EVAL6498L gate driving board

[Lello]

Hi there,

I am using EVAL6498L to test a boost converter having one switch and one diode.

I was wondering if I can use a synchronous rectifier in my boost converter, in other words if it is possible to control both switches (one high side switch and one low side switch), using EVAL6498L.

From the schematic I have found in the datasheet of 6498L gate driver, it seems that the 6498L IC is made on-purpose to control a high-side and a low-side switch in the same switching leg.

 

However, what I am not sure about is the connections on the "From Controller" on the left side of the drawing. In particular,

1) if I provide a PWM from a microcontroller which has one ground reference, connected to SGND, do I need to galvanically isolate the top PWM going to the gate driver? (i.e. does the PWM signal going to HIN need to be galvanically isolated? - that is not referenced to SGND)

2) I am a bit confused about SGND and PGND, I understand that these are signal and power ground, where the signal ground is connected to the microcontroller ground. The power ground is the converter ground. What I would like to clarify is that if these two grounds are connected inside the gate driver? and if not, is the connection of SGND and PGND recommended at all?

Thank you very much

Lello

[Cristiana SCARAMEL · Accepted solution]

Hello @Lello​ welcome back :smiling_face_with_smiling_eyes:

The L6498 outputs (LVG and HVG) cannot be simultaneously driven high due to the integrated interlocking function.

This feature to avoid the power stage cross-conduction.

If you need high voltage gate driver able to turn on both the output, I can suggest the L6395 (lower current capability).

Concerning your questions:

1) The signals coming from controller can be both referred to SGND. The internal level shifter generates the proper signals to drive the high-side floating section.

2) The SGND and PGND is not internally connected. The suggestion is to connect them together on the cold side of the sense resistor, not directly to the device pins.

You can find the suggest PCB layout example in the L6498 datasheet at page 11.

Let me know if I fully answered to you questions.

[Lello]

Hi @Cristiana SCARAMEL​ 

Thank you very much for your answer, it is very helpful. I do not mean to have both switches on at the same time​ (so no need to have LVG and HVG set to high at the same time, but it's good to know that some gate driver can do this).

1) It is great to ​know that I can have two pwm signals, coming from the same controller, one to LIN and one to HIN, with the same ground reference (SGND)

2) I understand that SGND and PGND can be connected at one point, close to the Source terminal of the low side switch. I am just wondering if this connection between the two grounds is needed, or not, for the circuit to work (pretty much I'd like to understand what happens if for instance SGND and PGND are not connected at all, would the circuit get damaged? Or not work properly?)

Thank you again :)

[Cristiana SCARAMEL]

Hi @Lello​ 

concerning to the connection between the two grounds: yes, it is needed.

The circuit would not work without that connection.

Please click on the 'Select as Best' button if my reply fully answered your question.