ADS7253IPW datasheet(60/71 Pages) TI1

60 / 71 page

SDO-A

SDO-B

SCLK

/CS

REFIO-A

REFGND-A

REFGND-B

REFIO-B

GND

CREF-A

CREF-B

CAVDD

CDVDD

AVDD

GND

DVDD

GND

CIN-A

CIN-B

ADS8353, ADS7853, ADS7253

SBAS584B – OCTOBER 2013 – REVISED AUGUST 2014

www.ti.com

11 Layout

11.1 Layout Guidelines

Figure 117 shows a board layout example for the ADS8353, ADS7853, and ADS7253 with the WQFN package.

Use a ground plane underneath the device and partition the PCB into analog and digital sections. Avoid crossing

digital lines with the analog signal path and keep the analog input signals and the reference input signals away

from noise sources. As shown in Figure 117, the analog input and reference signals are routed on the left side of

the board and the digital connections are routed on the right side of the device.

The power sources to the device must be clean and well-bypassed. Use 10-

μF, ceramic bypass capacitors in

close proximity to the analog (AVDD) and digital (DVDD) power-supply pins. Avoid placing vias between the

AVDD and DVDD pins and the bypass capacitors. Connect all ground pins to the ground plane using short, low

impedance paths.

The REFIO-A and REFIO-B reference inputs and outputs are bypassed with 10-

μF, X7R-grade, 0805-size, 16-V

rated ceramic capacitors (CREF-x). Place the reference bypass capacitors as close as possible to the reference

REFIO-x pins and connect the bypass capacitors using short, low-inductance connections. Avoid placing vias

between the REFIO-x pins and the bypass capacitors. Small 0.1-

Ω to 0.2-Ω resistors (RREF-x) are used in series

with the reference bypass capacitors to improve stability.

The fly-wheel RC filters are placed immediately next to the input pins. Among ceramic surface-mount capacitors,

COG (NPO) ceramic capacitors provide the best capacitance precision. The type of dielectric used in COG

(NPO) ceramic capacitors provides the most stable electrical properties over voltage, frequency, and temperature

changes. Figure 117 shows CIN-A and CIN-B filter capacitors placed across the analog input pins of the device.

11.2 Layout Example

Figure 117. Recommended Layout

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Product Folder Links: ADS8353 ADS7853 ADS7253

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