Fixed issues with LDOs, current limiting for negative LDO tied to negative Vin, not GND like on positive ones. Doh.
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Two 9V Lithium 6F22 accumulators hooked up on power input and output. No load connected.
Positive 8.5V LDO (they all adjustable, I call them this just for clarity, following schematics) = +7.917V output, taking 4mA idle
Negative 8.5 LDO = -7.772V output, taking 1.8mA idle
Positive 5.0V LDO = 5.006V output
Negative 5.0V LDO = -4.910V output
Voltage is set by resistors on pins, so don't worry about voltage levels, they are not important at this moment. I used random jellybean 5% resistors to match up with output voltages. Final will have proper 25ppm 1% ones. Here's are some scope shots with 8.5V voltages connected via direct 1:1 BNC cable:
![](http://xdevs.com/doc/xDevs.com/K1801/test/top_ldop.png)
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![](http://xdevs.com/doc/xDevs.com/K1801/test/top_ldon.png)
Start-up positive supply (left), negative supply (right)
Noise measurement, scope is AC coupled, minimum voltage scale (1mV/div, TDS5034B), impedance set to 50 Ohm
![](http://xdevs.com/doc/xDevs.com/K1801/test/noise_tops.png)
![](http://xdevs.com/doc/xDevs.com/K1801/test/noise_tops2.png)
You see anything? I don't see. Scope shows exactly same with inputs grounded. No surprises, noise well below measurement levels on usual gear
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![](http://xdevs.com/doc/xDevs.com/K1801/test/noise_tops3.png)
![](http://xdevs.com/doc/xDevs.com/K1801/test/noise_tops_psu.png)
1 second scale, same story. Right capture - LDO input power is taken from Agilent E3649A ±10V. PSU causing ~1mV ripple on positive, and ~2mV on negative output. Could be wiring antennae though, did not re-check.
![](http://xdevs.com/doc/xDevs.com/K1801/test/spectrum_ldo_batt.png)
Now need get those pesky EEPROMs, order rest of parts and we can unbox preamp module and try some real stuff.
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