Datasheet AD7414, AD7415 (Analog Devices) - 8

link to page 7 link to page 8
AD7414/ AD7415 Data Sheet
Figure 7 shows the method the AD7414/AD7415 used to
Table 5. A Grade Temperature Data Format
measure the ambient device temperature. To measure ΔVBE,
Temperature Digital Output DB9…DB0
the sensor (substrate transistor) is switched between operating −55°C 11 0010 0100 currents of I and N × I. The resulting waveform is passed −50°C 11 0011 1000 through a chopper stabilized amplifier that performs the −25°C 11 1001 1100 functions of amplification and rectification of the waveform to −0.25°C 11 1111 1111 produce a dc voltage proportional to ΔVBE. This voltage is 0°C 00 0000 0000 measured by the ADC to give a temperature output in 10-bit, +0.25°C 00 0000 0001 twos complement format. +10°C 00 0010 1000
TEMPERATURE DATA FORMAT
+25°C 00 0110 0100 The temperature resolution of the ADC is 0.25°C, which +50°C 00 1100 1000 corresponds to 1 LSB of the ADC. The ADC can theoretically +75°C 01 0010 1100 measure a temperature span of 255°C; the lowest practical value +100°C 01 1001 0000 is limited to −40°C due to the device maximum ratings. The +125°C 01 1111 0100 A grade can measure a temperature range of −40°C to +125°C (temperature data format is shown in Table 5). The grade temperature conversion formula follows: ADC Code (d) Positive e Temperatur  4 ADC Code ( ) 512 Negative e Temperatur  d 4 Note that DB9 is removed from the ADC code in the negative temperature formula. Rev. G | Page 8 of 19 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS THEORY OF OPERATION CIRCUIT INFORMATION FUNCTIONAL DESCRIPTION MEASUREMENT TECHNIQUE TEMPERATURE DATA FORMAT INTERNAL REGISTER STRUCTURE ADDRESS POINTER REGISTER CONFIGURATION REGISTER (ADDRESS 0x01) TEMPERATURE VALUE REGISTER (ADDRESS 0x00) AD7414 THIGH REGISTER (ADDRESS 0X02) AD7414 TLOW REGISTER (ADDRESS 0x03) SERIAL INTERFACE SERIAL BUS ADDRESS WRITE MODE Writing to the Address Pointer Register for a Subsequent Read Writing a Single Byte of Data to the Configuration Register, THIGH Register, or TLOW Register READ MODE SMBUS ALERT POWER-ON DEFAULTS OPERATING MODES Mode 1 Mode 2 POWER VS. THROUGHPUT Mode 1 Mode 2 MOUNTING THE AD7414/AD7415 SUPPLY DECOUPLING TEMPERATURE ACCURACY VS. SUPPLY TYPICAL TEMPERATURE ERROR GRAPH OUTLINE DIMENSIONS ORDERING GUIDE