SLPA020 May 2022 CSD13201W10 , CSD13202Q2 , CSD13302W , CSD13303W1015 , CSD13306W , CSD13380F3 , CSD13381F4 , CSD13383F4 , CSD13385F5 , CSD15380F3 , CSD15571Q2 , CSD16301Q2 , CSD16321Q5 , CSD16322Q5 , CSD16323Q3 , CSD16325Q5 , CSD16327Q3 , CSD16340Q3 , CSD16342Q5A , CSD16401Q5 , CSD16403Q5A , CSD16404Q5A , CSD16406Q3 , CSD16407Q5 , CSD16408Q5 , CSD16409Q3 , CSD16410Q5A , CSD16411Q3 , CSD16412Q5A , CSD16413Q5A , CSD16414Q5 , CSD16415Q5 , CSD16556Q5B , CSD16570Q5B , CSD17301Q5A , CSD17302Q5A , CSD17303Q5 , CSD17304Q3 , CSD17305Q5A , CSD17306Q5A , CSD17307Q5A , CSD17308Q3 , CSD17309Q3 , CSD17310Q5A , CSD17311Q5 , CSD17312Q5 , CSD17313Q2 , CSD17318Q2 , CSD17322Q5A , CSD17327Q5A , CSD17381F4 , CSD17382F4 , CSD17483F4 , CSD17484F4 , CSD17501Q5A , CSD17505Q5A , CSD17506Q5A , CSD17507Q5A , CSD17510Q5A , CSD17522Q5A , CSD17527Q5A , CSD17551Q3A , CSD17551Q5A , CSD17552Q3A , CSD17552Q5A , CSD17553Q5A , CSD17555Q5A , CSD17556Q5B , CSD17559Q5 , CSD17570Q5B , CSD17571Q2 , CSD17573Q5B , CSD17575Q3 , CSD17576Q5B , CSD17577Q3A , CSD17577Q5A , CSD17578Q3A , CSD17578Q5A , CSD17579Q3A , CSD17579Q5A , CSD17581Q3A , CSD17581Q5A , CSD17585F5 , CSD18501Q5A , CSD18502KCS , CSD18502Q5B , CSD18503KCS , CSD18503Q5A , CSD18504KCS , CSD18504Q5A , CSD18509Q5B , CSD18510KCS , CSD18510KTT , CSD18510Q5B , CSD18511KCS , CSD18511KTT , CSD18511Q5A , CSD18512Q5B , CSD18513Q5A , CSD18514Q5A , CSD18531Q5A , CSD18532KCS , CSD18532NQ5B , CSD18532Q5B , CSD18533KCS , CSD18533Q5A , CSD18534KCS , CSD18534Q5A , CSD18535KCS , CSD18535KTT , CSD18536KCS , CSD18536KTT , CSD18537NKCS , CSD18537NQ5A , CSD18540Q5B , CSD18541F5 , CSD18542KCS , CSD18542KTT , CSD18543Q3A , CSD18563Q5A , CSD19501KCS , CSD19502Q5B , CSD19503KCS , CSD19505KCS , CSD19505KTT , CSD19506KCS , CSD19506KTT , CSD19531KCS , CSD19531Q5A , CSD19532KTT , CSD19532Q5B , CSD19533KCS , CSD19533Q5A , CSD19534KCS , CSD19534Q5A , CSD19535KCS , CSD19535KTT , CSD19536KCS , CSD19536KTT , CSD19537Q3 , CSD19538Q2 , CSD19538Q3A , CSD22202W15 , CSD22204W , CSD22205L , CSD22206W , CSD23202W10 , CSD23203W , CSD23280F3 , CSD23285F5 , CSD23381F4 , CSD23382F4 , CSD25202W15 , CSD25211W1015 , CSD25213W10 , CSD25304W1015 , CSD25310Q2 , CSD25402Q3A , CSD25404Q3 , CSD25480F3 , CSD25481F4 , CSD25483F4 , CSD25484F4 , CSD25485F5 , CSD25501F3 , CSD75207W15 , CSD75208W1015 , CSD83325L , CSD85301Q2 , CSD85302L , CSD85312Q3E , CSD86311W1723 , CSD86330Q3D , CSD86336Q3D , CSD86350Q5D , CSD86356Q5D , CSD86360Q5D , CSD87312Q3E , CSD87313DMS , CSD87330Q3D , CSD87331Q3D , CSD87333Q3D , CSD87334Q3D , CSD87335Q3D , CSD87350Q5D , CSD87351Q5D , CSD87351ZQ5D , CSD87352Q5D , CSD87353Q5D , CSD87355Q5D , CSD87381P , CSD87384M , CSD87501L , CSD87502Q2 , CSD87503Q3E , CSD87588N , CSD88537ND , CSD88539ND , CSD88584Q5DC , CSD88599Q5DC
Paralleling power metal-oxide semiconductor field-effect transistors (MOSFETs) is a common way to reduce conduction losses and spread power dissipation over multiple devices to limit the maximum junction temperature. This application brief shares best practices and examples of paralleling power MOSFETs in various applications.
First, consider static operation with two FETs operating in parallel, as shown in Figure 1-2.
The current in each FET is proportional to the inverse of its on resistance, RDS(on). Naturally, the device with the lowest RDS(on) will carry more current. As it heats up, its RDS(on) increases, shifting some of the current to the other FETs. The junction temperatures of paralleled FETs with good thermal coupling will be roughly the same. Current sharing still depends on the relative on-resistance of each FET and will be within the RDS(on) tolerances specified in the MOSFET data sheet.
During dynamic operation, the FET with the lowest threshold voltage, VGS(th), turns on first and turns off last. This FET takes more of the switching losses and sees higher stresses during switching transitions. To some extent, the thermal sharing effect balances out the switching and conduction losses, and the FETs will operate at roughly the same temperature.
Here are helpful tips when using FETs in parallel:
Figure 1-3 shows a partial schematic and picture of the TPS2482 hot-swap evaluation module (EVM).
![]() |
As you can see in Figure 1-4, the TPS2482 EVM uses two CSD18501Q5A MOSFETs in parallel. The schematic shows how each FET has a 10-Ω gate resistor; the Zener diode is on the gate-driver output before the gate resistors. The FETs are placed close together on the same copper shape and use vias for good thermal coupling to spread the heat.
The next example, shown in Figure 1-4, is from the 18 V/1 kW, 160A Peak, >98% Efficient, High Power Density Brushless Motor Drive Reference Design.
![]() |
This reference design uses two CSD88584Q5DC power MOSFETs in parallel per phase. Attaching the MOSFETs to the same heat sink for good thermal coupling helps remove the heat through the top side of the package. The design includes individual 3.3-Ω gate resistors for each FET in the power block.
The final example, shown in Figure 1-5 is from the 48-VDC Battery Powered 5-kW Inverter Power Stage Reference Design for Forklift AC Traction Motor.
![]() |
This reference design uses five CSD19536KTT power MOSFETs in parallel for the high- and low-side switches in each phase. The FETs are mounted on an insulated metal substrate for cooling and good thermal coupling between devices. Each FET has an 8.2-Ω gate resistor.
Because of their inherent current- and thermal-sharing properties, paralleling MOSFETs can reduce conduction losses and limit their maximum junction temperature. Operating power MOSFETs in parallel can help solve the problems discussed in this article, but at a higher component count and cost, and a larger PCB area. If possible, use a single FET; if you cannot, carefully consider the design and layout of parallel FETs in your application to ensure success.
Check out the following technical articles:
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 © 2022, Texas Instruments Incorporated