Synchronous DC/DCs eliminate switch-node ringing in automotive applications

June 28, 2016 // By Graham Prophet
These 36-V, 2.1-MHz buck regulators enable designers to meet requirements such as low EMI, high power density and deep drop-out conditions, according to makers Texas Instruments; they eliminate switch-node ringing to reduce electromagnetic interference (EMI), improve power density, and operate in deep drop-out conditions.

The 2.5-A LM53625-Q1 and 3.5-A LM53635-Q1 regulators are designed for high-voltage DC/DC step-down applications such as automotive infotainment, high-end cluster, advanced driver assistance system (ADAS) and body power-supply systems. Wettable flank packaging enables optical inspection to reduce manufacturing costs. Use these step-down regulators together with TI’s WEBENCH Automotive Design tool.


Switch node ringing is inherent in all switch-mode power supplies. By reducing parasitic inductance and capacitance in the LM53625-Q1 and LM53635-Q1 regulators, these power solutions lower noise and EMI emissions by up to 15 dB at the system level, which requires less external EMI filtering, saves printed circuit board (PCB) area and simplifies compliance with CISPR 25 automotive EMI requirements. A video that proposes how to solve automotive EMI, thermal and system challenges with TI’s LM53635-Q1 is here.


A 3.5-V to 42-V operating range handles start-stop and load-dump conditions for 12-V lead acid automotive batteries. The regulators provide up to 93% efficiency at 2.1-MHz operation to support compact and high-temperature conditions in automotive applications. 18- µA quiescent current (IQ) in standby extends battery life in “always on” applications. Deep drop-out performance of less than 0.6V under full load and temperature conditions enables compliance with stringent cold-crank and start-stop conditions, saving system cost and solution size.


Download the “ Infotainment Power System Reference Design for Automotive ” to view a full off-battery front-end power supply for automotive infotainment systems. The reference design includes the LM53635-Q1 regulator, LM27313-Q1 boost converter and LM74610-Q1 smart diode controller. The reference design meets all industry tests including ISO 7637 pulse, cold crank, reverse battery, input over-voltage and CISPR 25 Class 5-conducted EMI.


In a 22-pin, 4 x 5-mm very thin quad flat no-lead (VQFN) package, the LM53625-Q1 is priced at $2.79 (1,000) and the LM53635-Q1 is priced at $3.22. There is an evaluation module, LM536253QEVM, and a PSpice transient model .