ADS8324

12

SBAS172A

www.ti.com

FIGURE 10. Basic Data Acquisition System.

ADS8324

V

CC

CS

D

OUT

DCLOCK

V

REF

+In

–In

GND

+

+

5

Ω

1

µF to

10

µF

1

µF to 10µF

0.1

µF

0V to 1.8V

0.9V

Reference

Microcontroller

1.8V

amp can drive the bypass capacitor without oscillation (the

series resistor can help in this case). Keep in mind that while

the ADS8324 draws very little current from the reference on

average, there are still instantaneous current demands placed

on the external input and reference circuitry.

Texas Instruments OPA627 op amp provides optimum per-

formance for buffering both the signal and reference inputs.

For low-cost, low-voltage, single-supply applications, the

OPA2350 or OPA2340 dual op amps are recommended.

Also, keep in mind that the ADS8324 offers no inherent

rejection of noise or voltage variation in regards to the

reference input. This is of particular concern when the

reference input is tied to the power supply. Any noise and

ripple from the supply will appear directly in the digital

results. While high frequency noise can be filtered out as

described in the previous paragraph, voltage variation due to

the line frequency (50Hz or 60Hz), can be difficult to

remove.

The GND pin on the ADS8324 should be placed on a clean

ground point. In many cases, this will be the “analog”

ground. Avoid connecting the GND pin too close to the

grounding point for a microprocessor, microcontroller, or

digital signal processor. If needed, run a ground trace di-

rectly from the converter to the power supply connection

point. The ideal layout will include an analog ground plane

for the converter and associated analog circuitry.

APPLICATION CIRCUITS

Figure 10 shows a basic data acquisition system. The

connected directly to the power supply. The 5

Ω resistor and

1

µF to 10µF capacitor filter the microcontroller “noise” on

the supply, as well as any high-frequency noise from the

supply itself. The exact values should be picked such that the

filter provides adequate rejection of the noise.