Data Sheet, Rev. 1
August 2004
USS-820FD
USB Device Controller
When using the USS-820FD in a self-powered device,
there are some additional considerations. The device
must refrain from supplying power through the pull-up
resistor if plugged into an unpowered bus. It must also
ensure that the DPLS and DMNS lines are in an appro-
priate state when the device is powered but not
plugged in. Figure 9 shows an example connection to
meet these requirements.
+3.3 V
±
0.3 V
CLOSE SWITCH ONLY WHEN
V
BUS
IS POWERED
1.5 kΩ
±
5%
DPLS
24
Ω ±
1%
1.5 MΩ
Electrical Characteristics
(continued)
Connection Requirements
USB Transceiver Connection
The physical connection of the USS-820FD to the USB
bus requires only minimal components to provide
proper USB electrical terminations.
Both DPLS and DMNS require 24
Ω ±
1% series resis-
tors for USB impedance matching. Additionally, a
1.5 kΩ pull-up resistor is required on DPLS for full-
speed/low-speed differentiation.
+3.3 V
±
0.3 V
1.5 kΩ
±
5%
DPLS
24
Ω ±
1%
DMNS
24
Ω ±
1%
1.5 MΩ
DMNS
24
Ω ±
1%
5-8120
5-8119
Figure 9. USB Transceiver Connection
Example for Self-Powered
Application
Figure 8. USB Transceiver Connection
Example for Bus-Powered
Application
Agere Systems Inc.
49
AGERE [ AGERE SYSTEMS ]
