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RSmoo.1
Visitor II
November 9, 2022
Solved

How can I apply small loads to the output of TDA7377?

  • November 9, 2022
  • 3 replies
  • 1531 views

According to the TDA7377 datasheet, the standby pin 7 must have currents smaller than 5 mA. I am using the dual bridge configuration and have applied a 10 ohm load across pins 1 and 2 and the amplifier works great. If I want to output 2 A of current (pins 1 and 2) and a resistance of about 1 ohm, how can I drive a small load like that?

From the datasheet, it seems that the standby pin would not allow such a small load. From page 6 of the datasheet, it says that the standby pin avoids the device being turned on when a resistive path of less than 16 ohms is present between the output and ground, but I need to support a load of 1 ohm between pins 1 and 2.

The chip is on a pre-purchased PCB. Can I just disconnect pin 7 from the rest of the pins to be able to drive this small load?

Thank you.

    This topic has been closed for replies.
    Best answer by Peter BENSCH

    I am sorry that this misprint appears in the data sheet. If you look closely, you can see a space before the F that replaces the lost µ.

    So for the capacitor at MUTE (pin 11) a value of about 33µF should be used.

    If the problem is solved, please mark this thread as answered by selecting Select as best, as also explained here. This will help other users find that answer faster.

    Good luck!

    /Peter

    3 replies

    P
    Peter BENSCH
    Technical Moderator
    November 10, 2022

    Welcome, @RSmoo.1​, to the community!

    First of all, the TDA7377 has been discontinued for many years and unfortunately there is no longer any support for it from STMicroelectronics. Nevertheless, I will try to help you a little, as I have dealt with such amplifiers in the past.

    Unfortunately, there is no chance to drive a load resistor of 1ohm with this amplifier, because the resulting current would lead to very large power dissipation in the TDA7377 and destroy it. For this reason, a simple overload limiter was also built in, but intended for loads against GND (operation as a car radio amplifier with 4 speakers). In your application with bridge operation, however, this limitation will not be effective.

    You will definitely not get an increase in current if you disconnect pin 7 (ST-BY).

    For 1ohm loads, there are other amplifiers, such as the TDA7575B.

    Does it answer your question?

    Regards

    /Peter

    R
    RSmoo.1Author
    Visitor II
    November 16, 2022

    Hi Peter,

    Yes, this does. Thank you for your response!

    I do have one more question about the TDA7391, which I realize may also be discontinued, but it's worth a shot to ask. In the TDA7391 datasheet, the application circuit shows a 33 F capacitor attached to pin 11.

    Is it necessary to use such a large capacitor? Will the device still function if I place a capacitor there on the order of uF?

    P
    Peter BENSCHAnswer
    Technical Moderator
    November 18, 2022

    I am sorry that this misprint appears in the data sheet. If you look closely, you can see a space before the F that replaces the lost µ.

    So for the capacitor at MUTE (pin 11) a value of about 33µF should be used.

    If the problem is solved, please mark this thread as answered by selecting Select as best, as also explained here. This will help other users find that answer faster.

    Good luck!

    /Peter

    R
    RSmoo.1Author
    Visitor II
    November 21, 2022

    I see, thank you for clarifying that typo.

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