Have you tried reading the TDA1543 datasheet? It might help, although it took me a while to understand it.
Also see my website.
Also see my website.
I think I get the point right now.
But I still can't explain that the philips guys use 3K as their Rref.
But use the 5V supply.
I've changed the Rref and RIV to 1K and 820ohm as suggestion.(I measure their shunt resister to the ground,correct!)
But the white noise comes back again and the volume level is very low.
And I also measure the DC voltage this time
AOL:1.15V
AOR:1.14V
VREF:1V
VDD:4.89V
I think that the AOL and AOR should be around 2.8V
And the Vref should be around 2.2V right?
But the white noise comes back again and the volume level is very low.
And I also measure the DC voltage this time
AOL:1.15V
AOR:1.14V
VREF:1V
VDD:4.89V
I think that the AOL and AOR should be around 2.8V
And the Vref should be around 2.2V right?
VDD of 5V is too low for correct operation with passive I/V. The best you could do according to my understanding is use Rref=920R and Riv=820R and accept some peak clipping.
Vref of 1V seems too low, although I can't remember what this voltage should be. Maybe your chip is damaged?
Philips can use Rref of 3k because they are not using passive I/V. They are simply adding an offset current to the output.
Vref of 1V seems too low, although I can't remember what this voltage should be. Maybe your chip is damaged?
Philips can use Rref of 3k because they are not using passive I/V. They are simply adding an offset current to the output.
Thank you for feedback savvas.
I do get no idea right now.
The calculation seems no problem at all but it just don't work
It seems that the Vref should fix at about 2.2V(as the datasheet mention)
But there's a voltage drop at Vref to about 1V as I use the Rref as 1K but I don't know why.
Doede Douma said:It works with lower voltages as well, but you need to re-trim the Ref and Rload as well.
So i think I can't just use the 1k5/2k2 on my 5V psu.
I think the main problem in my cdplayer as I changed to passive is the voltage drop
I do get no idea right now.
The calculation seems no problem at all but it just don't work
It seems that the Vref should fix at about 2.2V(as the datasheet mention)
But there's a voltage drop at Vref to about 1V as I use the Rref as 1K but I don't know why.
Doede Douma said:It works with lower voltages as well, but you need to re-trim the Ref and Rload as well.
So i think I can't just use the 1k5/2k2 on my 5V psu.
I think the main problem in my cdplayer as I changed to passive is the voltage drop
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Thank for your feedback savvas.
I do get no idea right now.
The calculation seems no problem at all but it just don't work(RIV=870 ohm Rref=1K)
It seems that the Vref will fix at about 2.2V(as the datasheet mention) no matter how the Rref been changed.
But there's a voltage drop at Vref to about 1V as I use the Rref as 1K but I don't know why.
Doede Douma said:It works with lower voltages as well, but you need to re-trim the Ref and Rload as well.
So i think I can't just use the 1k5/2k2 on my 5V psu.
So I should figure out the root cause of the voltage drop of the Vref on my cdplayer as I change the Rref.
I do get no idea right now.
The calculation seems no problem at all but it just don't work(RIV=870 ohm Rref=1K)
It seems that the Vref will fix at about 2.2V(as the datasheet mention) no matter how the Rref been changed.
But there's a voltage drop at Vref to about 1V as I use the Rref as 1K but I don't know why.
Doede Douma said:It works with lower voltages as well, but you need to re-trim the Ref and Rload as well.
So i think I can't just use the 1k5/2k2 on my 5V psu.
So I should figure out the root cause of the voltage drop of the Vref on my cdplayer as I change the Rref.
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My understanding is that there is no adjustment of Vref for this chip. Vref is whatever it is, and is supposed to be fixed. The resistor attached to the Vref pin sets a current offset on the output pins; it does not adjust Vref.
The output voltage is intended to be in the region of Vref too, so the idea of the offset current is to adjust the output current so that the output voltage (set by your I/V arrangements, whatever they are) is in the region of Vref. To do otherwise invites distortion and/or clipping.
At 5V and below you cannot avoid peak clipping with simple 'resistor to ground' passive I/V. This may or may not be audible - some modern CDs seem to be clipped already!
The output voltage is intended to be in the region of Vref too, so the idea of the offset current is to adjust the output current so that the output voltage (set by your I/V arrangements, whatever they are) is in the region of Vref. To do otherwise invites distortion and/or clipping.
At 5V and below you cannot avoid peak clipping with simple 'resistor to ground' passive I/V. This may or may not be audible - some modern CDs seem to be clipped already!
Yahh....I'm wondering if somebody has sucessed the passive IV
after tda1543 with 5V PSU
Raising the supply rail voltage is not supposed to raise Vout or Vref, so your chip is doing what it is supposed to do.
Raising the supply rail voltage gives you greater headroom so you can choose resistor values which result in no peak clipping. If the rail is too low then it is impossible to choose correct resistor values, as you have found.
The aim is to set Vout at about halfway between the limits set by the supply rail. To do this you need to use Ohm's Law on Rout to calculate the current, and then use Ohm's Law on Rref to adjust the current. Alternatively, see my webpage where I have given the answers.
Raising the supply rail voltage gives you greater headroom so you can choose resistor values which result in no peak clipping. If the rail is too low then it is impossible to choose correct resistor values, as you have found.
The aim is to set Vout at about halfway between the limits set by the supply rail. To do this you need to use Ohm's Law on Rout to calculate the current, and then use Ohm's Law on Rref to adjust the current. Alternatively, see my webpage where I have given the answers.
Yes I know about the head room issue.
The clipping issue didn't change as I pump up the VDD to 8V.
By the way.A simple math.
For 5v supply the Voltage swing should be 1.8V~3.8V
Thus the total swing is 2V.
And the full scale current is 2.3mA
That means the Rout should be 2V/2.3mA=0.87K ohm
Then we needs the Ibias from vref to rise the DC to 1.8V
We need 1.8V/0.87kohm=2.07mA for one side.
With the current gain of 2.
So we can simply calculate the Rref is 2.2V/2.07mA= 1.07Kohm
But the main problem for me is.
The Vref just not stand constant!!!
It varies from the Rref changes.....
I've tested several combination of the Resistors (including yours)
They don't work at all
The clipping issue didn't change as I pump up the VDD to 8V.
By the way.A simple math.
For 5v supply the Voltage swing should be 1.8V~3.8V
Thus the total swing is 2V.
And the full scale current is 2.3mA
That means the Rout should be 2V/2.3mA=0.87K ohm
Then we needs the Ibias from vref to rise the DC to 1.8V
We need 1.8V/0.87kohm=2.07mA for one side.
With the current gain of 2.
So we can simply calculate the Rref is 2.2V/2.07mA= 1.07Kohm
But the main problem for me is.
The Vref just not stand constant!!!
It varies from the Rref changes.....
I've tested several combination of the Resistors (including yours)
They don't work at all
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