ST1937 DC-DC Step-Up Converter for White LED Driver DESCRIPTION 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. 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. PIN CONFIGURATION SOT23-5L SOT-353 ( SC-70-5L ) APPLICATIONS z Battery Powered Devices z Digital Camera z PDA z GPS z Hand Held Communication Equipment z MP3/4 FEATURES PART MARKING z Fast 1.2MHz Switching Frequency z High Efficiency up to 85% z Drives up to Four LEDs From 3.2V Supply z Low Quiescent Current z Internal Over Temperature and Current Limiting Shutdown Function z Internal Soft-Start Circuit z Available in a Small SOT-23-5L & SOT-353 Package ORDERING INFORMATION Part Number Package Part Marking ST1937S25RG SOT-23-5L 37YW ST1937S35RG SOT-353 ( SC-70-5L ) 37YW ※ Week Code : A ~ Z( 1 ~ 26 ) ; a ~ z( 27 ~ 52 ) ※ ST1937S25RG : S25 : SOT-23-5 ; R : Tape Reel ; G : Pb – Free ※ ST1937S35RG : S35 : SOT-353 ; R : Tape Reel ; G : Pb – Free STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 ST1937 DC-DC Step-Up Converter for White LED Driver TYPICAL APPLCATION CIRCUIT PIN DESCRIPTION ST1937S25RG Pin Symbol Description 1 SW Switch Pin. 2 GND Ground Pin 3 FB 4 SHDN 5 VIN Feedback Pin. Shutdown Pin. Active-low enable Supply Voltage Input ST1937S35G Pin Symbol Description 1 SW Switch Pin. 2 GND Ground Pin 3 FB 4 SHDN 5 GND Ground Pin 6 VIN Supply Voltage Input Feedback Pin. Shutdown Pin. Active-low enable STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 ST1937 DC-DC Step-Up Converter for White LED Driver BLOCK DIAGRAM ABSOULTE MAXIMUM RATINGS (TA=25℃ unless otherwise specified) Symbol Parameter Value Unit VIN DC Supply Voltage 12 V VSW SW Voltage 36 V VFB FB Voltage 10 V SHDN Voltage 10 V -40～85 ℃ 125 ℃ -65～150 ℃ VSHDN TOPR TJ(Max) TS Operating Temperature Maximum Junction Temperature Storage Temperature 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. STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 ST1937 DC-DC Step-Up Converter for White LED Driver ELECTRICAL CHARACTERISTICS (Ta=25℃, VIN=3.6V, unless otherwise specified.) Symbol Parameter VIN Operating Voltage IFB Feedback Voltage Conditions Min. Typ. Max. Unit 2.4 ISW=100mA, Duty IS V mV 100 Cycle = 66% UVLO 12 FB Pin Bias Current Rin=10MΩ 100 Supply Current VSHDN > 0V 2.8 3.5 mA VSHDN = 0V 0.1 1.0 μA 1.2 1.6 MHz Fosc Switching Frequency D Maximum Duty Cycle 85 % Iout Switch Current Limit 320 mA ILEAKAGE Switch Leakage Current Vcesat Switch Vcesat ISHDN SHDN Pin Current SHDNH SHDN Voltage High SHDNL SHDN Voltage Low 0.8 nA VSW= 5V 0.01 5 ISW = 50mA 150 mV 1 nA 1.5 μA V 0.4 V STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 ST1937 DC-DC Step-Up Converter for White LED Driver SOT-23-5L PACKAGE OUTLINE STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 ST1937 DC-DC Step-Up Converter for White LED Driver SOT-353 PACKAGE OUTLINE STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1