Before we go on I am fully aware that these things must be respected. Potential bomb/fire/personal injury hazard if mistreated.
I have some 325F Maxwell caps that are paralleled and will be charged for 3v3 for various DAC psu rails....or atleast I am trying them out.
Tried initially with ebay purple LT3042 reg but the thing was burning up and would fault if the caps were empty as I guess they appear as dead short to the reg.
In the Ian Canada threads there are successful uses of his 3042/5 regs but they have a better ground plane for heatsinking.....as far as I am aware.
So I tried today with an ebay LT1963 and all went well. Reg chip got warm but not.so much to worry. The rectifier diodes got pretty toasty. Measured 360ma through them . I cant ID them so safe to swap those out for something beefier.
But my question sirs is do I need to isolate the charging reg from the supercaps when the charger is turned off.....otherwise won't the SCs discharge into the reg?
If this is the case I assume a relay is best for this but can diodes be used to prevent reverse 'flow'? Again I maybe assume thay the potential current would overwhelm the diodes?
Thanks for any advice. I do not go into this blindly and am taking no risks
I have some 325F Maxwell caps that are paralleled and will be charged for 3v3 for various DAC psu rails....or atleast I am trying them out.
Tried initially with ebay purple LT3042 reg but the thing was burning up and would fault if the caps were empty as I guess they appear as dead short to the reg.
In the Ian Canada threads there are successful uses of his 3042/5 regs but they have a better ground plane for heatsinking.....as far as I am aware.
So I tried today with an ebay LT1963 and all went well. Reg chip got warm but not.so much to worry. The rectifier diodes got pretty toasty. Measured 360ma through them . I cant ID them so safe to swap those out for something beefier.
But my question sirs is do I need to isolate the charging reg from the supercaps when the charger is turned off.....otherwise won't the SCs discharge into the reg?
If this is the case I assume a relay is best for this but can diodes be used to prevent reverse 'flow'? Again I maybe assume thay the potential current would overwhelm the diodes?
Thanks for any advice. I do not go into this blindly and am taking no risks
I would rather use some low voltage rated Shottky. Relay contacts may suffer from a DC current and wan't last long. A relay that will withstand DC current will be several times large than a suited Shottky diode.
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Quick answer is no, isolation is not needed. Refer to the LT1963 datasheet. The reverse current is less than 1.2mA.
"(10) Reverse output current is tested with the IN pin grounded and the OUT pin forced to the rated output voltage. This current flows into the OUT pin and out the GND pin."
But don't use Ebay (due to the risk of fakes), you can buy from Linear directly from their website and their prices are competitive.
"(10) Reverse output current is tested with the IN pin grounded and the OUT pin forced to the rated output voltage. This current flows into the OUT pin and out the GND pin."
But don't use Ebay (due to the risk of fakes), you can buy from Linear directly from their website and their prices are competitive.