Electronic Components Datasheet Search |
|
ADT7488AARMZ-RL Datasheet(PDF) 9 Page - ON Semiconductor |
|
ADT7488AARMZ-RL Datasheet(HTML) 9 Page - ON Semiconductor |
9 / 12 page ADT7488A http://onsemi.com 9 voltage and therefore has adequate headroom to cope with overvoltage. The full−scale voltage that can be recorded for each channel is shown in Table 6. Table 6. Maximum Reported Input Voltages Voltage Channel Full−Scale Voltage VCC 4.0 V 2.5 V 4.0 V VCCP 4.0 V Input Circuitry The internal structure for the analog inputs is shown in Figure 14. The input circuit consists of an input protection diode and an attenuator, plus a capacitor that forms a first−order, low−pass filter to provide input immunity to high frequency noise. Figure 14. Internal Structure of Analog Inputs 35pF 30pF 30pF MUX 68kΩ 71kΩ 3.3VIN 2.5VIN VCCP 45kΩ 94kΩ 17.5kΩ 52.5kΩ Voltage Measurement Command Codes The voltage measurement command codes are detailed in Table 7. Each voltage measurement has a read length of two bytes in little endian format (LSB followed by MSB). All voltages can be read together by addressing Command Code 0x12 with a read length of 0x06. The data is retrieved in the order listed in Table 7. Table 7. Voltage Measurement Command Code Voltage Channel Command Code Returned Data VCC 0x12 LSB, MSB 2.5 V 0x13 LSB, MSB VCCP 0x14 LSB, MSB Voltage Data Format The returned voltage value is in twos complement, 16−bit, binary format. The format is structured so that voltages in the range of ±32 V can be reported. In this way, the reported value represents the number of 1/1024 V in the actual reading, allowing a resolution of approximately 1 mV. Table 8. Analog−to−Digital Output vs. VIN Voltage Twos Complement LSB MSB 3.3 0000 1101 0011 0011 3.0 0000 1100 0000 0000 2.5 0000 1010 0000 0000 1.0 0000 0100 0000 0000 0 0000 0000 0000 0000 Temperature Measurement The ADT7488A has three dedicated temperature measurement channels: one for measuring the temperature of an on−chip band gap temperature sensor, and two for measuring the temperature of a remote diode, usually located in the CPU or GPU. The ADT7488A monitors one local and two remote temperature channels. Monitoring of each of the channels is done in a round−robin sequence. The monitoring sequence is in the order shown in Table 9. Table 9. Temperature Monitoring Sequence Channel Number Measurement Conversion Time (ms) 0 Local temperature 12 1 Remote 1 temperature 38 2 Remote 2 temperature 38 Temperature Measurement Method A simple method for measuring temperature is to exploit the negative temperature coefficient of a diode by measuring the base−emitter voltage (VBE) of a transistor operated at constant current. Unfortunately, this technique requires calibration to null the effect of the absolute value of VBE, which varies from device to device. The technique used in the ADT7488A measures the change in VBE when the device is operated at three different currents. Figure 15 shows the input signal conditioning used to measure the output of a remote temperature sensor. This figure shows the remote sensor as a substrate transistor, which is provided for temperature monitoring on some microprocessors, but it could also be a discrete transistor. If a discrete transistor is used, the collector is not grounded and should be linked to the base. To prevent ground noise from interfering with the measurement, the more negative terminal of the sensor is not referenced to ground, but is biased above ground by an internal diode at the D1− input. If the sensor is operating in an extremely noisy environment, C1 can be added as a noise filter. Its value should not exceed 1000 pF. To measure DVBE, the operating current through the sensor is switched between three related currents. Figure 15 shows N1 x I and N2 x I as different multiples of the current I. The currents through the temperature diode are switched between I and N1 x I, giving DVBE1, and then between I and N2 x I, giving DVBE2. The temperature can then be calculated using the two DVBE measurements. This method can also cancel the effect of series resistance on the temperature measurement. The resulting DVBE waveforms are passed through a 65 kHz low−pass filter to remove noise and then through a chopper−stabilized amplifier to amplify and rectify the waveform, producing a dc voltage proportional to DVBE. The ADC digitizes this voltage, and a temperature measurement is produced. To reduce the effects of noise, digital filtering is performed by averaging the results of 16 measurement cycles for low conversion |
Similar Part No. - ADT7488AARMZ-RL |
|
Similar Description - ADT7488AARMZ-RL |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |