POWER LOSS (W) LT8645S/LT8646S 65V, 8A Synchronous Step-Down Silent Switcher 2 with 2.5A Quiescent Current FEATURES DESCRIPTION n Silent Switcher 2 Architecture The LT 8645S/LT8646S synchronous step-down regulator n Ultralow EMI Emissions on Any PCB features second generation Silent Switcher architecture n Eliminates PCB Layout Sensitivity designed to minimize EMI emissions while delivering high n Internal Bypass Capacitors Reduce Radiated EMI efficiency at high switching frequencies. This includes the n Optional Spread Spectrum Modulation integration of bypass capacitors to optimize all the fast n High Efficiency at High Frequency current loops inside and make it easy to achieve advertised n Up to 95% Efficiency at 1MHz, 12V to 5V EMI performance by eliminating layout sensitivity. IN OUT n Up to 94% Efficiency at 2MHz, 12V to 5V IN OUT The fast, clean, low-overshoot switching edges enable n Wide Input Voltage Range: 3.4V to 65V high efficiency operation even at high switching frequen- n Ultralow Quiescent Current Burst Mode Operation cies, leading to a small overall solution size. Peak current n 2.5A I Regulating 12V to 3.3V (LT8645S) Q IN OUT mode control with a 40ns minimum on-time allows high n Output Ripple < 10mV P-P step-down ratios even at high switching frequencies. The n External Compensation: Fast Transient Response LT8646S has external compensation to enable current and Current Sharing (LT8646S) sharing and fast transient response at high switching n Fast Minimum Switch On-Time: 40ns frequencies. n Low Dropout Under All Conditions: 60mV at 1A n Adjustable and Synchronizable: 200kHz to 2.2MHz Burst Mode operation enables ultralow standby current n Peak Current Mode Operation consumption, pulse-skipping mode allows full switching n Output Soft-Start and Tracking frequency at lower output loads, or spread spectrum n Small 32-Lead 6mm 4mm LQFN Package operation can further reduce EMI emissions. n AEC-Q100 Qualified for Automotive Applications INTERNAL CAPS V COMP 150C GRADE C LT8645S Yes Internal No APPLICATIONS LT8646S Yes External No n Automotive and Industrial Supplies LT8645S-2* No Internal Yes n General Purpose Step-Down *See LT8645S-2 Data Sheet n GSM Power Supplies All registered trademarks and trademarks are the property of their respective owners. Protected by U.S. patents, including 8823345. TYPICAL APPLICATION 12V to 5V Efficiency IN OUT 5V 8A Step-Down Converter 100 4.0 95 3.5 2.2H V OUT V IN V SW 5V IN 90 3.0 5.5V TO 65V EFFICIENCY 8A 4.7F EN/UV BIAS 85 2.5 LT8645S 80 2.0 2.2pF 1M 100F 75 1.5 RT FB POWER LOSS 70 1.0 41.2k 243k GND 65 0.5 1MHz, L = 2.2H 8645S TA01a 2MHz, L = 1H f = 1MHz 60 0 SW 1 2 3 4 5 6 7 8 LOAD CURRENT (A) 8645S TA01b Rev. B 1 Document Feedback For more information www.analog.com EFFICIENCY (%)LT8645S/LT8646S ABSOLUTE MAXIMUM RATINGS (Note 1) V , EN/UV ................................................................65V Operating Junction Temperature Range (Note 2) IN PG .............................................................................42V LT8645SE/LT8646SE ......................... 40C to 125C BIAS ..........................................................................25V LT8645SI/LT8646SI........................... 40C to 125C FB, TR/SS ................................................................4V Storage Temperature Range .................. 65C to 150C SYNC/MODE Voltage ...............................................6V Maximum Reflow (Package Body) Temperature ...260C PIN CONFIGURATION LT8645S LT8646S TOP VIEW TOP VIEW 32 31 30 29 28 27 32 31 30 29 28 27 BIAS 1 26 RT BIAS 1 26 RT INTV 2 25 EN/UV INTV 2 25 EN/UV CC CC 33 34 33 34 GND GND GND GND 3 24 NC 3 24 NC NC NC V 4 23 V V 4 23 V IN IN IN IN V 5 22 V V 5 22 V IN IN IN IN 35 36 35 36 GND GND GND GND V 6 21 V V 6 21 V IN IN IN IN NC 7 20 NC NC 7 20 NC GND 8 19 GND GND 8 19 GND 37 38 37 38 GND GND GND GND GND 9 18 GND GND 9 18 GND 10 GND 10 17 GND GND 17 GND 11 12 13 14 15 16 11 12 13 14 15 16 LQFN PACKAGE LQFN PACKAGE 32-LEAD (6mm 4mm 0.94mm) 32-LEAD (6mm 4mm 0.94mm) JEDEC BOARD: = 30C/W, = 0.6C/W, JEDEC BOARD: = 30C/W, = 0.6C/W, JA JT JA JT = 28.5C/W, = 4.4C/W (NOTE 3) = 28.5C/W, = 4.4C/W (NOTE 3) JCTOP JC(PAD) JCTOP JC(PAD) DEMO BOARD: = 17C/W DEMO BOARD: = 17C/W JA JA EXPOSED PADS (PINS 33-38) ARE GND, SHOULD BE SOLDERED TO PCB EXPOSED PADS (PINS 33-38) ARE GND, SHOULD BE SOLDERED TO PCB Rev. B 2 For more information www.analog.com BST FB SW PG SW GND SW TR/SS SW SYNC/MODE SW CLKOUT BST FB SW PG SW V C SW TR/SS SW SYNC/MODE SW CLKOUT