CP2102

Rev. 1.2

11

5. USB Function Controller and Transceiver

The Universal Serial Bus function controller in the CP2102 is a USB 2.0 compliant full-speed device with integrated

transceiver and on-chip matching and pull-up resistors. The USB function controller manages all data transfers

between the USB and the UART as well as command requests generated by the USB host controller and

commands for controlling the function of the UART.

The USB Suspend and Resume signals are supported for power management of both the CP2102 device as well

as external circuitry. The CP2102 will enter Suspend mode when Suspend signaling is detected on the bus. On

entering Suspend mode, the CP2102 asserts the SUSPEND and SUSPEND signals. SUSPEND and SUSPEND

are also asserted after a CP2102 reset until device configuration during USB Enumeration is complete.

The CP2102 exits the Suspend mode when any of the following occur: (1) Resume signaling is detected or

generated, (2) a USB Reset signal is detected, or (3) a device reset occurs. On exit of Suspend mode, the

SUSPEND and SUSPEND signals are de-asserted.

Both SUSPEND and SUSPEND temporarily float high during a CP2102 reset. If this behavior is undesirable, a

strong pulldown (10 k

Ω) can be used to ensure SUSPEND remains low during reset. See Figure 6 for other

recommended options.

Figure 6. Typical Connection Diagram

Option 1: A 4.7 k

Ω pull-up resistor can be added to increase noise immunity.

Option 2: A 4.7 µF capacitor can be added if powering other devices from the on-chip regulator.

Option 3: Avalanche transient voltage suppression diodes should be added for ESD protection.

Option 4: 10 k

Ω resistor to ground to hold SUSPEND low on initial power on or device reset.

1

CP2102

SUSPEND

SUSPEND

11

12

REGIN

7

GND

3

RST

9

D+

4

D-

5

8

C2

0.1

µF

C1

1

µF

RI

DCD

CTS

RTS

RXD

TXD

DSR

DTR

2

1

28

27

26

25

24

23

2

3

External RS-232

transceiver or

UART circuitry

(to external circuitry

for USB suspend

states)

VBUS

D-

D+

USB

CONNECTOR

6

VDD

VBUS

VDD

R1

4.7 k

Ω

D1

D2

D3

Option 1

R2

10 k

Ω

Option 4

Option 3

C4

4.7

µF

Option 2