LM119QML: lm119

Hello Paul,

Thank you for your excellent reply.

I plan to connect the LM119 to a UC1710 gate driver to switch a FET with a VTH of approximately 2.5V and an input capacitance of 1.6 nF. Do you envisage any issues?

What is the power consumption of the LM119 and the UC1710?

Kind Regards,

Rajan. 

Rajan

I don't see any particular problem with what you are proposing and I would need to refer you to the supply current specifications in the datasheet for help on power consumption.  I presume you are asking about the current when the output is toggling at 400kHz which will elevate somewhat on the UC1710 having to charge and discharge the 1.6nF gate capacitance. 

Does your application require a space grade solution?  I was wondering because we have a comparator that may be sufficient for driving the FET directly called the TLV1805.  It is specified for driving a 4nF capacitive load but we only have an industrial and automotive rating on this device.

Chuck

Rajan

there has been so follow up responses on this thread, so I will be closing it out.

If you have any additional questions, please reply or open a new thread.

Thanks

Chuck

Hi Chuck,

How much current can the UC1710 sink from the FET's gate?

Kind Regrds,

Rajan

Hello Rajan,

UC1710 is a 6-A/6-A single-channel gate driver with 5-V UVLO and split ground. Let me know if you have any further questions.

Wei

I plan to connect the LM119 to a UC1710 gate driver to switch a FET with a VTH of approximately 2.5V and an input capacitance of 1.6 nF. Can I power the LM119 (used as a comparator) using a single 5V supply?

thank you

Rajan

Hello,

The UC1710 gate driver datasheet does not contain any application information regarding using or connecting the device.

How should the single-ended output from a LM911 connect to the differential input of the UC1710?

Thank you and kind regards,

Rajan.

Hello Rajan,

This driver is one of legacy devices therefore some of the IC's parameters may not be readily available. Maybe I can interest in our latest most optimized drivers likey UCC27511 and/or UCC27517 if the split ground is not a requirement in your application.

To drive the UC1710 with the LM119, you may connect the output of the comparator to the non-inverting input of the UC1710 and tie the inverting input to the logic GND.

Regards,

-Mamadou

what is the slew rate of the lm119 and does a SPICE model exist?

If I connect the lm119 to the  UC1710, where do I connect the latter's VC pin?

thank you

Rajan

Hello Rajan,

We do not have a model for the LM119. There is a model for the similar LM111-N single, but some specs are different.

The LM119 can be used on a single 5V supply, but the input is not ground-sensing and has a limited input range. It is really designed for high-voltage split supplies.

With a single 5V supply, the legal input range is 1V to 3V. Operating outside that range will cause increased prop delay or false outputs.

Is there a particular reason you need the LM119? Speed? There are better devices for low voltage. The LM193QML dual can have a similar speed when driven with large input voltages and has ground-sensing inputs (0 to 3V).

The fall-time is not specified, but seems to be around 30ns @ 5V, and the rise time is dependent on the pull-up resistor value and load capacitance.

Can you please provide a schematic or block diagram of what you are trying to accomplish?

Paul,

Thank you very much, I wasn't aware of the LM193 and will use it if this is better for 5V single-rail operation.

I need one comparator to generate a 400 kHz square wave and the other will drive a UC1710 with a PWM signal which in turn will drive a FET.

Can I use the LM193 for both these purposes. It is a tragedy that you do not offer SPICE models, how are we expected to verify before building?

Kind Regards,

Rajan

Mamadou,

I need a space-grade driver, I see you also offer the 1705, 1707, 1708 and 1709 devices.

What's the difference between these and the 1710 part?

Kind Regards,

Rajan

Mamadou,

Will an external resistor be required between the gate driver and the input to the FET?

Kind Regards,

Rajan.

I'm happy to consider the lm193 instead of lm119, however, the latter can source 25 mA while the former only 16 mA.

This means that the lm119 will take less time to charge a fet for example

what do you think?

The output sink current of the LM119 is slightly higher so it will be able to discharge a FET faster.  The charge time is set by the pullup resistor.  This can be slightly more aggressive (smaller value) for the LM119 since its saturation level is greater.  So the charge time can also be slightly faster.

You can use the model of the LM2903B for the LM193 because it has nearly identical performance to the LM193 if you want to simulate.  Unfortunately I do not believe there is a model for the LM119.

Chuck

Rajan,

In that case, please disregard those drivers. 

Regards,

-Mamadou

however, if lm193 is better with single 5V rail, I would prefer the lm193, why is lm193 is better for +5V?

I will use gate driver uc1710 between the comparator and fet

the fet has a capacitive load of 660 pF, a Qg of 22 nC and the switching frequency is 400 kHz, do you think i need a gate driver with the above comparators?

It still is probably preferred to use a gate driver since the both comparators being considered have open-collector output stages.  Ideally you would need a comparator with a push-pull output stage so your charge and discharge of the gate capacitance is symmetrical.  With the open collector outputs of the LM193 and LM119, charging the cap load will be slower than discharging.

The LM119 input range is limited on both the positive and negative side.  For a 5V single supply, the min input voltage is 1V and the max is 3V while the LM193 input range includes ground (0V) to 3V (VCC-2).  So it really depends on what is driving the inputs of the comparator.

Chuck