I'm trying to create a circuit that will pulse the TSAL6200
IR LED at 600mA with 600us on/off pulses with the 'on' pulses modulated at 38kHz. I've programmed an 8MHz ATtiny85V to generate the correct PWM waveform, verified to be correct on my scope. I'm powering the whole circuit from 3x1.2v AAA batteries supplying a MIC29152BT
adjustable low dropout regulator set to 3V.
According to the datasheet the TSAL6200 will have a forward voltage of about 2.2v at 600mA. Given that the BUZ72L
drops about 0.1V the series resistor should be (3-2.2-0.1)/0.6=1.16 ohms. The nearest I have to that is 1.5 ohms which would give 466mA.
The problem I'm having seems to be related to the current drawn by the LED circuit. If I wire up the circuit as in the diagram then the ATtiny85V is not happy at all. As soon as my program initiates PWM on pin 6 then the MCU resets itself. If I substitute the 1.5 ohm resistor with a 10 ohm resistor then the circuit will work (trace below), but the current through the LED is obviously nowhere near the level I'm hoping for.
Any ideas what I'm doing wrong here?