Datasheet AD7616 (Analog Devices) - 25

link to page 25 link to page 25 link to page 25
AD7616 Data Sheet
ing resistor on the VxAGND or VxBGND channel, an offset
ADC TRANSFER FUNCTION
error occurs on that channel. Use the input overvoltage clamp The output coding of the AD7616 is twos complement. The protection circuitry to protect the AD7616 against transient designed code transitions occur midway between successive overvoltage events. It is not recommended to leave the AD7616 integer LSB values, that is, 1/2 LSB and 3/2 LSB. The LSB size is in a condition where the clamp protection circuitry is active in full-scale range ÷ 65,536 for the AD7616. The ideal transfer normal or power-down conditions for extended periods. characteristics for the AD7616 are shown in Figure 46. The LSB
RFB
size is dependent on the analog input range selected.
AD7616 ANALOG R 1MΩ Vxx VIN 2.5V INPUT CLAMP ±10V CODE = × 32,768 × 10V REFINOUT SIGNAL R C 1MΩ VIN 2.5V CLAMP ±5V CODE = × 32,768 × VxxGND 5V REFINOUT V 2.5V
008
IN ±2.5V CODE = × 32,768 × R
1-
FB 2.5V REFINOUT
359
011...111
1
011...110
Figure 43. Input Resistance Matching on the Analog Input
E D +FS – (–FS) Analog Input Antialiasing Filter O 000...001 LSB = C 000...000 2N* C
An analog antialiasing filter (a first-order Butterworth) is also
111...111 AD
provided on the AD7616. Figure 44 and Figure 45 show the
100...010
frequency and phase response, respectively, of the analog
100...001 100...000
antialiasing filter. The typical corner frequency in the ±10 V
–FS + 1/2LSB 0V – 1/2LSB +FS – 3/2LSB
range is 39 kHz, and 33 kHz in the ±5 V range.
ANALOG INPUT 5 +FS MIDSCALE –FS LSB ±10V RANGE ±10V RANGE +10V 0V –10V 305µV ±5V RANGE ±5V RANGE +5V 0V –5V 152µV 0 ±2.5V RANGE ±2.5V RANGE +2.5V 0V –2.5V 76µV
09 -0
*WHERE N IS THE NUMBER OF BITS OF THE CONVERTER
591 13
–5 )
Figure 46. Transfer Characteristics
dB ( –10 INTERNAL/EXTERNAL REFERENCE TION A U
The AD7616 can operate with either an internal or external
N –15
reference. The device contains an on-chip 2.5 V band gap refer-
TTE A –20
ence. The REFINOUT pin allows access to the 2.5 V reference that generates the on-chip 4.096 V reference internally, or it
–25
allows an external reference of 2.5 V to be applied to the AD7616. An externally applied reference of 2.5 V is also amplified to 4.096 V
–30100 1k 10k 100k
44 2 using the internal buffer. This 4.096 V buffered reference is the
INPUT FREQUENCY (Hz)
591- 13 reference used by the SAR ADC. Figure 44. Analog Antialiasing Filter Frequency Response The REFSEL pin is a logic input pin that allows the user to select
6
between the internal reference and an external reference. If this
±10V RANGE ±5V RANGE
pin is set to logic high, the internal reference is selected and
5 ±2.5V RANGE
enabled. If this pin is set to logic low, the internal reference is disabled and an external reference voltage must be applied
4 )
to the REFINOUT pin.
(µs E 3
The internal reference buffer is always enabled. After a full reset,
S
the AD7616 operates in the reference mode selected by the
PHA 2
REFSEL pin. Decoupling is required on the REFINOUT pin for both the internal and external reference options. A 100 nF, X8R
1
ceramic capacitor is required on the REFINOUT pin to REFINOUTGND.
0100
46 The AD7616 contains a reference buffer configured to amplify
1k 10k 100k
2 1- 59 the reference voltage to ~4.096 V. A 10 μF, X5R ceramic capacitor
INPUT FREQUENCY (Hz)
13 Figure 45. Analog Antialiasing Filter Phase Response is required between REFCAP and REFGND. The reference voltage available at the REFINOUT pin is 2.5 V. When the AD7616 is configured in external reference mode, the REFINOUT pin is a high input impedance pin. Rev. 0 | Page 24 of 50 Document Outline FEATURES APPLICATIONS GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM TABLE OF CONTENTS REVISION HISTORY SPECIFICATIONS TIMING SPECIFICATIONS Universal Timing Specifications Parallel Mode Timing Specifications Serial Mode Timing Specifications ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE ESD CAUTION PIN CONFIGURATION AND FUNCTION DESCRIPTIONS TYPICAL PERFORMANCE CHARACTERISTICS TERMINOLOGY THEORY OF OPERATION CONVERTER DETAILS ANALOG INPUT Analog Input Channel Selection Analog Input Ranges Analog Input Impedance Analog Input Clamp Protection Analog Input Antialiasing Filter ADC TRANSFER FUNCTION INTERNAL/EXTERNAL REFERENCE SHUTDOWN MODE DIGITAL FILTER APPLICATIONS INFORMATION FUNCTIONALITY OVERVIEW POWER SUPPLIES TYPICAL CONNECTIONS DEVICE CONFIGURATION OPERATIONAL MODE INTERNAL/EXTERNAL REFERENCE DIGITAL INTERFACE HARDWARE MODE SOFTWARE MODE RESET FUNCTIONALITY PIN FUNCTION OVERVIEW DIGITAL INTERFACE CHANNEL SELECTION Hardware Mode Software Mode PARALLEL INTERFACE Reading Conversion Results Writing Register Data Reading Register Data SERIAL INTERFACE Reading Conversion Results Writing Register Data Reading Register Data SEQUENCER HARDWARE MODE SEQUENCER SOFTWARE MODE SEQUENCER BURST SEQUENCER Hardware Mode Burst Software Mode Burst DIAGNOSTICS DIAGNOSTIC CHANNELS INTERFACE SELF TEST CRC REGISTER SUMMARY ADDRESSING REGISTERS CONFIGURATION REGISTER CHANNEL REGISTER INPUT RANGE REGISTERS INPUT RANGE REGISTER A1 INPUT RANGE REGISTER A2 INPUT RANGE REGISTER B1 INPUT RANGE REGISTER B2 SEQUENCER STACK REGISTERS STATUS REGISTER OUTLINE DIMENSIONS ORDERING GUIDE