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ADS1174 EVM

Other Parts Discussed in Thread: ADS1174, ADS1178

1) On page 31 of

User's Guide
SBAU134–August 2008

we see a schematic of ADS1174EVM. The pin number 7 of ADS1174 is named "NC" and not connected. But on page 5 of

(ADS1174
ADS1178
 SBAS373B–OCTOBER 2007–REVISED SEPTEMBER 2008)

pin 7 named "DGND". Can I not connect it?

2)  in User's Guide
SBAU134–August 2008, page 31.

Why a 10uF capasitors is not plased at  power pins?  Is it  not necessary?  (

ADS1174
ADS1178
 SBAS373B–OCTOBER 2007–REVISED SEPTEMBER 2008 page 23

To achieve  rated performance, it is critical that the power supplies are bypassed with 0.1mF and 10mF capacitors placed as close as possible to the supply pins.)

 

P.S.

another questions:

in User's Guide
SBAU134–August 2008, pages 33-38 - PCB Layout,  I dont see  connection  J7(GND)  to GND net(page 32).

 

 

  • Looks like the updated schematics didn't make it into the user guide when it was revised in Sept 2008. We'll get that corrected. Pin 7 of the ADS1174 is DGND, and it is connected to DGND on the EVM.

    ADS1174EVM schematic: 4810.6496221_ADS1174_SCH_B.pdf

    ADS1274EVM schematic: 1732.6492534_ADS1274_SCH_B.pdf

    The 10uF bulk caps are located at the modular EVM power connector, while the 0.1uF bypassing is next to the device.

    J7 does have a ground connection.  Unfortunately due to the switcher and some other layout considerations, this series of boards does not have thermal relief on the ground plane.  For the PDF plots of the gerbers it appears there is no connection to ground when in fact there is.