AS1907, AS1908 , AS1909 Low-Voltage Microprocessor Reset Circuits 1 General Description 2 Key Features 3 Output Types: Push/Pull RESET, Push Pull RESETN, and The AS1907/AS1908/AS1909 microprocessor supervisory circuits Open Drain RESETN are ideal for monitoring the supply voltage of digital systems and microprocessors. Reset Threshold Range: 1.6 to 2.5V (~100mV increments) The devices are designed to initiate a reset if the supply voltage goes RESET/RESETN: below a predefined threshold. The duration of the reset is either 1.5, -Valid to VCC = 0.7V (AS1907 and AS1908) 30, or 150ms (typ.) after the supply voltage has risen above the pre- -Valid to VCC = 1.0V (AS1909) set threshold (see Ordering Information on page 9). The devices are available as the standard products listed in Table 1. Reset Pulse Widths: 1, 20, and 100ms Supply Voltage Range: +0.7 to +3.6V Table 1. Standard Products Supply Current Range: 2.6 to 7.0A Model Output Type Reset Type Power Supply Transient Immunity AS1907 Push/Pull Active-Low Requires No External Components AS1908 Push/Pull Active-High Operating Temperature Range: -40 to +125C AS1909 Open-Drain Active-Low 3-pin SOT23 Package The reset thresholds are factory-set between 1.6 and 2.5V in steps of approximately 100mV (see Table 5 on page 7). 3 Applications The devices exhibit excellent reliability, and can reduce system costs by eliminating the need for external components. The extremely low The devices are ideal for use in cordless and mobile phones, MP3 current consumption makes the devices ideal for use in portable players, CD and DVD players, PDAs, handheld computers, digital applications. cameras, hard drives, and any other application where power supply The integrated reset comparator was specifically designed to ignore supervisory control is required. fast transients on VCC. The devices are available in a 3-pin SOT23 package. Figure 1. Application Diagrams VCC VCC VCC VCC 3 VCC 3 VCC 3 VCC 3 VCC 3 VCC 3 Micro- Micro- Micro- processor processor processor RESETN 2 2 AS1907 AS1908 AS1909 RESET I/O RESET RESET I/O RESETN RESET I/O 2 GND 1 GND 1 GND 1 GND 1 GND 1 GND 1 www.ams.com/Supervisors/AS1907-09 Revision 1.8 1 - 10AS1907/AS1908/AS1909 Datasheet - Pin Assignments 4 Pin Assignments Figure 2. Pin Assignments (Top View) GND 1 AS1908/ 3VCC AS1907/ AS1909 RESET, 2 RESETN 4.1 Pin Descriptions Table 2. Pin Descriptions Pin Number Pin Name Description 1GND Ground Active-High Reset Output (AS1908). This pin stays high whenever VCC is below the RESET threshold VTH (see page 7), and for tTP (see page 4) after VCC rises above RESET VTH. 2 Active-Low Reset Output (AS1907, AS1909). This pin remains low while VCC is below the RESET threshold VTH (see page 7), and for tTP (see page 4) after VCC rises RESETN above VTH. Note: This pin is open-drain on the AS1909. 3 VCC Positive Supply Voltage. Connect to +0.7 to +3.6V supply. www.ams.com/Supervisors/AS1907-09 Revision 1.8 2 - 10