TUSB542: idle mode takes too long to enter?

Yosy Shmuly85

Prodigy 155 points

Part Number: TUSB542

according to data sheet "Delay from U0 to electrical idle" should be 6ns typical

on our measurements we see that it takes the TUSB542 about 400ms from U3 to enter the low power state

(we repeat the test with and without the TUSB542 and this was the difference)

this is way longer then what the USB spec requires

can we do something to improve it?

over 8 years ago

0 Diego Cortes over 8 years ago

TI__Mastermind 36085 points

Hello Yosy,

Please describe the test procedure, the device should take only a couple of uS to exit from U2/U3. Also makes no sense the exit from U3 to low power state, since U3 is a low power state. Please see the datasheet section 6.9 there you will find all the timing requirements.

Regards,

Diego.

0 Yosy Shmuly85 over 8 years ago in reply to Diego Cortes

Prodigy 155 points

I am sorry i meant U0 not U3

the test was as follows:

we measured the time from U3 trigger (comming from a sniffer) to actual low current consumption on two cases:

1st one is our board with the TUSB542 (MUX) assembelled

it took the the current around 400ms to be low from the U3 Trigger

2nd one is our board with the TUSB542 (MUX) removed

immediately after the U3 trigger the current consumption got low

0 Yosy Shmuly85 over 8 years ago in reply to Yosy Shmuly85

Prodigy 155 points

0 Diego Cortes over 8 years ago in reply to Yosy Shmuly85

TI__Mastermind 36085 points

Hello Yosy,

Update from the meeting with Yosy: The 400ms delay is caused by an internal timer, this delay has been included based on the required timing for entering U1 (300mS), the 6ns in the datasheet is related to the actual transmission without the internal timer. This ticket is being handled internally.

Regards,
Diego.

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TUSB542: idle mode takes too long to enter?