Datasheet AD7817, AD7818 (Analog Devices) - 8

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AD7817/AD7818 Data Sheet PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS CONVST 1 16 RD/WR BUSY 2 15 SCLK OTI 3 14 DIN AD7817 CS 4 TOP VIEW 13 DOUT (Not to Scale) AGND 5 12 DGND REF 6 IN 11 VDD V 7 IN1 10 VIN4
04
V 8
0
IN2 9 VIN3
1316- 0 Figure 4. AD7817 Pin Configuration
Table 4. AD7817 Pi n Function Descriptions Pin No. Mnemonic Description
1 CONVST Logic Input Signal. The convert start signal. A 10-bit analog-to-digital conversion is initiated on the falling edge of this signal. The falling edge of this signal places track-and-hold in hold mode. Track-and-hold goes into track mode again at the end of the conversion. The state of the CONVST signal is checked at the end of a conversion. If it is logic low, the AD7817 powers down. See the Operating Modes section. 2 BUSY Logic Output. The busy signal is logic high during a temperature or voltage A/D conversion. The signal can be used to interrupt a microcontroller when a conversion has finished. 3 OTI Logic Output. The overtemperature indicator (OTI) is set logic low if the result of a conversion on Channel 0 (temperature sensor) is greater that an 8-bit word in the overtemperature register (OTR). The signal is reset at the end of a serial read operation, that is, a rising RD/WR edge when CS is low. 4 CS Logic Input Signal. The chip select signal is used to enable the serial port of the AD7817. This is necessary if the AD7817 is sharing the serial bus with more than one device. 5 AGND Analog Ground. Ground reference for track-and-hold comparator and capacitor DAC. 6 REFIN Analog Input. An external 2.5 V reference can be connected to the AD7817 at this pin. To enable the on-chip reference, tie the REFIN pin to AGND. If an external reference is connected to the AD7817, the internal reference shuts down. 7 VIN1 to VIN4 Analog Input Channels. The AD7817 has four analog input channels. The input channels are single-ended with respect to to AGND (analog ground). The input channels can convert voltage signals in the range 0 V to VREF. A channel is selected 10 by writing to the address register of the AD7817. See the Control Byte section. 11 VDD Positive Supply Voltage, 2.7 V to 5.5 V. 12 DGND Digital Ground. Ground reference for digital circuitry. 13 DOUT Logic Output with a High Impedance State. Data is clocked out of the AD7817 serial port at this pin. This output goes into a high impedance state on the falling edge of RD/WR or on the rising edge of the CS signal, whichever occurs first. 14 DIN Logic Input. Data is clocked into the AD7817 at this pin. 15 SCLK Clock Input for the Serial Port. The serial clock is used to clock data into and out of the AD7817. Data is clocked out on the falling edge and clocked in on the rising edge. 16 RD/WR Logic Input Signal. The read/write signal is used to indicate to the AD7817 whether the data transfer operation is a read or a write. Set the RD/WR logic high for a read operation and logic low for a write operation. Rev. E | Page 8 of 20 Document Outline FEATURES APPLICATIONS FUNCTIONAL BLOCK DIAGRAMS GENERAL DESCRIPTION PRODUCT HIGHLIGHTS TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS TIMING CHARACTERISTICS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS TERMINOLOGY CONTROL BYTE Address Register Overtemperature Register CIRCUIT INFORMATION CONVERTER DETAILS TYPICAL CONNECTION DIAGRAM ANALOG INPUTS Analog Input DC Acquisition Time AC Acquisition Time ON-CHIP REFERENCE ADC TRANSFER FUNCTION TEMPERATURE MEASUREMENT TEMPERATURE MEASUREMENT ERROR DUE TO REFERENCE ERROR SELF-HEATING CONSIDERATIONS OPERATING MODES Mode 1 Mode 2 POWER vs. THROUGHPUT AD7817 SERIAL INTERFACE Read Operation Write Operation Simplifying the Serial Interface AD7818 SERIAL INTERFACE MODE Read Operation Write Operation OUTLINE DIMENSIONS ORDERING GUIDE