I'm using a front end op-amp as a differential receiver, need a low impedance to drive the highpass filter stage that follows it.
Looks something like this (don't recall the C values offhand):
Input C's make a 1st order highpass around 30Hz, feedback C's make a lowpass just below 30KHz.
Looks something like this (don't recall the C values offhand):
Input C's make a 1st order highpass around 30Hz, feedback C's make a lowpass just below 30KHz.
And one more...are you synching to pin 16 SYNC (nominally 100 kHz) and using as is or multiplying by 4 to get the TPA PWM frequency? I'm designing my first buck converter to power a Bluetooth (KC Wirefree) and Apple AirPlay board as inputs to a MiniDSP and am concerned about noise (maybe too much so). The plan is for the board to plug into the mini DSP headers to simplify the wiring.
Realized that error and got rid of the synchronization feature.
I thought about using a pair of timers on the AVR to throw 100KHz/400KHz synchronization clocks at the TPA and buck, but with the two running asynchronously I couldn't measure any difference on the TPA output with the buck on or off. Decided to leave the two parts unsynchronized.
Thanks. By the way, I must complement you got your contributions here. Your explanations are very approachable and you document engineering issues in a way that have helped expand my horizons (eg. your ramblings on filter calculations and your documentation of how you worked through the turn mute challenge for the wiener).
Thank you.
P.S. If you are so inclined, I'd be interested in reading a breakout thread outlining the considerations in sensing and coding the turn on mute micro.
I could do that. I'm holding off releasing the code for public consumption - trying to keep chinese wieners at bay for as long as I can.
The basic operation is:
- start up with MUTE high, SDZ low
- if amp is enabled, sense power supply voltage. If voltage isn't sensible, stay off. If it is, raise SDZ.
- Read turn-on delay pot, calculate a power-on delay and wait for that delay.
- Just before unmuting, sense power supply voltage again. If it's no good, turn back off. Remember this sensed value.
- Unmute amp.
- While amp is unmuted, check power supply voltage. If it drops below the sensed value * some scale factor, turn off and restart.
The basic operation is:
- start up with MUTE high, SDZ low
- if amp is enabled, sense power supply voltage. If voltage isn't sensible, stay off. If it is, raise SDZ.
- Read turn-on delay pot, calculate a power-on delay and wait for that delay.
- Just before unmuting, sense power supply voltage again. If it's no good, turn back off. Remember this sensed value.
- Unmute amp.
- While amp is unmuted, check power supply voltage. If it drops below the sensed value * some scale factor, turn off and restart.
What Viktor said 🙂 We're quite proud of the design. What you get:
- 20 watt MPPT solar charger, also allows charging from 19.5V or 24V wall adapters.
- Good quality TPA3118 amplifier implementation, comparable in performance to my Wiener card - similar decoupling, good Coilcraft output inductors, film output capacitors, etc.
- Integrated 'ground loop breaker' audio input and 2nd order highpass filter configured for Boominator system.
- 5V USB dedicated charging output with TI TPS2514A controller, seamlessly charges both Android and iStuff if you wire up the data lines.
- Microprocessor controlled low battery protection, a status LED that blinks out the state of the battery, etc.
Even at 120 USD, I don't believe you'll be able to piece together the same feature set for the same price.
- 20 watt MPPT solar charger, also allows charging from 19.5V or 24V wall adapters.
- Good quality TPA3118 amplifier implementation, comparable in performance to my Wiener card - similar decoupling, good Coilcraft output inductors, film output capacitors, etc.
- Integrated 'ground loop breaker' audio input and 2nd order highpass filter configured for Boominator system.
- 5V USB dedicated charging output with TI TPS2514A controller, seamlessly charges both Android and iStuff if you wire up the data lines.
- Microprocessor controlled low battery protection, a status LED that blinks out the state of the battery, etc.
Even at 120 USD, I don't believe you'll be able to piece together the same feature set for the same price.