A Keystone 2 EVM Board for TI - K2EVM-HK

Hi,

1. TLV1117-33CDCY used to generate VCC3V3_MP_ALT.Here Vin is 12V. But as per the datasheet of the TLV1117 part, Vin has to be 4.75 V to 10 V for a 3.3V output. can someone clarify ?

As I see in TLV1117 Datasheet (www.ti.com/.../tlv1117.pdf) the input voltage can be between 4.7 and 15V. So the EVM is on feeding it with 12V.

2. 3.3V – VDD33 (1A? it is mentioned as TBD in EVM) powering the DVDD of the SOC is generated using UCD7242 device and VCC3V3_Aux (2.57A) – used by other peripherals is generated using TPS54620 device. Is there any reason to generate separately? Is it just for isolation?

VDDA33 is used for USB I/Os. Not sure what are the considerations here... perhaps to match their power consumption model.

3. 0.75V generated using LDOàI see 2 ICs used to generate 0.75V for DIMMs and Discrete ICs. Total current consumption on VTT(including DIMM and Discrete ICs) would not exceed 3A in total. Do we really need to have two ICs to generate the same?

Again not sure what their power consumption spreadsheet showed. The TPS51200 can support maximum of 4.5 A at the output rail. If they calculated more, based on the DIMM & DDR datasheets than this is the reason for using two ICs. 

4. 1.5V for DDR- consumption is 6A (3A for DIMM + 3A For DDR IC), But why is it designed for 12A?

I've asked the design team to elaborate here.

5. How is the loop compensation controlled for the PWM controller(UCD9244) + Power stage (UCD74120)?

Have a look at page 41 of 66AK2H12 EVM (K2HEVM) schematics. Also see the UCD9244 Datasheet:

  TYPICAL APPLICATION SCHEMATIC

6. UCD7242- output inductor is chosen to be 0.47uF (17.5A) while the requirement is 5A. Is there any reason for it?

The output inductor should be calculated as given in the UCD7242 Datasheet. See the INDUCTOR SELECTION section.

7. UCD74120 sourcing the CVDD DSP+ARM coreà How is the output inductor decided? What is the inductor ripple current? Also the output is a variable voltage between 1.8V to 1V- how is this controlled/ programmed?

The following threads will provide some information on this:
 

Best Regards,
Yordan

Vidhya,

Note that the EVM design pre-dated the earliest 66AK2H14 samples.  Early samples often draw far more current than production devices.  Once the silicon fabrication process has been tuned, the current draw is less.  You need to use the power estimation spreadsheet to determine the required power solution.  The EVM created later for the 66AK2E05 showcases a more cost-effective power solution.  Please refer to the documentation for the individual power devices to implement them properly.

Tom

The K2E EVM design documentation is available at: .

Tom

Vidhya,

Please refer to the other E2E threads linked by Yordan a few weeks back.  They provide more detail on the questions and concerns that you have.

The ARM and DSP AVS core supplies (CVDD) are combined on the TCI6638K2K and on the 66AK2H14.  (These are similar parts with different features.)  The fixed core supplies CVDDT also associate with the ARM and DSP portions of the chip.

I was not aware that the UCD9244 was now NRND.  This decision was made by the power supply product team independent of us.  I expect that it will be available long term but the NRND indication means that detailed support for new designs is not available.  Based on this I would recommend that you use the design implemented on the K2E EVM as discussed above.  Please refer to the Generating AVS SmartReflex Core Voltage, PMBus for K2E Using TPS544C25 & LM10011 Reference Design TI Design.  This is equally applicable to the digital design solution implemented on the TCI6638K2K EVM.

Tom

Vidhya,

What is the problem with the single PowerGood output from the TPS65400?  The TPS65400 is a good part for this design.  Alternately, TI has a large selection of devices that can be implemented individually.  You should follow-up on the power forum for generic support.

Proper power supply turn-on sequencing is a requirement.  You also need to monitor for power supply failures to prevent damage to the processor.  The UCD9090 is a good choice for this sequence and monitoring solution.  However, this can be implemented individually with supervisor devices like the TPS3808 or using discrete or programmable logic or by using a microcontroller.  All of these are valid solutions.

The attached document provides some additional solution options and details.

Tom

5582.TI Analog Solutions for Keystone2 Family.pdf

Vidhya,

Actually, it is rated "Pb-Free (RoHS Exempt)".  There are multiple terms related to the environmental rating.

I am not aware of a drop-in replacement but one may exist.  You should follow the guidance under the "Quality and Packaging" tab and the "View" link.  It recommends that you discuss this with your sales contact.  You can also post on the power supply forums for more assistance.

Tom

Vidhya,

This is a thermal system design question.  The TPS544C25 is rated for 30A.  It can operate at loads up to 30A.  However, at higher current levels, the device will dissipate more heat.  This heat must be managed to prevent the device from overheating.  If you cannot conduct the heat away, then the device cannot operate at 30A.  Please see the temperature versus current derating curves on page 15 of the datasheet.

The TI power devices that contain internal FET power transistors will all need to be thermally controlled since they provide small packages resulting in higher power density.  If you design must operate at high power levels without sufficient thermal mitigation, then the design must change to a lower density power solution that meets the current requirements.  TI has a range of Buck power supply controllers that drive external FETs.  This provides more flexibility for thermal management but requires more components and design analysis.  The TPS40322 is a possible device for this solution.  It can be implemented in a dual-phase, single-output configuration that can provide the required 30A in a solution that distributes the heat among several FETs and results in a design that can operate at much higher ambient temperatures.  Please contact the power forum for detailed device selection and implementation support on this family for devices.

Tom

Vidya,

This thread is closed.  Please open a new thread.

Tom