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MSP430F2003 current consumption ADC SD16_A

Other Parts Discussed in Thread: MSP430F2003

Hello everybody,

I have got some questions about the current consumption of the 16bit ADC of the MSP430F2003. Lets say I want to work with 1MHz at 3V and a gain of 1 is enough. In this case the Datasheet tells me, that the current consumption of the ADC-module is 730µA (SD16LP = 0).

1) does the TemperatureSensor take additional current?
2) does every channel take this 730µA?
3) is there a possibility to turn channels selectively off (in order to save power)?
4) are those 730µA maximum ratings or may the ADC even take more current in special settings?

I did not found any information regarding my questions in the Datasheet or UsersGuide.

Thanks in advance. Regards.

Ben

  • Ben Thie said:
    1) does the TemperatureSensor take additional current?

    Yes. The temperature sensor is mroe or less a (silicon) resistor with a high temperature coefficient, which is stuffed by a constant current from the reference. Since SD16 requires a constant conversion stream, the sensor needs to be on all the time until you deactivate the SD16 or switch it to a different channel. And the current through the sensor increases the reference voltage current consumption (beond the datasheet value, as it doesn't include load currents)

    Ben Thie said:
    2) does every channel take this 730µA?

    If your MSP has multiple SD16 units, then each one consumes that much. If you have only one SD16 and switch input channels, you're sampling only one at a time, so you only consume the current once.

    Ben Thie said:
    3) is there a possibility to turn channels selectively off (in order to save power)?

    If you only have one SD16, then all channels you don't use are not used. Only one at a time. If you have mroe than one SD16 (soem MSPs have up to 7), then those which are deactivated are deactivated, and with them the inputs.

    Ben Thie said:
    4) are those 730µA maximum ratings or may the ADC even take more current in special settings?

    If oyu draw current from the reference output (if available), this adds. This includes the temperature sensor operation. The SD16 operation itself draws current or not, but it doesn't vary (or at least only by a negligible amount) with different settings. Except one thing: if oyu change the clock on which the SD16 operates, this affects its operating current. Basically, digital CMOS devices (including the digital parts of the SD16) only draw a charge, not a constant current. When a state changes, a certain amount of electron charge is required or dismissed. So the faster you change states, the more electrons you draw and dismiss, which over time is integrated to an average 'current'. Btu it is rathe rvery short peaks of high currents when the state changes, and then no current for a (relatively) long time. The more peaks, the higher is the 'rated' (average) current.