10 years, 8 months ago.  This question has been closed. Reason: wrong topic

Poor power supply with OpenSDA-USB port on FRDM-KL25Z

Hi,

I'm having some problems with the power supply on my FRDM-KL25Z. When hooked up to the PC via the OPenSDA USB port there seems to be some problem with the onboard voltage regulators / the power supply circuit. I first noticed the issue when trying to use the onboard RGB-led: the red one is quite bright but the blue and green ones are really dim. When powered by the KL25Z-USB port all leds are as bright as expected.

I measured the voltages on the different pins on the connector

powered by the OpenSDA port:

• VIN: 3.6V
• 5V-USB: 4.0V
• 3.3V: 2.3V

powered by the KL25Z port:

• VIN: 4.5V
• 5V-USB: 4.8V
• 3.3V: 2.9V

I'm on a mac mini 2010 model and also tried a powered USB-Hub, the voltages where a little higher, but not as high as you would expect.

Next thing I tried : another USB-cable, results:

more Volts at the pins with both USB connectors and brighter LEDs. AND:

magic smoke from diode D2 :(

Diode D2 is in the power supply circuit right before the 3.3V voltage regulator protecting it from reverse volatge (I guess).

Next thing I tried was powering the board from an external 8V power supply (+8V on VIN and GND to GND, nothing else connected to the board) witch resulted in diode D1 going up in smoke as well :(

Does anybody has an idea whats going wrong on my board?

Cheers

Max