求大神指导msp430内部温度传感器的问题

大家好，最近遇到个问题，就是用msp430FR5949内部温度传感器测温度，程序写好后，用仿真器在线测试，不接外部电源的时候，可以正确采集数据，但是接上外部电源的话，采集的原始数据就变成了4095，希望大家帮帮我，在此非常感谢！以下是程序

#include <msp430fr5949.h>

#define CALADC12_12V_30C *((unsigned int *)0x1A1A) // Temperature Sensor Calibration-30 C
//See device datasheet for TLV table memory mapping
#define CALADC12_12V_85C *((unsigned int *)0x1A1C) // Temperature Sensor Calibration-85 C

unsigned int temp;
volatile float temperatureDegC;
volatile float temperatureDegF;

int main(void)
{
WDTCTL = WDTPW + WDTHOLD; // Stop WDT

// Initialize the shared reference module
// By default, REFMSTR=1 => REFCTL is used to configure the internal reference
while(REFCTL0 & REFGENBUSY); // If ref generator busy, WAIT
REFCTL0 |= REFVSEL_0 + REFON; // Enable internal 1.2V reference

/* Initialize ADC12_A */
ADC12CTL0 &= ~ADC12ENC; // Disable ADC12
ADC12CTL0 = ADC12SHT0_8 + ADC12ON; // Set sample time
ADC12CTL1 = ADC12SHP; // Enable sample timer
ADC12CTL3 = ADC12TCMAP; // Enable internal temperature sensor
ADC12MCTL0 = ADC12VRSEL_1 + ADC12INCH_30; // ADC input ch A30 => temp sense
ADC12IER0 = 0x001; // ADC_IFG upon conv result-ADCMEMO

while(!(REFCTL0 & REFGENRDY)); // Wait for reference generator
// to settle
ADC12CTL0 |= ADC12ENC;

while(1)
{
ADC12CTL0 |= ADC12SC; // Sampling and conversion start

__bis_SR_register(LPM0_bits + GIE); // LPM4 with interrupts enabled
__no_operation();

// Temperature in Celsius. See the Device Descriptor Table section in the
// System Resets, Interrupts, and Operating Modes, System Control Module
// chapter in the device user's guide for background information on the
// used formula.
temperatureDegC = (float)(((long)temp - CALADC12_12V_30C) * (85 - 30)) /
(CALADC12_12V_85C - CALADC12_12V_30C) + 30.0f;

// Temperature in Fahrenheit Tf = (9/5)*Tc + 32
temperatureDegF = temperatureDegC * 9.0f / 5.0f + 32.0f;

__no_operation(); // SET BREAKPOINT HERE
}
}

#if defined(__TI_COMPILER_VERSION__) || defined(__IAR_SYSTEMS_ICC__)
#pragma vector=ADC12_VECTOR
__interrupt void ADC12ISR (void)
#elif defined(__GNUC__)
void __attribute__ ((interrupt(ADC12_VECTOR))) ADC12ISR (void)
#else
#error Compiler not supported!
#endif
{
switch(__even_in_range(ADC12IV, ADC12IV_ADC12RDYIFG))
{
case ADC12IV_NONE: break; // Vector 0: No interrupt
case ADC12IV_ADC12OVIFG: break; // Vector 2: ADC12MEMx Overflow
case ADC12IV_ADC12TOVIFG: break; // Vector 4: Conversion time overflow
case ADC12IV_ADC12HIIFG: break; // Vector 6: ADC12BHI
case ADC12IV_ADC12LOIFG: break; // Vector 8: ADC12BLO
case ADC12IV_ADC12INIFG: break; // Vector 10: ADC12BIN
case ADC12IV_ADC12IFG0: // Vector 12: ADC12MEM0 Interrupt
temp = ADC12MEM0; // Move results, IFG is cleared
__bic_SR_register_on_exit(LPM4_bits); // Exit active CPU
break;
case ADC12IV_ADC12IFG1: break; // Vector 14: ADC12MEM1
case ADC12IV_ADC12IFG2: break; // Vector 16: ADC12MEM2
case ADC12IV_ADC12IFG3: break; // Vector 18: ADC12MEM3
case ADC12IV_ADC12IFG4: break; // Vector 20: ADC12MEM4
case ADC12IV_ADC12IFG5: break; // Vector 22: ADC12MEM5
case ADC12IV_ADC12IFG6: break; // Vector 24: ADC12MEM6
case ADC12IV_ADC12IFG7: break; // Vector 26: ADC12MEM7
case ADC12IV_ADC12IFG8: break; // Vector 28: ADC12MEM8
case ADC12IV_ADC12IFG9: break; // Vector 30: ADC12MEM9
case ADC12IV_ADC12IFG10: break; // Vector 32: ADC12MEM10
case ADC12IV_ADC12IFG11: break; // Vector 34: ADC12MEM11
case ADC12IV_ADC12IFG12: break; // Vector 36: ADC12MEM12
case ADC12IV_ADC12IFG13: break; // Vector 38: ADC12MEM13
case ADC12IV_ADC12IFG14: break; // Vector 40: ADC12MEM14
case ADC12IV_ADC12IFG15: break; // Vector 42: ADC12MEM15
case ADC12IV_ADC12IFG16: break; // Vector 44: ADC12MEM16
case ADC12IV_ADC12IFG17: break; // Vector 46: ADC12MEM17
case ADC12IV_ADC12IFG18: break; // Vector 48: ADC12MEM18
case ADC12IV_ADC12IFG19: break; // Vector 50: ADC12MEM19
case ADC12IV_ADC12IFG20: break; // Vector 52: ADC12MEM20
case ADC12IV_ADC12IFG21: break; // Vector 54: ADC12MEM21
case ADC12IV_ADC12IFG22: break; // Vector 56: ADC12MEM22
case ADC12IV_ADC12IFG23: break; // Vector 58: ADC12MEM23
case ADC12IV_ADC12IFG24: break; // Vector 60: ADC12MEM24
case ADC12IV_ADC12IFG25: break; // Vector 62: ADC12MEM25
case ADC12IV_ADC12IFG26: break; // Vector 64: ADC12MEM26
case ADC12IV_ADC12IFG27: break; // Vector 66: ADC12MEM27
case ADC12IV_ADC12IFG28: break; // Vector 68: ADC12MEM28
case ADC12IV_ADC12IFG29: break; // Vector 70: ADC12MEM29
case ADC12IV_ADC12IFG30: break; // Vector 72: ADC12MEM30
case ADC12IV_ADC12IFG31: break; // Vector 74: ADC12MEM31
case ADC12IV_ADC12RDYIFG: break; // Vector 76: ADC12RDY
default: break;
}
}