Acutechnology Semiconductor Inc.

AQ533

www.acutechnology.com

6

Rev. 1.7 September 13, 2006

Application Notes

1. Typical Application

Notes:

1. Output voltage is 1.22V * (R1 +R2)/R2

2. Input and output capacitors should be located close to the device.

3. The AQ533 will remain stable with C1 and C3 as low as 0.1 µF and 1.0 µF respectively.

Overall transient performance is improved with increased capacitance and the addition of C2.

be driven by either a digital or analog signal to control either turn-on time or to give full

control of risetime.

voltage (0.95V).

2. Stability

An Enable capacitor is recommended. A 100nF capacitor is a suitable input bypass for

almost all applications. A larger capacitor is also suitable depending on the cleanliness of the

Enable source.

A Vin Capacitor is also recommended. A 1µF capacitor is a bypassing for almost all applications.

The Output capacitor is critical in maintaining regular stability. The AQ533 is stable with an

output capacitor greater than 1µF. Any increase of the output capacitor will merely improve

the loop stability and the load transient response.

Tantalum Capacitors exhibit the best stability over a wide range of loads and are recommended.

3. Output Voltage

The AQ533 meets all specifications down to 1.22V output. It does not suffer from

performance degradation issues such as experienced with CMOS LDO’s. Drop out voltage

The AQ533 develops a 1.22V reference voltage between the adjust pin terminal and ground.

This voltage is applied across the resistor R2 to generate a constant current (I2). The current