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USB port in my radio car Pioneer deh 4000ub stopped working. I measured voltage between USB Vcc and GND and it's about 0V. It seems to be a problem with high side power switch (R5523N), because there is 0V on the output pin. I also checked other pins and the voltages are as followed:

  1. EN- there is 5V for a moment when I turn the radio on and then 0V,
  2. GND- 0V,
  3. FLG- +5V,
  4. VIN- +5V,
  5. VOUT- same as on ENABLE pin, 5V for a sec, then 0V.

I don't know whether there should be constant voltage on ENABLE pin or not, but can I just short VIN and EN to give it constant 5V? Or maybe I can omit whole high side power switch, connect USB Vcc directly to 5V wire and then be careful what devices I plug to USB port?

circuit from Pioneer deh4000ub service manual

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    \$\begingroup\$ "EN- there is 5V for a moment when I turn the radio on and then 0V," that seems to imply that the problem isn't the switch, but rather that whatever is controlling it has decided the switch shouldn't be on. \$\endgroup\$ – Chris Stratton Oct 21 '17 at 17:17
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The R5523N is a normal hi-side switch, its datasheet is openly available. To get VOUT enabled, the EN pin must stay HIGH.

One possible scenario of the failure is that your USB port has developed a short to ground on VBUS pin (US5V), some TVS (transient voltage supressor = protection against ESD) went bad, or something. Then the 5523 IC senses an overcurrent, asserts the overcurrent FLG for few milliseconds, and the main controller shuts the IC down by turning EN off. In the OFF state the overcurrent condition (and this the FLG) gets cleared, so you see the +5 V steady voltage on FLG.

To test the above scenario, you would need to monitor the FLG pin, preferably with an oscilloscope, or maybe a DMM could be enough. You can test if the R5523N IC is any good by shorting its pin1 to pin4 (make EN high), but don't do it for long time, since it could trigger IC's thermal shutdown if there is a short in VBUS/US5V line. Alternatively you can make sure that the IC VOUT is disconnected from the other port circuitry (not shown in your schematics), then the VOUT should stay at +5V if the above scenario is correct.

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