LMC6062: Current generator

CLAVERIE Alain

Intellectual 410 points

Part Number: LMC6062

Following my first request on current generator with LM6062 I come back after a long .."COVID" period

As proposed i increase the current of generator by reducing R100 to 68koms instead of 91K

I alsol increase currnt throug the relay wich pwr the LM and adujust it ton 10MA

All that inmprove the bad start up of my current generator

BUT the problem is still present (about 1 start up fail on 20 )

Any more ideas ?

Or do you have any other module or schematic to propose to me the aim in test 300 K resistor with maximum DDP of 13 V at resistor sides

Thanks for all

over 4 years ago

0 kai klaas69 over 4 years ago

Guru 140200 points

Bonjour Alain,

can you please show your schematic?

Kai

0 CLAVERIE Alain over 4 years ago in reply to kai klaas69

Intellectual 410 points

Bonjour

Thanks for your answer

My mail is re open on my original post you can find here with all informations

***e2e.ti.com/support/amplifiers/f/14/t/887964***

Add https: before and realease **

because link is not working here

if problem contact me I will repost my schematic

Thanks

0 Marek Lis over 4 years ago in reply to CLAVERIE Alain

TI__Guru 62290 points

Did you try to solder relay connection to see if contact is the issue as Kai suggested in previous post - see below.

" many relais cannot switch ultra small currents but need a minimum current. For switching 27µA you should choose a relay suited for so called "dry switching". This is a relais with gold covered contacts and which is filled with an inert gas.

To see whether the relais contacts are the issue here, just remove the relais and have solder connections instead."

0 CLAVERIE Alain over 4 years ago in reply to Marek Lis

Intellectual 410 points

Hi and tanks for your answer

I've not tested the CC of the relay BUT regarding the answer I have increase the current through the relay by adding a resistor on C115 (the 15 V for the LM6062)

and I have a 10 mA of current through the relay ..

As told I've less problem with this solution AND current value adjust to 2./5V/68Kohms

But always about 1 on 20 bad start ..

Regards

0 Marek Lis over 4 years ago in reply to CLAVERIE Alain

TI__Guru 62290 points

This circuit configuration has two solutions: the one you want (see Fig 1) and another one, with VF1~0, you don't want (see in Fig 2). Since micro-power op amps, like LMV6062, may have a problem starting up in Howland current pump type configuration (with a positve feedback), please add a cap, C1, between the Vcc and Vout so as you turn-on Vcc supply, it will help the circuit to converge on the desired state instead of zero output solution - see below.