TRS-80 PC-2 Regulator replacement module

Regulator modules for the TRS-80 PC-2 (TRS80 PC2), Sharp PC-1500 and Sharp PC-1500A pocket computers.

• Regulator factory adjusted to 4.700V +/- 10mV at VCC under full load = 75mA.
• No minimum current to maintain regulation.
• After installation:  (1) Apply 6V to battery terminals.  (2) Adjust right pot at 25C to read 1.000V relative to ground on pin 4 of the module (Vdisp controls LCD contrast).

Improved drop in replacement for OEM module

• Dropout voltage is < 30mV at full load vs OEM module which is over 1V.  Drop out is low enough that the computer will operate with only 3AA cells installed.
  
• Current consumption with VCC off (Computer sleeping) is about 75% of the original but active current with VCC on (Computer on) is 500uA lower due to the use of a PMFET for the VCC switch vs the original PNP.  Since the active current is about 4mA, that is a 10% power savings for the new regulator.
• Load regulation is better than 10mV from zero to full load.  Original module could drift up to about 5V when the computer goes to sleep.
  
• Module can withstand 42V at input however practical limit is a function of the computer VBAT circuits.
• Module is thermally protected.
• Module can be subjected to output short circuit indefinitely...
• ...Due to short circuit tolerance of this regulator, the computer reset function operates by shorting VGG to ground where the OEM regulator simply disabled the regulator.  This has the benefit of allowing the computer to be instantly reset where it could take the original configuration upwards of a minute to bleed off the VGG to the point where the reset was detected.