LC87F1A32A

No.A0704-11/26

USB Reference Power Option

When a voltage 4.4 to 5.5V is supplied to VDD1 and the internal USB reference voltage circuit is activated, the

reference voltage for USB port output is generated. The active/inactive state of reference voltage circuit can be switched

by the option select. The procedure for marking the option selection is described below.

(1)

(2)

(3)

(4)

Option select

USB Regulator

USE

USE

USE

NONUSE

USB Regulator at HOLD mode

USE

NONUSE

NONUSE

NONUSE

USB Regulator at HALT mode

USE

NONUSE

USE

NONUSE

Reference voltage circuit

state

Normal state

active

active

active

inactive

HOLD mode

active

inactive

inactive

inactive

HALT mode

active

inactive

active

inactive

When the USB reference voltage circuit is made inactive, the level of the reference voltage for USB port output is

equal to VDD1.

Selection (2) or (3) can be used to set the reference voltage circuit inactive in HOLD or HALT mode.

When the reference voltage circuit is activated, the current drain increase by approximately 100A compared with

when the reference voltage circuit is inactive.

Example 1: VDD1=VDD2=3.3V

Inactivating the reference voltage circuit (selection (4)).

Connecting VDD3 to VDD1 and VDD2.

Example 2: VDD1=VDD2=5.0V

Activating the reference voltage circuit (selection (1)).

Isolating VDD3 from VDD1 and VDD2, and connecting capacitor between VDD3 and VSS.

VSS1 VSS2 VSS3

VDD1

VDD2

VDD3

Power supply

3.3V

For

backup

LSI

D+

D-

UFILT

To USB connector

27 to 33



5pF

0



2.2

F

1.5k



P70

VSS1 VSS2 VSS3

VDD1

VDD2

VDD3

Power supply

5V

For backup

LSI

D+

D-

UFILT

0



2.2

F

To USB connector

27 to 33



5pF

1.5k



P70

2.2

F

0.1µF