Datenblatt-Suchmaschine für elektronische Bauteile |
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ADM1021 Datenblatt(PDF) 5 Page - Analog Devices |
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ADM1021 Datenblatt(HTML) 5 Page - Analog Devices |
5 / 12 page ADM1021 –5– REV. 0 FREQUENCY – Hz 10 0 50 50M 500 5k 50k 500k 5M 6 5 4 2 1 3 10mV SQ. WAVE 9 8 7 100k 25M Figure 8. Temperature Error vs. Differential-Mode Noise Frequency CONVERSION RATE – Hz 200 0 0.0625 8 0.125 0.25 0.5 1 2 4 180 80 60 40 20 140 100 160 120 VCC = +5V VCC = +3.3V Figure 9. Operating Supply Current vs. Conversion Rate SUPPLY VOLTAGE – Volts 100 40 –20 0 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.5 4.5 80 60 20 0 ADDX = HI-Z ADDX = GND Figure 10. Standby Supply Current vs. Supply Voltage TIME – Sec 125 100 0 T = 0 T = 10 T = 2 T = 4 T = 6 T = 8 75 50 25 IMMERSED IN +115 C FLUORINERT BATH Figure 11. Response to Thermal Shock FUNCTIONAL DESCRIPTION The ADM1021 contains a two-channel A-to-D converter with special input-signal conditioning to enable operation with remote and on-chip diode temperature sensors. When the ADM1021 is operating normally, the A-to-D converter operates in a free- running mode. The analog input multiplexer alternately selects either the on-chip temperature sensor to measure its local tem- perature, or the remote temperature sensor. These signals are digitized by the ADC and the results stored in the Local and Remote Temperature Value Registers as 8-bit, twos complement words. The measurement results are compared with Local and Remote, High and Low Temperature Limits, stored in four on-chip regis- ters. Out-of-limit comparisons generate flags that are stored in the status register, and one or more out-of-limit results will cause the ALERT output to pull low. The limit registers can be programmed, and the device con- trolled and configured, via the serial System Management Bus. The contents of any register can also be read back via the SMBus. Control and configuration functions consist of: • Switching the device between normal operation and standby mode. • Masking or enabling the ALERT output. • Selecting the conversion rate. MEASUREMENT METHOD A simple method of measuring temperature is to exploit the negative temperature coefficient of a diode, or the base-emitter voltage of a transistor, operated at constant current. Unfortu- nately, this technique requires calibration to null out the effect of the absolute value of Vbe, which varies from device to device. The technique used in the ADM1021 is to measure the change in Vbe when the device is operated at two different currents. This is given by: ∆V be = KT/q × ln (N) where: K is Boltzmann’s constant q is charge on the electron (1.6 x 10 –19 Coulombs) T is absolute temperature in Kelvins N is ratio of the two currents |
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Ähnliche Beschreibung - ADM1021 |
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