Good day.
I've been struggeling with this LM3478 design. I've a LiPo Battery (3.7V to 4.3V) which I need to boost to 12V for an 12V Piezo buzzer (50mA).
Webench was configured for this: VIN = 3.5-4.3V, VOUT = 12V and IOUT of 0.2A.
The startup, instead of 4ms according to the simulation, can take up to 4-5 seconds. With this design, I get a max of 75mA to 100mA (depending on the temperature of the MOSFET).
Which apparently is not enough to cover the initial current needed for the 12V Piezo Buzzer. The voltage will fall down to VIN (arround 4V) and the MOSFET will heat up.
Webbench:
(Couldnt get Webbench to have a similiar configuration -> Had to scan it)
Altium:
Some of the key components:
Inductor: Würth 74404054220 22uH 1.5A
Mosfet: BSC340N08NS3 (80V / 23A)
Schottky Diode: Vishay SS14-E3 (Vf <= 0.5V)
RSens: Vishay WSL2512R0600FEA (2512 / 1W)
If the Booster is working (between 0 - 75mA manual increase) the switching frequency is at arround 550kHz, so RFA combined with the BSS138 is working as expected.
If I increase VBat to 4.5V I can pull a lot more current (Up to 250mA before breakdown), but thats not really an option for a LiPo Cell.
Any hints or tips what could be wrong?
Many thanks.
