LC87F1HC4A

No.A0955-11/27

USB Reference Power Option

When a voltage 4.5 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 the reference voltage circuit can be

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

(1)

(2)

(3)

(4)

USB regulator

USE

USE

USE

NONUSE

USB regulator at HOLD mode

USE

NONUSE

NONUSE

NONUSE

Option settings

USB regulator at HALT mode

USE

NONUSE

USE

NONUSE

Normal mode

active

active

active

inactive

HOLD mode

active

inactive

inactive

inactive

Reference voltage circuit state

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 increases by approximately 100μA 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 VSS2VSS3

VDD1

VDD2

VDD3

Power Supply

3.3V

For backup

LSI

UHD+

UHD-

UFILT

15k

Ω

To USB connector

33

Ω

5pF

0

Ω

2.2

μF

VSS1 VSS2 VSS3

VDD1

VDD2

VDD3

Power Supply

5V

For backup

LSI

UHD+

UHD-

UFILT

0

Ω

2.2

μF

15k

Ω

To USB connector

33

Ω

5pF

2.2

μF

0.1

μF