Datasheet AD7817, AD7818 (Analog Devices) - 9

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Data Sheet AD7817/AD7818 CONVST 1 8 RD/WR OTI 2 AD7818 7 SCLK TOP VIEW GND 3 (Not to Scale) 6 DIN/OUT
-005
VIN 4 5 VDD
16 013 Figure 5. AD7818 Pin Configuration
Table 5. AD7818 Pi n Function Descriptions Pin No. Mnemonic Description
1 CONVST Logic Input Signal. The convert start signal initiates a 10-bit analog-to-digital conversion 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 AD7818 powers down. See the Operating Modes section. 2 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. 3 GND Analog and Digital Ground. 4 VIN Analog Input Channel. The input channel is single-ended with respect to GND. The input channel can convert voltage signals in the range 0 V to 2.5 V. The input channel is selected by writing to the address register of the AD7818. See the Control Byte section. 5 VDD Positive Supply Voltage, 2.7 V to 5.5 V. 6 DIN/OUT Logic Input and Output. Serial data is clocked in and out of the AD7818 at this pin. 7 SCLK Clock Input for the Serial Port. The serial clock is used to clock data into and out of the AD7818. Data is clocked out on the falling edge and clocked in on the rising edge. 8 RD/WR Logic Input. The read/write signal is used to indicate to the AD7818 whether the next 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. Rev. E | Page 9 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