Yes, I have seen errors and omissions on datasheets.just because the data sheet does not mention (or even know about) a remedy, does not mean that remedy should not be implemented.
Datasheet tells to discharge the capacitors.(I gave an excerpt of the datasheet in post #17)If a diode is needed then surely the datasheet would say so.
Millions of audio amplifiers use a coupling capacitor to feed the speaker because the power supply has only a single polarity. They do not discharge the capacitor when the power supply is turned off because the circuit uses the output transistors to keep the input to the capacitor always at half the supply voltage. Then when the supply voltage drops when the power supply is turned off the capacitor is discharged by the amplifier circuit.
If a diode is needed then surely the datasheet would say so.
EDIT:
Pins numbers were mentioned instead of pins functions. The BYPASS pin is pin 9, not the output pin that I was thinking about.
The 4.7uF capacitor on pin 9 might have a horrible tolerance and be actually be 20uF? Then the "wakeup time" would be about 2 seconds.
But the capacitor value is not changed by the power supply type as happens with the problem.
- - - Updated - - -
How can the output capacitor charge to -10V when there is no negative power supply?
Your schematic shows +12V and ground. Do you also have a -12V supply?
" Quote Originally Posted by djnik1362 View Post
I put output voltage on scope and see when i reset power this capacitors charged to about -10V
it eventually reach to zero and then after a loud click my speakers responding.
I change 100k resistors to 4.7k and my problem solved mostly."
This can only happen when your loudspeakers have no DC continuity. Have you actually checked their resistance?
Frank
Also from the data sheet:
" In order eliminate "clicks and pops", all capacitors must be discharged before turn-on. Rapidly switching VDD may
not allow the capacitors to fully discharge, which may cause "clicks and pops".
There is a relationship between the value of CIN and CBYPASS that ensures minimum output transient when power
is applied or the shutdown mode is deactivated. Best performance is achieved by selecting a CBYPASS value that
is greater than twelve times CIN's value."
helps to read it in detail...
perhaps you should connect a diode from pins 4 & 7 to the Vcc (two diodes, kathode to Vcc) this will return the charge on the caps to the Vcc at power down. I note the IC is supposed to take care of clicks and pops in the speakers at power up, due to the 470uF caps, but perhaps it is not so good for short power interruptions as you are suggesting, certainly putting 4k7 in parallel with the speakers should have no noticeable effect, perhaps you are putting them on the other side?
Impossible. Nothing in your circuit will have a negative voltage because there is no negative power supply voltage.I probe negative pin of the capacitor and it was about -10V and it slowly reach to zero.
Impossible. Nothing in your circuit will have a negative voltage because there is no negative power supply voltage.
The black lead of your multimeter always connects to the circuit ground and the negative wire of each output capacitor also connects to the circuit ground through the speakers. Then the voltage is zero. The positive wire of each output capacitor is probably at half the positive supply voltage then that voltage drops when the power supply is turned off.
Hi,
This all tells that there is an issue with your speakers or the connection.
With the connected speaker the negative voltage will exist only for milliseconds.
It seems like there is a relay, any other switching device, diode or capacitor in series with the speaker. Or your measurement is wrong.
What DC value does the scope show at normal operation?
Klaus
Slowly... this isnot a good description.about -10V and it slowly reach to zero.
Hi,
-10V with a 12V supply? .. I maximally expect -6V...with an immediate plop. --> this is the speaker voltage.
Slowly... this isnot a good description.
We technicians like values.
Some may find milliseconds "fast", sone may find them "slow".
--> Please try to give more detailed informations. Like a scope picture...with the timing setting and the gain setting.
Klaus
But the common wire (ground wire) of your 'scope is connected to the circuit's 0V (ground) and the speaker connects the (-) wire of the capacitor also to the circuit's 0V (ground) then the 'scope will show zero.suppose positive polarity of the capacitor be at zero voltage then if you have charge in the capacitor then negative polarity of capacitor will be at negative voltage
even if you have not have negative supply in your circuit.
I probe it with scope and it was negative.
But the common wire (ground wire) of your 'scope is connected to the circuit's 0V (ground) and the speaker connects the (-) wire of the capacitor also to the circuit's 0V (ground) then the 'scope will show zero.
If the (+) wire of the capacitor is at a positive voltage then its (-) wire is still connected to 0V (ground) through the speaker.
If the capacitor is charged and you connect your 'scope to its (-) wire (without the speaker connected) then connect the capacitor's (+) wire to 0V (ground), the 'scope will show the negative voltage.
That is why we ask if the speaker is not connected.
The LM4952 stereo amplifier is class-AB so with a +12V supply its output pins are about +6V and the datasheet says the bypass pin is also at "half the supply voltage". Then each output capacitor has 6V across it.
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