SA57031-XX Datasheet, PDF (8/13 Pages) NXP Semiconductors – Micropower 150 mA, low-noise, low dropout linear regulator with on/off

Philips Semiconductors
Micropower 150 mA, low-noise, low dropout linear
regulator with on/off
Product data
SA57031-XX
TECHNICAL DISCUSSION
As illustrated in Figure 16, the SA57031 consists of a band-gap
voltage reference, an error amplifier, P-channel pass transistor,
current limit circuit and an internal feedback voltage divider. The
output voltage is fed back through an internal resistor voltage divider
connected to the VO pin.
The reference is connected to the error amplifier’s inverting input.
The error amplifier compares the reference with the feedback
SA57031-XX
V_I
3
voltage and amplifies the difference. If the feedback voltage is lower
than the reference voltage, the pass transistor’s gate is pulled lower,
which allows more current to pass to the output and increase the
output voltage. If the feedback voltage is too high, the pass
transistor gate is pulled up, allowing less current to pass to the
output, resulting in a decrease in output voltage.
2
V_O
ON/OFF 4
V_REF
CURRENT
LIMITER
Figure 16. Block diagram (bottom view).
1
GND
SA00634
2003 Jun 23
8