Datasheet
MAX1725/MAX1726
12V, Ultra-Low I
Q
, Low-Dropout
Linear Regulators
5
Maxim Integrated
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
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
).
INPUT
2.5V TO 12V
OUTPUT
1.5V TO 5V
MAX1725
OFF
ON
IN OUT
FB
SHDN
GND
R1
R2
1.2MΩ
C
OUT
1µF
C
IN
1µF
IN OUT
FB (MAX1725 ONLY)
(MAX1726 ONLY)
SHDN
BIAS
CIRCUITRY
THERMAL
SHUTDOWN
GND
1.245V
MAX1725
MAX1726
Figure 1. Typical Application Circuit
Figure 2. Functional Diagram