SA57005 Datasheet, PDF (7/12 Pages) NXP Semiconductors – Multiple output low noise, low dropout linear regulator

Philips Semiconductors
Multiple output low noise, low dropout linear regulator
Product data
SA57005
TECHNICAL DISCUSSION
As illustrated in the circuit diagram, each of the regulators in the
SA57005 consists of a 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 output voltage pins.
The reference will be activated if any of the PS1 and PS2/3 switches
is turned on.
V_IN
PS1
4
1
The reference is connected to the error amplifier’s non-inverting
input. The error amplifier compares the reference with the feedback
voltage and amplifies the difference. If the feedback voltage is lower
than the reference voltage the output of the error amplifier goes up,
which pulls down the pass transistor’s gate. This allows more
current to pass to the output and increase the output voltage. On the
other hand, if the feedback voltage is too high the pass transistor
gate is pulled up, allowing less current to pass to the output,
resulting a decrease in output voltage.
7 V_o1
TERMINAL
PROTECT
PS2/3
2
6 V_o2
5 V_o3
2002 Jun 20
Figure 10. Functional diagram.
7
8 GND
SL01705