AS1907, AS1908 , AS1909

Low-Voltage Microprocessor Reset Circuits

www.ams.com/Supervisors/AS1907-09

Revision 1.8

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1 General Description

The AS1907/AS1908/AS1909 microprocessor supervisory 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 components. The extremely low

current consumption makes the devices ideal for use in portable

applications.

The integrated reset comparator was specifically designed to ignore

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 increments)



RESET/RESETN:



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

GND 1

RESET I/O

RESETN

2

AS1907

GND 1

Micro-

processor

RESET I/O

2

RESETN

AS1909

Micro-

processor

GND 1

RESET I/O