AQ120EX Datasheet, PDF (4/6 Pages) Acutechnology Semiconductor – LDO Regulator Controller SOT23-5 Package

Acutechnology Semiconductor Inc.
APPLICATION
AQ120
(Figure 1)
GENERAL DESCRIPTION
The AQ120 is a linear LDO voltage regulator controller. It drives a discrete PNP transistor while
comparing the output to a 1.25V reference. The output voltage is programmable through an external
resistor divider. VOUT can be set to any value above 1.25 Volts. The collector of the external PNP
transistor provides the output current to the load. Vin range is 2.5V to 18V. The Maximum Load current
is Beta of the PNP times IDRIVE. IDRIVE range is 0.1 mA to 20 mA (max).
SETTING THE OUTPUT VOLTAGE
The AQ120 VREF pin is the input to an amplifier comparing to a precision 1.25V reference.
With VREF tied back to the output, it will drive the base of the external PNP to maintain output voltage
with changing load current and VCC. The regulated output voltage can be set by selecting the proper
ratio of R1 and R2.
The Output Voltage is set by:
( ) Vout
=
V_REF
∗
R1 + R2
R2
= 1.25V
∗
1+
R1 _R2
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Rev. 1.2 April 1, 2006