Datasheet

EVM Operation

www.ti.com

Note that if an external reference voltage is input to J1.20, it will be filtered through a first-order, low-pass

RC filter. To input your own reference signal without this filter, connect the reference signal directly to TP1

or TP2. Figure 1 shows the reference test points on the EVM.

Figure 1. Reference Test Points

6 EVM Operation

This section provides information on the analog input, digital control, and general operating conditions of

the DAC8234EVM.

6.1 Analog Output

The DAC8234 has four analog outputs that are available through the J1 header or the J4 header. The J4

header is designed to use 90-degree Samtec pins (not installed) when multiple EVMs are stacked to be

used in daisy-chain mode.

Jumpers J5-J8 control the gain of the individual output channels by connecting additional feedback

resistors to the internal op amp buffer. See the DAC8234 data sheet for more information on setting the

gain. Each analog output is able to swing ±16V in bipolar mode and 0 to 20V in unipolar mode.

The signal ground, SGND-N (for the output signals), are connected to header J1 and are short-circuited to

the board ground. All of the output signals are referenced to the ground of the board.

MON

is the channel monitor output. It can relay any of the four analog output signals or the A

signal. The

MON

signal is buffered and current-limited through the OPA227 (U2). By default, the V

MON

pin is in 3-state

mode, causing the op amp to saturate. In order to avoid the op amp saturating to a rail, a 200kΩ resistor is

put in place. The resistor serves as a load for the op amp when the V

MON

pin is in 3-state mode. However,

as a result, there is an error of ~1% on the V

MON_BUF

signal when relaying a signal.

6.2 Digital Control

The digital control signals can be applied directly to J1 (top or bottom side). The modular DAC8234EVM

can also be connected directly to a DSP or microcontroller interface board.

No specific evaluation software is provided with this EVM; however, various code examples are available

that show how to use EVMs with a variety of digital signal processors from Texas Instruments. Check the

respective product folders or send an e-mail to dataconvapps@list.ti.com for a listing of available code

examples. The EVM Gerber files are also available on request.

DAC8234EVM SBAU160–October 2009

Submit Documentation Feedback