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MSP430 Active current

Ushan Karunathilaka
Intellectual 695 points
Other Parts Discussed in Thread: MSP430F2418

Hello All,

I m using a MSP430F2418TPNR operating at 16 MHz in my project. I have measured sleep mode current and it is in the rage given in the datasheet.

My concern is the active current. According to datasheet, active current should be 6mA. when i measure the current in my circuit it is around 14mA.

when the code is halted in a break point after all variables and GPIO are initialized, active current is 3mA.

 

According to my observation, 3mA is consumed by the other parts of the circuit. Processor core consumes approximately 10-11mA.

 

then i reduce the speed and active currents are 4, 8,10 in 1Mhz, 8 mHz and 12 mHz respectively.

 

After that i have used a simple program in development kit and set all the GPIO to output. After initializing the GPIO i have implemented a never ending loop [   while (1) {} ].

still the active current is around 10-11 mA. then i set all the GPIO to input. still the result is same.

 

How can i reduce the active current to 6mA?

Ushan

 

 

  • 0
    Genius 4925 points

    On which page did you see an active current for 16MHz of 6mA?

    I'm not sure as you haven't  specified how you set the frequency but I'm suspecting you are using the DCO.

    Now the active currents are according to the diagram on page 31 of the data sheet of the MSP430F2418:

    16 MHz: 9.2-10.2 mA
    12 MHz: 6.2-7.8 mA
    8 MHz: 2.9-5.3 mA
    1 MHz: 0.4-0.8 mA

    All values approximately as you cannot read the values very clearly.

    So based on that I'd say your MSP is fine - by the way the current is strongly dependent on the voltage you apply so maybe you could give us the supply voltage you use as well for better evaluation?

  • 0
    Guru 227245 points

    For 16MHz, the required minimum voltage is 3.3V. A look in the datasheet reveals that for 3,3V and 16MHz, the active mdoe current is >9mA. Almost 11mA for 3,6V
    The 6mA you quoted are for 3V operation and 12MHz.

    However, the active current depends on many things. Part of it is consumed by the DCO. Part by teh CPU core. Whiel the DCo part is constant (for a given frequency), the CPU current may be higher or lower depending on the operation executed.
    a 'jump in place' that does only require the instruction fetch, will consume less energy than a series of shift operations on memory cells. Not much bit a bit.
    Also, it makes a huge difference whether the code is in ram or flash. Especially on higher frequencies. And temperature has a small effect too.

    When you hit a breakpont, the MCLK and the CPU are stopped. No operations happens. Only the DCO is continuing. This dramatically reduces the current consumption. It is more or less equivalent to entering LPM0 (or even LPM1, I don't know)

    Or do you use a crystal for 16MHz? On 16MHz, XT2 consumes about 1,6mA.

    Ushan Karunathilaka said:
    How can i reduce the active current to 6mA?

    Lower the supply voltage to 3,0V and the speed to <12MHz. That's it.

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