USS-820FD
USB Device Controller
Data Sheet, Rev. 1
August 2004
Application Notes
1.
The RESET input must remain asserted for a minimum period of time after power is stable. If internal oscillator
clocking mode is used, this time is t
OSC
, the amount of time required to allow the internal oscillator output to
become stable. If external oscillator clocking mode is used, this time is tRST. The USS-820FD WRN and RWUPN
pins must not both be active (low) at the time that the RESET input is deasserted.
2.
After changing the size (RXFFSZ/TXFFSZ), type (isochronous vs. nonisochronous), enabled status (RXEPEN/
TXEPEN) of a FIFO/endpoint or chip features (FEAT, BDFEAT), firmware must guarantee that at least 16 t
CLK
periods have elapsed before attempting to access the FIFO data. This is required to allow the internal FIFO RAM
to be reallocated.
3.
Register writes are triggered by the rising edge of either WRN or IOCSN, whichever comes first, and are synchro-
nized to the internal 12 MHz clock. Therefore, the actual write may not occur until as much as t
CLK
ns after that
first rising edge. This latency must be taken into account when performing subsequent register reads or writes.
4. The IRQN and SOFN pins require external pull-ups or pull-downs if the external controller will be powered off dur-
ing suspend. In that situation, those pins will be 3-stated until the USS-820FD has fully resumed. The pull-up or
pull-down is needed to establish the desired level at the controller for the time interval from when the controller is
powered on to the time when the USS-820FD has completed the resume. The same requirements hold for the
USBR and DSA outputs if they are connected to devices that will be powered off during suspend.
5. In applications where the external controller is powered off during suspend (firmware has set SSR.SUSPPO), the
SOFN pin must be connected to an external pull-down even if the pin is not functionally required. The pin is actu-
ally bidirectional, where the input mode is only used in chip test modes. The pull-down is required to avoid exces-
sive power consumption by the input stage when the device is suspended.
USB Application Support Contact Information
E-mail: usb@agere.com
Absolute Maximum Ratings
Stresses in excess of the absolute maximum ratings can cause permanent damage to the device. These are abso-
lute stress ratings only. Functional operation of the device is not implied at these or any other conditions in excess of
those given in the operations sections of this data sheet. Exposure to absolute maximum ratings for extended peri-
ods can adversely affect device reliability.
Table 42. Absolute Maximum Ratings
Parameter
Ambient Operating Temperature Range
Storage Temperature
Power Supply Voltage with Respect to Ground
Symbol
T
A
T
stg
V
DD
Min
–20
–40
—
Max
85
125
4.2
Unit
°C
°C
V
Table 43. Absolute Maximum Voltage Ratings
(0 °C
≤
TA
≤
85 °C)
Parameter
Voltage on Any Non-USB Pin with Respect to Ground
Symbol
Min
V
SS
−
0.3
Max
5.5
Unit
V
—
Table 44.
Absolute Maximum Voltage Ratings
(–20 °C
≤
T
A
≤
0 °C)
Parameter
Persistent* Voltage on Any Non-USB Pin with Respect to Ground
Non-persistent* Voltage on Any Non-USB Pin with Respect to
Ground
* A persistent voltage level is considered to be one which lasts for more than 25 ns.
Symbol
—
—
Min
V
SS
−
0.3
V
SS
−
0.3
Max
3.6
5.5
Unit
V
V
46
Agere Systems Inc.
AGERE [ AGERE SYSTEMS ]
