3.3V Power supply – Linear Voltage Regulator

As usual i will start with the main points / the lowdown

1- Car voltage can (Depending on car) can go up to 15.3 when bulk charging the battery, the maximum voltage for the LD1117AV33 is 15V, so it is a no go.

2- My DoIt esp12F devkit came fitted with the AMS1117.

The regulator that shipped with my DoIT esp12F devkit is the AMS1117, which seems to be an excellent choice providing up to 1A of current, and accepting input voltages of up to 18V ! Yet, the voltage regulator is not fitted with a heat sink, hence, it will provide nowhere close to 1A reliably

the three liniar regulators I will be comparing in this post are


 ld1117v33  lf33abv  TC1262
Maximum Input Voltage 15V 16V 6V
Minimum input voltage (Based on dropout voltage) 4.3V 4.3V 4.3V
Can we change the input voltage while application is switched on  Yes   Yes   Yes
Maximum current draw (Is it enough for my application)
Higher is better
800 500 500
Quiescent current
Current drawn with no load (Not too relevant to cars)
Lower is better
5.5 mA  0.5 mA  0.070 mA


Even though i have always used the LD1117AV33 Linear Voltage Regulator in IOT projects, simply because it can provide up to 800 MA of current at 3.3V, I had to look at other voltage regulators for this particular project because it involves a vehice, Now, you may want to skip to the comparison table if your IOT project is not for a car, but


As usual, I post my research in this blog for my own use and so that others can benefit from it, so sometimes it looks as though it is not well written, but it could spare you a long time of research

First thing you need to know, is that not all cars have the same voltage, the  12V car battery voltage is nominal, a car battery is usually full and in good health when it’s voltage is around 12.8 or even 12.9 (while the car is off), and because the charging circuit differs from car to car,  A car alternator might step up the voltage to up to 15.3 when it is bulk charging the battery, and float charge a car battery at 14.2 or 14.3 when it considers it full, so bottom line, a linear voltage regulator needs to tolerate at least 15.5V


Even though i have always been using the LD1117AV33 step down, and indeed it is a reliable thing, I can not find any document that states that going above the maximum input voltage of 15V is okay, hence, the regulator is disqualified from the word go




Leave a Reply

Your email address will not be published. Required fields are marked *