MAX8862 Просмотр технического описания (PDF) - Maxim Integrated

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MAX8862

Low-Cost, Low-Dropout, Dual Linear Regulator

Maxim Integrated 

Low-Cost, Low-Dropout, Dual Linear Regulator

1N1

SHDN1

BIAS

R1

50mV

OUT1

PWROK1

1.25V

IN2

SHDN2

BIAS

G1

SET1

GND

R2

80mV

GND

OUT

R3

MAX8862

REF2

1.25V

G1

SET2

GND

R4

80mV

GND

Figure 1. Functional Diagram

Output Voltage Selection

The MAX8862’s Dual Mode operation allows a fixed or

adjustable output voltage. In preset/internal-feedback

mode (SET1/SET2 = GND), output voltages are factory

preset to 4.95V (L), 3.175V (T), or 2.85V (R).

In adjustable/external feedback mode, output voltage is

adjusted between 2V and 11V with two external resis-

tors connected as a voltage divider to SET1/SET2

(Figure 2). Since the input bias current at SET1/SET2 is

<0.1µA, large resistance values can be used for R1

and R2 to minimize power consumption without losing

accuracy. Select R2 in the 10kΩ to 400kΩ range. R1 is

given by:

R1 = R2 (VOUT / VSET - 1)

where VSET = 1.25V.

Power-Good Comparator

The MAX8862’s main regulator features a power-good

indicator that asserts when the output voltage falls out

of regulation. In internal-feedback mode, the open-

drain PWROK1 output goes low when OUT1 falls 4%

below its nominal value. When used in external feed-

back mode, PWROK1 goes low when VSET1 falls below

1.2V. A 100kΩ pull-up resistor from PWROK1 to VIN1

provides a logic-control signal. This resistor also mini-

mizes current flow to the input in case the battery is

reversed. PWROK1 can be used to reset a microcon-

troller or to drive an external LED for indicating a power

failure.

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