I'm using MAX756 as a DC-DC boost converter to provide 3.3V from of a single 1.5 AA battery. I've implemented the circuit on page 1 of datasheet with 1N5819 instead of 1N5817 and 144uF caps between Vin and Gnd instead of 150uF. Also Vin comes from bench power supply.
I've tested three 22uH inductors with different current capabilities (all above the required 1.2A due to datasheet (page 6).
3/~5 is connected to
LBO is left open.
The problem is the Vout is 3.3V in no-load. But as soon as I insert the 220Ohm resistors, Vout drops and in Iout = 60mA, the Vout drops below 2V.
I've shown the other two inductors that I tested.
Anyone knows where the problem might be? Thanks in advance.
Glenn W9IQ says:
Take a bench supply capable of 2 amps output and set it to 7 volts. Put a 4.7 ohm, 10 watt non inductive resistor in series with your inductor and put this circuit across the supply. Monitor the inductor voltage with your scope. You should see a nice exponential, asymptotic curve that heads toward zero when power is applied. This will happen within 1 us of applying power. If the beginning of the curve has a different slope, your inductor is in saturation at less then 1.5 amps. But your problem is more likely the ESR of your inductor and capacitor. Use the right parts - it makes a difference! –
I've paralleled 5 , 2 Watts 22 Ohms resistor (so 4.4 Ohm in theory and 4.7 due to DMM).
Here is the circuit: