"El Guapo" my silly TA8251AH project

[Russ White]

I have no particular reason for building this amp other that I have about 10 of these chips I picked up in a lot I baught off ebay.

I need some help from those who might understand the datasheet better than I.

I have never seen this chip before, and I am a little puzzled by the mute and stby pins, and how to implement them. I also could use some advice on the output part (zobel values and such).

Here is the datasheet:
toshiba datasheet

And here is my design so far:

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[slackman]

Mute control:
Pin 25 of chip must be pulled up with a resistor (5...10 k) to positive voltage. Then with a transistor you have to switch pin 25 as shown in page 5 of the datasheet. If the transistor gets active high on its base he will mute the circuit.

Michael

 

[slackman]

Standby control:

same as mute but reversed: pin 2 has to be pulled DOWN with a resistor and if pin 2 gets high, amp will go into standby (page 3 of datasheet)

Michael

 

[Russ White]

Mute control:
Pin 25 of chip must be pulled up with a resistor (5...10 k) to positive voltage. Then with a transistor you have to switch pin 25 as shown in page 5 of the datasheet. If the transistor gets active high on its base he will mute the circuit.

Michael

Ok, I am not sure I understand how that works, but If I want it never to be muted, can I simply put a 10K resistor between VCC and pin 25? Also, do I need to do anything with pins 1(SMOOTHING) and 10(RIP).

 

[Russ White]

Standby control:

same as mute but reversed: pin 2 has to be pulled DOWN with a resistor and if pin 2 gets high, amp will go into standby (page 3 of datasheet)

Michael

Are you sure about that? I read it as it needs to be pulled up for "on" and down for "off/stby" , so if I had it connect to gnd the amp is in stby and if it is connected to V+ it is on.

 

[slackman]

aaaah! Error!
Sorry: '...must NOT be pulled up'

for never mute leave the mute pin unswitched, for mute switch it to low.

 

[slackman]

and yes... your'e right with standby: low is out and high is on - silly me. 😉

 

[Russ White]

aaaah! Error!
Sorry: '...must NOT be pulled up'

for never mute leave the mute pin unswitched, for mute switch it to low.

So for never mute do you think I can simply leave pin25 connected to nothing (neither pulled up or down)?

 

[slackman]

yepp!
(see page 7, note on the lower end of the page)

Michael

 

[Russ White]

yepp!
(see page 7, note on the lower end of the page)

Michael

Ahhh! great! So I imagine then I should also leave pin 1 open too.

Now I wish I knew what to do with pin 10.

 

[Russ White]

I am just going to put a 47UF cap on pin 10 like the datasheet shows for the test circuit, even though I am not sure why.

 

[Russ White]

Can anybody comment on the zobels for output, and also check if my parallel output scheme looks sane?

 

[slackman]

Hi,
why in parallel? These are lowvoltage amps (car hifi) and they are designed for 4R speakers. If you put them in parallel the voltage will only be half then in bridgemode. Do you have 2R speakers?

Maybe two chips in bridged parallel?

mic

 

[Russ White]

I did parralel because the amps look like they are already bridged (based on the datasheet). Also, because I only need 2 channels. 😀

I will only be driving 4ohm speakers, I figured a little extra current couldn't hurt. 🙂

I wouldn't mind trying a BP configuration, but I am not sure where to start.