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Power Supplies

The SCLK signal and the CS signal can each be controlled by multiple pins on J2. Pins J2.3 and J2.5

have been shorted together to control SCLK. J2.1, 2.7 and J2.9 have been shorted together to control CS.

Pins J2.2, J2.6, J2.8, J2.12, J2.14, J2.15, J2.17, and J2.19 have weak pull-up/-down resistors. These

resistors provide default settings for many of the control pins. These signals can be controlled through the

digital interface or jumpers found directly on the EVM. By default, these signals are pulled high through

10kΩ resistors. J2.1, J2.3, J2.5, J2.7, J2.9, J2.11 are the control line signals for the DAC8718. They are

connected directly to the DAC through 33Ω resistors. The J2 header is the only way to access these pins.

See the DAC8718 product data sheet for complete details on these pins.

The load DAC (LDAC) pin is connected via jumper JP12 to either the J2.15 pin or the J2.17 pin. Updating

the DAC registers can be completed in two different ways. First, the LDAC pin can be held low; in this

approach, the input registers are immediately updated. Alternatively, the LDAC pin can be held high, and

the DAC registers update when LDAC is taken low. By default, LDAC is pulled high through a 10kΩ

resistor. A shunt can be placed across jumpers JP14.9 and JP14.10 to connect LDAC to the ground. See

the DAC8718 data sheet for more information on updating the DAC.

GPIO signals GPIO0 and GPIO1 can be accessed at JP14 or the J2 header. GPIO2 can only be

accessed at JP14. By default, these signals are each pulled high through a 10kΩ resistor. However, they

can be tied to ground by vertically applying a shunt across the individual pins on JP14.

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 4 lists the configuration details for J3. The voltage inputs to the

DAC can be applied directly to the device. The DAC8718 requires multiple power supplies to operate.

, AV

, DV

, and IOV

are required to properly power the DAC. The power should be applied in the

order: IOV

, DV

, then AV

and AV

, followed by reference voltage.

CAUTION

This sequence must be followed in order to prevent damage to the device.

Table 4. J3 Configuration: Power-Supply Input

Pin No. Pin Name Function Required

J3.1 +VA +4.75V to +24V analog Yes

supply

J3.2 –VA -18V to -4.75V analog Yes

supply

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 VD1 Not used No

J3.9 +3.3VD 3.3V digital supply Optional

J3.10 +5VD +5V Optional

NOTE: To avoid damage to the DAC8718, DV

must stay greater

than or equal to IOV

SBAU158A–February 2010–Revised May 2011 DAC8718EVM

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