fixed voltage regulator pins

Thread Starter

denison

Joined Oct 13, 2018
312
Hi, I have a 5v voltage regulator which is marked LD50V3. Can't find anywhere the pin outs of this regulator. Sent a message to the supplier on ebay but he probably does not know himself.
I know with a triac there is a fixed resistance between the gate and one of the other pins and the gate is always on the right of the face.
Is there something like this with fixed voltage regulators to tell which terminal is which? I don't want to bust it by using the wrong terminals.
In the future this would be handy to know instead of spending hours searching the internet. Thanks.
 

Ian0

Joined Aug 7, 2020
6,713
It depends on the circuitry inside the regulator, as to what is connected to the underside of the chip, because that is what ends up connected to the centre pin and tab of a TO220 package.
for Bipolar transistors, it’s always the collector, MOSFETs the drain, thyristors the anode and triacs MT2.
LDO regulators differ fro standard ones as to whether the output is on a collector or an emitter, so the pinout is unfortunately not so predictable.

I think that LD50 is a 5V version of LD33, and I’ve seen a few links to its datasheet
 

crutschow

Joined Mar 14, 2008
31,129
Suggest you make a best guess as to the connections (such as for the LD33) and then slowly increase the input voltage from 0 while monitoring the input current and output voltage.
If the output voltage doesn't start to rise after the input goes above 2-3V, or the input current goes above a few mA, then the connection is probably not correct.
 

Dodgydave

Joined Jun 22, 2012
10,591
Usually on T0220 cases ( positive regulator) the Centre pin is connected to the heatsink and is the ground ,left pin input, right pin output.
 

Thread Starter

denison

Joined Oct 13, 2018
312
It depends on the circuitry inside the regulator, as to what is connected to the underside of the chip, because that is what ends up connected to the centre pin and tab of a TO220 package.
for Bipolar transistors, it’s always the collector, MOSFETs the drain, thyristors the anode and triacs MT2.
LDO regulators differ fro standard ones as to whether the output is on a collector or an emitter, so the pinout is unfortunately not so predictable.

I think that LD50 is a 5V version of LD33, and I’ve seen a few links to its datasheet
There are links to the LD50 and some of them show a face picture of it but does not give the pin outs. Very annoying. It was a low drop out and that is why I wanted it. I will have to give this a miss and use a 7805 TO-220 case or 78L05 TO-92 case. These from JAYCAR also showing pin outs on download data sheet.
 

Thread Starter

denison

Joined Oct 13, 2018
312
Suggest you make a best guess as to the connections (such as for the LD33) and then slowly increase the input voltage from 0 while monitoring the input current and output voltage.
If the output voltage doesn't start to rise after the input goes above 2-3V, or the input current goes above a few mA, then the connection is probably not correct.
Too difficult. I will get a regulator that gives the pinouts such as 7805/LM340T5 from JAYCAR.
 

MisterBill2

Joined Jan 23, 2018
13,805
Hi, I have a 5v voltage regulator which is marked LD50V3. Can't find anywhere the pin outs of this regulator. Sent a message to the supplier on ebay but he probably does not know himself.
I know with a triac there is a fixed resistance between the gate and one of the other pins and the gate is always on the right of the face.
Is there something like this with fixed voltage regulators to tell which terminal is which? I don't want to bust it by using the wrong terminals.
In the future this would be handy to know instead of spending hours searching the internet. Thanks.
You can try doing a web search for a data sheet on that part number. Yo will get a few thousand hits that want to sell them, but someplace there will be a data sheet.
Ebay is typical with their line "we have it, what is it?" They claim to have everything even with no clue as to what it is..
 

Irving

Joined Jan 30, 2016
3,190
Hmmm, my search for the marking LD50 comes back to a L1117#50 from either UTC or STM as a 5v 800mA fixed output LDO with pinout GND, OUT(+tab), IN on the TO-220 version looking face-on, pins down.

I'd hazard a guess that the V3 is a non-standard batch marking, yield selected for a large end-user. These often end up as 'surplus stock' sold off cheap to 3rd party resellers.
 
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