2015-07-31 09:58 AM
Hello,
I'm modifying a device that no works very well. This device includes one amplifier TDA7384A, and in the old design I found several mistakes or parameters that haven't calculated. I saw the datasheet and i didn't know how can i calculate some parameters with the information in the datasheet:- If the power supply is 12V, How can I calculate the power dissipated?- Apart of power dissipated, for calculate the size of the sink, Is not necessary to know the Rcd of the Flexiwatt25? - The device have a load resistance of 8 Ohm and the TDA7384A is designed for 4 Ohm. Can a 8 Ohm load modify the response of the amplifier or only decrease the power?ThanksCarlos2015-08-02 08:05 PM
Hi Carlos ,
the power dissipation could be calculated with below formula , TDA7384 is single supply BTL output configuration power amplifier , then the power dissipation is :Pd= 2*(VCC^2)/((3.14^2)*RL). to calculate the heatsink size , you need to check the thermal impedance between heatsink and ambient , then you can consider that the power dissipation is as current , thermal impedance is as resistor , then ambient temperature , IC case temperature and IC junction temperature as voltage potential level. when the target temperature had been set , you can choose suitable heatsink. the Rth of package is 1C/W , means that the temperature difference between junction and case will be 10C , when dissipation power is 10W . the 8 ohm load will just decrease the output power . Thanks , YT2015-08-03 03:16 AM
Hello YT!
Thanks for your quick response! It has been very useful2015-08-07 02:33 AM
Hello,
I have another doubt of TDA7384A. For calculate the power supply:First, I have looked the Figure 8 and for a power supply of 12V I have 18W of power output (THD 10%). Secondly, I have looked the Figure 13 and the total power dissipation (for the four channels in 13.2V) is 35W for 18W of power output. Is that means that I need a power supply of (PS = (18*4) + 35) 107W (approx.)? or Are there another method to calculate the power supply? (PS = Io^2*Rload)Sorry for all of questions, the University teachs a lot of theoretical aspects but very little practical experience.Thanks,Carlos2015-08-25 12:34 AM
Hi Carlos ,
Yes, in theroy you need 107W power supply to provide enough power to amplifier for 4 channels 18W continous output power . due to music signal is dynamic signal and the average power is around 1/3 continous output power ,or you can consider to delivery full power continously in stereo channel , so you can use a 70W (12V @ 5A ) supply to reach similar speaker output loudness, of cource , you need to put big VCC bypass capacitor close to power amplifier IC to provide high transient current. Thanks, YT2015-09-28 12:51 AM
Hi,
If we use this formula Pd= 2*(VCC^2)/((3.14^2)*RL) for VCC=13.2V and RL=4 ohm than Pd=8.82W and for 4 channel it will be 4X8.82W=35.30W.But from datasheet fig 8 at 13.2V Pout will be 22Watt@10% THD and from Fig 13 power dissipation at 22W will 30Watt.There is a ~5Watt difference between formula and datasheet. Please tell which Pd should be used?regardsVinod2015-10-09 06:22 PM
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