AS1907, AS1908, AS1909
Low-Voltage Microprocessor Reset Circuits
www.austriamicrosystems.com/Supervisors/AS1907-09 Revision 1.06 1 - 10
Datasheet
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
(see Ordering Information on page 9).
The devices are available as the standard products
listed in Table 1.
The reset thresholds are factory-set between 1.6 and
2.5V in steps of approximately 100mV (see Table 5 on
page 7).
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.
Figure 1. Application Diagrams
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
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.
Table 1. Standard Products
Model Output Type Reset Type
AS1907 Push/Pull Active-Low
AS1908 Push/Pull Active-High
AS1909 Open-Drain Active-Low
2
RESET
AS1908
Micro-
processor
VCCVCC
GND 1
VCC 3 VCC 3
RESET I/O
RESETN
2
AS1907
GND 1
VCC 3
GND 1
Micro-
processor
V
CC 3
RESET I/O
GND 1
2
RESETN
AS1909
Micro-
processor
VCC
GND 1
VCC 3 VCC 3
RESET I/O
GND 1
