Texas Instruments DAC7716EVM manual EVM Operation, Analog Output, Digital Control

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

6EVM Operation

This section provides information on the analog input, digital control, and general operating conditions of the DAC7716EVM.

6.1Analog Output

The DAC7716 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 DAC7716 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.

VMON is the channel monitor output. It can relay any of the four analog output signals or the AIN signal. The VMON signal is buffered and current-limited through the OPA227 (U2). By default, the VMON 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 VMON pin is in 3-state mode. However, as a result, there is an error of ~1% on the VMON_BUF signal when relaying a signal.

6.2Digital Control

The digital control signals can be applied directly to J1 (top or bottom side). The modular DAC7716EVM 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.

6 DAC7716EVM	SBAU159 –October 2009
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