MSP430F2274-EP: excessive current draw at low negative temperatures

The red line is currrent draw, the blue line is temperature.  Code seemed not to stick, lets try that again!

#include "msp430.h"

void configWDT();
void configClocks();
void configGPIO();

static volatile char mode_set;

void main(void)
{                                           //Configuration routines
    configWDT();                            //Watchdog Timer+ Registers
    configGPIO();                           //General purpose pin io registers
    configClocks();                         //Basic Clock Module+ Registers

    mode_set = 0;

    while(1)
    {
        if(mode_set == 0)
            __bis_SR_register(LPM3_bits + GIE);     // Enter Low Power Mode 3 (LPM3) w/interrupt

        else if(mode_set == 1)
            __bis_SR_register(GIE);
    }
}

void configWDT(void)
{
    WDTCTL = WDTPW + WDTHOLD;   // Disable the watchdog timer.
                                // WDTPW        (bits 15 to 8)  = 5Ah.  WDT password.
                                // WDTHOLD      (bit 7)         = 1h.   Disables the WDT.
}


void configClocks()
{
    /* original clock functionality with XTAL and external crystal oscillator */
    //DCOCTL = 0x00;
    //BCSCTL1 = XT2OFF + DIVA_3;
    //BCSCTL2 = SELM_3 + DIVM_3;
    //BCSCTL3 = XCAP_3;

    /* clock functionality with VLO */
    DCOCTL = 0x00;
    BCSCTL1 = XT2OFF + DIVA_3;
    BCSCTL2 = SELM_3 + DIVM_3 + SELS;
    BCSCTL3 = LFXT1S_2 + XCAP_3;
}

void configGPIO(void)       // GPIO Register configuration
{
    //P1
    P1OUT = 0xFF;
    P1DIR = 0x00;
    P1SEL = 0x00;

    P1REN = BIT2;          // P1.2 Enable Pullup/Pulldown
    P1OUT = BIT2;          // P1.2 pullup
    P1IE = BIT2;           // P1.2 interrupt enabled
    P1IES = BIT2;          // P1.2 Hi/lo falling edge
    P1IFG = 0x00;

    //P2
    P2DIR = BIT0;
    P2OUT = 0x00;
    P2SEL = 0xC0;
    P2IE = 0x00;
    P2IES = 0x00;
    P2IFG = 0x00;

    //P3
    P3OUT = 0x00;
    P3DIR = 0xFF;

    //P4
    P4OUT = 0x00;
    P4DIR = 0xFF;
}


// Port 1 interrupt service routine
#pragma vector=PORT1_VECTOR
__interrupt void Port_1(void)
{
    P2OUT ^= BIT0;
    P2IFG &= ~BIT0;
    P1IFG = 0x00;                             // P1.2 IFG cleared

    mode_set = P2OUT;
    __bic_SR_register_on_exit(LPM3_bits);
}

Hi Lukas,

Thanks for the quick response.  Did you go to -35C?  Until we get down to -10 or -15, the current is stable, then it goes up (as the graph shows).   However at room temp, of course, current draw is fine.

Was this on a F2274-EP device?  Can you run down to -55C and if its possible provide a current draw graph?   How are you monitoring the current draw?

P1 has a button attached so we can simulate an interrupt if we wish to do so and exit LPM3.

P2 I think the intent was to just set P2.0 for input, not all the ports.

To make sure I understand:

Set P1,P2,P3 and P4 ports to output (PxDIR = 0xFF)  x=1 to 4 and set PxREN = 0x00 

Reading the datasheet it said unused pins should be pulled high, why set them to low??  

Another engineer had worked on this code primarily, so I am going through and sorting this out.  

Thank you,

Charles

Hi Charles,

I measured the current down to -55C, there was no change.

The graph would look like a straight line at 0.6 uA.

I put an Amperemeter between the power supply and the DVCC pin.

If you set them to output, you don't need to take care about PxREN, correct set PxDIR to 0xFF, exxcept the button and the LED.

You can also as alternative set them as input (PxDIR = 0x00) and enable Pull up resistor PxREN = 0xFF and PxOUT =0xFF.

Do you see this on every unit? How many have you tested so far?

Lukas