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Rev. 1.00
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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Analog to Digital Converter –
ADC
Analog to Digital Converter –
ADC
Temperature Sensor
A temperature sensor circuit is provided to measure the temperature which the designer can use
to adjust some measured parameters. The temperature sensor output voltage is proportional to the
temperature increment and can be amplified by the PGA. The accompanying diagram illustrates the
basic relationship between the measured temperature and the voltage output. However, the designer
should consider that the temperature sensor output voltage might be affected by the manufacturing
process.
The ADC temperature sensor input channel is selected by the ACS4 bit. The TSEN bit in the
ADCR1 register controls the temperature sensor enable/disable function. When the function is
disabled, the temperature sensor defaults to an unknown state and any A/D conversion performed
on the sensor will generate undefined data.
A/D Reference Voltage Source
The A/D can obtain its reference voltage from three different sources, the VCCA3 power supply
pin, an externally supplied reference voltage supplied on pin VREF or from the internal voltage
reference generator. Two bits control which reference source is selected, these are the VREFIS and
VREFAS bits.
A/D Converter Voltage Reference Select
VREFIS
VREFAS
Reference Source
0
0
VCCA3 pin
0
1
Exte�nall� s�pplied on VREF pin
1
0
VCCA3 pin
1
1
Inte�nal Voltage Refe�ence Gene�ato�