Document Number: 001-76294 Rev. *F Page 8 of 21
Bus Powered Design using External Regulator
Figure 4 illustrates the use of CY7C64225 in bus powered mode
but running at 3.3 V. This design can be adopted when the circuit
operating at 3.3 V is desired (RX, TX, RTS, CTS, DSR, DTR at
3.3 V).
This design uses an external 5 V to 3.3 V regulator to supply the
3.3 V to CY7C64225 from VBUS. The 3.3 V to CY7C64225 can
also be provided from a regulator which is already available on
the circuit board, being used for other components on the board.
Since the circuit is operating at 3.3 V, a voltage divider is used to
provide 3.3 V from VBUS of USB port to ‘VBUS’ pin of
CY7C64225.
Figure 4. Bus Powered Design using External Regulator
CY7C64225
1k
0.01uF
VDD
WAKEUP
10k
24
24
RESET
VDD
VDD
Rx_LED
VCFG
Tx_LED
SUSPEND
TxD
RxD
RTS
CTS
DTR
DSR
SW2
GND
GND
VDD
VBUS
D+
D-
D+
D-
VBUS
GND
5V to 3.3V
Regulator
VBUS
VBUS
VDD
VDD
560
560
560
20k
NO CONNECT
