MAX1822ESA Ver la hoja de datos (PDF) - Maxim Integrated

Número de pieza

componentes Descripción

Fabricante

MAX1822ESA

High-Side Power Supply

Maxim Integrated 

High-Side Power Supply

VOUT

S8

11V

8.5V

C3

S7

VINT

C2

S6

S4

RC OSCILLATOR

+

CONTROL LOGIC

OVERVOLTAGE

COMPARATOR

POWER-READY

COMPARATOR

S3

C1

S2

S1

S5

VCC

PR

PR DRIVER

TWO-STAGE CHARGE PUMP

(SWITCHES SHOWN IN REFRESH MODE)

Figure 1. MAX1822 Block Diagram

Detailed Description

Charge-Pump Operation

The MAX1822 is a multistage charge-pump power sup-

ply. Although the charge pump is capable of multiply-

ing VCC up to four times, the output is regulated to VCC

+ 11V by an internal feedback circuit for inputs above

4V. The charge pump typically operates at 90kHz, but

regulates by pulse skipping. When VOUT exceeds VCC

+ 11V, the oscillator shuts off. As VOUT dips below VCC

+ 11V, the oscillator turns on.

Power-Ready Output

The Power-Ready Output (PR) signals control circuitry

when the high-side voltage reaches a preset level. This

feature can be used to protect external FET switches

from excess dissipation and damage by preventing them

from turning on, except when adequate gate drive levels

are present. When power is applied, PR remains low until

GND

VOUT reaches approximately VCC + 8.5V. PR also goes

low if VOUT falls below this level during operation, i.e., if

the output is overloaded. The PR high level is VCC.

Applications Information

Quiescent Supply Current

MAX1822 quiescent supply current varies with VCC and

with the values of C1, C2, and C3 (Typical Operating

Characteristics). Even with no external load, the device

must still pump to overcome internal losses. Large ratios

between C3 and C1 or C2 require more charge-pump

cycles to restore VOUT. As VCC falls below 5V, quiescent

current rises fairly rapidly to about 1mA at 4V (Typical

Operating Characteristics). This rise occurs because

VOUT no longer pulse skips to regulate at low input volt-

ages; the oscillator runs continuously, so supply current

is higher. Figure 2 shows the test circuit for the

MAX1822 quiescent supply current.

_______________________________________________________________________________________ 5

Share Link: