AD7839 DAC

Question

Hello Mam/Sir, 
 
 I am using AD7839 with a TI TMS320c28346 micro controller experimental kit. I am powering the VDD WITH +15V, VSS WITH -15V, VCC WITH +5V, AND DGND WITH -5V. I am using a 36(DAC side) to 25 (controller side) pin converter cable to communicate the controller with the DAC. I have connected pin one of 25 pin connecter with CL/WR, 2 TO 7 WITH THE DATA PIN, 8, 9, AND 17 WITH THE SELECTION BITS, AND 22 WITH GND OF THE CONTROLLER BOARD. THE TI CONTROLLER WORKS ON 3.2 VOLTS, i.e IT WILL GIVE 3.2 VOLTS WHEN ANY OF THE I/OS ARE ON. WHEN I CHECK THE VOLTAGE BETWEEN OUT GROUND AND VOUT A THE VOLTAGE THAT IT SHOWS IS 0 V. 
 
 1) iS THERE ANY THING ELSE THAT I NEED TO DO APART FROM THIS, TO MAKE THE DAC BOARD RUN. 
 2) ALSO I SEE NO LED INDICATION ON THE BOARD WHICH WOULD INDICATE THAT THE BOARD SYSTEM IS HEALTHY. 
 3) PLEASE PROVIDE ME WITH THE BASIC WIRING DETAILS AND THE STEP THAT I SHOULD FOLLOW FOR RUNNING THIS DAC BOARD. 
 
 REGARDS, 
 PRANAV PARIKH

EZAdministrator · Accepted Answer

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ADIApproved · Answer

You do not need to use LDAC. This pin is pulled to GND by a resistor so the pin can be left unconnected. 
 LK1 should be in position B to connect pin 29 (Vss on the AD7839) to the Vss supply. 
 CLR is connected to DB13 on the AD7839 evaluation board and this pin will need to be kept high when you are writing to the U4 latch. 
 For the supplies, you will need +15V connected to Vdd (J32-3), -15V on Vss (J32-1) and +5V on J31-1. GND should be connected to J32-2. You do not need a -5V supply. 
 To write to the DAC you will need to put data on the data bus DB0 to DB12. You have to do this in 3 stages by putting data on the parallel bus of the TI micro and pulsing the Latch Enable (LE) pins. 
 For example if you want to write 0b1110010101111 (13 bits of data) to the DAC you will need to do the following 
 
 Put 0b101111 on the TI uC bus and pulse LE1 low. This will put 0b101111 onto D0 to DB5 of the AD7839 
 Put 0b110010 on the TI uC bus and pulse LE2 low. This will put 0b101111 onto D6 to DB11 of the AD7839 
 Put 0b ABC 11 on the TI uC bus and pulse LE3 low. This will put 0b1 onto DB12 and set the CLR pin high (CLR is shown as DB13/CLR on the schematic). ABC are 1's or 0's depending on the values you want for A2, A1 and A0 and will select which DAC to update 
 
 4. Pulse CS/WR to transfer the data to the DAC and the output should change.