LC87F1HC8AUWA-2H Datasheet, PDF (11/27 Pages) ON Semiconductor – 8-bit 1-chip Microcontroller with USB-host controller

LC87F1HC8A
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)
Option settings
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 mode
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 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.
Power Supply
3.3V
For backup
LSI
VDD1
VDD2
VDD3
UHD+
UHD-
UFILT
VSS1 VSS2 VSS3
33Ω
To USB connector
5pF
15kΩ
0Ω
2.2μF
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.
Power Supply
5V
For backup
LSI
VDD1
VDD2
UHD+
UHD-
2.2μF
VDD3
UFILT
0.1μF
VSS1 VSS2 VSS3
33Ω
To USB connector
5pF
15kΩ
0Ω
2.2μF
No.A0956-11/27