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HT7850 SOT-89 5V Voltage Regulator

Some voltage regulators are known for their inefficiency, and some for their stability. The HT78XX series of regulators are touted as:

... a series of positive, linear regulators feature low quiescent current (5uA typ.) with low dropout voltage, making them ideal for battery applications. The devices are capable of supplying 500mA of output current continuously. They are available with several fixed output voltages ranging from 1.8V to 5.0V. Although designed primarily as fixed voltage regulators, these devices can be used with external components to obtain variable voltages and currents. These rugged devices have Thermal Shutdown and Current Limiting to prevent device failure under the "worst" of operating conditions.

I wondered if "500mA of output current continuously" is true, and also what are "worst" conditions and can I replicate that? Firstly though, what do you do with SOT-89 packages if you want to test a component on a breadboard in a circuit? I found a few options in the buckets including a legit SOT-89 to DIP adapter, a SOIC-8 to DIP-8 adapter and finally a standard two sided blank prototyping PCB.

These little blighters aren't cheap, and one thing spotted AFTER ordering (¯\_(ツ)_/¯) is that they have a max input voltage of 8V - not much compared to say the LM78XX which is happy with a 35V input. Anyway the "fun part" for me is the soldering so away to the bench.

Clipped prior to soldering

On the way to making the adapter

The DIP-8 version having headers added

The frankenstein version on a bog standard PCB

So now that we have the soldered versions ready to test - let's try a few variations on a theme, using the suggested "basic circuit" from the datasheet with a load of a resistor and 3W LED.

The last thing to try is maybe use this little linear regulator instead of a zener diode in the QX5252 circuit. 

So you can see from the above that at 1V input to the joule thief, I replaced the 5.1V Zener with the HT7805 and it works! Not only for an LED, but wafting the ergs out to an Attiny13 with a blinky sketch also worked fine - now that could be very interesting for the future - watch this space.