Hello everyone,
Does the LM3940 have a minimum load requirement?
My LM3940 outputs about 4V but I do not know why.
Best regards,
Keiichi
Hi Keiichi,
There is no minimum load requirement mentioned in the datasheet so we can assume there isn't. Is the output oscillating? If it is, here is the probable reason why. At lower loads, the stable region as shown below (taken from the datasheet pg.10) has tighter ESR requirement. Too high or too low ESR can make the device become unstable thus output would oscillate. If you are using ceramic capacitors (or MLCC-multi layer ceramic capacitors) which normally have very low ESR, try to add a resistor (~0.1ohm) in series with your output capacitor. OR replace the ceramic capacitors with an electrolytic capacitors because which relatively have higher ESR.
A scope shot showing Vin/Vout and a schematic would be helpful to narrow down your problem. please send them if you can.
Regards,
Chito
