fireball003 said:
I was changing my adapters and the voltage in pin 4/5 was changing a bit (between 1.21v to 1.35v). Now I fixed an adapter and now the voltage in pin 4/5 is 1.32volt.
I don't have 20-25 ohm resistor in my hand now. So I connected 47 ohm resistor between 5v and gnd. the voltage is same(1.32v) and current is 130 mA.
If the current across the 47R resistor is 130mA then definitely the voltage is not 1.32v (hope your DVM is calibrated).
If you use another DVM in order to read the voltage across the resistor when you measure the current of 130mA with the second DVM, then you can see that voltage are closer to the output of your AC-DC adaptor.
Otherwise, I can't see 100mA coming from your hand into DVM probes when current is measured through 47R resistor.
What's weird is the 1,21V measured first time which is exactly the internal voltage reference. Like the internal R1 = 0 with voltage on SET pin lower than 65mV
Just a presumption, though you can ask why MAX1659 and not MAX1658, too.
Are you sure that your first used power adapter has a DC output ?
Or did you use one with AC output, then you figure out and changed with a proper DC one?
It's true that one of the MAX1659 features is reverse battery protection allowed down to -17v.
But in the same time don't provides reverse current protection. If Vout is greater than Vin by more than 300mV, reverse current will flow.