I have a cheap mp3 player (GPD2846A TF Card MP3 Decoder Board) that I want to drive with a MOSFET. The mp3 player uses 5V and no more than 600mA when connected to a 2W 8ohm speaker.
I initially connected it using an IRLZ44N MOSFET, but the mp3 player turned on as soon as I powered the circuit despite pin 12 being written LOW. Also, it turned on even when I unplugged the jumper going to pin 12. It was like the MOSFET was biased even though it wasn't. When I swapped out the IRLZ44N with an IRL540N, the mp3 player did not turn on (as expected). I moved the jumper from pin 12 to +5V and the mp3 player turned on.
I compared datasheets, and they look to be pretty similar. Why does the circuit work as expected with the IRL540N, but not the IRLZ44N?
Edit: Not able to upload picture of the circuit because I keep getting an error message. The gate is connected to pin 12 through a 1k resistor. +5V connects to the V+ of the mp3 player, GND of the mp3 player is connected to the drain pin of the MOSFET. The source is connected to ground.
On the IRLZ44N MOSFET I would place a 10 Resistor between the Gate and Ground. This makes sure the MOSFET is off when it should be, Gate low.
Why the difference? I am not sure. The IRL540n is a logic level mosfet and the IRLZ44n is not if you look at Vgs. I see the IRL540n as the better choice between the two.
Ron_Blain:
On the IRLZ44N MOSFET I would place a 10 Resistor between the Gate and Ground. This makes sure the MOSFET is off when it should be, Gate low.
Why the difference? I am not sure. The IRL540n is a logic level mosfet and the IRLZ44n is not if you look at Vgs. I see the IRL540n as the better choice between the two.
Ron
They are both logic-level. I suspect one got zapped with static in handling - MOSFETs are very static sensitive, most have no protection built in.
MarkT:
They are both logic-level. I suspect one got zapped with static in handling - MOSFETs are very static sensitive, most have no protection built in.
Thanks Mark for pointing that out. I looked at the part number IRLZ44N MOSFET and never caught or picked up on the "L" large as life.
Ron_Blain:
On the IRLZ44N MOSFET I would place a 10 Resistor between the Gate and Ground. This makes sure the MOSFET is off when it should be, Gate low.
Thanks for the reply & input. I tried it with a 10k resistor, but the mp3 player still turned on as soon as I powered the circuit.
MarkT:
They are both logic-level. I suspect one got zapped with static in handling - MOSFETs are very static sensitive, most have no protection built in.
I tried 4 different IRLZ44Ns with the same result. I guess they could all be damaged, but I thought that was unlikely.
