search & cldn't find TPS3833 on web...
Doctor, mind sharing TPS3833 auto-mute schematic ?
many would find such hack-mod most useful on FX502Spro
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Great, this looks simple to implement & I am feeding TPA3250 at similar PVDD 31~32V as well.
Some amateurish questions:
1# Power dissipation requirements:
BZX84C4V7 is rated for 1/4w.
So can i use lowest dissipation /smallest package on MCP120, BZX84C4V7?
ie. MCP120T(T092/SOT23)
2# Confirm of Trip point voltage:
~ MCP120 for 3.0v, right?
~ Can any 4.7v zener diode be use instead?
Thks Doctor for the great sharing, pardon my amateurish questions here:
- you used TPS3801 or TPS3802K33DCKR? what trip voltage, at 3.3V?
- which resistor to modify if my PVDD is heading 31~32V？
- any power dissipation requirements on the component package: 1/4w?
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1- That zener is just for protection of MCP120 which has absolute maximum voltage of 7V. There are no requirements on power and you can feel free to not use it. Its just for piece of mind.
2- Its 3V version of MCP120. Don't substitute it with zener, its something completely different.
For 31-32V power supply I would suggest resistors 10k and 1k2. That will unmute TPA at about 28V + 350ms delay.
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If you choose 10k for the upper Resistor, the lower is: 10k/8.485=1.18k so choose 1.2k.
Powerrating:
PVDD=32V
Current into TPS380X or MCP120 is negligible. We only calculate for the combined voltage divider.
10k+1.2k=11.2k
Current is then:
32V/11.2k=0.0028571429A or 2.86mA
Power follows I^2*R, so for the 10k:
2.86mA^2 * 10k = 82mW -> 1/10W is fine
for the 1.2k:
2.86mA^2 * 1.2k = 9.82mW -> 1/10W is more than fine
Nothing to worry about. The zener conducts only at overvoltage and is then roughly limited to
P_zener = U_zener * ((PVDD - U_zener)/R_upper)
Because differential resistance of the diode is much smaller than R_lower (1.2k) and R_upper (10k)
For 40V overvoltage we have:
P_zener = 4.7V * ((40V-4.7V)/10k) = 17mW
The upper resistor would need a power rating of:
P = ((40V-4.7V)^2)/10k = 125mW = 1/8W
If this overvoltage will occur for long time. If it's just pulses, 1/10W is still fine.
Someone correct me please if I'm wrong.
Want to say word of appreciation for Doctormord, also DarkOne -
It is people like you - cared to lend a helpful hand, which kept diyAudio and many enthusiasts going!
Doctormord, after you are done posting, if can could help by sharing a link of your website i can reference exactly what pin to mod? thks.
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Thanks for the compliments and pictures. Would be great if you can take them front/back with heatsink removed to see all traces and bias with much (soft) light to keep noise and exposure time low to have it nice and sharp. This amp doesn’t feature a voltage supervisor at all. (Or am i blind?)
Then i will put all annotations in where to patch.
Thanks a lot.
Then i will put all annotations in where to patch.
Thanks a lot.
