YB1200 – High Accuracy
Ultra-Low-Noise, High PSRR LDO Regulator
Functional Block Diagram
IN
EN
SHUTDOWN AND
POWER-ON CONTROL
ERROR
AMP
MOS DRIVER
WITH
LIMIT
P
OUT
THERMAL
SENSOR
REFERENCE
AND NOISE BYPASS
GND
Figure 3. Block Diagram
Functional Description
The YB1200 is an ultra-low-noise,
low-quiescent current, low-dropout linear
regulator. It is supplied in a SC-70 and
SC-82 package for space and noise
sensitive applications. These devices can
supply loads up to 150mA. As shown in the
Functional Block Diagram,
the YB1200
consists of a reference and noise bypass
circuit, error amplifier, output drive
transistor, internal feedback voltage divider,
thermal sensor, and short circuit current
limiter. The internal reference is connected
to the error amplifier’s inverting input. The
error amplifier compares this reference with
the feedback voltage and amplifies the
difference. If the feedback voltage is lower
than
the
reference
voltage,
the
pass-transistor gate is pulled low. This
allows more current to pass to the output
and increases the output voltage. If the
feedback voltage is too high, the pass
YB1200 MRev.1.4
transistor gate is pulled high, allowing less
current to pass to the output. The parts are
available with preset output voltages
ranging from 1.8V to 3.3V.
Stability
The YB1200 is a high performance LDO
emphasizing stability with low output
capacitance. It is able to maintain stability
with an output capacitor as low as 0.47uF.
The output capacitor can also be increased
to optimize performance. The YB1200 will
remain stable and in regulation with no load,
unlike many other voltage regulators.
Internal P-Channel Pass Transistor
The YB1200 features a low impedance
P-channel MOSFET pass transistor. This
provides several advantages over similar
designs using a PNP pass transistor,
including low operating power and longer
8
www.yobon.com.tw
YOBON [ YOBON TECHNOLOGIES,INC. ]
