IL1937 IKSEMICON | Alldatasheet
Document overview
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Technical content
Features
Internally determined LED current High Efficiency: 84% Typical Drives Up to 4 LEDs from a 3.2V Supply Drives Up to 6 LEDs from a 5V Supply 36V rugged bipolar switch Fast 1.2MHz switching frequency Uses tiny 1mm Tall Inductors Requires only 0.22uF output capacitor
Applications
Cellular Phones PDAs, Handheld Computers Digital Cameras MP3 Players GPS Receivers Pin Description IL1937
2011, April, Ver. 01 Block diagram A1 – error amplifier; A2 – addrer; A3 – PWM – comprator; A4 – comparator; A5 –driver; C1 – capacitor; R1 – R4 – resistor; VT1 – transistor Te device contain, switch on/off circuit; output current overrising protection unit, driver -buffer, output switch. Reference voltage source 03 06 RS - -flip-flops Sawtooth voltage generator Oscilator 02,05 SHDN VIN FB SW GND R4 C1 A1 A3 A5 A4 A2 VT1
2011, April, Ver. 01 Absolute maximum ratings Symbol Parameter Absolute max i- mum ratings Unit Min. Max. VIN Input voltage - 10 V VSW SW pin Voltage - 36 V VFB FB pin Voltage - 10 V V SHDN SHDN pin Voltage - 10 V TJ Junction Temperature - 150 oC Тstg Storage Temperature -60 150 oC * Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the d e- vice. These are stress ratings only and functional operation of the device at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. Recommended operating mode Symbol Parameter Recommended operating mode Unit Min. Max. VIN Input voltage 2,5 10 V TJ Junction Temperature - 125 oC Electric Parameters Parameter, unit Symbol Value Testing mode Ambient temperature, C Min. Max. Minimum input voltage, V VIN MIN 2,5 2,5 - V SHDN = 3,0 V 25 10 -40 … +125 Maximum input voltage, V VIN MAX - 10 Feedback Voltage, mV VFB 86 104 114 VIN = 3,0 V, V SHDN = 3,0 V, ISW = 100 mA Duty Cycle 66 % FB pad Bias Current, nA IFB 10 100 150 VIN = 3,0 V, V SHDN = 3,0 V Supply Current, IQ mA - 2,5 3,75 VIN = 3,0 V, V SHDN = 3,0 V ua - 1,0 2,0 VIN = 3,0 V, V SHDN = 0 V Switching Frequency, Mhz fS 0,8 0,6 1,6 1,8 VIN = 3,0 V, V SHDN = 3,0 V Maximum Duty Cycle, % DCMAX 85 - VIN = 3,0 V, V SHDN = 3,0 V Switch Leakage Current, uA ILSW - 5,0 7,5 VIN = 3,0 V, V SHDN =3,0V, VSW = 5,0 V
2011, April, Ver. 01 Parameter, unit Symbol Value Testing mode Ambient temperature, C Min. Max. SHDN Voltage High, V VIH 1,5 1,5 - VIN = 3,0 V Note 1 25 10 -40 … +125 SHDN Voltage Low , V VIL - 0,4 0,4 VIN = 3,0 V Note 1 Notes
1 During VIH & VIL measurements threth hold voltage is tested, which has to be within range
from 0,4 to 1,5 V
2 Symbol descriptions :
- V SHDN - Shutdown pad voltage - VFB – Feedback Voltage pad voltage - VSW – Switch pad voltage - ISW – Switch pad current Typical Electric Parameters Symbol Parameter, unit Testing mode Typ.value Unit ICL Output transistor current limit VIN = 3,0 V, V SHDN = 3,0 V 320 mA VCESAT Output transistor saturation voltage VIN = 3,0 V, V SHDN = 3,0 V, ISW = 250 мА 350 mV ISHDN SHDN pad (pin) bias current VIN = 3,0 V, V SHDN = 3,0 V 65 uA VSHDN, V VIL=0,4V VIH=1,5V IC is switched on IC is switched off VI, V
2011, April, Ver. 01 OPERATION DESCRIPTION The IL1937 consist of following units: voltage switch on/off circuit, sawtooth generator, rectangular pulse generator P WM –comparator RS-latch, error amplifier, output buffer, output switch, current - limit circuit for output switch. The IL1937 uses a constant frequency, current mode control scheme to provide excellent line and load regulation. At the start of each oscillator cycle, signal from oscillator applied to S-pin of the RS-latch, the latch output high level voltage is set. This voltage through buffer turns on the power switch (transistor VT1). A voltage proportional to the switch current is added to a stabilizing sawtooth voltage and the resulting sum is applied to the positive terminal of the PWM comparator A 3. When this voltage exceeds the level at the negative input of A3, the SR latch is reset turning off the power switch VT1. The level at the negative input of A3 is set by the error amplifier A1, and is simply an amplified ver- sion of the difference between the feedback voltage and the reference voltage of 95mV. In this way, the error amplifier A1 contols the peak current level to keep the output in regulatio n. If the error amplifier’s output increases, more current is delivered to the output; if it decreases, less current is delivered. Typical application diagramm (3 white LED driver supplied by Li-ion battery) SHDN VIN SW FB GND IL1937 ON 22uHn 1мк 0,22uF 6,34Ohm VD1 VD2 VD3 VD4 VIN OFF 3 to 5 V 15 mA
2011, April, Ver. 01 PACKAGE DIMENSION SOT-23-6 Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 1.050 1.250 0.041 0.049 A1 0.000 0.100 0.000 0.004 A2 1.050 1.150 0.041 0.045 b 0.300 0.500 0.012 0.020 c 0.100 0.200 0.004 0.008 D 2.820 3.020 0.111 0.119 E 1.500 1.700 0.059 0.067 E1 2.650 2.950 0.104 0.116 e 0.950TYP 0.037TYP e1 1.800 2.000 0.071 0.079 L 0.600REF 0.024REF L1 0.300 0.600 0.012 0.024 θ 0° 8° 0° 8°