TPA3144D2 Volume Control

Enrique Ugarte

Other Parts Discussed in Thread: TPA3144D2

Hello, I'm new with audio amplifiers, I'm building a Bluetooth Speaker and I'm using the TPA3144D2 to accomplish my goals but I have some questions about control, I hope you can help me out:

*My bluetooth module will have 4 push buttons: Play/Pause, Mute, Volume+ and Volume-. I understand if you push the Play/Pause and Mute buttons, te BT module will stop sending signal from its output to the TPA3144D2 L and R inputs, but HOW IS THE VOLUME CONTROLED?!

Thanks and best regards,

over 8 years ago

0 Mike Tripoli over 8 years ago

Genius 3295 points

Hi Enrique,

Gain on this device is controlled by a resistor divider connected to the GAIN pin. These values are "read" and fixed when /SD is made active. Set this to the maximum output you think you need, then...

Volume control can be done with a simple mechanical pot on the input to the device. Do not forget you want a capacitor "on both sides" of the pot (input and wiper) to make sure you don't hear "scratchy" sounds when turning the pot.

If you are using a microcontroller you could replace the mechanical pot with a digital pot. In my designs, I use a µC with an integral ADC. Use a "log" or "audio" pot for volume controls. Many digital pots are 256 steps; as such, if the ADC is also 8 bits then you can simply read the ADC channel with the mechanical pot and write that exact value to the digital pot. When doing this with an audio taper pot you are also "reading the taper" of the pot, so the digital linear pot appears as an audio pot to the circuit. When using single-ended digital pots (+5V for instance) remember you have to offset the input signal by Vcc/2 .

Mike T.

0 Enrique Ugarte over 8 years ago in reply to Mike Tripoli

Intellectual 315 points

Thank you very much for your answer Mike! IT has been very useful and clarifying for me, I'm wondering if you have an schematic example you can provide (I'm using a microcontroller) to clarify some other questions in the design and to avoid mistakes at the schematic design time...?

Thanks again.

0 Mike Tripoli over 8 years ago in reply to Enrique Ugarte

Genius 3295 points

Hi Enrique,

I've attached a LTSpice .asc file here. If you're not using LTSpice, I highly advise getting a copy (it's completely free), learn the basics and run the file. If you haven't used this program, install it, open the attached file and click on the "running man" on the toolbar. Then start probing the circuit, looking at the resulting waveforms. The op amp chosen is simply from the included library; I in fact use only TI audio op amps in my stuff. Remove the ".txt" from the end of the file to use it.

The series connected "50k" resistors represent a 100K pot in each case. Probe around the circuits, looking at each waveform. The underlying theme is the input is "ground referenced", on the "other side" of the input cap the signal is riding on a +2.5V offset and the output is again capacitively coupled; the output signal is again ground referenced.

You have two choices when using digital pots (DP); those that can handle bi-polar power supplies (Microchip has one), hence, bi-polar signals and those that can only pass a signal between ground and Vcc (most DP's) as presented in the LTC file. To use single-ended DP's one must offset the signal, usually by Vcc/2. This is demonstrated in various configurations; the configuration you choose depends on many factors outside the scope of this post. The circuits presented have a bandwidth of ~ 25Hz to 20kHz. They are not "complete" circuits; they don't show decoupling of the supplies, etc. If you go this route, TI also has a "rail splitter" that makes generating a low noise, low output impedance Vcc/2 simple.

POT_EXAMPLES.asc.txt

Version 4
SHEET 1 1580 852
WIRE 1152 32 1120 32
WIRE 1248 32 1216 32
WIRE 368 48 336 48
WIRE 464 48 432 48
WIRE -448 96 -480 96
WIRE -352 96 -384 96
WIRE 912 128 896 128
WIRE 1008 128 976 128
WIRE 1120 128 1120 32
WIRE 1120 128 1088 128
WIRE 1152 128 1120 128
WIRE 1248 128 1248 32
WIRE 1248 128 1232 128
WIRE 128 144 112 144
WIRE 224 144 192 144
WIRE 336 144 336 48
WIRE 336 144 304 144
WIRE 368 144 336 144
WIRE 464 144 464 48
WIRE 464 144 448 144
WIRE 896 144 896 128
WIRE -1344 160 -1408 160
WIRE -1248 160 -1280 160
WIRE 112 160 112 144
WIRE -1248 176 -1248 160
WIRE -688 192 -736 192
WIRE -592 192 -624 192
WIRE -480 192 -480 96
WIRE -480 192 -512 192
WIRE -448 192 -480 192
WIRE -352 192 -352 96
WIRE -352 192 -368 192
WIRE -1408 208 -1408 160
WIRE -736 240 -736 192
WIRE -1248 272 -1248 256
WIRE -1152 272 -1248 272
WIRE -1040 272 -1088 272
WIRE -1248 288 -1248 272
WIRE -480 288 -480 192
WIRE -464 288 -480 288
WIRE -352 304 -352 192
WIRE -352 304 -400 304
WIRE -256 304 -352 304
WIRE 1120 304 1120 128
WIRE 1136 304 1120 304
WIRE -1408 320 -1408 288
WIRE -464 320 -480 320
WIRE -256 320 -256 304
WIRE 336 320 336 144
WIRE 352 320 336 320
WIRE 1248 320 1248 128
WIRE 1248 320 1200 320
WIRE 1344 320 1248 320
WIRE 464 336 464 144
WIRE 464 336 416 336
WIRE 560 336 464 336
WIRE 912 336 864 336
WIRE 1040 336 1040 320
WIRE 1040 336 976 336
WIRE 1136 336 1040 336
WIRE 1344 336 1344 320
WIRE -736 352 -736 320
WIRE -480 352 -480 320
WIRE 128 352 80 352
WIRE 256 352 256 336
WIRE 256 352 192 352
WIRE 352 352 256 352
WIRE 560 352 560 336
WIRE 256 384 256 352
WIRE 864 384 864 336
WIRE -1248 400 -1248 368
WIRE 80 400 80 352
WIRE -896 416 -896 400
WIRE -256 416 -256 400
WIRE -192 416 -256 416
WIRE -96 416 -128 416
WIRE -256 432 -256 416
WIRE 1344 432 1344 416
WIRE 1408 432 1344 432
WIRE 1504 432 1472 432
WIRE -1040 448 -1040 432
WIRE 560 448 560 432
WIRE 624 448 560 448
WIRE 720 448 688 448
WIRE 1344 448 1344 432
WIRE 560 464 560 448
WIRE 864 496 864 464
WIRE -896 512 -896 496
WIRE -784 512 -896 512
WIRE -736 512 -784 512
WIRE 80 512 80 480
WIRE -896 528 -896 512
WIRE -784 544 -784 512
WIRE -256 544 -256 512
WIRE 1344 560 1344 528
WIRE 560 576 560 544
WIRE -896 624 -896 608
WIRE -784 624 -784 608
FLAG -1040 272 out1
FLAG -1408 320 0
FLAG -96 416 out2
FLAG -736 352 0
FLAG -256 544 0
FLAG -1040 528 0
FLAG -1040 432 +Vcc
FLAG -432 336 0
FLAG -736 512 Vcc/2
FLAG -432 272 +Vcc
FLAG -896 400 +Vcc
FLAG -896 624 0
FLAG -784 624 0
FLAG -480 432 Vcc/2
FLAG -1408 160 in1
FLAG -736 192 in2
FLAG 720 448 out3
FLAG 80 512 0
FLAG 560 576 0
FLAG 384 368 0
FLAG 384 304 +Vcc
FLAG 112 160 0
FLAG 256 256 +Vcc
FLAG 256 464 0
FLAG 80 352 in3
FLAG -1248 400 Vcc/2
FLAG 1504 432 out4
FLAG 864 496 0
FLAG 1344 560 0
FLAG 1168 352 0
FLAG 1168 288 +Vcc
FLAG 896 144 0
FLAG 864 336 in4
FLAG 1040 240 Vcc/2
SYMBOL res -1264 160 R0
SYMATTR InstName R1
SYMATTR Value 50k
SYMBOL res -1264 272 R0
SYMATTR InstName R2
SYMATTR Value 50k
SYMBOL cap -1280 144 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C1
SYMATTR Value 1�
SYMBOL cap -1088 256 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C2
SYMATTR Value 1�
SYMBOL voltage -1408 192 R0
WINDOW 3 -209 58 Left 2
WINDOW 123 -209 86 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V1
SYMATTR Value SINE(0 .5 1000)
SYMATTR Value2 AC 1
SYMBOL res -272 304 R0
SYMATTR InstName R3
SYMATTR Value 50k
SYMBOL res -272 416 R0
SYMATTR InstName R4
SYMATTR Value 50k
SYMBOL cap -128 400 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C4
SYMATTR Value 1�
SYMBOL voltage -736 224 R0
WINDOW 3 18 97 Left 2
WINDOW 123 43 56 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V3
SYMATTR Value SINE(0 .5 1000)
SYMATTR Value2 AC 1
SYMBOL Opamps\\LT1014 -432 240 R0
SYMATTR InstName U1
SYMBOL voltage -1040 432 R0
WINDOW 123 0 0 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V4
SYMATTR Value 5
SYMBOL res -352 176 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R5
SYMATTR Value 10k
SYMBOL res -912 400 R0
SYMATTR InstName R7
SYMATTR Value 47k
SYMBOL res -912 512 R0
SYMATTR InstName R8
SYMATTR Value 47k
SYMBOL cap -800 544 R0
SYMATTR InstName C3
SYMATTR Value 10�
SYMBOL res -496 336 R0
SYMATTR InstName R9
SYMATTR Value 5k
SYMBOL res -496 176 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R10
SYMATTR Value 10k
SYMBOL cap -624 176 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C5
SYMATTR Value 0.47�
SYMBOL cap -384 80 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C6
SYMATTR Value 1n
SYMBOL res 544 336 R0
SYMATTR InstName R6
SYMATTR Value 50k
SYMBOL res 544 448 R0
SYMATTR InstName R11
SYMATTR Value 50k
SYMBOL cap 688 432 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C7
SYMATTR Value 1�
SYMBOL voltage 80 384 R0
WINDOW 3 11 107 Left 2
WINDOW 123 37 73 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V5
SYMATTR Value SINE(0 .5 1000)
SYMATTR Value2 AC 1
SYMBOL Opamps\\LT1014 384 272 R0
SYMATTR InstName U2
SYMBOL res 464 128 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R12
SYMATTR Value 10k
SYMBOL res 320 128 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R14
SYMATTR Value 10k
SYMBOL cap 192 128 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C8
SYMATTR Value 0.47�
SYMBOL cap 432 32 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C9
SYMATTR Value 1n
SYMBOL cap 192 336 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C10
SYMATTR Value 1�
SYMBOL res 240 240 R0
SYMATTR InstName R13
SYMATTR Value 100k
SYMBOL res 240 368 R0
SYMATTR InstName R15
SYMATTR Value 100k
SYMBOL res 1328 320 R0
SYMATTR InstName R16
SYMATTR Value 50k
SYMBOL res 1328 432 R0
SYMATTR InstName R17
SYMATTR Value 50k
SYMBOL cap 1472 416 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C11
SYMATTR Value 1�
SYMBOL voltage 864 368 R0
WINDOW 3 11 107 Left 2
WINDOW 123 37 73 Left 2
WINDOW 39 0 0 Left 2
SYMATTR InstName V2
SYMATTR Value SINE(0 .5 1000)
SYMATTR Value2 AC 1
SYMBOL Opamps\\LT1014 1168 256 R0
SYMATTR InstName U3
SYMBOL res 1248 112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R18
SYMATTR Value 10k
SYMBOL res 1104 112 R90
WINDOW 0 0 56 VBottom 2
WINDOW 3 32 56 VTop 2
SYMATTR InstName R19
SYMATTR Value 10k
SYMBOL cap 976 112 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C12
SYMATTR Value 0.47�
SYMBOL cap 1216 16 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C13
SYMATTR Value 1n
SYMBOL cap 976 320 R90
WINDOW 0 0 32 VBottom 2
WINDOW 3 32 32 VTop 2
SYMATTR InstName C14
SYMATTR Value 1�
SYMBOL res 1024 224 R0
SYMATTR InstName R20
SYMATTR Value 470k
TEXT -1562 376 Left 2 !.tran 10m

Good luck!

Mike T.

0 Enrique Ugarte over 8 years ago in reply to Mike Tripoli

Intellectual 315 points

Thank you very much again Mike, I just downloaded the LTSpice. I will follow the instructions and see the results.

Best regards!

0 Enrique Ugarte over 8 years ago in reply to Enrique Ugarte

Intellectual 315 points

Hello again Mike,

Sorry for all the inconvenience but I have an other question. I have made a great progress with your responses and the info you have sent me but I have one last problem (I think). I have done all the connections with the TPA3144D2 and the interface with the speakers and the bluetooth module but reading the datasheet I found in page 8 something about Output Power vs Supply Voltage I hope you can help me out:

I have a 3.7V battery, this will be my supply and the datasheet in that page says that I need at least 4.5V to deliver less than 2W of Output Power and at least 9V to deliver 6W of Output Power with 2 speakers of 8 Ohms (one for each output), and I don't know if I got this right... did I get it right? Should I rise my 3.7V to 9V supply to get 6W of Output Power?

Thanks and best regards!

0 Enrique Ugarte over 8 years ago in reply to Enrique Ugarte

Intellectual 315 points

Enrique Ugarte said:

Hello again Mike,

Sorry for all the inconvenience but I have an other question. I have made a great progress with your responses and the info you have sent me but I have one last problem (I think). I have done all the connections with the TPA3144D2 and the interface with the speakers and the bluetooth module but reading the datasheet I found in page 8 something about Output Power vs Supply Voltage I hope you can help me out:

I have a 3.7V battery, this will be my supply and the datasheet in that page says that I need at least 4.5V to deliver less than 2W of Output Power and at least 9V to deliver 6W of Output Power with 2 speakers of 8 Ohms (one for each output), and I don't know if I got this right... did I get it right? Should I rise my 3.7V to 9V supply to get 6W of Output Power?

Thanks and best regards!

Audio

Audio forum

TPA3144D2 Volume Control