Texas Instruments ADS1224EVM, User Manual

Controls

1-4

1.4

Controls

The ADS1224EVM is configured using seven slide switches and a jumper
block.

Switches S1−S4 select the input signal provided to the first two multiplexer
inputs on the ADS1224. For each pair of switches, one switch controls the
source for the positive input, and one controls the source for the negative input.
Each of these controls can be switched between external, zero, and V

REF

.

Switches S5 and S6 select the reference input. The possible combinations
allow for several different reference configurations. See Section 2.3.2 on page
2-11 for details.

Switch S7 selects the system clock source for the ADS1224. You can select
between the onboard 4MHz oscillator or an external clock.

Jumper block J4 contains jumpers for supply current measurement and digital
power supply level selection. It also has a jumper for connecting the digital and
analog grounds on the power connector together. See Section 2.2 on page 2-7
for details.

1.5

Setting Up

The ADS1224EVM is configured according to its use. Thus, there is no single
correct procedure to follow in order configure the test fixture.

Nevertheless, it is useful to remember the following things when you are set-
ting up the board:

-

Make certain that the digital supply level is correct. The jumper block
has three positions that correspond to different voltage supply lines. A
shorting block must be placed on one, and only one, of these supply
lines for the device to operate. See Section 2.2.2 on page 2-8 for addi-
tional details.

-

If you are not measuring the supply current for the ADS1224, remem-
ber to place shorting blocks in the appropriate positions on jumper
block J4. Without these shorting blocks, the ADS1224 will not be pow-
ered on, and will not work properly.

-

Depending on your supply configuration, you may need to place a
shorting block on the analog-digital ground jumper. Some mother-
boards connect these grounds externally, but some do not. If there is
no connection between analog and digital ground, the board will not
operate.