Datasheet
CP2102/9
Rev. 1.8 15
6. USB Function Controller and Transceiver
The Universal Serial Bus function controller in the CP2102/9 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 CP2102/9 device as well
as external circuitry. The CP2102/9 will enter Suspend mode when Suspend signaling is detected on the bus. On
entering Suspend mode, the CP2102/9 asserts the SUSPEND and SUSPEND
signals. SUSPEND and SUSPEND
are also asserted after a CP2102/9 reset until device configuration during USB Enumeration is complete.
The CP2102/9 exits 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 CP2102/9 reset. If this behavior is undesirable, a
strong pulldown (10 k) can be used to ensure SUSPEND
remains low during reset. See Figure 5 for other
recommended options.
Figure 5. Typical Connection Diagram
1
CP2102/9
SUSPEND
SUSPEND
11
12
REGIN
7
GND
3
RST
9
D+
4
D-
5
8
C4
0.1 F
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+
GND
4
5
6
USB
CONNECTOR
6
VDD
VBUS
VDD
R1
4.7 k
D1 D2 D3
Option 1
Option 3
C3
4.7 F
Option 2
Option 1: A 4.7 k 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 3: Use Littlefuse p/n SP0503BAHT or equivalent.
Option 4: 10 k resistor to ground to hold SUSPEND low on initial power on or device reset.
Option 5: A 4.7 µF capacitor can be added for in-system programming (CP2109 only).
VPP
C5
4.7 F
Option 5
18
R2
10 k
Option 4
C2
0.1 F
C1
1.0 F