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ADM1022ARQ データシート(PDF) 9 Page - Analog Devices |
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ADM1022ARQ データシート(HTML) 9 Page - Analog Devices |
9 / 19 page REV. 0 ADM1022 –9– R/ W 0 SCL SDA 1 0 1 1 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 ACK. BY ADM1022 START BY MASTER 19 1 ACK. BY ADM1022 9 D7 D6 D5 D4 D3 D2 D1 D0 ACK. BY ADM1022 STOP BY MASTER 1 9 SCL (CONTINUED) SDA (CONTINUED) FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 ADDRESS POINTER REGISTER BYTE FRAME 3 DATA BYTE Figure 11a. Writing a Register Address to the Address Pointer Register, then Writing Data to the Selected Register R/ W 0 SCL SDA 1 0 1 1 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 ACK. BY ADM1022 START BY MASTER 19 1 ACK. BY ADM1022 9 FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 ADDRESS POINTER REGISTER BYTE STOP BY MASTER Figure 11b. Writing to the Address Pointer Register Only R/ W 0 SCL SDA 1 0 1 1 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 NO ACK. BY MASTER START BY MASTER 19 1 ACK. BY ADM1022 9 FRAME 1 SERIAL BUS ADDRESS BYTE FRAME 2 DATA BYTE FROM ADM1022 STOP BY MASTER Figure 11c. Reading Data from a Previously Selected Register TEMPERATURE MEASUREMENT SYSTEM Internal Temperature Measurement The ADM1022 contains an on-chip bandgap temperature sen- sor. The on-chip ADC performs conversions on the output of this sensor and outputs the temperature data in 8-bit twos comple- ment format. The format of the temperature data is shown in Table II. External Temperature Measurement The ADM1022 can measure the temperature of two external diode sensors or diode-connected transistors, connected to Pins 9 and 10 or 11 and 12. Pins 9 and 10 are a dedicated temperature input channel. The default function of Pins 11 and 12 is the THERM input/output and a general purpose logic input (GPI), but they can be config- ured to measure a diode sensor by setting Bit 7 of the Configu- ration Register to 1. The forward voltage of a diode or diode-connected transistor, operated at a constant current, exhibits a negative temperature coefficient of about –2 mV/ °C. Unfortunately, the absolute value of VBE, varies from device to device, and individual calibra- tion is required to null this out, so the technique is unsuitable for mass-production. The technique used in the ADM1022 is to measure the change in VBE when the device is operated at two different currents. This is given by: ∆VBE = KT/q × ln(N) where: K is Boltzmann’s constant q is charge on the carrier T is absolute temperature in Kelvins N is ratio of the two currents Figure 12 shows the input signal conditioning used to mea- sure the output of an external temperature sensor. This figure shows the external sensor as a substrate transistor, provided for temperature monitoring on some microprocessors, but it could equally well be a discrete transistor. |
同様の部品番号 - ADM1022ARQ |
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同様の説明 - ADM1022ARQ |
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