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High supply current consumtion in MSP430F2330

Other Parts Discussed in Thread: MSP430F2330

We have recently experienced a number of failures in a design using the MSP430F2330 that has been in production for a couple of years.  The problem seems to be associated with higher than normal supply current (normal is 2.2ma) that varies randomly over time in some cases from 5 to 20ma, sometime it returns to 2.2ma and holds for a period of time, then resumes the erratic higher currents.  In some cases, the current has increased to as much as 63ma and stays locked at that value.  This board connects to another board via a 6-conductor cable that includs power/ground, two I/O lines and the /RST and TCK lines which are used for BSL programming.

I suspect there may have been ESD damage.  Has anyone seen similar behavior of this type?

  • There are several reasons for increased supply current. The first quesiton is, whether it is really MSP supply current (into VCC input) or total circuit supply current.

    If it is MSP supply current, the unly reason for increased current is an increased load on an output pin. The only other reason I can think of for an increased current into the MSP is extremely unlikely: melting of the clamp diodes on one pin in both directions, VCC and GND, effectively building an internal shortcut. In this case, the MSP would most likely be non-functional.

    These clamp diodes may also be a reason for increased current throught he external circuitry. They protect the port pins against over/undervoltage by shorting excess voltage to VCC/GND. If you apply a voltage above VCC to an MSP port pin, it is shorted to VCC and (hopefully) breaks down to VCC then. This shortcut current must not exceed 2mA rated current. If it does, the diode may melt and either the protection is lost (and the port pin will be damaged) or it shortcuts this pin to VCC. At this point, larger currents may from in and out the port pin depending on attached load/source.

    Direct ESD damage isn't really likely,a s hte rated current won't be that high - usually. But maybe the power supply (voltage regulator) has been damaged too and the MSP is now operating outside specs.

    Well, without holding such a defective device in hands, all is plain guessing.

  • "a number of failures in a design using the MSP430F2330 that has been in production for a couple of years"

    When does the failure occur? Can you describe the step/process where the failures are discovered? During a step in an assembly line? I have seen a few cases where devices showed higher current consumption than normal due to an ESD event.

     

  • Phil Maltby said:
    I suspect there may have been ESD damage.  Has anyone seen similar behavior of this type?

     The connection between external devices even the second board are correctly EMC and ESD protected?

     The higher current stay forever at value or same board sometimes return to regular current drain?

     Is that corrent draw from MSP or other part can sink current from?

     Too less parameter to evaluate a cause and a cure. Please be more specific and try do more measurement.

  • Jens-Michael Gross said:

    If it is MSP supply current, the unly reason for increased current is an increased load on an output pin. The only other reason I can think of for an increased current into the MSP is extremely unlikely: melting of the clamp diodes on one pin in both directions, VCC and GND, effectively building an internal shortcut. In this case, the MSP would most likely be non-functional.

     Hi Jens, I agree on first part but not on diode. Exceeding limit can be a big fault and MSP become irresponsive, damage to diode is quite impossible due all substrate parasitic come to a short from power rail and just power down remove it. The only one time I powered from a 12V rail MSP stopped working at all, diode max current IMHO is intended as parasitic thyristor gate turn on so exceeding current result in power fault. No data is present nor an ESD model, MSP is a robust chip and also if ESD damage can do similar behaviour remain stable. I can suppose some software update can do that or some problem on pcb too...

     Again this case has to be done on the field or with complete data about all current from pin and vcc rail and not from remote help just asking for usual magic ball;)

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