| US 7,522,659 B2 | ||
| Universal serial bus (USB) 2.0 legacy full speed and low speed (FS/LS) mode driver | ||
| Cameron Lacy, Milton (Canada); Dino A. Toffolon, Stoney Creek (Canada); and Scott Howe, Campbellville (Canada) | ||
| Assigned to Synopsys, Inc., Mountain View, Calif. (US) | ||
| Filed on Sep. 19, 2005, as Appl. No. 11/230,421. | ||
| Prior Publication US 2007/0064778 A1, Mar. 22, 2007 | ||
| Int. Cl. H04B 1/38 (2006.01) | ||
| U.S. Cl. 375—219 [326/83; 327/108] | 20 Claims |
| 1. A Universal Serial Bus (USB) 2.0 transceiver comprising a legacy full speed and low speed (FS/LS) USB driver, the legacy
FS/LS USB driver comprising:
a first output terminal;
a first plurality of driver output stages, each of the first plurality of driver output stages comprising a first pull-up
PMOS transistor, a first pull-down NMOS transistor, and a first output resistor, a first terminal of the first output resistor
being connected to the first output terminal and a second terminal being connected to shared terminals of the first pull-up
PMOS transistor and the first pull-down NMOS transistor; and
a first USB data distribution circuit for sequentially providing a USB data signal value to the first plurality of driver
output stages,
wherein each of the first plurality of driver output stages connects the second terminal of the first output resistor to a
first supply voltage in response to the USB data signal value,
wherein resistance values of the first plurality of driver output stages change as the first plurality of driver output stages
sequentially switch between logic states, and
wherein the first plurality of driver output stages provide a first predetermined, total parallel resistance as the first
plurality of driver output stages sequentially switch between logic states.
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