Adc Connections And Decoupling - Texas Instruments ADS1258EVM-PDK User Manual

Analog Interface

3.2 ADC Connections and Decoupling

Figure 3-2 shows all ADC connections. Each power-supply and reference connection have a 100-nF decoupling
capacitor. Place these capacitors as close as possible to the ADC pins and make sure each component has a
low-impedance connection to the GND plane.
Each digital pin of the ADC has a 49.9-Ω series resistor. These resistors smooth the edges of the digital signals
so that the signals have minimal overshoot and ringing. A resistor is most important on the serial clock (SCLK)
trace because the SCLK signal can toggle as quickly as 8 MHz. Resistors on the other pins are not strictly
required, though these components can be included in the final design to improve digital signal integrity.
Pullup resistors R8, R9, R10, and R11 prevent CS, START, RESET, and PWDN, respectively, from floating when
not driven. The differential voltage across test points TP4 and ground is the reference voltage used by the ADC.
AVDD DVDD
Place
capacitors
C6 C7
near ADC
100nF 100nF
supply pins
GND GND
TP4
REFOUT
REFOUT
C8
100nF
GND
Figure 3-2. ADS1258EVM ADC Power-Supply Decoupling and Analog and Digital Connections
6 ADS1258EVM-PDK Evaluation Module
ADS1258
U3
6
AVDD GPIO0
28
DVDD GPIO1
GPIO2
31
VREFP GPIO3
30
VREFN GPIO4
GPIO5
A0
4
AIN0 GPIO6
A1
3
AIN1 GPIO7
A2
2
AIN2
A3
1
AIN3
A4
48
AIN4 DRDY
A5
47
AIN5 SCLK
A6
46
AIN6
A7
45
AIN7 DOUT
A8
40
AIN8
A9
39
AIN9 START
A10
38
AIN10 RESET
A11
37
AIN11 PWDN
A12
36
AIN12
A13
35
AIN13 XTAL1
A14
34
AIN14 XTAL2
A15
33
AIN15
ACOM
32
AINCOM CLKIO
ADCINP
42
ADCINP CLKSEL
ADCINN
41
ADCINN
PLLCAP
MUXOUTP
MUXOUTN
AVSS
DGND
ADS1258IRTCR
Copyright © 2023 Texas Instruments Incorporated
DVDD
R8
100k
R9
100k
GPIO0
14
GPIO1
15
GPIO2
16
GPIO3
17
GPIO4
18
GPIO5
19
GPIO6
20
GPIO7
21
27
CS
25
22
23
DIN
24
26
11
10
8
9
CLK
13
12
DVDD
7
MUXOUTP
44
MUXOUTN
43
49
EP
5
29
GND
SBAU126E – MAY 2007 – REVISED JUNE 2023
www.ti.com
R10
100k
R11
100k
R12
ADC.CS
49.9
R13
ADC.DRDY
49.9
R14
ADC.SCLK
49.9
R15
ADC.DIN
49.9
R16
ADC.DOUT
49.9
R18
ADC.START
49.9
R19
ADC.RESET
49.9
R20
ADC.PWDN
49.9
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