KWAIDA ST1937 DC/DC Step-Up Converter Step Up Converter for LED Driver DESCRIPTION The ST1937 is a step-up DC/DC converter for white LED driver with constant current. The device can driver one to four LEDs in series from a single cell Lithium Ion battery. Internal functions include current limiting; thermal shutdown and soft-start to prevent damage operate status. The ST1937 DC/DC converter operates at 1.2MHz and low output capacitor as small as 0.22uF; apply to Lithium-Ion powered systems. A low 100mV reference voltage minimizes power loss in the current setting resistor for better efficiency. APPLICATIONS PIN CONFIGURATION SOT23-5L Battery Powered Devices Digital Camera PDA GPS Hand Held Communication Equipment MP3/4 SOT-353 ( SC-70-5L ) FEATURES Fast 1.2MHz Switching Frequency High Efficiency up to 85% Drives up to Four LEDs From 3.2V Supply Low Quiescent Current Disconnects LEDs in Shutdown Mode Internal Over Temperature and Current Limiting Shutdown Function Internal 18V Rugged Switch Internal Soft-Start Circuit Available in a Small SOT-23-5L & SOT-353 Package PART PACKING TEL:0755-82914455 0755-82911749 1 FAX:0755-82913146 WWW.KWAIDA.COM KWAIDA DC/DC Step-Up Converter Step Up Converter for LED Driver ST1937 TYPICAL APPLCATION CIRCUIT PIN DESCRIPTION ST1937S25RG Pin Symbol 1 SW 2 GND 3 FB 4 SHDN 5 VIN ST1937S35G Pin Symbol 1 SW 2 GND 3 FB 4 SHDN 5 GND 6 VIN TEL:0755-82914455 Description Switch Pin. Ground Pin Feedback Pin. Shutdown Pin. Active-low enable Supply Voltage Input Description Switch Pin. Ground Pin Feedback Pin. Shutdown Pin. Active-low enable Ground Pin Supply Voltage Input 0755-82911749 2 FAX:0755-82913146 WWW.KWAIDA.COM KWAIDA ST1937 DC/DC Step-Up Converter Step Up Converter for LED Driver BLOCK DIAGRAM ORDERING INFORMATION ※ ※ ※ Part Number Package ST1937S25RG SOT-23-5L ST1937S35RG SOT-353 ( SC-70-5L ) Week Code : A ~ Z( 1 ~ 26 ) ; a ~ z( 27 ~ 52 ) ST1937S25RG : Tape Reel ; Pb – Free ST1937S35RG : Tape Reel ; Pb – Free TTEL:0755-82914455 0755-82911749 Part 3 Marking 37YW 37YW FAX:0755-82913146 WWW.KWAIDA.COM KWAIDA DC/DC Step-Up Converter Step Up Converter for LED Driver ST1937 ABSOULTE MAXIMUM RATINGS (TA=25℃ unless otherwise specified) Symbol Parameter VIN DC Supply Voltage VSW SW Voltage VFB FB Voltage VSHDN SHDN Voltage TOPR Operating Temperature TJ(Max) Maximum Junction Temperature TS Value 10 36 10 10 -40〜85 125 -65〜150 Storage Temperature Unit V V V V ℃ ℃ ℃ The IC has a protection circuit against static electricity. Do not apply high static electricity or high voltage that exceeds the performance of the protection circuit to the IC. ELECTRICAL CHARACTERISTICS (Ta=25℃, VIN=3.6V, unless otherwise specified.) Symbol VIN VFB Parameter Operating Voltage Feedback Voltage Conditions Min. Typ. Max. Unit V 2.4 ISW=100mA, Duty Cycle = 66% Rin=10MΩ VSHDN > 0V VSHDN = 0V mV 100 UVLO IS FB Pin Bias Current Supply Current Fosc Switching Frequency D Maximum Duty Cycle 85 nA 3.5 mA 1.0 µA 1.6 MHz % Iout Switch Current Limit 320 mA ILEAKAGE Vcesat ISHDN Switch Leakage Current Switch Vcesat 0.8 VSW= 5V ISW = 50mA 0.01 150 SHDN Pin Current SHDNH SHDN Voltage High SHDNL SHDN Voltage Low 100 2.8 0.1 1.2 5 µA mV nA 1 V 1.5 0.4 V SOT-23-5L PACKAGE OUTLINE TEL:0755-82914455 0755-82911749 4 FAX:0755-82913146 WWW.KWAIDA.COM KWAIDA DC/DC Step-Up Converter Step Up Converter for LED Driver ST1937 TEL:0755-82914455 0755-82911749 5 FAX:0755-82913146 WWW.KWAIDA.COM KWAIDA DC/DC Step-Up Converter Step Up Converter for LED Driver ST1937 SOT-353 PACKAGE OUTLINE TEL:0755-82914455 0755-82911749 6 FAX:0755-82913146 WWW.KWAIDA.COM