ELM900x CMOS White LED flashlight driver ■General description ELM900x is CMOS white LED flashlight driver. This series can drive two series connected white LED by 1.5V to 3.0V input voltage. ELM900 series uses an external inductor as voltage booster and consists of an oscillator circuit and a driving transistor. The input DC power is transformed to constant current pulse when the external inductor is switched on and repeatly at the frequency : 35kHz, 55kHz. ■Features • • • • ■Application Low noise : 35kHz, 55kHz (constant frequency switching) Constant average power control High efficiency Package : SOT-89 • White LED flashlight • Laser pointer • LCD backlighting ■Maximum absolute ratings Parameter Max.voltage (Vdd to Vss) Max.voltage (LX to Vss) Max.current LX Power dissipation Operating temperature Storage temperature Symbol Vdd Vlx Ilx Pd Top Tstg Limit 12 12 200 500 -20 to +70 -55 to +125 Unit V V mA mW °C °C ■Selection guide ELM900x-x Symbol a Switching frequency b Taping direction B: Frequency 35kHz D: Frequency 55kHz S: Refer to PKG file N: Refer to PKG file ■Pin configuration ELM900 x - x ↑ ↑ a b ■Block diagram SOT-89(TOP VIEW) � � � Pin No. 1 2 3 ��� Pin name VSS VDD LX ��� ��� 2-1 ����������� �� ELM900x CMOS White LED flashlight driver ■Appliaction circuit 1cell 1LED 2cell 2LED ����� � ���� ����� � ��� � ����� ��� ������� ���� � ����� ��� ������� ����� ��� ��� � � ■Electrical characteristics Parameter Power voltage Current consumption Output current of LX pin Leakage current of LX pin Oscillation frequency : 35kHz Oscillation frequency : 55kHz Duty ratio : switching 35kHz Duty ratio : switching 55kHz Symbol Condition Vdd Iss Vdd=3.0V Ilx Vdd=3.0V Ilxl Vdd=LX=6.0V Fosc Vdd=3.0V Duty Vdd=3.0V Min. 1.0 90.0 22 35 45 45 Typ. 7.0 35 55 55 55 Top=25°C Max. Unit 5.0 V 14.0 μA mA 1.0 μA 55 kHz 75 65 % 75 ■Marking SOT-89 � � � � a, b : Product IC code 90 c : the assembly lot No.1 Products ELM900B ELM900D Lot No. 0 to 9 A to Z (I, O, X expected) d : the assembly lot No.2 Products ELM900B ELM900D Lot No. A to Z (I, O, X expected) 0 to 9 2-2