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MC34708 4 sec power down does not work when USB OTG port is connected

Question asked by Michel Verhagen on Jul 22, 2014
Latest reply on Aug 1, 2014 by Michel Verhagen

We have found a strange issue with the MC34708:

 

Note: In our system OTG is always client.

 

  1. If we have nothing connected to the USB OTG port we can reset the device by pressing the power button (PWNON1) for >4 seconds (that's how we configured the MC34708).
  2. If we have a cable connected from the USB OTG port to a host port on a PC, we CAN NOT reset the device by pressing the power button (PWNON1) for >4 seconds.

 

The reset button (GLBRST) still works as expected, in both cases.

 

After power on reset, we set the MC34708 like this:

 

SW1AMODE = 0x0C

SW2MODE = 0x0C

SW3MODE = 0x0

SW4AMODE = 0x0C

SW4BMODE = 0x0C

SW5MODE = 0x0C

SWBSTMODE = 0x02 (but also tried 0x00, no difference)

SW1 VOLT = 1100 mV

SW1 STDBY = 850 mV

SW2 VOLT = 1300 mV

SW2 STDBY = 950 mV

 

Regulator Mode 0

VUSBSEL = 0x01

 

USB Control

SWHOLD = 0x0 (but also tried 0x01, no difference)

 

Power Control 2:

RESTARTEN = 1

PWRON1RSTEN = 1

STANDBYINV = 1

GLBRSTTMR = 1

WDIRESET = 1

 

The above settings are done in the bootloader, after that, the PMIC is not touched anymore.

 

OS = WEC7 (but for this question the OS shouldn't matter)

 

Anybody any idea what could cause this behavior and how to fix it?

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