Texas Instruments DAC7716EVM Power Supplies, Reference Voltage, Pin No Pin Name Function Required

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4Power Supplies

Samtec part numbers SSW-105-22-F-D-VS-K and TSM-105-01-T-DV-P provide a 5-pin, dual-row, header/socket combination at J3. Table 3 lists the configuration details for J3. The voltage inputs to the DAC can be applied directly to the device. The DAC7716 requires multiple power supplies to operate. AVDD, AVSS, DVDD, and IOVDD are required to properly power the DAC.

Table 3. J3 Configuration: Power-Supply Input

Pin No.	Pin Name	Function	Required
J3.1	+VA	+4.75V to +24V analog supply	Yes
J3.2	–VA	–18V to –4.75V analog supply	Yes
J3.3	+5VA	+5V analog supply	No
J3.4	–5VA	–5V analog supply	No
J3.5	DGND	Digital ground input	Yes
J3.6	AGND	Analog ground input	Yes
J3.7	+1.8VD	1.8V digital supply	Optional
J3.8	+3.3VD	3.3V digital supply	Optional
J3.9	VD1	Not used	No
J3.10	+5VD	+5V	Yes

The Digital and Analog ground inputs are short-circuited internally through a ground plane.

The dc logic voltage for the DAC7716 (IOVDD) is selectable between +3.3VD, +1.8VD, or +5VD via the JP8 jumper. These power-supply voltages are referenced to digital ground.

The DAC7716EVM is designed to work in either unipolar and bipolar mode. Each mode requires different power-supply connections. Consult the DAC7716 data sheet for the restrictions on the power supplies for the two operating modes.

5Reference Voltage

The DAC7716EVM has the ability to use two different reference sources simultaneously for different

output channels. REFA and REFB control the reference voltages for the DAC. Output channels VOUT-0 and VOUT-1 use REFA as a reference. REFB is used as a reference for output channels VOUT-2 and VOUT-3.

The evaluation module has three options for supplying reference voltages to the DAC7716. Switch S3 (REFA) and S2 (REFB) can select the reference voltage from the REF5050 (U5), REF5025 (U4) or use an external reference. The REF5050 supplies 5.0V to the reference. The REF5025 supplies 2.5V to the reference. These reference voltages are additionally filtered through an RC filter before connecting to the DAC7716. The TL751L08 is used to voltage regulate +VA to properly power the REF5025 and REF5050.

When using an external reference, make sure that the ground terminal (from the external source) is connected to the ground of the EVM board. There is a built-in diode in the DAC7716 that does not allow the RefGND-A/RefGND-B to have more than a 0.3V difference from the board AGND on the DAC. A jumper across pins 2 and 3 on JP6 and JP7 connects the RefGND-A and RefGND-B to the ground of the board.

SBAU159 –October 2009	DAC7716EVM 5
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