Texas Instruments DAC7741EVM manual EVM Basic Functions

EVM Basic Functions

The REF102 precision reference derives its power of ±15-V supply through J10 or J7 terminal. The (plus) 15 V connects through J10-1 or J7-2 terminals, while the (minus) -15 V connects through J10-3 or J7-4 terminals. They are both referenced to analog ground through J10-2 and J7-1.

The DAC7741 has a REFEN pin to enable the internal reference circuit or disable it and select an external reference source. The REFEN pin can be hardware driven through W2 jumper. Likewise, it can also be software driven

through J2-11 terminal via W2 jumper by shorting pins 1 and 2. The REFOUT pin of the DAC7741 must be connected to the REFIN pin to use the internal

voltage reference. This can be done through W3 jumper by shorting pins 1 and 2. Shorting pins 2 and 3 of W3 selects the external voltage reference source.

The on-chip reference buffer output is channeled out through VREF pin which is used to set up the DAC7741 output amplifier into one of three voltage output modes. VREF can also be used to drive other system components that require external voltage reference.

When applying an external voltage reference through TP1 or J4-20, make sure that it does not exceed 10 V maximum. Otherwise, this can permanently damage the DAC7741, U11, device under test.

1.3 EVM Basic Functions

The DAC7741 EVM is a functional evaluation platform to test certain functional characteristics of the DAC7741 digital-to-analog converter. Functional evaluation of the DAC device can be accomplished with the use of any microprocessor, TMS320VC33 DSP, or some sort of a waveform generator.

The headers, J1, J2 and J3 are provided to channel in the necessary control signals and data needed to interface a microprocessor/microcontroller, TI’s DSP starter kit or waveform generator to the DAC7741 EVM, through a custom cable.

A specific adapter interface card is also available for most of TI’s DSP starter kit (DSK) and the card model depend on the type of the DSP starter kit to be used. The user must specify the DSP used as an interface to acquire the right adapter interface card. Call or email TI for more information regarding the adapter interface card.

The output of the DAC can be monitored through two different access points which are as follows; a BNC connector (J5, if installed), and also a header through pin 2 of J4. The 6-pin header, W13, provides different options of the DAC output, but requires the output op-amp, U2, to be configured correctly first for the desired waveform characteristic. Shorting pins 1 and 2 of W13 allows the user to monitor the raw output of the DAC7741.

EVM Overview 1-3