POWER LOSS (mW) LT3973/LT3973-3.3/LT3973-5 42V, 750mA Step-Down Regulator with 2.5A Quiescent Current and Integrated Diodes FEATURES DESCRIPTION n Ultralow Quiescent Current The LT 3973 is an adjustable frequency monolithic buck n 2.5A I at 12V to 3.3V switching regulator that accepts a wide input voltage range Q IN OUT n up to 42V, and consumes only 2.5A of quiescent current. Low Ripple Burst Mode Operation n A high efficiency switch is included on the die along with Output Ripple < 10mV P-P n the catch diode, boost diode, and the necessary oscillator, Wide Input Voltage Range: 4.2V to 42V Operating n control and logic circuitry. Low ripple Burst Mode operation Adjustable Switching Frequency: 200kHz to 2.2MHz n maintains high efficiency at low output currents while keep- Integrated Boost and Catch Diodes n ing the output ripple below 10mV in a typical application. 750mA Output Current A minimum dropout voltage of 530mV is maintained when n Excellent Start-Up and Dropout Performance the input voltage drops below the programmed output volt- n Fixed Output Voltages: 3.3V, 5V age, such as during automotive cold crank. Current mode n 1.9A I at 12V Q IN topology is used for fast transient response and good loop n Accurate Programmable Undervoltage Lockout stability. A catch diode current limit provides protection n Low Shutdown Current: I = 0.75A Q against shorted outputs and overvoltage conditions, with n Internal Catch Diode Current Limit thermal shutdown providing additional fault protection. An n Power Good Flag accurate programmable undervoltage lockout feature is n Thermal Shutdown available, producing a low shutdown current of 0.75A. n Small, Thermally Enhanced 10-Lead MSOP and A power good flag signals when V reaches 90% of OUT (3mm 3mm) DFN Packages the programmed output voltage. The LT3973 is available in small, thermally enhanced 10-lead MSOP and 3mm APPLICATIONS 3mm DFN packages. n Automotive Battery Regulation L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks n Power for Portable Products of Linear Technology Corporation. All other trademarks are the property of their respective owners. n Industrial Supplies n Gate Drive Bias Efficiency TYPICAL APPLICATION 90 1000 V = 12V IN 5V Step-Down Converter V IN 80 100 5.6V TO 42V C3 0.47F V BOOST IN 70 10 L1 LT3973 15H V OUT OFF ON EN/UVLO SW 5V 60 1 750mA PG BD OUT 15pF 1M C1 C2 RT FB 50 0.1 4.7F 22F GND 215k 316k 40 0.01 3973 TA01a f = 600kHz 0.01 0.1 1 10 100 LOAD CURRENT (mA) 3973 TA01b 3973fb 1 For more information www.linear.com/LT3973 EFFICIENCY (%)LT3973/LT3973-3.3/LT3973-5 ABSOLUTE MAXIMUM RATINGS (Note 1) V , EN/UVLO Voltage ...............................................42V Operating Junction Temperature Range (Note 2) IN BOOST Pin Voltage ...................................................55V LT3973E/LT3973E-X .......................... 40C to 125C BOOST Pin Above SW Pin .........................................25V LT3973I/LT3973I-X ............................ 40C to 125C FB/V , RT, PG Voltage .............................................6V LT3973H/LT3973H-X ......................... 40C to 150C OUT BD Voltage ................................................................25V Storage Temperature Range .................. 65C to 150C OUT Voltage ..............................................................14V Lead Temperature (Soldering, 10 sec) MSE Only ..........................................................300C PIN CONFIGURATION TOP VIEW TOP VIEW *FB/V 1 10 RT OUT *FB/V 1 10 RT OUT OUT 9 PG 2 OUT 2 9 PG 11 11 EN/UVLO 3 8 BD EN/UVLO 3 8 BD GND GND V 4 7 BOOST IN V 4 7 BOOST IN GND 5 6 SW GND 5 6 SW MSE PACKAGE 10-LEAD PLASTIC MSOP DD PACKAGE = 45C/W, = 10C/W JA JC 10-LEAD (3mm 3mm) PLASTIC DFN EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB = 40C/W, = 5C/W JA JC EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB * FB for LT3973, V for LT3973-3.3, LT3973-5. OUT ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT3973EDD PBF LT3973EDD TRPBF LGCH 10-Lead (3mm 3mm) Plastic DFN 40C to 125C LT3973IDD PBF LT3973IDD TRPBF LGCH 10-Lead (3mm 3mm) Plastic DFN 40C to 125C LT3973HDD PBF LT3973HDD TRPBF LGCH 10-Lead (3mm 3mm) Plastic DFN 40C to 150C LT3973EMSE PBF LT3973EMSE TRPBF LTFYS 10-Lead Plastic MSOP 40C to 125C LT3973IMSE PBF LT3973IMSE TRPBF LTFYS 10-Lead Plastic MSOP 40C to 125C LT3973HMSE PBF LT3973HMSE TRPBF LTFYS 10-Lead Plastic MSOP 40C to 150C LT3973EMSE-3.3 PBF LT3973EMSE-3.3 TRPBF LTGGB 10-Lead Plastic MSOP 40C to 125C LT3973IMSE-3.3 PBF LT3973IMSE-3.3 TRPBF LTGGB 10-Lead Plastic MSOP 40C to 125C LT3973HMSE-3.3 PBF LT3973HMSE-3.3 TRPBF LTGGB 10-Lead Plastic MSOP 40C to 150C LT3973EDD-3.3 PBF LT3973EDD-3.3 TRPBF LGGC 10-Lead (3mm 3mm) Plastic DFN 40C to 125C LT3973IDD-3.3 PBF LT3973IDD-3.3 TRPBF LGGC 10-Lead (3mm 3mm) Plastic DFN 40C to 125C LT3973HDD-3.3 PBF LT3973HDD-3.3 TRPBF LGGC 10-Lead (3mm 3mm) Plastic DFN 40C to 150C LT3973EMSE-5 PBF LT3973EMSE-5 TRPBF LTGGD 10-Lead Plastic MSOP 40C to 125C LT3973IMSE-5 PBF LT3973IMSE-5 TRPBF LTGGD 10-Lead Plastic MSOP 40C to 125C LT3973HMSE-5 PBF LT3973HMSE-5 TRPBF LTGGD 10-Lead Plastic MSOP 40C to 150C 3973fb 2 For more information www.linear.com/LT3973