Hello together!
Since the forum and google search did help, here is my current issue:
I measure a power consumption of about 2.6W (mute on) and 2.7W (idle) for one LM3886 in my diy amp. The measurement includes the losses in the psu. The psu provides +/-25V=.
Is 2.7W a normal value?
Redards.
Since the forum and google search did help, here is my current issue:
I measure a power consumption of about 2.6W (mute on) and 2.7W (idle) for one LM3886 in my diy amp. The measurement includes the losses in the psu. The psu provides +/-25V=.
Is 2.7W a normal value?
Redards.
The datasheet gives you all information about the maximum power consumption/output/dissipation an how to calculate the correct heatsink but it was no help (for me) to figure out the power consumption in idle/mute mode.
Oh, okay, I must be mistaken. 2.6W does sound a tad on the high side, but I suspect most of that is in the PSU. Can you take a measurement of just the chip?
Unfortunately it is not mainly the psu. The losses in the psu should be minimal compared to the consumption of the power stage.
The setup:
1x psu, 1x microcontroller+mixer, 1xpower-amp with 3xlm3886.
The measuements I already made:
- The psu+microcontroller-board alone: 6.85W
- All connected, mute on: 14.65W
- All connected, mute off: 15.0W
- All connected, mute disconnected*: 14,65W
*the mute is switched by the micro.
This results in approx. 2.6W-2.7W per lm3886.
The schematic is mainly the basic datasheet suggestion.
The ripple voltage of the psu is <=200mV (peak-peak) for the +rail and <=120mV for the -rail while playing music at low volume @+/-26V.
The setup:
1x psu, 1x microcontroller+mixer, 1xpower-amp with 3xlm3886.
The measuements I already made:
- The psu+microcontroller-board alone: 6.85W
- All connected, mute on: 14.65W
- All connected, mute off: 15.0W
- All connected, mute disconnected*: 14,65W
*the mute is switched by the micro.
This results in approx. 2.6W-2.7W per lm3886.
The schematic is mainly the basic datasheet suggestion.
The ripple voltage of the psu is <=200mV (peak-peak) for the +rail and <=120mV for the -rail while playing music at low volume @+/-26V.
Sounds very reasonable. 2.7watts and a 50 volt supply is around 54ma. The data sheet say 50ma as typical and 85ma as a max so its spot on.
Is that what you mean 🙂
Thanks a lot!
Now I found it too, on page 4 electrical characteristics (what a surprise!):
I+ (Note 4) Total Quiescent Power Supply Current VCM = 0V, Vo = 0V, Io = 0A 50 85 mA (max)
I am sorry for that unnecessary thread! Sometimes you do not see the wood for the trees. :-/
Now I found it too, on page 4 electrical characteristics (what a surprise!):
I+ (Note 4) Total Quiescent Power Supply Current VCM = 0V, Vo = 0V, Io = 0A 50 85 mA (max)
I am sorry for that unnecessary thread! Sometimes you do not see the wood for the trees. :-/
That quiescent current stated in the specification is for normal no-signal operating condition.
I cannot see a specification value for current when in mute mode.
When I look at the mute circuit on p7, it appears that the mute only attenuates the gain of the input stages. It does not show any connections to the power stages. That's where the big current consumption will be. The earlier stages will probably be more like opamps in current consumption.
I cannot see a specification value for current when in mute mode.
When I look at the mute circuit on p7, it appears that the mute only attenuates the gain of the input stages. It does not show any connections to the power stages. That's where the big current consumption will be. The earlier stages will probably be more like opamps in current consumption.
I'm testing a new amp using LM3886 and I've done the current measurement running idle (no input signal):
I = 40mA (powered using +15V and -15V)
Regards
I = 40mA (powered using +15V and -15V)
Regards
Well inside the specification limits.
And possibly just 10% to 20% above the typical stats stated by National.
And possibly just 10% to 20% above the typical stats stated by National.
Could be the power supply; mine was +15V and -15V for 40mA, in the specs V+ = +28V, V− = −28V
look at the datasheet.
It shows a plot of current vs Vsupply.
@ +-15V it shows typical @ ~35mA depending on Tj.
It shows a plot of current vs Vsupply.
@ +-15V it shows typical @ ~35mA depending on Tj.
soda74, HOW are you measuring this? ON the mains side? Voltage times Ampere? This will be VA, not watts.
peranders,
I used a simple energy cost measurement device which shows the effective power (Watts not VA). I disregarded the efficiency of the transformer (~90%) and so on, since I only needed an estimation...
Regards.
I used a simple energy cost measurement device which shows the effective power (Watts not VA). I disregarded the efficiency of the transformer (~90%) and so on, since I only needed an estimation...
Regards.
My 4 x LM3886 stereo bridge/BTL AMP consumes 390 mA at Vtt = 39 V (+/- 19,5V).
So 97,5 mA per LM3886, out of extreme specs of 85mA. Makes 3.8W per piece.
At Vtt = 30V same current (so less power).
It seems not to osccillate.
DC offset output is only 6,5 mV (2 x 6,5 mV / 4 Ohm = ca. 3,25 mA) ; so, that cannot be the problem. Speakers disconnected does not make any difference in the current, which is consistent with de DC offset measurment.
Should I be worried?
So 97,5 mA per LM3886, out of extreme specs of 85mA. Makes 3.8W per piece.
At Vtt = 30V same current (so less power).
It seems not to osccillate.
DC offset output is only 6,5 mV (2 x 6,5 mV / 4 Ohm = ca. 3,25 mA) ; so, that cannot be the problem. Speakers disconnected does not make any difference in the current, which is consistent with de DC offset measurment.
Should I be worried?
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Measure also the current between the amps. Measure the voltage across the sharing resistors at the outputs.