefined threshold. The duration
of the reset is either 1.5, 30, or 150ms (typ.) after the
supply voltage has risen above the pre-set threshold
The devices are available as the standard products
listed in
Table 1. Standard Products
Model
AS1907
AS1908
AS1909
Output Type
Push/Pull
Push/Pull
Open-Drain
Reset Type
Active-Low
Active-High
Active-Low
2 Key Features
!
3 Output Types: Push/Pull RESET, Push Pull
RESETN, and Open Drain RESETN
Reset Threshold Range: 1.6 to 2.5V (~100mV incre-
ments)
RESET/RESETN:
- Valid to V
CC
= 0.7V (AS1907 and AS1908)
- Valid to V
CC
= 1.0V (AS1909)
Reset Pulse Widths: 1, 20, and 100ms
Supply Voltage Range: +0.7 to +3.6V
Supply Current Range: 2.6 to 7.0µA
Power Supply Transient Immunity
Requires No External Components
Operating Temperature Range: -40 to +125ºC
3-pin SOT23 Package
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The reset thresholds are factory-set between 1.6 and
2.5V in steps of approximately 100mV
The devices exhibit excellent reliability, and can reduce
system costs by eliminating the need for external com-
ponents. The extremely low current consumption makes
the devices ideal for use in portable applications.
The integrated reset comparator was specifically
designed to ignore fast transients on V
CC
.
The devices are available in a 3-pin SOT23 package.
!
3 Applications
The devices are ideal for use in cordless and mobile
phones, MP3 players, CD and DVD players, PDAs,
handheld computers, digital cameras, hard drives, and
any other application where power supply supervisory
control is required.
Figure 1. Application Diagrams
V
CC
V
CC
3
V
CC
3
V
CC
V
CC
3
V
CC
3
V
CC
V
CC
3
V
CC
3
Micro-
processor
Micro-
processor
Micro-
processor
AS1907
RESETN
2
RESET I/O
AS1908
2
RESET
RESET I/O
AS1909
2
RESETN
RESET I/O
GND
1
GND
1
GND
1
GND
1
GND
1
GND
1
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