LPC4370 / Is it possible to apply a specified voltage to the USB pin when the device power is off?

[yasushihasegawa]

Dear All,

Our device is implemented with LPC 4370.
There is a question about the case where our device is not powered on and voltage is supplied from the target host side via the USB cable.

[Background]
(1) Our device is a USB device, not a host.
(2) Our device is "self-powered device", not "bus-powered device".
(3) The other USB host device and our device are connected by a USB cable, and a voltage within the specified range is supplied to the USB cable from the USB Host device.

[conditions]
(1) The device power supply is OFF, and the following pins of LPC4370 are not powered.

  VDD (IO)
  VDD (REG) (3 V 3)
  VDDA (3 V 3)
  USB0_VDDA3V_DRIVER
  USB 0 _ VDDA 3 V 3
  Vprog (pf)

(2)Voltage is applied to our device from the other host's side via the USB cable under the above conditions.

[Question]
Is there a problem in applying a voltage within the specified range to the following USB pins of LPC 4370? 
In other words, will internal latch-up and malfunctions not occur?

  Pin name / specified range
  USB0_VBUS / min 0[V], max 3.6[V]
  USB0_DP / min 0[V], max 3.6[V]
  USB0_DM / min 0[V], max 3.6[V]
  USB0_ID / min 0[V], max 3.6[V]

Best Regards,
Yasushi

[soledad · Accepted solution]

Hi,

The data sheet provides absolute max rates for a scenario similar to yours (Vddio=0v) as it is specified in table 10.

so you shouldn't have issues if you are careful with voltage spikes when restoring the supply to the device.

Have a great day,
Sol

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[yasushihasegawa]

Dear Soledad,

Thank you for your support.
I satisfy with your answer and advice.

Best Regards,
Yasushi Hasegawa