George Lakkas
As my colleague Yann said in an earlier technical article, there is a growing shortage of multilayer ceramic capacitors (MLCCs), and the situation is likely to persist through 2020. MLCCs are used in almost every type of electronic equipment, due to their reliability and small footprint.
Manufacturers are now looking to replace ceramic capacitors with polymer or other capacitor types. TI D-CAP+™ control mode multiphase controllers, converters and modules (like the TPSM831D31) can help hardware designers reduce the MLCC count on their motherboard versus competitive solutions.
D-CAP+ control mode is a TI proprietary pulse-width modulation controller and converter control architecture that enables very easy loop compensation and excellent loop stability in the presence of varying conditions such as input voltage and the number of phases.
It is a current-mode constant on-time control that uses a true inductor current-sense implementation rather than the injected or emulated ripple current schemes used in the D-CAP2™ and D-CAP3™ control topologies. The D-CAP+ control mode has fixed on-time in steady state and adaptive off-time during load transient conditions (AC response), in which the off time is adjusted and more pulses are generated (pulled in) to respond quickly to load transients and maintain the output voltage in regulation.
Since the on-time is regulated, there’s a natural period stretching in discontinuous conduction mode (DCM), producing higher efficiency and smooth control when crossing the continuous conduction mode and DCM boundary. D-CAP+ control mode is extremely easy to compensate and does not require the complex type-3 compensation circuits required in voltage-mode control architectures. For more information on D-CAP+ control mode, see the 2014 Power Supply Design Seminar paper, “Choosing the Right Variable Frequency Bulk Regulator Control Strategy”
Because D-CAP+ control mode can respond much faster to a processor/application-specific integrated circuit/field-programmable gate array load transient than a fixed-frequency control architecture, it can meet tight tolerance specifications without the number of MLCCs that you would otherwise need for discharging or charging to provide the required energy to the load.
Figure 1 compares a TI voltage-mode controller vs. a D-CAP+ controller during such a load transient. The TPS53647 D-CAP+ control-mode controller has lower overshoot and undershoot, despite having a lower crossover frequency.
The results are similar when making comparisons to competing multiphase controllers with non-D-CAP+ control. Figure 2 compares a 60-A load step from 180 A to 240 A at a 1-kHz load transient repetition rate. The D-CAP+ controller, again, results in lower overshoot and undershoot. These results were replicated on the same motherboard under the exact same conditions. The TPS53681 D-CAP+ controller can achieve better load transient response and faster output voltage settling.
As a final example, let’s compare a central processing unit (CPU) vendor’s reference design to our own Vcore design. The thermal design current (TDC) was 116 A, while the maximum current (IMAX) was 395 A.
The test data shows that the D-CAP+ controller enables a faster load transient response, which translates to significant MLCC savings vs. the CPU vendor reference design.
Figure 3 summarizes the results. The D-CAP+ control solution still meets the CPU overshoot and undershoot specifications while eliminating 42 MLCCs and >700 µF of output capacitance. The Figure 3 comparison is applicable to any D-CAP+ control-mode voltage regulator vs. competing regulators.
MLCC shortages are not going away anytime soon. If you want to reduce the MLCC count in your design bill of materials so that you can get new projects to market faster, consider using TI’s D-CAP+ controllers, converters and modules.
TI PROVIDES TECHNICAL AND RELIABILITY DATA (INCLUDING DATASHEETS), DESIGN RESOURCES (INCLUDING REFERENCE DESIGNS), APPLICATION OR OTHER DESIGN ADVICE, WEB TOOLS, SAFETY INFORMATION, AND OTHER RESOURCES “AS IS” AND WITH ALL FAULTS, AND DISCLAIMS ALL WARRANTIES, EXPRESS AND IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD PARTY INTELLECTUAL PROPERTY RIGHTS.
These resources are intended for skilled developers designing with TI products. You are solely responsible for (1) selecting the appropriate TI products for your application, (2) designing, validating and testing your application, and (3) ensuring your application meets applicable standards, and any other safety, security, or other requirements. These resources are subject to change without notice. TI grants you permission to use these resources only for development of an application that uses the TI products described in the resource. Other reproduction and display of these resources is prohibited. No license is granted to any other TI intellectual property right or to any third party intellectual property right. TI disclaims responsibility for, and you will fully indemnify TI and its representatives against, any claims, damages, costs, losses, and liabilities arising out of your use of these resources.
TI’s products are provided subject to TI’s Terms of Sale (www.ti.com/legal/termsofsale.html) or other applicable terms available either on ti.com or provided in conjunction with such TI products. TI’s provision of these resources does not expand or otherwise alter TI’s applicable warranties or warranty disclaimers for TI products.
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2023, Texas Instruments Incorporated