September 2000

1

MIC2012/2072

MIC2012

Micrel

MIC2012/MIC2072

USB Power Controller

Advance Information

General Description

The MIC2012 is a dual channel USB power switch designed

to support the power distribution requirements for USB Wakeup

from the ACPI S3 state. The MIC2012 will directly switch its

two outputs between a 5V main supply and a 5V auxiliary

supply normally provided in ATX style power supplies.

The MIC2012 will adjust its current-limit threshold according

to the ACPI state it is in. In the normal active S0 state the

current-limit is set at 500mA minimum per channel satisfying

the USB continuous output current specification. In the S3

state the current-limit can be reduced to only 100mA per

channel to minimize the current that is supplied by the

auxiliary supply thereby ensuring that voltage regulation is

maintained even during fault conditions.

The MIC2012 provides make-before-break switching to en-

sure glitch-free transitions between the S3 and S0 states.

Each channel is also thermally isolated from the other so that

a fault in one channel does not effect the other. FAULT status

output signals are also provided indicating overcurrent and

thermal shutdown conditions.

The MIC2072 option latches the output off upon detecting an

overcurrent condition for more than 5ms minimum. The

output can be reset by either toggling the EN inputs of the

MIC2072-1, -2 or by removing the load. Latching the output

off provides a circuit breaker mode of operation which re-

duces power consumption during fault conditions.

Typical Application

MIC2012P

D+

D–

GND

MAIN

AUX

OUT1

Downstream

USB

Port 1

100

µF

5V MAIN

ATX Power Supply

S3#

FAULT1#

FAULT2#

D+

D–

GND

Downstream

USB

Port 2

OUT2

GND

5V STANDBY

82801AA or Equivalent

SLP S3#

SLP S5#

OC0

OC1

Overcurrent Port 1

S3 Control

Overcurrent Port 1

100

µF

Figure 1. USB Wakeup with Control Input

Features

• Compliant to USB power distribution specifications

• Two completely independent switches

• Integrated switching matrix supports ACPI S0/S3 state

transitions without external FET circuits

• Make-before-break switching ensures glitch-free

transitions

• No back-feed of auxiliary supply onto main supply

during standby mode

• Bi-level current-limit preserves auxiliary supply voltage

regulation in standby mode

• Thermally isolated channels

• Thermal shutdown protection

• Fault status outputs with filter prevents false assertions

during hot-plug events

• Latched thermal shutdown options with auto-reset

(MIC2072)

• Undervoltage lockout

Applications

• Desktop PCs

• Notebook PCs

• Notebook Docking stations

• LAN Servers

• PC Motherboards

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