G914 데이터 시트보기 (PDF) - Global Mixed-mode Technology Inc
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G914 Datasheet PDF : 6 Pages
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Global Mixed-mode Technology Inc.
Pin Description
G914
PIN NAME
1
IN
2
GND
3
SHDN
4
ADJ
5
OUT
FUNCTION
Regulator Input. Supply voltage can range from +2.5V to +5.5V. Bypass with 1µF to GND
Ground. This pin also functions as a heatsink. Solder to large pads or the circuit board ground plane to
maximize thermal dissipation.
Active-Low Shutdown Input. A logic low reduces the supply current to less than 1µA. Connect to IN for normal
operation.
Adjust (Input): Adjustable regulator feedback input. It can connect to an external resistor divider for ad-
justable output voltage. It also must connect ≥470pF ceramic capacitor from ADJ pin to GND for reduce
output noise.
Regulator Output. Fixed or adjustable from +2.5V to +5.5V. Sources up to 150mA. Bypass with a 1µF,
＜0.2Ω typical ESR capacitor to GND.
Detailed Description
The block diagram of the G914 is shown in Figure 1. It
consists of an error amplifier, 1.25V bandgap refer-
ence, PMOS output transistor, shutdown logic, over
current protection circuit, and over temperature protec-
tion circuit.
The G914 can be adjusted to a specific output voltage
by using two external resistors (Figure 2). The resis-
tors set the output voltage based on the following
equation:
VOUT =1.250V X
R2
R1
+1
This equation is correct due to the configuration of the
bandgap reference. The bandgap voltage is relative to
the output, as seen in the block diagram. Traditional
regulators normally have the reference voltage relative
to ground and have a different VOUT equation. Resistor
values are not critical because ADJ (adjust)has a high
input impedance, but for best results use resistors of
470kΩ or less. A capacitor from ADJ to ground pro-
vides greatly improved noise performance.
IN
SHDN
SHUTDOWN
LOGIC
OVER TEMP. &
OVER CURRENT
PROTECTION
1.25V
ref
ERROR
AMP.
＋
GND
Figure 1. Functional Diagram
OUT
ADJ
Ver 0.1 Preliminary
Nov 05, 2001
TEL: 886-3-5788833
http://www.gmt.com.tw
3
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