NEC switch - Manual (Page 162)

User’s Manual U12978EJ3V0UD
162
CHAPTER 10 REGULATOR
The
µPD789800 incorporates a regulator that powers the USB driver/receiver. The features are as follows.
• Generates V
REG (3.3
±0.3 V) from V
DD0 , V DD1 (4.0 to 5.5 V) and outputs it to the REGC pin.
• Supports power-saving mode, reducing power consumption in mode.
Figure 10-1. Block Diagram of Regulator and USB Driver/Receiver
Regulator
PD789800
RXD
USB driver/
receiver
SEP
SEM
TXDP
TXDM
TXEN
RXEN
V DD0
V SS0
V SS
V REG
V DD0
V SS0
USBDM
Hub
REGC
22 F
1.5 k Ω
USBDP
µ
µ
Cautions 1. To stabilize the V
REG
voltage, connect the REGC pin to V
SS
via 22 µµµµF capacitor.
2. Connect the pull-up resistor (1.5 k Ω Ω Ω Ω) for the USBDM pin to the REGC pin.