Suddenly you’ll like bipolarity

As it turns out, bipolar is not just a useful label to put on your ex-girlfriend/boyfriend. It’s also something a power supply can be, and in the PCB presented here, you’ll need one of those.

The new PCB for the TCD1304 arrived some weeks ago, I’ve just been too busy with my actual job to do anything with it (exam-periods are stressful for teachers too). But here it is:

7x05-pcb

The circuit requires a ±7.5V PSU (±9V is fine too, it just has to be higher than the drop-out voltage for the 7×05 regulators, but not too high – you know, like Goldilock).

The circuit looks like this:

7x05circuit-p1

R1, R2, R4 and R5 should be chosen according to output voltages of the TCD1304 as explained here: https://tcd1304.wordpress.com/adc-input-conditioning/, and pad1 and pad3 should read +7.5V and -7.5V

The PCB depicted above was intended to have a variable voltage divider between Vref and V-, but I’ve later learned this is not a good design, hence the wire-mess on the left side. It’s since been corrected and the voltage divider is now between Vref and AGND. Here are the eagle files (corrections included).

Mind you that it’s still not fully tested, so don’t go off and send it to the board house just yet. It’ll be june 17th before I have time to fully confirm if it’s working.

If I were to redo it, I would substitute the 78L05 and 79L05 voltage regulators (U3-4 and U2) with LDOs LT1761 and with LT1964.

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