Datasheet AD7457 (Analog Devices) - 8

AD7457 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS VDD 1 8 VREF SCLK 2 AD7457 7 VIN+ SDATA 3 TOP VIEW 6 VIN– (Not to Scale) CS 4 5 GND 03157-0-002
Figure 4. 8-Lead SOT-23 Pin Configuration
Table 4. Pin Function Descriptions Pin No. Mnemonic Description
1 VDD Power Supply Input. VDD is 2.7 V to 5.25 V. This supply should be decoupled to GND with a 0.1 µF capacitor and a 10 µF tantalum capacitor. 2 SCLK Serial Clock. Logic input. SCLK provides the serial clock for accessing data from the part. This clock input is also used as the clock source for the conversion process. 3 SDATA Serial Data. Logic output. The conversion result from the AD7457 is provided on this output as a serial data stream. The bits are clocked out on the falling edge of the SCLK input. The data stream of the AD7457 consists of four leading zeros followed by the 12 bits of conversion data that are provided MSB first. The output coding is straight (natural) binary. 4 CS Chip Select. This input provides the dual function of powering up the device and initiating a conversion on the AD7457. 5 GND Analog Ground. Ground reference point for all circuitry on the AD7457. All analog input signals and any external reference signal should be referred to this GND voltage. 6 VIN– Inverting Input. This pin sets the ground reference point for the VIN+ input. Connect to ground or to a dc offset to provide a pseudo ground. 7 VIN+ Noninverting Analog Input. 8 VREF Reference Input for the AD7457. An external reference in the range 100 mV to VDD must be applied to this input. The specified reference input is 2.5 V. This pin should be decoupled to GND with a capacitor of at least 0.33 µF. Rev. A | Page 7 of 20 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION PRODUCT HIGHLIGHTS SPECIFICATIONS TIMING SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TERMINOLOGY THEORY OF OPERATION CIRCUIT INFORMATION CONVERTER OPERATION ADC TRANSFER FUNCTION TYPICAL CONNECTION DIAGRAM ANALOG INPUT ANALOG INPUT STRUCTURE DIGITAL INPUTS REFERENCE SECTION SERIAL INTERFACE POWER CONSUMPTION MICROPROCESSOR INTERFACING AD7457 to ADSP-218x APPLICATION HINTS GROUNDING AND LAYOUT OUTLINE DIMENSIONS ORDERING GUIDE