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Power Supplies
4
Power 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 b3.3VD, +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.
5
Reference 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 V
OUT
-0 and
V
OUT
-1 use REFA as a reference. REFB is used as a reference for output channels V
OUT
-2 and V
OUT
-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 reVA 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.
5
SBAU159 – October 2009
DAC7716EVM
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