Texas Instruments OMAP5912 Reference Manual page 1607

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USB D+, D- Pulldown for USB Function Controller

System implementations that use the OMAP5912 USB function controller and

are sensitive to supply current requirements can implement weak pulldown

resistors on the USB D+ and D- signals associated with the USB Type-B

receptacle. When there is no host controller attached upstream of the USB

Type-B receptacle, the undriven D+ and D- wires can float to voltages that

cause excessive current consumption by the USB transceiver. Weak

pulldowns can help prevent this problem. Selection of pulldown resistors

depends on transceiver characteristics, D+ pullup resistor implementation,

and board layout, and must be designed to meet USB D+ and D- signal

requirements. The OMAP5912 integrated USB transceiver includes

programmable weak pulldowns:

When USB_TRANSCEIVER_CTRL.CONF_USB0_PWRDN_DN is 0, the

internal weak pulldown is enabled for OMAP5912 pin USB.DM.

When USB_TRANSCEIVER_CTRL.CONF_USB0_PWRDN_DP is 0, the

internal weak pulldown is enabled for OMAP160 pin USB.DP.

USB OTG Controller

Universal Serial Bus (USB)

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