December 1998

1

MIC29311

MIC29311

Micrel

MIC29311

3A Fast-Response LDO Regulator for USB

Preliminary Information

General Description

The MIC29311 is a 3A, fast response, low-dropout (LDO)

voltage regulator. Using Micrel’s proprietary Super

βeta

PNP™ process, the MIC29311 offers exceptional dropout

(600mV at 3A) and low ground current (60mA at 3A). Fast

transient response allows it to recover quickly from large load

changes while maintaining a steady output. The device can

be sent into a “zero-current” off mode when the TTL compat-

ible enable is brought low.

Designed specifically for Universal Serial Bus (USB) applica-

tions, the MIC29311 works with USB power switches to

provide an economical solution for self-powered hubs. The

5.1V output voltage is optimized to work with lower-cost high

on-resistance USB power switches (300m

Ω) to provide a

minimum of 4.75V at 500mA to downstream ports. Used with

MIC2527 quad USB power switches, the MIC29311 can

power up to 6 downstream ports.

Features of the MIC29311 include thermal shutdown, current

limit, reversed-battery and reversed-lead insertion protec-

tion. An overvoltage clamp is available to maintain a safe

output when the input voltage exceeds 8V. An error flag is

also available to indicate of the output falls out of regulation,

or when an overcurrent condition occurs.

The MIC29311 is available in a 5-pin TO-220 or TO-263

package with a fixed 5.1V output voltage.

For other high current, low-dropout voltage regulators, please

see the MIC29150/300/500/750 and the MIC29310,

MIC29510, MIC29710.

Typical Application

ON/OFF

OVERCURRENT

3.3V USB Controller

D+

D–

GND

D+

D–

GND

MIC5207-3.3

LDO Regulator

IN

OUT

GND

33µF

Ferrite

Bead

D+

D–

GND

D+

D–

V+

Bold lines indicate

0.1" wide, 1-oz. copper

high-current traces.

Downstream

USB

Port 1

4.75V min

500mA max.

33µF

D+

D–

GND

33µF

0.01µF

0.01µF

0.01µF

4.7

µF

1.0

µF

GND

33µF

6.3Vac

3A

IN

OUT

GND

MIC29311-5.1

LDO Regulator

5.8V @ 3A

5.1V

FLAG

EN

10k

47µF

10k

Downstream

USB

Port 2

4.75V min

500mA max.

Downstream

USB

Port 6

4.75V min

500mA max.

100mA

max.

AC

Line

Upstream

USB Port

Simple USB Stand-Alone 6-Port Self-Powered Hub

Features

• Fast transient response

• 3A output current over full temperature range

• 600mV dropout voltage at full load

• Low ground current

• 3% total accuracy

• “Zero” off-mode current

• Thermal Shutdown

• Current Limiting

• Reversed battery protection

• Fixed 5.1V Output

Applications

• Self-powered USB hubs

• USB power switching

• High-efficiency linear power supplies

• High-efficiency switching supply post-regulator

Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com