ST1938 dc-dc step-up converter for white led driver stanson technology 120 bentley square, mountain view, ca 94040 usa www.stansontech.com ST1938 2008. v1 description the ST1938 is a step-up dc/dc converter for whit e led driver with over voltage protection. the device can driver one to four leds in se ries from a single cell lithium ion battery. internal functions include current limiting; thermal shutdown; ovp and soft-start to prevent damage operate status. the ST1938 operates at 0.8mhz and from low input voltages as low as 1.5v; apply to lithium-ion po wered systems. a low 95mv refe rence voltage minimizes power loss in the current setting resi stor for better efficiency. the ST1938 is available in small package sot-23-6l pin configuration sot23-6l part marking applications z battery power equipment z notebook computers z pda z cellular phone features z current source with over voltage protection z fast 0.8mhz switching frequency z high efficiency up to 87% z drives up to four leds from 3.2v supply z drives up to six leds from a 5v supply z low quiescent current z disconnects leds in shutdown mode z internal over temperature and current limiting shutdown function z internal soft-start circuit z 36v rugged bipolar switch z available in a small sot-23-6l package
ST1938 dc-dc step-up converter for white led driver stanson technology 120 bentley square, mountain view, ca 94040 usa www.stansontech.com ST1938 2008. v1 ordering information part number package part marking ST1938s26rg sot-23-6l 98yw week code : a ~ z( 1 ~ 26 ) ; a ~ z( 27 ~ 52 ) ST1938s26rg : s25 : sot-23-6 ; r : tape reel ; g : pb ? free typical applcation circuit pin description ST1938s26rg pin symbol description 1 sw switch pin. 2 gnd ground pin 3 fb feedback pin. 4 shdn shutdown pin. active-low enable and pwm control pin for led dimming 5 vin supply voltage input 6 ovp over voltage protection and connect to the output capacitor of the converter
ST1938 dc-dc step-up converter for white led driver stanson technology 120 bentley square, mountain view, ca 94040 usa www.stansontech.com ST1938 2008. v1 block diagram absoulte maximum ratings (ta=25 unless otherwise specified) symbol parameter value unit vin dc supply voltage 7 v vsw sw voltage 36 v vfb fb voltage 7 v vshdn shdn voltage 7 v topr operating temperature -40 85 tj(max) maximum junc tion temperature 125 ts storage temperature -65 150 the ic has a protection circuit against st atic electricity. do not apply high static electric ity or high voltage that exceeds the performance of the protection circuit to the ic.
ST1938 dc-dc step-up converter for white led driver stanson technology 120 bentley square, mountain view, ca 94040 usa www.stansontech.com ST1938 2008. v1 electrical characteristics (ta=25 , vin=3.6v, unless otherwise specified.) symbol parameter conditions min. typ. max. unit vin operating voltage 2.4 7 v vfb feedback voltage isw=100ma, duty cycle = 66% 86 110 mv ifb fb pin bias current 150 na vshdn > 0v 2.8 3.5 ma is supply current vshdn = 0v 0.05 1.0 a fosc switching frequency 0.68 0.8 1.0 mhz d maximum duty cycle 85 % iout switch current limit 320 ma ileakage switch leakage current vsw= 5v 0.01 5 a vcesat switch vcesat isw = 200ma 150 mv ishdn shdn pin current 90 ua vshdnh shdn voltage high 1.5 v shdnl shdn voltage low 0.4 v vovp over voltage preotection vout rising 21 v
ST1938 dc-dc step-up converter for white led driver stanson technology 120 bentley square, mountain view, ca 94040 usa www.stansontech.com ST1938 2008. v1 sot-23-6l package outline
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