USB84604 datasheet(37/61 Pages) MICROCHIP

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 2014-2016 Microchip Technology Inc.

DS60001295C-page 37

USB84604

8.0

FUNCTIONAL DESCRIPTIONS

This chapter provides additional functional descriptions of key device features. Alternatively links to references are pro-

vided.

8.1

Battery Charger Charging

The USB84604 supports downstream battery charging. The application note AN 26.19 USB Battery Charging with the

Microchip/SMSC USB2534 Hub Controller [ 8] provides additional information about battery charging.

8.2

SOF Clock Output

The USB84604 provides an 8 kHz clock output synchronized to the USB host SOFs. The SOF output is generated from

the previous SOF packet on the USB line. The device includes an internal free running frame counter to generate inter-

nal start of frame and end of frame events. The internal counter is re-synchronized every time a successful packet is

received and decoded. The internal counter is advanced to compensate for the packet decode time. If the incoming SOF

jitters early or late, the jitter will be visible in the next frame SOF output clock rising edge.

If one or two SOFs are missing, the SOF output will continue based on the internal frame counter. If more than two SOF

are missing, the SOF output signal will stop. The clock is guaranteed to stop in a low state. When enabled or disabled,

there will never be a short cycle.

8.3

Flex Connect

This feature allows the upstream port to be swapped with downstream physical port 1. Only downstream port 1 can be

swapped physically. Using port remapping, any logical port (number assignment) can be swapped with the upstream

port (non-physical). For details refer to the FlexConnect Applications [ 9]

FIGURE 8-1:

SOF OUTPUT TIMING

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