MAX1725(2003) 데이터 시트보기 (PDF) - Maxim Integrated
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MAX1725 Datasheet PDF : 7 Pages
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12V, Ultra-Low IQ, Low-Dropout
Linear Regulators
The error amplifier compares 1.245V to the selected
feedback voltage and amplifies the difference. If the
feedback voltage is lower than 1.245V, the pass-tran-
sistor gate is pulled lower, allowing more current to
pass, and thus increasing the output voltage. If the
feedback voltage is higher than 1.245V, the pass-tran-
sistor gate is driven higher, allowing less current to
INPUT
2.5V TO 12V
IN
CIN
1µF
OUT
MAX1725
ON
OFF
SHDN
GND
FB
OUTPUT
1.5V TO 5V
COUT
1µF
R1
R2
1.2MΩ
Figure 1. Typical Application Circuit
pass to the output. The output voltage is fed back
through either an internal resistor voltage-divider con-
nected to OUT (MAX1726) or an external resistor net-
work connected to FB (MAX1725). Additional features
include an output current limiter, reverse-battery protec-
tion, a thermal sensor, and shutdown logic.
Internal P-Channel Pass Transistor
The MAX1725/MAX1726 feature a P-channel MOSFET
pass transistor. This provides advantages over similar
designs using PNP pass transistors, including longer
battery life. The P-channel MOSFET requires no base
drive, which reduces quiescent current considerably.
PNP-based regulators waste considerable current in
dropout when the pass transistor saturates; they also
use high base-drive currents under large loads. The
MAX1725/MAX1726 do not suffer from these prob-
lems, and consume only 2µA of quiescent current
throughout their load range (see the Typical Operating
Characteristics).
Shutdown
To enter shutdown, drive the SHDN pin below 0.5V.
When the MAX1725/MAX1726 are shut down, the output
IN
SHDN
BIAS
CIRCUITRY
MAX1725
MAX1726
THERMAL
SHUTDOWN
1.245V
OUT
(MAX1726 ONLY)
FB (MAX1725 ONLY)
GND
Figure 2. Functional Diagram
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