Comparing the merits of integrated power modules versus discrete regulators Rich Rosen Field Applications Engineer Texas Instruments Modern integration technologies have brought about improvements to the modular DC DC power module voltage regulator Time to market cost size constraints reliability and design capabilities are among the motivating factors in choosing modular power versus a traditional controller plus external components design Each approach has its advantages and disadvantages And often times it is not possible to predict which choice will better satisfy the list of design criteria until the design process has been completed for each approach What is a modular voltage regulator The basic building blocks of a simple non isolated DC DC switching voltage regulator can be seen in the schematics shown in Figure 1 PWM control current switching inductance and capacitance for storing energy are all required The power module integrates the current switches and inductor while these are separate entities in a discrete design Since the values of the energy storing capacitors tend to be well over 1 f they are integrated less often into a monolithic package How to choose between discrete and modular power Typically the tradeoff is between cost of ownership design effort and performance The cost of ownership is the bill of materials BOM cost in addition to power designer labor fees plus test potential redesign labor fees and finally manufacturing assembly costs Other potential costs can include those associated with quality issues with an improperly designed supply Clearly the design effort behind using a fully integrated power module is less than that of a discrete supply But within the discrete regulator designs available there exists a range of integration For example some regulators have built in FET switches that remove the task of choosing the FETs and gate drive considerations Controller ICs are the most flexible of choices but require a more expert level of design capability Should one decide to tackle a non modular approach they should further investigate how discretely they wish to dive into the design Fortunately there are excellent tools available such as TI s WEBENCH online design tool that allow novice power supply designers to easily assemble discrete supply designs VIN VIN ISWITCH 1 ILOAD VSW VOUT ISWITCH 2 ILOAD VOUT ISWITCH 1 ISWITCH 2 Discrete controller Integrated module Figure 1 DC DC buck regulator integration levels Comparing the merits of integrated power modules versus discrete regulators 2 September 2016 To demonstrate the relative ease of design between the two approaches TI s WEBENCH design tool will be used to design circuits around the LM3152 3 3V SIMPLE SWITCHER controller and LMZ14203 SIMPLE SWITCHER power module The easy to use WEBENCH tool offers too large a complement of design tools to highlight at this time but it can be thoroughly examined online at TI com webench The desired output will focus on the schematic BOM costs component land area of the PCB output noise analysis efficiencies and thermal simulation Schematics and bill of materials Figure 2 shows the discrete design using the LM3152 3 3 V controller This design was accomplished using the WEBENCH tool and took about 30 minutes including a few part changes to optimize for cost savings and some design simulation to verify proper operation Design without the aid of a CAD program might take anywhere from a couple of hours to an entire day for circuit calculations and component searches Integrated modules streamline design and layout challenges but do not completely eliminate the process At a minimum the designer must evaluate the power specifi cation of the design this includes assessing requirements of input and output voltage current allowed temperature rise noise issues safety and emissions and possibly other considerations Even the simplest modular solution is not exempt from careful planning Circuit performance is multifaceted and application dependent Where output noise might be most critical in an RF circuit supply temperature rise and size of the circuit can be the driving specifications in a hearing aid Design example It would be impossible to examine the pros and cons of each approach with all possible values of voltage and current but the following design analysis will expose the benefits and drawbacks of a modular design versus a design with a discrete controller IC for a common set of parameters The design specifications will be the same between the two approaches VIN 24 V VOUT 3 3 V Output current 3 0 A maximum Ambient temperature 55 C 24V CIN 1 f Cbyp 100n CSS 15 nf CVCC 2 2 f 0V U1 EN VIN SS FB NC NC VCC 3 2 6 4 7 8 1 HG BST SW LG DAP SGND SGND SGND 11 12 10 13 15 5 9 14 Cbst 470 f L1 39 H 1 M1 1 M2 3 2 3 2 COUT 47 f Part Cbst Cbyp CIN COUT CSS CVCC L1 M1 M2 U1 Attribute 470 nF 16 V 100 nF 50 V 1 F 50 V 47 F 16 V 15 nF 50 V 2 2 F 10 V 10 H 4 A 80 V 30 m 80 V 30 m LM3152MH 3 3 Total BOM Price 0 02 0 01 0 05 0 41 0 01 0 02 0 54 0 39 0 39 2 30 4 14 3 3V 0V Figure 2 Discrete design LM3152 3 3V controller and bill of materials Comparing the merits of integrated power modules versus discrete regulators 3 September 2016 7 6 4 8 VOUT FB GND EP U1 VIN EN SS RON 1 3 5 2 CSS 10 nf Ron 49 9k CIN 10 F Rent 68 1k Renb 11 8k 24V 0V Rfbt 3 32k Rfbb 1 07k Cf 22 nF COUT 47 F 3 3V 0V Part Cf CIN COUT CSS Renb Rent Rfbb Rfbt Ron U1 Attribute 22 nF 50 V 10 F 50 V 47 F 6 3 V 10 nF 50 V 11 8 K 68 1 K 1 07 K 3 32 K 49 9 K LMZ14203 Price 0 01 0 43 0 18 0 02 0 01 0 01 0 01 0 01 0 01 9 50 Total BOM 10 19 Figure 3 Modular design LMZ14203 integrated power module and bill of materials Figure 3 shows the schematic of the modular design using the LMZ14203 integrated power module With fewer design choices to make and limited opportunities for error the design process is almost instantaneous with the WEBENCH design tool The data sheet provides instruction on choosing the capacitors and resistors The task of searching through catalogs for the FETs and the inductor is eliminated Comparing the BOM cost between the two designs there is clearly a cost benefi t to the discrete design Note that the power module price is based on a 500 piece list price whereas the controller price is based on a 1000 quantity list price All costs shown are generated by the WEBENCH tool and are published catalog prices typically at 1000 unit or cut tape quantities Simplicity of PCB layout Figure 4 shows evaluation boards that