Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - LDO voltage regulator Positive, fixed or adjustable uMax 8

General Description

The MAX1857 low-dropout linear regulator operates

from a +2.5V to +5.5V supply and delivers a guaran-

teed 500mA load current with low 120mV dropout. The

high-accuracy (±1%) output voltage is preset at an

internally trimmed 4.75V or can be adjusted from 1.25V

to 5.0V with an external resistive divider.

An internal PMOS pass transistor allows the low 135µA

supply current to remain independent of load, making

this device ideal for portable battery-operated equip-

ment such as personal digital assistants (PDAs), cellu-

lar phones, cordless phones, base stations, and

notebook computers.

Other features include an active-low open-drain reset

output with a 4.5ms timeout period that indicates when

the output is out of regulation, a 0.1µA shutdown mode,

short-circuit protection, and thermal shutdown protec-

tion. The device is available in a miniature 8-pin µMAX

package. For higher power applications, refer to the

MAX1792 and MAX1793 data sheets.

________________________Applications

Notebook Computers

Cellular and Cordless Telephones

PDAs

Palmtop Computers

Base Stations

USB Hubs

Docking Stations

Features

♦ Guaranteed 500mA Output Current

♦ Low 120mV Dropout at 500mA

♦ Up to ±1% Output Voltage Accuracy

Preset at 4.75V

Adjustable from 1.25V to 5.0V

♦ Reset Output with 4.5ms Timeout Period

♦ Low 135µA Ground Current

♦ 0.1µA Shutdown Current

♦ Thermal Overload Protection

♦ Output Current Limit

♦ Tiny µMAX Package

MAX1857

500mA, Low-Dropout,

Ripple-Rejecting LDO in µMAX

________________________________________________________________ Maxim Integrated Products 1

SET

GNDSHDN

OUT

OUTIN

RST

µMAX

TOP VIEW

MAX1857

Pin Configuration

MAX1857

OFF

1µF

SHDN

OUT

RST

GNDSET

OUT

3.3µF

µC

= +5V V

OUT

= 4.75V

RST

100k

Typical Operating Circuit

19-1812; Rev 0; 1/01

Ordering Information

PART*

TEMP. RANGE

PIN-PACKAGE

MAX1857EUA47

-40°C to +85°C

8 µMAX

*Contact factory for other preset output voltages.

For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,

or visit Maxim’s website at www.maxim-ic.com.

Summary of content (10 pages)

PAGE 1
9-1812; Rev 0; 1/01 500mA, Low-Dropout, Ripple-Rejecting LDO in µMAX The MAX1857 low-dropout linear regulator operates from a +2.5V to +5.5V supply and delivers a guaranteed 500mA load current with low 120mV dropout. The high-accuracy (±1%) output voltage is preset at an internally trimmed 4.75V or can be adjusted from 1.25V to 5.0V with an external resistive divider.
PAGE 2
MAX1857 500mA, Low-Dropout, Ripple-Rejecting LDO in µMAX ABSOLUTE MAXIMUM RATINGS IN, SHDN, RST, SET to GND ....................................-0.3V to +6V OUT to GND ................................................-0.3V to (VIN + 0.3V) Output Short-Circuit Duration ........................................Indefinite Continuous Power Dissipation (TA = +70°C) 8-Pin µMAX (derate 4.5mW/°C above +70°C) .............362mW Operating Temperature Range ...........................
PAGE 3
500mA, Low-Dropout, Ripple-Rejecting LDO in µMAX ((VIN = +5.25V, VOUT = 4.75V, SHDN = IN, SET = GND, TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS 0.01 0.1 V 5.5 V 100 nA RESET OUTPUT Reset Output Low Voltage VOL RST sinking 1mA Operating Voltage Range for Valid Reset RST sinking 100µA RST Output High Leakage Current V RST = +5.5V RST Threshold RST Release Delay tRP 1.
PAGE 4
ELECTRICAL CHARACTERISTICS (continued) (VIN = +5.25V, VOUT = 4.75V, SHDN = IN, SET = GND, TA = -40°C to +85°C, unless otherwise noted.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN MAX UNITS 0.1 V 5.5 V 100 nA RESET OUTPUT Reset Output Low Voltage RST sinking 1mA VOL Operating Voltage Range for Valid Reset RST sinking 100µA RST Output High Leakage Current V RST = +5.5V RST Threshold Rising edge, referred to VOUT(NOMINAL) 83 89 % Rising edge of OUT to rising edge of RST 1.
PAGE 5
00mA, Low-Dropout, Ripple-Rejecting LDO in µMAX POWER-SUPPLY REJECTION RATIO vs. FREQUENCY MAX1857 toc04 COUT = 3.3µF IOUT = 50mA 70 PSRR (dB) LOAD-TRANSIENT RESPONSE MAX1857 toc05 80 4.80V 60 4.75V 50 4.70V 40 600mA 30 400mA 20 200mA 10 0 A B 0 0.01 0.1 1 10 100 1000 10µs/div A: VOUT = 4.75V, 50mV/div B: IOUT = 5mA TO 500mA, 200mA/div VIN = 5.
PAGE 6
MAX1857 500mA, Low-Dropout, Ripple-Rejecting LDO in µMAX Pin Description PIN NAME FUNCTION 1, 2 IN Regulator Input. Supply voltage can range from +2.5V to +5.5V. Bypass with a 1µF capacitor or greater to GND (see Capacitor Selection and Regulator Stability). Connect both input pins together externally. 3 RST Open-Drain, Active-Low Reset Output. RST remains low while the output voltage (VOUT) is below the reset threshold and for at least 4ms after VOUT rises above the reset threshold.
PAGE 7
500mA, Low-Dropout, Ripple-Rejecting LDO in µMAX MAX1857 Detailed Description The MAX1857 is a low-dropout, low-quiescent-current ripple rejector designed primarily for audio and video applications. The device supplies loads up to 500mA and is available with a preset output voltage of 4.75V. As shown in Figure 1, the MAX1857 consists of a 1.25V reference, error amplifier, P-channel pass transistor, and internal feedback voltage-divider. The 1.
PAGE 8
shut down, RST is held low independent of the output voltage. If unused, leave RST grounded or unconnected. 0.7 Current Limit 0.6 Thermal Overload Protection Thermal overload protection limits total power dissipation in the MAX1857. When the junction temperature exceeds TJ = +170°C, a thermal sensor turns off the pass transistor, allowing the device to cool.
PAGE 9
500mA, Low-Dropout, Ripple-Rejecting LDO in µMAX Chip Information TRANSISTOR COUNT: 845 Input-Output (Dropout) Voltage A regulator’s minimum input-to-output voltage differential (dropout voltage) determines the lowest usable supply voltage. In battery-powered systems, this determines the useful end-of-life battery voltage.
PAGE 10
MAX1857 500mA, Low-Dropout, Ripple-Rejecting LDO in µMAX 8LUMAXD.EPS Package Information Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.