Last month I was trying to add a voltage doubler circuit to the egodriver,
so I drew it and made the board.
Today I just finished it and I took the DM to measure my ic voltages,
when I turn on the voltage doubler, pin 8 of opamp is 7.5v (instead on my switch pin is 15v)
and when is off is 8.05v using and 8.05v battery.
I believe when its off everything works well but when is on something going wrong.
Here my schematic.
Where is my mistake ?
Pin 6 on the charge pump shouldn't be connected to ground for supply inputs greater than 3.5V.
From the spec sheet.
Quote
The voltage regulator portion of the TC1044S is an integral part of the anti-latch-up circuitry. Its inherent voltage drop can, however, degrade operation at low voltages. To improve low-voltage operation, the "LV" pin should be connected to GND, disabling the regulator. For supply voltages greater than 3.5V, the LV terminal must be left open to ensure latch-up-proof operation and prevent device damage.
Edit: if you are using the MAX1044, it's not quite as severe, but you should still leave the LV pin disconnected.
Also, I think your caps need to be bigger, around 10µF and preferably low ESR type electrolytics. I don't know if these are your issues, but they could be part of the problem.
My caps are 10uF so thats not the problem,
I just leave opened pin 6 and I have 9.5 when its off and 7.8 when its on (battery voltage 8.0v)
Any other suggestions?
Which charge pump are you using?
Quote from: RobA on July 29, 2013, 11:16:26 PM
Which charge pump are you using?
I am using max 1044.
http://datasheets.maximintegrated.com/en/ds/ICL7660-MAX1044.pdf
Well, the Max chip is supposed to be OK when the LV pin is connected at high voltage. Other charge pumps can be damaged. I'd guess that's not the problem.
If your circuit is pulling too much current, the output voltage will drop. The Max1044 is limited to about 20mA and a bit less with the boost pin used. This can be even lower if your caps have high ESR. Can you check to see how much current you are drawing through the circuit?
As a note, I don't think the circuit should be pulling too much current. It's just that if something else is wrong and it is, then that could show up on the charge pump output.
Quote from: RobA on July 29, 2013, 11:37:04 PM
Well, the Max chip is supposed to be OK when the LV pin is connected at high voltage. Other charge pumps can be damaged. I'd guess that's not the problem.
If your circuit is pulling too much current, the output voltage will drop. The Max1044 is limited to about 20mA and a bit less with the boost pin used. This can be even lower if your caps have high ESR. Can you check to see how much current you are drawing through the circuit?
How can I check the current draw?
Here is my board if anything helps.
If your multimeter has a current setting, you can use that. If not, then you can put a really small resistor, 10Ω or so, in series with the power input and just measure the voltage drop across it and then use Ohm's law.
I've got to be away from the computer for a while, but I'll look at the board in a bit.
I just looked at your schematic again and realized that you have a 100Ω on the input. You can just measure the voltage drop across that and use Ohm's law.
I measured across 100R resistance 7.49v so my current draw is 74.9mA.
My battery has 7.91v
Is that normal?
Quote from: teknoman2 on July 30, 2013, 07:35:47 AM
I measured across 100R resistance 7.49v so my current draw is 74.9mA.
My battery has 7.91v
Is that normal?
Is that measured from one side of the resistor to the other? Or, is that the voltage from ground to the output side of the resistor?
If it's across the resistor (leads on either side of the resistor), that seems really high for this circuit. If it's from ground to the output side, then you are at about 4mA and that seems reasonable. If you really are at 75mA draw, I'd suspect a short somewhere.
If it is at 75mA, then I doubt if the MAX1044 can supply that much current especially in the boost mode.
I was just looking at your schematic again and I thought that it would probably be good if you had the 9V/18V switch setup as a DPDT that in addition to the voltage switching it would cut the power to the charge pump. That way, in 9V mode it wouldn't need to power the charge pump and the charge pump wouldn't be putting noise on the power rails.
If you have the charge pump socketed, try taking it out and measuring the current draw when in 9V mode.
Thank you again for your time,
my values are measured from ground to the output of the resistor , so my current draw as you said 4mA
is normal.
In my board I am using an SPDT ON-ON do you believe is the cause of my issue?
I will take out the charge pump and I will measure the current draw in 9v.
No, I don't think the switch is your problem. I just thought it would be a nice addition to the way your circuit is setup now.
With only a 4mA draw, the charge pump should be OK at delivering the doubled voltage and you should be seeing something around 15V on the power supply.
Perhaps the charge pump is damaged or there is an issue with one of the caps. Or, since you are seeing 15V at the pin to the switch (is this both the input and output of the switch?) there is a solder bridge or something like that. It doesn't seem likely though because the voltage is right with the charge pump out of the circuit.
I took off max1044 and I measured the current draw (from ground to output of the resistor).
Also I changed battery to have more accurate resuslts cause the last one was dying.
My battery voltage is 9.4v and my voltage across the resistor is 9.0v,
so I have 4mA current draw.
When I measured pin 8 of TL082 I have 7.7v when its off and when its on 9v,
I dont understand why is this happening.
Do you have the voltages measured at the pads of the switch (all three pads)?
I'd first look for solder bridges around the switch and check for possible issues in the switch itself as a first step.
When the swith is on I have :
pin1=8.8v
pin2=8.8v
pin3=17v
When its off
pin1=6.7v
pin2=10.5v
pin3=10.5v
But your battery is at 9.4V and the output side of the 100Ω is at 9.0V in both switch positions?
I just saw Fred Briggs Super OCD schematic
http://1.bp.blogspot.com/-mdmZKzXJusA/T00EjAPiDyI/AAAAAAAABA8/gwhJo9nX90Y/s1600/briggs_super_ocd.jpg
It has pins 5 and 6 open,
so I measured having 5 and 6 open.
When its onn
pin1=8.8v
pin2=8.8v
pin3=17v
When its off
pin1=7.3v
pin2=12.1v
pin3=12.1v
Quote from: RobA on July 30, 2013, 08:54:55 AM
But your battery is at 9.4V and the output side of the 100Ω is at 9.0V in both switch positions?
I dont have the same voltage on both positions,
when its on is 8.9v and when its off is 6.7v
I believe the 6.7v measurement is strange.....
You definitely want pin 6 not connected as it's the low voltage pin and you are above 3.5V. All of the spec sheets show pin 5 connected to ground for the voltage double circuit.
What happens when you have pin 6 lifted but pin 5 in place?
Quote from: teknoman2 on July 30, 2013, 09:03:15 AM
I believe the 6.7v measurement is strange.....
Yes, me too. It makes me think that either there is a short or the chip or switch is bad.
Now I am at work and I dont have another max1044 but when I return back home I will change it,
I lift pin 6 and now I have 8.8v across resistor when its on
and 7.3v when its off (21mA current draw is too much I believe).
My switch woltages are
On=8.8v, 17v, 17v.
Off=7.3v, 12.1v, 12.1v.
I just realise that when I take out max1044 the current draw is the same 4mA.
In both positions of the switch I have 8.8v across the 100R resistor.
If there were a short probably the 7.3v measurement will reappear even when the max will still missing,
am I correct?
Depends on where the short is.
I'm breadboarding this with a MAX1044 to see what my voltages look like. I'll let you know when I get it measured.
Thanx mate,
if finally gonna solve it I will send you an pcb of this one.
Again thank you for your time.
Hey, no problem. I have an ulterior motive anyway. I ordered a couple of the MAX1044's a bit ago and haven't had a reason to put any thing together with them yet. I wanted to check them out to see where the oscillator frequency noise was on them. On all of the TC1044SCP and 7660's I've tested so far the oscillator was in the audible range even with the boost pin on. The only charge pump I've found that consistently performs well is the LT1054. So, as soon as I give you these voltages, I'm going to scope the rails with the MAX1044 in place and see where it's at.
I built just the power supply section of your circuit on breadboard. The current draw from the MAX1044 is tiny, ~4mA. So, you really shouldn't see much in the way of a voltage change at the output of your 100Ω resistor with the 1044 in place or out.
First off, on my breadboard, your schematic for the power supply works just like you want it to. The switch flips between 18V and 9V perfectly.
I didn't connect pin 6 to ground and I don't really want to try (at least not yet) as it might damage the device. I might be up for a little destructive testing after I check out other areas of the charge pump ;D.
My input is 9.41V and 9.38V after the 100Ω.
The output of the switch is either 9.38V or 18.02V.
There is no change on either side of the switch with position of the switch.
IC voltages:
Pin 1 : 9.38V
Pin 2 : 4.69V
Pin 3 : 0V
Pin 4 : N.C.
Pin 5 : 0V
Pin 6 : N.C. but at 5.06V
Pin 7 : N.C. but at 7.58V
Pin 8 : 9.38V
I'm using Nichicon PS series 10µF caps. They are a low ESR cap and this does seem to help a bit with charge pumps. It shouldn't be significant for your issue. But it might help the MAX1044 in the frequency area I'm going to test next. One other thing to note is that if I move to using 1N5817 diodes, the output voltage goes up to 18.68V.
I just double check again my voltages and I found that something odd,
I measure ground voltage 0.03-0.1V
Is that normal?
Also I took out the max and measure the switch pins,
in every position pin1 is the same 8.6v
but on pin3 is 8.1v and 7.4v
So I believe something wrong is on this side of circuit.
From what you said the normal are pin1 and pin3 voltage of switch must not change.
Am I right?
Quote from: teknoman2 on July 30, 2013, 11:08:09 AM
I just double check again my voltages and I found that something odd,
I measure ground voltage 0.03-0.1V
Is that normal?
Yeah pretty normally. It rarely will read at exactly zero and it'll fluctuate around a bit too.
Quote from: teknoman2 on July 30, 2013, 11:23:35 AM
Also I took out the max and measure the switch pins,
in every position pin1 is the same 8.6v
but on pin3 is 8.1v and 7.4v
So I believe something wrong is on this side of circuit.
From what you said the normal are pin1 and pin3 voltage of switch must not change.
Am I right?
Yes, I think you are right. The voltages on pins 1 and 3 shouldn't change with switch position. With the IC out, pin 1 should be a couple of diode drops below pin 3 and should stay the same no matter the switch position. I still think that this points to a switch problem or a solder bridge either at the switch or the PCB. Some of the other numbers with the IC look strange, but those may all disappear when you get the switch issue fixed.
One other thing that could be consistent with the problem here though is to make sure that you have D3 and D4 in right. I don't think that's the issue, but it's worth checking.
Personally I believe that isn't a switch problem,
I measured on D4 positive pin and on C13 positive pin is 7.6v.
So its normal on switch pin to have the same voltage.
I think that D3 and D4 (1n4001) are damaged.
Do you think worth changing them is a good idea?
It could be that there is a problem with them. If you have a diode setting on your multimeter, you should be able to check them in the circuit. I just tested it on my breadboard in the circuit and it's a tiny bit off, but does show the diode drop pretty close.
Just so you'll know, the MAX1044 did really well in the noise/oscillator frequency test. It was at 47kHz with the boost pin on. So, way outside the audio region.
I have to go get some sleep. Good luck tracking it down. I'll check back in when I wake up.
Thanx mate I will keep you posted if anything change,
Thanx again.
Finally I managed to find my issue but we dont know the cause.
For some mysterious reason when I use max 1044 I measure grater voltage drop across the resistor.
Thats why we have different voltages on the switch.
Now I just lift up 1044 pin1,
So when switch is on we have:
10mA voltage drop
8.8v battery and 7.8v across the 100R and 14v on pin 8 of TL082.
switch lungs 7.8v, 14v, 14v.
When the switch is off :
5mA voltage drop
8.8v battery and 8.5v across the 100R and 8.5v on pin 8of TL082.
switch lungs 8.5v, 8.5v, 16v
That all does make sense. (I was reading on and off for the switch backwards last night -- had me confused.) The efficiency of the charge pump is reduced when you are in boost mode. So, it drops more voltage when it draws more current in boost mode than it does in normal operation with pin 1 disconnected. The problem is that the MAX1044 is way down in the audible range if you don't use the boost pin.
Also, I don't think it should be dropping that much voltage for the amount of current that circuit should pull. Could be that there is a short somewhere that is drawing too much current when the charge pump is being used. I doubt that. It could be that the charge pump is damaged. It should be able to supply about 20mA and at least 10mA in boost mode without that much drop.
The types of caps you use can have a pretty big impact on the charge pump. Using a low ESR type is best and I did some experiments that showed up to a 10% difference with some caps. Moving the caps up in value can help, but too big can hurt. Paralleling a big cap with a small might help.
Going to a smaller resistor on the input will lower the voltage drop there a bit, 10Ω-20Ω might be good. Using 1N5817's for the diodes will get you back quite a bit of voltage too.
I'm going to breadboard the rest of the circuit to see what I get for the current drop in both modes.
OK. I bread bordered the whole schematic. It sounds good.
At first I had it with the 100Ω and 1N4001's. The voltage numbers were very similar to the numbers you last posted.
Then I moved to a 10Ω and that alone makes things much better. After putting in the 1N5817's, things improved more. With the 10Ω and the 1N5817 diodes these are the numbers for currents and voltages;
Switch On:
Current: 8mA
9.19V
17.74V
17.74V
Switch Off:
Current: 4.3mA
9.13V
9.13V
18.10V
I tried with the LT1054 as well and it gets a tiny bit more voltage, but I don't think it's really worth it.
I suspect something is going on between the input resistor and the input impedance of the charge pump and the 100Ω is high enough that it is working like a voltage divider.
I'd give it a try just changing the resistor and see what you get. It's definitely worth moving to the 1N5817's too, but the 10Ω resistor seems to be the first order fix. You might even be able to get by without a resistor there at all.
Your design works well for me with that one fix.
Edit: I would leave LV pin disconnected too so that it can work with other charge pumps as well as the MAX. I had it off in all my testing.
I just bought some 1n5817 and by the end of the day I will make these changes.
I will post my results.
I made the changes as you suggested,
100Ω to 10Ω
all diodes 1n5817
change max1044 to icl7660 (they have the same datasheet)
left open Lv pin6.
These are my measurements.
Switch On:
8.58V
17.1V
17.1V
Switch Off:
8.9V
17.9V
17.9V
every works fine now...
thanx again for your help and your time.
please PM me your address to send you one board for your help.
Excellent. Congrats on the design and your board working. I'll PM you my address. It'll be cool to build this one.
I did a bit of playing around with the charge pumps when I had it on the breadboard. I found the Microchip TC7660H gave me the best results, highest voltage combined with highest clock frequency and least current draw from the charge pump. They are pretty cheap too, about $1.20US from Mouser I think.
Thanx again for your help,
I am going to make an order to mouser
including both tc1044 and tc7660h.
Since we managed to solve it,
I jump to the 'mangler' using a charge pump for negative supply.
If you want I can PM you the schematic for this one as well.
I would like to ask you one last thing,
Why we have to connect Boost with V (pin1 with pin8).
From a brief looking none of the datasheets indicates that we have to do this.
Do you know the reason of this connection?
I believe I found it,
if we connect Boost with V+ we increase the oscillation frequency from 10kHz to 45-47kHz.
which is out of range of guitar frequency.
Yeah, that's it. Not all of the charge pumps use it. It'll actually cause problems for the LT1054. So, if someone wants to use that charge pump in a circuit with the boost connection in place, you have to do something to disconnect it (cut pin 1 or something). The TC7660H doesn't need it either since it's always boosted, but pin 1 is an NC on the TC7660H so it doesn't matter if you leave it connected.