H Bridge Driver Design

ikon

Other Parts Discussed in Thread: DRV8412

Hi Support,

I am designing a H bridge driver for a dual channel LEDs but am stuck with a dead band design to prevent short circuit at the MOSFET side when the PWM changes its states.

The problem with this design is that at the transition from High to Low or Low to High from the PWM, there might be a situation that both P and N MOSFET will turn ON thus causing SHORT.

Could you advise how to overcome this?

Thanks.

over 6 years ago

0 Rick Duncan over 6 years ago

TI__Guru** 114905 points

Hi ikon,

Using a "break before make" circuit prevents the possibility of shoot-through. There are many motor driver H-bridge devices that have this feature integrated.

What is the current and input PWM frequency desired? How many LED channels?

0 ikon over 6 years ago in reply to Rick Duncan

Genius 5355 points

Hi Rick,

Max Current input: 4A per channel, each channel will have 3 or 7 LEDs
Frequency of PWM : 15.625Khz (Default)
Resolution of PWM 256 step:

smallest pulse width: 64usec

Thanks.

0 Rick Duncan over 6 years ago in reply to ikon

TI__Guru** 114905 points

Hi ikon,

The smallest pulse width 64us is 100% of frequency of PWM (15.265kHz.

Can you explain:
What is the smallest high pulse?
Is the PWM frequency fixed at 15.625kHz?
Does the PWM pulse width change by 250ns?

0 ikon over 6 years ago in reply to Rick Duncan

Genius 5355 points

Hi Rick,

The smallest pulse width is 250nsec.

Yes, is fixed at 15.625khz.

Thanks.

0 Rick Duncan over 6 years ago in reply to ikon

TI__Guru** 114905 points

Hi ikon,

The DRV8412 and DRV8432 are the closest match in the motor drive portfolio.

These devices have fast response time so the 250ns pulse width can be met.
The devices cannot operate at 100% duty cycle. It is recommended to turn on the low side FET for at least 50ns for each PWM cycle. (section 7.3.2.1 of the datasheet).

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H Bridge Driver Design