TPS53667EVM-769: TPS53667EVM-769

Hello na, 

Thanks for posting on the E2E forum. I'm looking at your post, and this will take me a little time to get a response together. I'll reply here in 24 hours. 

Kind regards,

Nick Z

• 1、 the ones given in fusion designer determine the ramp value
• 2 、I give the wrong information. Multiple experiment results show that vcomp changes as the load current varies.
• 3、 The experimental waveforms under different working conditions show that the value of Visum is always lower than the value of the Pin COMP (for example fig.5), which is inconsistent with the information provided in the datasheet(fig.6).
• 4、 Another question is what is the relationship between the vcomp and the pin COMP in the fig. 7 ? Shouldn't they be equal?
• 5、can you provide more accurate waveforms of several input signals of the modulator (The part marked in red in fi.8) and a more accurate schematic diagram than fig. 6?Thanks very much! Have a nice day!

48 hours passed and there is still no response.

TPS53667EVM-769: TPS53667EVM-769 - Power management forum - Power management - TI E2E support forums

Hi Na, 

Thanks for your patience, apologies for the delay. 

1. Glad you found the result here. The table table included in the datasheet indicates some recommendations, however the register is there for some fine-tuning. 

2. This behaviour is expected. Higher load currents will cause more droop, leading to VCOMP to change as well.

3. What pins are you measuring for this oscilloscope screenshot? I presume the waveform for "VISUM" is actually ISUM, and the waveform labelled "VCOMP" is measuring the COMP pin?

4. COMP and VCOMP are not the same thing. Please note that these block diagrams are functional representations-- much more is happening inside the device, as you can see VCOMP is used in several blocks of the controller's internal functions, including USR/OSR, PWM generation, and control loop. Please note that COMP pin will not equal VCOMP voltage, but VCOMP is used when determining what voltage should be output through the COMP pin. This table is in 6.5 Electrical Characteristics of the datasheet:

5. Inner device rails such as VISUMA and VRAMPP and N are inside the controller, there is no reasonable way to capture these signals, nor are they necessary for getting TPS53667 up and running. I cannot provide deeper schematics to the device, either. 

Kind regards,
Nick Z

Hi Nick,

Thanks for your reply.

2. What is the difference between LL(Loadline) and Droop,shown in the following? I can choose zero load-line in the fusion designer. Is there another register or other position to turn off the Droop function?

3. Yes. The following diagram describes the relationship more clearly:

4. Is there a clear relationship between COMP and VCOMP? I cannot get relevant information from the table you mentioned.

5. I use the TPS53667 to verify the small signal of the loop gain and the output impedance, not just to get it running.  

Thanks again!

Best regards

Hi Na, 

2. Some droop will be inherent in the system as load increases, the LL feature reduces the voltage setpoint ("adding" droop) to provide extra margin to avoid overshoot when the load releases. Another benefit is reducing total system power consumption. I've attached a couple figures that better explain the functionality of zero LL versus non-zero LL: 

3 + 4. VCOMP and COMP are not the same thing. Yes, VCOMP does feed into the COMP pin, but the other signals are also incorporated, such as VDAC and VFB_DRP. 
Still looking to understand your scope, is the yellow waveform is the PWM? I encourage you to observe PWM and V_ISUM when the system is under load. PWM would only go high when the zero crossing of ISUM and VCOMP+VRAMP has been detected. I want to emphasize this is fundamental operation of the control topology of the device.

Kind regards,
Nick Z

The answer is useless and wastes everyone's time, you, me and others who read this thread. Don't beat around the bush - get to the point!