lp2985-28d NXP Semiconductors, lp2985-28d Datasheet - Page 8

• Manufacturer Part Number: lp2985-28d
• Description: Lp2985-xx Micropower 150 Ma Low Noise, Low Dropout Linear Regulator
• Manufacturer: NXP Semiconductors

output voltage is fed back through an internal resistor voltage divider
Philips Semiconductors
TECHNICAL DISCUSSION
As illustrated in Figure 21, the LP2985-XX consists of a band-gap
voltage reference, an error amplifier, P-channel pass transistor,
current limit circuit and an internal feedback voltage divider. The
connected to the V
The reference is connected to the error amplifier’s 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 pass transistor’s gate is pulled lower,
which allows more current to pass to the output and increase the
2003 Oct 31
Micropower 150 mA low noise,
low dropout linear regulator
OUT
pin.
ON/OFF
NOISE
GND
V
IN
3
1
4
2
REFERENCE
BIAS
LP2985-XX
Figure 21. Block diagram.
SHUTDOWN
THERMAL
8
DRIVER
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.
An external bypass capacitor connected to the NOISE pin reduces
noise at the output.
Additional functional blocks include a current-limiter, thermal sensor
and shut-down logic. The current-limiter monitors and controls the
pass-transistor’s gate voltage, limiting the output current to its
specified maximum value. Thus it can withstand a short-circuited
output for an indefinite amount of time without damaging the part.
CURRENT
LIMIT
SL01545
5
V
OUT
LP2985-XX
Product data