UCC28950: DELAB and DELCD resistance calculations

mehmet özdemir

Part Number: UCC28950

Tool/software:

Hello ,

While performing DELAB and DELCD resistance calculations, what changes in these resistance calculations if the ADEL and ADELEF pins are short-circuited with GND? The calculations made in the SLUA560 document were made for the use of the "adaptive delay" function, but my circuit works very noisy in this function, so I short-circuited the ADEL and ADELEF pins with gnd.

Also do you think connecting these units with a slightly higher resistance than required will cause a regulation problem in the output voltage?

Regards

over 1 year ago

0 Mike O' over 1 year ago

TI__Guru* 86266 points

Hello,

Your inquiry is under review and I will get back to you shortly.

Regards,

0 Mike O' over 1 year ago in reply to Mike O'

TI__Guru* 86266 points

Hello,

Application note SLUA560 uses a fixed delay approach.

If you short ADEL and ADELF pins to ground the delay equation that has CS*Kx becomes 0 in the delay equations.

The turn on delays are set to achieve ZVS. If they are the same value it should not have affect on duty cycle.

Regards,

0 mehmet özdemir over 1 year ago in reply to Mike O'

Prodigy 120 points

Hello,

Shortening the ADEL and ADELF pins to ground allows the system to work smoothly, but are there any disadvantages and situations that I should pay attention to?

For example, is there something I should pay attention to in light -load studies?

Regards,

0 mehmet özdemir over 1 year ago in reply to mehmet özdemir

Prodigy 120 points

in addition, should it be written 0 instead of "Vadel" in the equation given below ?

0 mehmet özdemir over 1 year ago in reply to mehmet özdemir

Prodigy 120 points

In the calculation made in the above cases, the DELAB and DELCD value turns out to be around 3 kOhm, which is an inappropriate value "it should be at least 13k" what do you recommend to me in this case ?

0 Mike O' over 1 year ago in reply to mehmet özdemir

TI__Guru* 86266 points

Hello,

Your inquiry is under review and I will get back to you shortly.

Regards,

0 Mike O' over 1 year ago in reply to mehmet özdemir

TI__Guru* 86266 points

Hello,

The app note used a voltage divider to set RDELAB and RDELCB so VADEL should not be 0 V.

0 Mike O' over 1 year ago in reply to Mike O'

TI__Guru* 86266 points

Hello,

In regards to RDELAB and RDELCB being too small a value. Try adjusting the ADEL voltage to increase the size of RDELAB and RDELCB so it is 13 k ohms or greater.

Regards,

0 mehmet özdemir over 1 year ago in reply to Mike O'

Prodigy 120 points

Hello,

What is the voltage of the "Vadel" pin if the ADEL and ADELF pins are shortened to ground?

Regards,

0 Mike O' over 1 year ago in reply to mehmet özdemir

TI__Guru* 86266 points

Hello,

If you shorted them to ground and the delay you need requires a resistor to < 13 k ohms. You cannot use that setting.

You can use the voltage divider from VREF to ADEL to set the timing. This will allow you to use larger resistors than would have been achievable by tying ADEL to ground.

Regards,