Hi guys. I have a layout using a MAX1044 charge pump IC to boost 9V to 18V(ish) and generate a -9V line at the same time. It is working well and the circuit action is absolutely clear. I want to expand its level of supply to include more chips. The datasheet shows it may be possible but I may be on the edge as far as potential current is concerned. I am talking about a handful of TL072 opamps, (2.5mA current per opamp), here with no real load to drive so it isn't huge amounts I am looking for. The MAX1044 is supposed to drive up to about 20mA but I will be on the verge of that.

LTspice is no help with this chip's performance. A model doesn't seem to be available, but the similar LT1054 is there and it doesn't simulate well with loads. It droops and collapses well below the 20mA current that the MAX1044 is supposed to supply. I know of the MAX660 which is a higher current design. It looks on paper to be a drop in replacement for the MAX1044 but, not having ever used it before, I wondered if there is someone out there who can confirm it is a plug in compatible upgrade for the MAX1044 in a socketed circuit with plenty of available current from the external supply. Changing supporting component values to accommodate is not a problem so pump and reservoir capacitors will be changed if required.

So... Anyone know the chips well enough to confirm it is a drop in replacement?

 

Hi guys. I have a layout using a MAX1044 charge pump IC to boost 9V to 18V(ish) and generate a -9V line at the same time. It is working well and the circuit action is absolutely clear. I want to expand its level of supply to include more chips. The datasheet shows it may be possible but I may be on the edge as far as potential current is concerned. I am talking about a handful of TL072 opamps, (2.5mA current per opamp), here with no real load to drive so it isn't huge amounts I am looking for. The MAX1044 is supposed to drive up to about 20mA but I will be on the verge of that.

LTspice is no help with this chip's performance. A model doesn't seem to be available, but the similar LT1054 is there and it doesn't simulate well with loads. It droops and collapses well below the 20mA current that the MAX1044 is supposed to supply. I know of the MAX660 which is a higher current design. It looks on paper to be a drop in replacement for the MAX1044 but, not having ever used it before, I wondered if there is someone out there who can confirm it is a plug in compatible upgrade for the MAX1044 in a socketed circuit with plenty of available current from the external supply. Changing supporting component values to accommodate is not a problem so pump and reservoir capacitors will be changed if required.

So... Anyone know the chips well enough to confirm it is a drop in replacement?

It will probably be quicker to get some and run the experiment.

 

Ahhh! Just noticed the max supply voltage of the MAX660. It's only +6V. I'm running from +9V to generate +18V(ish) and -9V. So it's a nogo from the start I'm afraid. You are right. At the end of the day it may just be easier to breadboard and test but I didn't want to go to the expense of buying and waiting for something which wouldn't even fit on my currently designed (and manufactured) PCB.

So back to the drawing board. Testing the current MAX1044 to see the extent of the problem (or not) is called for first I think. Thanks for the support Papabravo.

 

Ahhh! Just noticed the max supply voltage of the MAX660. It's only +6V. I'm running from +9V to generate +18V(ish) and -9V. So it's a nogo from the start I'm afraid. You are right. At the end of the day it may just be easier to breadboard and test but I didn't want to go to the expense of buying and waiting for something which wouldn't even fit on my currently designed (and manufactured) PCB.

So back to the drawing board. Testing the current MAX1044 to see the extent of the problem (or not) is called for first I think. Thanks for the support Papabravo.

Reading datasheets carefully, then going back and reading them AGAIN, is a profoundly intelligent thing to do. Props to you.