UCC21750-Q1: I would like to inquire about the delay time of ucc21750

Junehee Park

Part Number: UCC21750-Q1
Other Parts Discussed in Thread: UCC21750

Tool/software:

The UCC21750 Datasheet states that Tpdhl and Tpdlh are max 130ns.
However, when we measured the ucc21750 on the PCB we made, the delay time was 340ns.
What causes the delay time difference?

9 months ago

0 Sean Cashin 9 months ago

TI__Mastermind 23226 points

Hi Junehee,

You have to measure from the input high threshold of 1.85V, not the base of the PWM input. It seems that the 340ns value might include some of the rising RC constant. Also, the output does not rise instantaneously, and propagation delay only measures from when the input passes the threshold until when the output starts to rise. The total turn-on time can be longer, especially if a large external gate resistor is used.

Best regards,

Sean

0 Junehee Park 9 months ago in reply to Sean Cashin

Intellectual 320 points

is it right below point?

VCC 5V, Out H : 20V, Out L : -3V

0 Sean Cashin 9 months ago in reply to Junehee Park

TI__Mastermind 23226 points

Hi Junehee,

This method is much closer. However, the input threshold of this device is 1.85V, not 2.5V, and you should start your propagation delay measurement from 1.85V.

Best regards,

Sean

0 Junehee Park 9 months ago in reply to Sean Cashin

Intellectual 320 points

Does this mean that the threshold is 1.85V regardless of operating voltage?

0 Sean Cashin 9 months ago in reply to Junehee Park

TI__Mastermind 23226 points

Hi Junehee,

That is indeed the case for the UCC21750:

Other devices do have an operating voltage dependency, but not UCC21750.

Best regards,

Sean

Power management

Power management forum

UCC21750-Q1: I would like to inquire about the delay time of ucc21750