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| DC-DC Step-Up Converter for White LED Driver ST1937 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 Battery Powered Devices Digital Camera PDA GPS Hand Held Communication Equipment MP3/4 FEATURES PART MARKING Fast 1.2MHz Switching Frequency High Efficiency up to 85% Drives up to Four LEDs From 3.2V Supply Low Quiescent Current Internal Over Temperature and Current Limiting Shutdown Function Internal Soft-Start Circuit 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 DC-DC Step-Up Converter for White LED Driver ST1937 TYPICAL APPLCATION CIRCUIT PIN DESCRIPTION ST1937S25RG Pin 1 2 3 4 5 Symbol SW GND FB SHDN VIN Switch Pin. Ground Pin Feedback Pin. Shutdown Pin. Active-low enable Supply Voltage Input Description ST1937S35G Pin 1 2 3 4 5 6 Symbol SW GND FB SHDN GND VIN Switch Pin. Ground Pin Feedback Pin. Shutdown Pin. Active-low enable Ground Pin Supply Voltage Input Description STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 DC-DC Step-Up Converter for White LED Driver ST1937 BLOCK DIAGRAM ABSOULTE MAXIMUM RATINGS (TA=25 unless otherwise specified) Symbol VIN VSW VFB VSHDN TOPR TJ(Max) TS SW Voltage FB Voltage SHDN Voltage Operating Temperature Maximum Junction Temperature Storage Temperature Parameter DC Supply Voltage Value 12 36 10 10 -4085 125 -65150 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. STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 DC-DC Step-Up Converter for White LED Driver ST1937 ELECTRICAL CHARACTERISTICS (Ta=25, VIN=3.6V, unless otherwise specified.) Symbol VIN IFB UVLO IS Fosc D Iout Vcesat ISHDN SHDNH SHDNL Parameter Operating Voltage Feedback Voltage FB Pin Bias Current Supply Current Switching Frequency Maximum Duty Cycle Switch Current Limit Conditions ISW=100mA, Duty Cycle = 66% Rin=10M VSHDN > 0V VSHDN = 0V Min. Typ. Max. Unit 2.4 100 100 2.8 0.1 0.8 1.2 85 320 3.5 1.0 1.6 12 V mV nA mA A MHz % mA 5 A mV nA V 0.4 V ILEAKAGE Switch Leakage Current Switch Vcesat SHDN Pin Current SHDN Voltage High SHDN Voltage Low VSW= 5V ISW = 50mA 1.5 0.01 150 1 STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 DC-DC Step-Up Converter for White LED Driver ST1937 SOT-23-5L PACKAGE OUTLINE STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 DC-DC Step-Up Converter for White LED Driver ST1937 SOT-353 PACKAGE OUTLINE STANSON TECHNOLOGY 120 Bentley Square, Mountain View, Ca 94040 USA www.stansontech.com ST1937 2005. V1 |
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