MAX1658CSLASHD datasheet(6/10 Pages) MAXIM

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Detailed Description

The MAX1658/MAX1659 are micropower, low-dropout

linear regulators featuring Dual Mode operation, which

allows them to deliver an adjustable (1.25V to 16.5V) or

preset (3.3V for the MAX1658, 5V for MAX1659) output.

They supply up to 350mA while requiring only 120μA

of supply current (typically 30μA with no load). The

devices include thermal-shutdown circuitry, output current

limiting, a p-channel pass transistor, a Dual Mode compar-

ator, and a feedback voltage-divider. Figure 1 shows the

functional diagram.

The 1.21V reference is connected to the amplifier’s

inverting input. The error amplifier compares this

reference with the selected feedback voltage and ampli-

fies the difference. The error signal applies the drive to the

p-channel pass transistor. If the feedback voltage is lower

than the reference voltage, the transistor’s gate is pulled

lower, increasing output current.

The output voltage is fed back through an internal resistor

network or an external user-selected network. The Dual

Mode comparator examines the voltage at the SET

pin and selects either the internal or external feedback

path. If SET is below 65mV, internal feedback sets the

MAX1658’s output voltage to 3.3V and the MAX1659’s

to 5V. Otherwise, external feedback is used for an

adjustable output between 1.25V and 16.5V. Additional

features include internal current limiting, reverse-battery

protection, thermal-overload protection, and a 1μA

shutdown mode.

Figure 1. Functional Diagram

OUT

SET

SHDN

MOSFET

DRIVER

WITH

CURRENT

LIMIT

65mV

GND

DUAL-MODE

COMPARATOR

1.21V

REFERENCE

THERMAL

SENSOR

ERROR

AMPLIFIER

MAX1658

MAX1659

MAX1658/MAX1659

350mA, 16.5V Input,

Low-Dropout Linear Regulators

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