Datasheet AD7887 (Analog Devices) - 8

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Data Sheet AD7887 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS CS 1 8 SCLK CS 1 8 SCLK AD7887 V AD7887 V 7 DOUT DD 2 7 DOUT DD 2 TOP VIEW GND 3 6 TOP VIEW DIN GND 3 6 DIN (Not to Scale)
003 004
AIN1/V (Not to Scale) AIN1/V 5 AIN0 REF 4 5 AIN0 REF 4
06191- 06191- Figure 3. SOIC_N Pin Configuration Figure 4. MSOP Pin Configuration
Table 4. Pin Function Descriptions Pin No. Mnemonic Description
1 CS Chip Select. Active low logic input. This input provides the dual function of initiating conversions on the AD7887 and also frames the serial data transfer. When the AD7887 operates in its default mode, the CS pin also acts as the shutdown pin such that with the CS pin high, the AD7887 is in its power-down mode. 2 VDD Power Supply Input. The VDD range for the AD7887 is from 2.7 V to 5.25 V. When the AD7887 is configured for two-channel operation, this pin also provides the reference source for the part. 3 GND Ground Pin. This pin is the ground reference point for all circuitry on the AD7887. In systems with separate AGND and DGND planes, these planes should be tied together as close as possible to this GND pin. Where this is not possible, this GND pin should connect to the AGND plane. 4 AIN1/VREF Analog Input 1/Voltage Reference Input. In single-channel mode, this pin becomes the reference input/output. In this case, the user can either access the internal 2.5 V reference or overdrive the internal reference with the voltage applied to this pin. The reference voltage range for an externally applied reference is 1.2 V to VDD. In two- channel mode, this pin provides the second analog input channel, AIN1. The input voltage range on AIN1 is 0 to VDD. 5 AIN0 Analog Input 0. In single-channel mode, this is the analog input and the input voltage range is 0 to VREF. In dual- channel mode, it has an analog input range of 0 to VDD. 6 DIN Data In. Logic Input. Data to be written to the AD7887’s control register is provided on this input and clocked into the register on the rising edge of SCLK (see the Control Register section). The AD7887 can be operated as a single-channel, read-only ADC by tying the DIN line permanently to GND. 7 DOUT Data Out. Logic output. The conversion result from the AD7887 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 consists of four leading zeros followed by the 12 bits of conversion data, which is provided MSB first. 8 SCLK Serial Clock. Logic input. SCLK provides the serial clock for accessing data from the part and writing serial data to the control register. This clock input is also used as the clock source for the AD7887’s conversion process. Rev. E | Page 7 of 24 Document Outline Features Applications Functional Block Diagram General Description Product Highlights Table of Contents Revision History Specifications Timing Specifications6F Absolute Maximum Ratings ESD Caution Pin Configurations and Function Descriptions Typical Performance Characteristics Terminology Control Register Theory of Operation Circuit Information Converter Operation ADC Transfer Function Typical Connection Diagram Analog Input On-Chip Reference Power-Down Options Power-Up Times Power vs. Throughput Rate Modes of Operation Mode 1 (PM1 = 0, PM0 = 0) Mode 2 (PM1 = 0, PM0 = 1) Mode 3 (PM1 = 1, PM0 = 0) Mode 4 (PM1 = 1, PM0 = 1) Serial Interface Microprocessor Interfacing AD7887 to TMS320C5x AD7887 to ADSP-21xx AD7887 to DSP56xxx AD7887 to MC68HC11 AD7887 to 8051 AD7887 to PIC16C6x/PIC16C7x Application Hints Grounding and Layout Outline Dimensions Ordering Guide Automotive Products