temperature sensor and two-stage amplifiler

emugine — Fri, 17 Mar 2006 14:50:27 GMT

I want to use the temperature sensor in the MC68HC908SR12.In data sheet

24.14.1 table 24-12,it said temperature slope:VDD=5V±10%,GAINA=2,GAINB=6
MIN 1.275 ADCsteps/C,Typ 1.338ADCsteps/C,Max 1.372ADCsteps/C,
I set

AMGCR=81;//GAINA=2,GAINB=6
AMSCR=34;
AMCR=240;

as the expert told me,now I get ADC value 693 or 724,I want to know what

is the MC68HC908SR12 real temperature?any help will be appreciated.

Re: temperature sensor and two-stage amplifiler

emugine — Fri, 17 Mar 2006 17:35:11 GMT

I set

word AD_word;
AMGCR=81;//GAINA=2,GAINB=6
AMSCR=34;//00100010
         //AMCDIV[1:0]=00 Analog Module Clock Divider Control Bits,
                  // Set AMCDIV1 and AMCDIV0 bits to
                  //zero for optimum analog module performance.
         //OPIFR =1 Amplifier Ready Interrupt Flag Reset,
                  //1 = Clear OPIF bit
         //OPIF=0 Amplifier Ready Interrupt Flag
                 // 1 = Two-stage amplifier output is ready
         //0
         //DOF=0 DC Offset Flag, This is a reserved bit.
         //CDIFR=1 Current Detect Interrupt Flag Reset,
                    //Writing a logic 1 to this write-only
                    //bit clears the CDIF bit.
         //CDIF=0 Current Detect Interrupt Flag,
                   //1 = Current detect interrupt has occurred
AMCR=240;//11110000       Analog Module Control Register (AMCR)
//PWR1 PWR0=1 1 CurrentDetectModule=On
                    //TemperatureSensor=On Two-StageAmplifier=On
//OPCH1 OPCH0 1 1   Internal temperature sensor
//AMIEN =0 Analog module CPU interrupt requests disabled
//DO[2:0]=000 DC Offset Control Bits
                //Set these bits to zero for optimum analog module performance.

while(!AMSCR_OPIF);//wait for Amplifier Ready
ADICLK=0x54;//01010100
            //010 ADIV2 ADIV1 ADIV0 ADC INPUT CLOCK/4
            //1   ADICLK select internal clock
            //01 MODE1 MODE0 Right justified mode
ADSCR=0x00|13;//select OPOUT
while(!ADSCR_COCO);
AD_word= (ADR0H&0x03)*256+ ADR0L;

thank you for your help again!

Re: temperature sensor and two-stage amplifiler

emugine — Fri, 17 Mar 2006 18:02:34 GMT

(724/(2*6))/1.338=45.09,

real temperature=45.09-20=25.09

am i right?

but the data keep from 695~724 even after a few hours or when I use the iron head approach the cpu,did i set anything wrong?

help me.

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