Usb Host Port; Figure 2-1. Usb D+ And D- During Full Speed Transaction - Motorola APX 7500 Detailed Service Manual

Theory of Operation: System Communications Overview

2.3.13 USB Host port

The USB host port uses a Philips ISP1105 transceiver (U303), which is connected to OMAP Pin
Group 2. This transceiver is USB 1.1 compliant, low and full speed. Upon connection of an external
USB device to the USB host port, the Consolette Mainboard provides VBUS to the device by
enabling over-current IC TPS2041B (U1706), which provides over-current and short circuit
protection for VBUS. If U1706 detects an over-current condition, then the USB2_OC line is pulled
low. Over-current is detected when the current draw exceeds 500 mA. If a current higher than one
Amp is detected, then the output is disabled. The Host port has 15kOhm pull down resistors for D+
and D- and also contains the same ST202 filter as the Device circuit to protect the USB Host data
lines from ESD and RFI.
The enumeration process is started by detecting a pull-up on D+ or D- (Full or Low speed). The
Consolette Mainboard then supplies VBUS to the attached device and performs the USB Host
protocol. The USB Host port uses a standard USB type A connector.
NOTE: The USB Host port only supports allowable devices; please see the Target Peripheral List for
the details of these approved accessories.
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Figure 2-1. USB D+ and D- during full speed transaction

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September 9, 2011