5121X

Global Mixed-mode Technology Inc. G5121 Fixed Frequency White LED Step-Up Converter Features Inherently Matched LED Current High Efficiency: 87% Drives Up to Five LEDs from 2.5V Supply 24V Internal Power Switch Fast 1MHz Switching Frequency Uses Tiny 1mm Tall Inductors Requires Only 1µF Output Capacitors 19.5V Over Voltage Protection SOT-23-6 Package General Description The G5121 is a step-up DC/DC converter specifically designed to drive up to 5 series white LEDs with constant current. Series connection of the LEDs provides identical LED currents resulting in uniform brightness and eliminates the need for ballast resistors. The G5121 switches at 1MHz, allowing the use of tiny external components. A low 0.254V feedback voltage minimizes power loss in the current setting resistor for high efficiency. The OVP pin monitors the output voltage and turns off the converter whenever the LEDs are open. The G5121 is available in low profile SOT-23-6 package. Applications White LED Backlight Display for PDA Pocket PC Smart Phones Handheld Devices Cellular Phones Ordering Information ORDER NUMBER G5121TB1U MARKING 5121x TEMP. RANGE -40°C ~ +85°C PACKAGE (Pb free) SOT-23-6 Note: TB : SOT23-6 U: Tape & Reel Pin Configuration Typical Application Circuit L1 VIN 2.7V to 4.2V D1 SW 1 6 VCC VCC VCC 4.7µH SW OVP C2 1µF/25V 5 LEDs GND 2 G5121 5 OVP C1 4.7µF/6.3V PWM Dimming Waveform G5121 SHDN GND FB RS FB 3 SOT-23-6 4 SHDN C1:TAIYO YUDEN, JMK212BJ475KD C2:TAIYO YUDEN, TMK316BJ105KD Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw 1 Global Mixed-mode Technology Inc. Absolute Maximum Ratings VCC, SHDN to GND.….....................……-0.3V to +7V FB to GND.....................….........................-0.3V to VCC SW, OVP to GND……….……..…………..-0.3V to +24V Operating Temperature.….…………….....-40°C to 85°C G5121 Junction Temperature......................….................125°C Storage Temperature……....……..….….-65°C to 150°C Reflow Temperature (soldering, 10sec)……...…260°C ESD Rating (Human Body Model)………….….……2kV Stress beyond those listed under “Absolute Maximum Rating” may cause permanent damage to the device. Electrical Characteristics (VCC=V SHDN =3.6V, TA=25°C) PARAMETER Input Voltage Range Input Voltage UVLO Over Voltage Protection Threshold Over Voltage Protection Threshold OVP Pin Input Current Quiescent Current trigger release Vovp = 16V VFB = 0.3V (no switching) VFB = 0.2V (switching) V SHDN = 0V Initial Accuracy Temperature Coefficient VFB = 0.2V ISW = 150mA VSW = 20V CONDITIONS MIN 2.5 1.7 18.5 13.5 --------- TYP --- MAX 6 2.3 21 16.5 UNITS V V V V µA µA mA µA mV ppm/°C MHz % Ω µA mA µs V V 2.0 19.5 15 40 80 --- 60 120 2 1 264 --- 0.1 254 100 1.0 --- FB Comparator Trip Point Switching Frequency Maximum Duty Switch RDS(ON) Switch Leakage Current Switch Current Limit Soft Start Time SHDN Pin Voltage High 244 --- 0.8 85 ----- 1.2 --- 0.7 0.1 600 120 --- 1.0 10 700 ----- 500 --- 2 --- SHDN Pin Voltage Low --- 0.8 Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw 2 Global Mixed-mode Technology Inc. Typical Performance Characteristics (VCC= +3.6V, V SHDN = +3.6V, L=4.7µH, TA=25°C, unless otherwise noted.) G5121 Stability for Driving 4 WLEDs Stability for Driving 5 WLEDs Stability for Driving 3 WLEDs Stability for Driving 2 WLEDs Inrush Current for Driving 5 WLEDs Inrush Current for Driving 4 WLEDs Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw 3 Global Mixed-mode Technology Inc. Typical Performance Characteristics (continued) Inrush Current for Driving 3 WLEDs G5121 Inrush Current for Driving 2 WLEDs OVP Waveform Dimming Control for Driving 4 WLEDs Efficiency vs. Load Current 90 80 70 Efficiency (%) 60 50 40 30 20 10 0 5 10 15 Load Current (mA) 20 25 5LEDs, CO=1µF V IN=2.7V V IN=3.6V V IN=4.2V Efficiency (%) 90 80 Efficiency vs. Load Current V IN=2.7V 70 60 50 40 30 20 10 0 5 10 15 Load Current (mA) V IN=3.6V V IN=4.2V 4LEDs, CO=1µF 20 25 Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw 4 Global Mixed-mode Technology Inc. Typical Performance Characteristics (continued) Efficiency vs. Load Current 90 80 VIN=2.7V 70 Efficiency (%) 60 50 40 30 20 10 0 5 10 15 Load Current (mA) 20 25 3LEDs, CO=1µF VIN=3.6V VIN=4.2V Efficiency (%) 90 80 VIN=2.7V 70 60 50 40 30 20 10 0 5 10 15 Load Current (mA) G5121 Efficiency vs. Load Current VIN=3.6V VIN=4.2V 2LEDs, CO=1µF 20 25 IQ_NoSW vs. Input Voltage 130 120 110 100 90 80 70 60 50 40 30 20 10 0 2 2.5 3 3.5 4 4.5 Input Voltage (V) 5 5.5 6 100 90 80 IQ_NoSW (uA) 70 60 50 40 30 20 10 0 -40 IQ_NoSW vs. Temperature IQ_NoSW (uA) -20 0 20 40 60 Temperature (°C) 80 100 Frequency vs. Input Voltage 1 0.95 Frequency (MHz) 0.9 0.85 0.8 0.75 0.7 2 2.5 3 3.5 4 4.5 Input Voltage (V) 5 5.5 6 Frequency (MHz) 1.1 1.05 1 0.95 0.9 0.85 0.8 0.75 0.7 -40 Frequency vs. Temperature -20 0 20 40 60 Temperature (°C) 80 100 Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw 5 Global Mixed-mode Technology Inc. Typical Performance Characteristics (continued) OVP Trigger Threshold vs. Input Voltage 21 20.5 20 19.5 19 18.5 18 17.5 17 2 2.5 3 3.5 4 4.5 Input Voltage (V) 5 5.5 6 OVP Trigger Threshold (V) OVP Trigger Threshold (V) 21 20.5 20 19.5 19 18.5 18 17.5 17 -40 -20 0 20 40 G5121 OVP Trigger Threshold vs. Temperature 60 80 100 Temperature (°C) OVP Release Threshold vs. Input Voltage 17 16.5 OVP Release Threshold (V) 16 15.5 15 14.5 14 13.5 13 2 2.5 3 3.5 4 4.5 Input Voltage (V) 5 5.5 6 OVP Release Threshold (V) 17 16.5 16 15.5 15 14.5 14 13.5 13 OVP Release Threshold vs. Temperature -40 -20 0 20 40 60 Temperature (°C) 80 100 OVP Pin Input Current vs. Input Voltage 60 50 40 30 20 10 0 2 2.5 3 3.5 4 4.5 Input Voltage (V) 5 5.5 6 60 50 40 30 20 10 0 OVP Pin Input Current vs. Temperature OVP Pin Input Current (uA) OVP Pin Input Current (uA) -40 -20 0 20 40 60 Temperature (°C) 80 100 Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw 6 Global Mixed-mode Technology Inc. Recommended Minimum Footprint SOT-23-6 G5121 Block Diagram FB OVP SW COMPENSATION COMPARATOR A1 + A2 + R S Q CONTROL DRIVER M1 0.254V VREF RAMP GENERATOR + OC 1MHz OSCILLATOR VCC SHDN GND Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw 7 Global Mixed-mode Technology Inc. Pin Description PIN 1 2 3 4 5 6 G5121 NAME SW GND FB SHDN FUNCTION Switch Pin. The drain of the internal NMOS power switch. Connect this pin to inductor. Ground Pin. Feedback Pin. Connect current setting resistor Rs from this pin to ground. The LED current is set as 0.254V/ Rs. Active Low Shutdown Pin. Over Voltage Protection Sense Pin. Input Supply Pin. Bypass this pin with a capacitor as close to the device as possible. OVP VCC Function Description Normal Operation The G5121 uses a constant frequency control scheme to provide excellent line and load regulation. Operation can be best understood by referring to the block diagram. At the start of each oscillator cycle, the SR latch is set, which turns on the power switch M1. An artificial ramp is generated to the positive terminal of the PWM comparator A2. When this voltage exceeds the level at the negative input of A2, the SR latch is reset turning off the power switch. The level at the negative input of A2 is set by the error amplifier A1, and is simply an amplified version of the difference between the feedback voltage and the reference voltage of 0.254V. In this manner, the error amplifier sets the correct peak current level to keep the output in regulation. If the error amplifier’s output increases, more current is delivered to the output, if it decreases, less current is delivered. Over Voltage Protection Over voltage protection function is designed to prevent the damage of internal NMOS switch in case the increased impedance of the LED load (include the LED opened). Once the device detects over voltage (typical 19.5V) at the output, the internal NMOS switch is kept off until the output voltage drops below 15V. Since the G5121 is designed to operate in discontinuous mode, the inductor current reaches zero during discharge phase. After the inductor current reaches zero, the switch pin exhibits ringing due to the LC tank circuit formed by the inductor in combination with switch and diode capacitance. This ringing is not harmful; far less spectral energy is contained in the ringing than in the switch transitions. The ringing can be damped by application of a 300Ω resistor across the inductor, although this will degrade efficiency. Capacitor Selection The small size of ceramic capacitors makes them suitable for G5121 applications. X5R and X7R types are recommended because they retain their capacitance over wider voltage and temperature ranges than other types such as Y5V or Z5U. A minimum 1µF capacitor for output is required for most applications. Larger input/output capacitor minimizes input/output ripple. Diode Selection Schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for G5121 applications. The forward voltage drop of a Schottky diode represents the conduction losses in the diode, while the diode capacitance (CT or CD) represents the switching losses. For diode selection, both forward voltage drop and diode capacitance need to be considered. Schottky diodes with higher current ratings usually have lower forward voltage drop and larger diode capacitance, which can cause significant switching losses at the 1MHz switching frequency of the G5121. A Schottky diode rated at 500mA is sufficient for most G5121 applications. Application Information Inductor Selection A 4.7µF inductor is recommended for G5121 applications. Small size and high efficiency are the major concerns for most G5121 applications. Inductor with low core losses and small DCR (cooper wire resistance) at 1MHz are good choice for G5121 applications. Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw 8 Global Mixed-mode Technology Inc. Package Information G5121 C L D E H e1 e θ1 A2 A A1 b Note: 1. Package body sizes exclude mold flash protrusions or gate burrs 2. Tolerance ±0.1000 mm (4mil) unless otherwise specified 3. Coplanarity: 0.1000mm 4. Dimension L is measured in gage plane SYMBOL A A1 A2 b C D E e H L θ1 MIN. 1.00 0.00 0.70 0.35 0.10 2.70 1.40 ----2.60 0.37 1º DIMENSION IN MM NOM. 1.10 ----0.80 0.40 0.15 2.90 1.60 1.90(TYP) 2.80 -----5º MAX. 1.30 0.10 0.90 0.50 0.25 3.10 1.80 ----3.00 ----9º MIN. 0.039 0.000 0.028 0.014 0.004 0.106 0.055 ----0.102 0.015 1º DIMENSION IN INCH NOM. 0.043 ----0.031 0.016 0.006 0.114 0.063 0.075(TYP) 0.110 ----5º MAX. 0.051 0.004 0.035 0.020 0.010 0.122 0.071 ----0.118 ----9º Taping Specification PACKAGE SOT-23-6 Feed Direction SOT- 23-6 Package Orientation GMT Inc. does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and GMT Inc. reserves the right at any time without notice to change said circuitry and specifications. Q’TY/REEL 3,000 ea Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw 9