MAX1598 Datasheet, PDF (6/9 Pages) Maxim Integrated Products – Low-Noise, Low-Dropout, 200mA Linear Regulator

Low-Noise, Low-Dropout, 200mA
Linear Regulator
______________________________________________________________Pin Description
PIN
NAME
FUNCTION
1
IN
Regulator Input. Supply voltage can range from 2.5V to 6.5V. Bypass with a 1µF capacitor to GND
(see the Capacitor Selection and Regulator Stability section).
2
GND
Ground. This pin also functions as a heatsink. Solder to a large pad or the circuit-board ground
plane to maximize power dissipation.
3
SHDN
Active-Low Shutdown Input. A logic low reduces the supply current to 10nA and causes the output
voltage to discharge to GND. Connect to IN for normal operation.
4
BP
Reference-Noise Bypass. Bypass with a low-leakage, 0.01µF ceramic capacitor for reduced noise at
the output.
5
OUT
Regulator Output. Sources up to 200mA. Bypass with a 2.2µF (<0.2Ω typical ESR) capacitor to GND.
Detailed Description
The MAX1598 is a low-noise, low-dropout, low-quies-
cent-current linear regulator designed primarily for bat-
tery-powered applications. The part is available with
preset output voltages from 2.5V to 5V in 100mV incre-
ments. This device can supply loads up to 200mA. As
illustrated in Figure 1, the MAX1598 consists of a 1.25V
reference, error amplifier, P-channel pass transistor,
and internal feedback voltage-divider.
The 1.25V bandgap 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
lower, which allows more current to pass to the output
and increases the output voltage. If the feedback volt-
age is too high, the pass-transistor gate is pulled up,
allowing less current to pass to the output. The output
voltage is fed back through an internal resistor voltage-
divider connected to the OUT pin.
An external bypass capacitor connected to the BP pin
reduces noise at the output. Additional blocks include a
current limiter, reverse battery protection, thermal sen-
sor, and shutdown logic. The MAX1598 also includes
an autodischarge function, which actively discharges
the output voltage to ground when the device is placed
in shutdown mode.
IN
SHDN
REVERSE
BATTERY
PROTECTION
MAX1598
SHUTDOWN
AND
POWER-ON
CONTROL
ERROR
AMP
MOS DRIVER
WITH I_LIMIT
THERMAL
SENSOR
1.25V
REF
GND
P
OUT
N
BP
Figure 1. Functional Diagram
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