ProtoDAC TDA1387 X8 project

[hifinet]

Do you mean getting the 5V from the pin 2 and/or 4 of the RPi GPIO? I don't think the voltage differential will be enough. The voltages are usually less than 5.1V, and that is right on the margin of the dropout voltage of the LT1963 to get 5.0V with the current draw of ProtoDAC. You will need at least a 100mV differential. If the voltage differential is less than indicated in the chart on page 1 of the datasheet, the LT1963 won't regulate.

Thanks, so I can get 5v from pin 2/4, but LT1963 will most likely not work. Understand.

The way it could be done is to change one of the resistors on the board. See the adjustable regulator Figure 2 on page 14 of the datasheet. Just omit Iadj * R2 to simplify the formula, because Iadj is only 3 microamps. The two resistors setup the output voltage of the regulator. They do make some LT1963 boards that use through hole resistors.

On my module, R3 is 0R, R2 is 470 Ohms and R1 is 1500 Ohms (top to bottom). R1 on the module is equal to R2 in the LT1963 schematic. R2 + R3 = R1 in the LT1963 schematic. Using the simplified forumula (without Iadj * R2) it works out to be 5.07V. 

The above was updated based on a detailed look at my LT1963 module and the pin connections.