Hello
I have designed and built prototype amplifier circuits using the TPA2025D1 chip and the design largely mirrors the schematic found in the TPA2025D1EVM datasheet. I am using the circuits to drive 8 ohm voice coil shakers.
The problem is that when I connect a coil to a circuit output, the TPA2025D1 chip usually gets very hot and some of the circuits (not all) turn off after a few seconds.
I'm guessing that it's an over-current issue. The datasheet for the voice coil I'm using reports a 57 mA average current consumption at maximum volume so that's what I assumed the circuit would be drawing from the power supply.
I measured the DC current being drawn by pin B3 (Vbat) of one of my circuits. The circuit was in an open casing in a cool environment (below 20°C).
First measurement with a brand new (unused) circuit:
- Only PSU connected, circuit draws 2.3 mA (in accordance to the TPA2025D1 datasheet).
- PSU and audio in connected, circuit draws 3 mA.
- PSU, audio in and audio out (voice coil) connected, circuit draws 340 mA. TPA2025D1 chip gets very hot. Audio output turns off after about 5 seconds.
I then disconnect the PSU and audio in- and outputs. Let the chip cool down for a few minutes.
Second measurement:
- Only PSU connected, circuit draws 260 mA (compared to 2.3 mA in the same condition for measurement 1). Chip gets extremely hot right away.
Some questions that I have:
Does this sound to you like the chips are getting fried by over-current?
What is the current range that I should expect to see with the 8 ohm voice coil connected to the output, at moderate input level?
I did not include Transient Voltage Suppressing diodes (TVS) on the outputs in my design. Do you think adding them will fix the issue?
Is there anything else that you can think of that might be causing this?
Kind regards,
