OMAP L138 USB 2.0

Inderjit Bains

Questions on USB 2.0 on the L138 (Table 3 of SPRUFM9C):

1. Can USB0_ID pulldown for host mode be less than 10K: 6.49K? This is just for parts consolidation.

2. Is the USB0_VDDA12 cap value 0.1uF or 0.22uF (Logic PD Schematic). Same question for SATA_REG pin.

3. USB0_VBUS: please explain the following:

For host mode of operation, pull-up the USB power signal on the USB connector to 5V also. Shouldn't it just be a connection to the 5V USB supply?

Also, for host-only mode, should USB0_VBUS be pulled (through a 1K resistor) directly to the always-on 5V supply, or the USB 5V supply that can be turned off?

over 16 years ago

0 Inderjit Bains over 16 years ago

Expert 2745 points

Any answers on this?

0 tlee over 15 years ago

TI__Guru 62975 points

Inderjit,

For Host mode you should be able to use a different resistor value for USB0_ID pulldown.
A value of 0.22uF is ok on USB0_VDDA12, and a value of 0.1uF is recommended on SATA_REG.
For Host mode the USB0_VBUS signal needs to be connected to the 5V supply; for Device mode the 5V supply needs to be disconnected.

-Tommy

0 Inderjit Bains over 15 years ago in reply to tlee

Expert 2745 points

Just to be clear:

2. Can I use 0.1uF on USB0_VDDA12 instead of 0.22uF?

3. Is USB0_VBUS connected to the always-on +5V supply on the board, or the +5V supply on the connector (which can be turned off) for host-only mode?

0 Inderjit Bains over 15 years ago in reply to Inderjit Bains

Expert 2745 points

Follow up for #3: if it's +5V (not switched), can I just pull up USB0_VBUS to +3.3V instead of +5V?

0 tlee over 15 years ago in reply to Inderjit Bains

TI__Guru 62975 points

You should use a .22uF on USB0_VDDA12.

USB0_VBUS needs to be 5V nom.

0 Inderjit Bains over 15 years ago in reply to tlee

Expert 2745 points

The reason I'm asking: if USB0_VBUS was 5V tolerant, it wouldn't need a series 1K resistor. The resistor is usually used to limit the input current so that a voltage converter is not required. If it's a 3.3V logic input, I'd rather connect it to 3.3V.

0 tlee over 15 years ago in reply to Inderjit Bains

TI__Guru 62975 points

It's a 5V nominal pin.

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OMAP L138 USB 2.0