PSU7 LM78H05K Replacement

This is a 5V 5A switch-mode voltage regulator. It is a high-efficiency replacement for popular three-terminal LM78H05K linear regulators and it is pin-to-pin compatible with the common and now obsolete LM78H05K linear regulators. The mechanical design allows the PSU7 to fit anywhere where an LM78H05K  was used. The bottom of the PCB is ground, just like the case of the LM78H05K . The maximum continuous output current is 5A and at room temperature the PSU7 does not need a heatsink to maintain this current indefinitely. All the required capacitors are included on the module, no external capacitors are required and additional input capacitors do no harm. The output voltage guaranteed to be within +/-1% as the load varies. The module has a (tiny) trim potentiometer and the voltage is factory adjusted to within 50mV of 5V with a 12V input and a 3A load. The original LM78H05K had a rather loosely specified output voltage and it could vary by as much as 250mV without load and at room temperature. Many designs incorporated some circuitry to raise the output voltage to prevent under voltage resets of microprocessors. The PSU7 LM78H05K replacement design can be adjusted by up to 250mV in either direction with the trim pot to ensure compatibility with almost all circuits that used the LM78H05K . The module has thermal shutdown and current limit protection. The absolute maximum input voltage is 28V. The PSU7 can be mounted on existing heatsinks, even ones that use sockets under the heatsink. The hole diameters and pin diameter is exactly the same as the original package dimensions.

For most applications the PSU5_NN is a better choice to replace the LM78H05K.  The PSU7 has a feature where it does not turn on reliably unless the output voltage is nearly fully discharged.  This behavior is part of the design of the device and is necessary to guarantee stability of the control loop during turn on.  The difference in current capability between the PSU5 and PSU7 hardly ever matters when they are used to replace linear regulators because the original design was almost certainly limited by the heatsink and not the current limit of the IC.  The LM78H05K was often chosen over the LM323K because it had a slightly lower thermal resistance and tighter control of the output voltage.  The PSU5 and PSU5_NN can sustain 4A for long periods of time without a heatsink and 5A for short periods of time, far longer than a LM78H05K can when powered from similar input voltages.

Features:

• Drop-in replacement of the obsolete LM78H05K or equivalent linear voltage regulator.
• Guaranteed 5A output current.
• Identical input voltage range of 7.2V to 28V
• Suitable for use in Pinball machines and video game consoles
• High efficiency switching regulator design reduces power disspation with superior voltage regulation compare to the LM78H05K .
• Thermal shutdown and current limit protection
• Board dimensions are identical to the TO3 package of the LM78H05K .
• Heatsinks are optional.
• All components are mounted on one side of the PCB
• Highest component is the inductor at 5mm above the PCB.
• Available with or without pins.
• Gold plated pins.
• Can drive inductive loads such as solenoids and DC motors.
• 800kHz Switching Frequency
• Made in the USA
• The photographs shows a PSU7 module next to a (fake) LM78H05K  for a size comparison.