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

Question asked by Yasushi Hasegawa on Jan 16, 2017
Latest reply on Jan 27, 2017 by Yasushi Hasegawa

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

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