PCB with current Limiter Circuit

Hello,

I am designing one PCB with comparator (LMH6629). In this I need to add one current limiting part(which should reduce 18 mA to 12 mA). Can I add FET at my output side? or which is suitable for this? but there should not be a voltage drop.

There's no FET current limiter without (any) voltage drop. To achieve this, you need to limit the current with an active negative feedback control circuit.

Thanks for your response.

My output signal should be( 2V to 0.6V) Square pulse and the current should br less than 12 mA How can I achieve this?

Hi,

your information is not complete, therefore it is imossible to answer.

As said: there is no current limiter without voltage limitiation.
You can´t have a 2V signal without voltage drop, but current limited to 12mA.

Maybe it´s better to tell us what´s the use of your circuit.
Supply voltages, output voltage_range_low, output voltage_range_high, frequency, load (range) and so on.

Klaus

Hi,

I need to design the PCB (comparator ckt).The output of this board is connected to the Daughter card of FPGA board.
The I/O standard of the daughter card pin is LVCMOS25. Single ended 50 ohm termination

As per the daughter card details, the current should not exceed 12mA, based on this I need to design the board.

Input : 0V to 2V
Output: (2V-0.6V)
output voltage_range_low: 0.6V
output voltage_range_high: 2V
Comparator: LMH6629
Supply voltage of comparator: 2.9V
Termination:50 ohm

Hi,

There´s something wrong with your specification:

*****
You said: "comparator (LMH6629)"
But this is no comparator, it is an amplifier.
--> If you want a comparator, then use a comparator. If you want an amplifier, then use an amplifier.
Using an amplifier as a comparator has it´s drawbacks, because it is not designed for this.
There are already threads about this topic.
*****

Please use Ohm´s law:

you said:
* 12mA limit
* 50 Ohms termination
* Output_voltage_high: 2V

This is not possible:
12mA into an 50Ohms load will give just 600mV, impossible to get about 2V.

--> review your specifications

***
Supply voltage: 2.9V
--> single: 0V/2.9V or dual +/-2.9V?

Give correct and complete specifications. Best is to give the datasheets. And a schematic.

Don´t make the thread more lengthy than necessary.

Klaus