LMG1210: Voltage shift for +/- power supply on the bridge.

Federico Aghemo

Part Number: LMG1210

Hello,

I want to use the LMG1210 with a non-symmetrical power supply as shown in the attached figure. As I understood reading a related post, in this setup, is it necessary to supply two isolated 5V DCDCs to HB-HS and VDD-VSS? Also, how should I connect the heatsink pads? both to GND as shown in the figure, or connected to HS and VSS to each thermal pad? And finally, is it correct to remove the boostrap diode D1?

Is there anything else I need to consider?

Thanks in advance.

over 3 years ago

0 Mamadou Diallo over 3 years ago

TI__Genius 13445 points

Hello,

You may use a floating supply on HB_HS to maintain the C1 voltage above the UVLO threshold in order to charge the high-side gate if you want to accomplish high duty cycle operation.

For the low-side, you do not need an isolated supply as powering VDD will be enough to charge the low-side gate.

You may connect the pads as shown on the EVM schematic below.

https://www.ti.com/lit/ug/snvu572/snvu572.pdf?ts=1620777580530&ref_url=https%253A%252F%252Fwww.google.com%252F

Regards,

-Mamadou

0 Federico Aghemo over 3 years ago in reply to Mamadou Diallo

Prodigy 10 points

Hello Mamadou,

Thank you very much for your answer, this clarifies how the circuit should be. However, I don´t understand some details of the thermal pads, if vss = -35V, I cannot configure the IC as EVM because in the schematic VSS = GND=PGND.

1. I guess I need to tie the VSS pin and the source pin of the low side mosfet to -35V rail.

2. Using this configuration, is LS_DAP (thermal pad) still connected to GND?

I hope to be clear on my doubt.

Kindest regards,

Federico

0 Richard Herring over 3 years ago in reply to Federico Aghemo

TI__Mastermind 20950 points

Hello Federico,

Mamadou is out of the office for the moment, he should respond to your question shortly.

Regards,

0 Mamadou Diallo over 3 years ago in reply to Richard Herring

TI__Genius 13445 points

Hi Federico,

The VSS should be tied to low-side source preferably through a kelvin connection.

The daps (LS and HS) should be connected to its respective grounds i.e VSS and HS according to the d/s pin descriptions.

Why do you need the -35V rail, keep in mind regardless of the operating conditions, the signals on the pins should be within the abs max specified to prevent damage.

I suggest you verify that IN_VSS and all the low-side signals do in fact respect the recommended operating conditions.

Regards,

-Mamadou

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LMG1210: Voltage shift for +/- power supply on the bridge.