MSP430FE427a does not start with quick power dissconnect /connect

Sameh Abou Hadima

Other Parts Discussed in Thread: MSP430FE427A

I'm using the MSP430FE427A the datasheet mentioned that the Avcc (Analog Vcc) should not be started before the Dvcc (digital Vcc) so I have a 10 ohm Resistor and 10uf Cap. supplying the Avcc from the Dvcc (a simple delay circuit like the one used in the meter application note)

I noticed that when I lose the powe for 1-15 seconed then when the power comes back the MCU does not start again until I reset the device.

but if I lost the power for more than 15 sec. then I reconnect it, the MCU works fine!!

I was suspecting that the Cap. at the Avcc was not losing the charge a quick as the Cap. at the Dvcc. (by so the Avcc is suppled before the Dvcc when the power comes back) So I hocked the osilloscope to both caps. I noticed that in normal case the Avcc is lower than the Dvcc (which is expected because there is a R souce the Avcc from the Dvcc) then when I lose the power both loses the charges togather until they have the same voltage (around 2.9V) and stay togather for a 10-15 seconed then they drop quickly to 0v.

Case 2: MCU work fine then I disconnect then I connected the power quickly withen 1-15 sec. the MCU will not start and the Dvcc and Avcc will have the same voltage like they were internally shorted. and the device will not work until I reset it

Am I working in the right area? how can I fix this issue?

over 14 years ago

0 Harman over 14 years ago

TI__Expert 7845 points

The AVcc and DVcc are not completely separated and must not be supplied with different voltages. However, a RC power supply filter (R ~ 20 ohms) can be inserted between DVcc and AVcc. AVcc and DVcc must always be sourced from the same power supply source and come up at the same time. Please see this link for a reference.

0 Sameh Abou Hadima over 14 years ago in reply to Harman

Prodigy 150 points

So how do you explain the hanging issue I have? is it from some thing else?

0 Harman over 14 years ago in reply to Sameh Abou Hadima

TI__Expert 7845 points

I am not sure where the source of that is. So I recommend the following to isolate the cause(device, hardware, software):
1. Use a TI Target board:
http://focus.ti.com/docs/toolsw/folders/print/msp-ts430pm64.html

2. Use the simple code example "fet410_1.c" from the following zip file:
http://www.ti.com/lit/zip/slac017

3. Place the device in the TI target board and download the above code example on it and run your power cycle test to see if the device hangs up.

0 Steve Underwood over 14 years ago

TI__Intellectual 2595 points

When used correctly, the MSP430FE427A is extremely robust in the face of quirky power conditions and severe EMI/ESD attacks. However, you need to manage the SVS properly to achieve that robustness.

I would guess (because it is a common failing in applications code) that you have set the CPU core clock to 8MHz, without programmng the SVS to cause a reset if Vcc falls below a safe operating voltage for 8MHz. Your Vcc is falling to the point where the core may crash at 8MHz, but it isn't falling far enough for the BOR circuitry to take effect. If the SVS is managed properly your problem should go away.

Steve

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MSP430FE427a does not start with quick power dissconnect /connect