G5126 Global Mixed-mode Technology Inc. High Efficiency, Constant Current, Boost DC/DC White-LEDs Drive Features General Description The G5126 boost converter contains a 0.7Ω internal switch. The IC operates at constant frequency 1MHz, allowing the use of tiny, low cost and low height inductors and capacitors. The IC operates from a 2.7V to 5.5V supply voltage. High inrush current at start-up is eliminated using the soft-start function. Constant frequency current mode PWM architecture results in low, predictable output noise. The G5126 includes cycle-by-cycle 850mA current limiting to maximum inductor current and over-temperature protection circuit. The over-voltage protection will be enabled when VOUT exceeds 28V. The current of LED is set by a resistor connected between FB and GND. The G5126 is available in SOT-23-6 package. Operating Voltage：2.7V to 5.5V High Operating Frequency：1MHz High Output Voltage：28V Shutdown Current：<1µA Over-Voltage Protection Digital Dimming Control Built-in Cycle-by-Cycle Current-Limiting Soft-Start Function 0.2V Low Reference Voltage Tiny SOT-23-6 Package Applications LED Module Compact Back Light Module Constant Current Source Ordering Information ORDER NUMBER MARKING TEMP. RANGE PACKAGE (Pb free) G5126TB1U 5126x -40°C to 85°C SOT-23-6 Note: TB: SOT-23-6 1 : Bonding Code U: Tape & Reel Pin Configuration Typical Application Circuit 10µH VOUT VIN=2.7V to 5.5V G5126 LX 1 6 IN GND 2 5 OVP FB 3 4 EN CIN 4.7µF COUT 1µF LX IN OVP G5126 G963 FB EN PWM Dimming GND I=20mA SOT-23-6 10 R1 TEL: 886-3-5788833 http://www.gmt.com.tw Ver: 0.5 Jan 11, 2008 1 G5126 Global Mixed-mode Technology Inc. Continuous Power Dissipation (TA = +25°C)* SOT-23-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400mW Operating Temperature Range1 . . . . . -40°C to +85°C Junction Temperature . . . . . . . . . . . . . . . . . . . +150°C Storage Temperature . . . . . . . . . . . . -65°C to +150°C Reflow Temperature (soldering, 10sec) . . . . . . .260°C Absolute Maximum Ratings IN to GND. . . . . . . . . . . . . . . . . . . . . . . . . . .-0.3V to 7V LX, OVP to GND. . . . . . . . . . . . . . . . . . . . -0.3V to 35V EN to GND. . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to VIN FB to GND. . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to VIN Thermal Resistance Junction to Ambient, (θJA)* SOT-23-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240°C/W Note: 1. It is guaranteed to meet performance specifications from 0°C to 85°C. Specifications over the -40°C to 85°C operating temperature range are assured by design, characterization and correlation with statistical process controls. * Please refer to “Recommended Minimum Footprint”. Electrical Characteristics VIN=VEN=3.6V, TA = 25°C. PARAMETER CONDITIONS MIN TYP MAX UNITS Operating Input Voltage 2.7 --- 5.5 V Over-voltage Threshold --- 28 --- V --- 2 --- V Quiescent Current No Switching --- 0.2 0.3 mA Shutdown Supply Current VIH EN Input Level VIL EN=0V --1.5 0 --- 1 --- µA V Over-voltage Hysteresis --- --- 0.8 V 2 2.25 2.5 V ----0.19 1 90 0.2 ----0.21 --- 700 --- MHz % V mΩ --500 --850 10 1300 µA mA Trigger --- 120 --- °C Hysteresis ----- 20 0.5 ----- °C ms UVLORISING Oscillator Frequency Maximum Duty Cycle Feedback Regulation Voltage NMOS RDS-ON ILX=200mA LX Leakage Current Switching Current Limit EN=0, VLX=28V VIN=3.0V,duty cycle=80% Over Temperature Soft Start TEL: 886-3-5788833 http://www.gmt.com.tw Ver: 0.5 Jan 11, 2008 2 G5126 Global Mixed-mode Technology Inc. Typical Performance Characteristics (VCC= +3.6V, VEN= +3.6V, L=47µH, TA=25°C, unless otherwise noted.) Stability Waveform-3 LEDs Stability Waveform-6 LEDs Inrush Current Waveform-3 LEDs Inrush Current Waveform-6 LEDs Dimming Control Waveform-3 LEDs Dimming Control Waveform-6 LEDs TEL: 886-3-5788833 http://www.gmt.com.tw Ver: 0.5 Jan 11, 2008 3 Global Mixed-mode Technology Inc. G5126 Typical Performance Characteristics (Continued) OVP Waveform Recommended Minimum Footprint SOT-23-6 TEL: 886-3-5788833 http://www.gmt.com.tw Ver: 0.5 Jan 11, 2008 4 G5126 Global Mixed-mode Technology Inc. Pin Descriptions PIN Name 1 2 LX GND 3 4 FB EN 5 6 OVP IN FUNCTION Power Switching Output Ground Pin. Feedback Input. Enable Input. Drive EN high to turn on the regulator, drive it low to turn it off. Over-voltage protection input. Connect to the output. Power Input Pin. It must be bypassed with a low-ESR capacitor. Block Diagram IN CURRENT SENSE CURRENT LIMIT REFERENCE LX + CONTROL FB EN ON/OFF CONTROL GND OVP OVP TEL: 886-3-5788833 http://www.gmt.com.tw Ver: 0.5 Jan 11, 2008 5 G5126 Global Mixed-mode Technology Inc. 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 large diode capacitance, which can cause significant switching losses at the 1MHz switching frequency of the G5126. Operating The G5126 step-up DC-DC converter operates from a 2.7V to 5.5V supply. The device includes an internal switching MOSFET with a 0.7Ω on-resistance and consumes 200μA of supply current. During startup, the G5126 limits the maximum on-time to limit initial battery inrush current. Adjusting the output voltage by changing the resistance of R1 and the number of LEDs that connect in series from VOUT to FB the output voltage may up to 28V. The current of LED is set by the resistor R1 which connect from FB to GND. The current equals to voltage of FB (0.2V) to divide the resistance of R1. The G5126 built in a cycle-by-cycle 850mA current-limit function to maximum inductor current. The G5126 consumes 0.1μA when voltage of EN is Low. The over-voltage protection is included. LED Current setting LED current can be set with feedback resister (R1) ILED = 0.2 / R1 LED Dimming Control, Softstart LED dimming control by PWM signal to EN pin LED dimming control is pos sible by forcing PWM signal to EN pin. When the power-on or start up with EN pin, softstart function works, however, after that, if the EN pin is set as “L” and set EN pin “H” again during the shutdown delay time, softstart function is disabled and starts up fast to normal mode, therefore 200Hz to 20kHz PWM signal is standard. By the EN pin input, LED turns on and off. Average LED current varies depending on the duty cycle of EN input. Too high frequency PWM signal is not effective because of its delay. Application Information Inductor Selection The inductor’s saturation current rating should be greater than the peak switching current. The large inductance prevents the large inductor’s current ripple to induce maximum current limit in on-time period and output voltage ripple can be reduced also. Inductor with low core losses and small DCR (cooper wire resistance) is recommended. Capacitor Selection The small size of ceramic capacitors makes them suitable for G5126 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. EN G5126 FB R1 Diode Selection Schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for G5126 applications. The forward voltage drop of a Dimming control by EN pin input TEL: 886-3-5788833 http://www.gmt.com.tw Ver: 0.5 Jan 11, 2008 6 Global Mixed-mode Technology Inc. G5126 Duty=0% to 100% PWM signal duty cycle can be used up to the maximum LED current and minimum LED current as in the next formulas. Dimming control by DC voltage LED dimming control is also possible by using the DC voltage to FB pin. LED current is adjustable by DC voltage and resisters, R1 and R2 in the following figure. ILEDMIN=(0.2 − R2 × (VH − 0.2) / (R3 + R4)) / R1 ILEDMAX=(0.2 − R2 × (VL − 0.2) / (R3 + R4)) / R1 ILED = (VDC − 0.2) / R2 − 0.2 / R1 For example, supposed that the PWM signal level is set as 3.3V/0V, to adjust the LED current range from 0mA to 20mA by the duty cycle, our recommendation external components values are, R1=10Ω, R2=12kΩ, R3=39kΩ, R4=150kΩ or around. G5126 R2 VDC FB C3 should be set large enough to regard the PWM signal as adjustable DC voltage by the filter. In this method, higher frequency control than the frequency against the EN pin can be used for dimming control. R1 Dimming control by DC voltage Dimming control by feedback voltage and filtered PWM signal LED dimming control is also possible by using the feedback voltage and filtered PWM signal. LED current is adjustable according to the “H” level (VH) and “L” level (VL) of PWM signal and resisters. G5126 R2 FB R1 R3 R4 VH VL C3 Dimming control by DC voltage TEL: 886-3-5788833 http://www.gmt.com.tw Ver: 0.5 Jan 11, 2008 7 G5126 Global Mixed-mode Technology Inc. Package Information C D L H E θ1 e e1 A A2 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 MIN. DIMENSION IN MM NOM. MAX. MIN. DIMENSION IN INCH NOM. MAX. A A1 1.00 0.00 1.10 ----- 1.30 0.10 0.039 0.000 0.043 ----- 0.051 0.004 A2 b 0.70 0.35 0.80 0.40 0.90 0.50 0.028 0.014 0.031 0.016 0.035 0.020 C D 0.10 2.70 0.15 2.90 0.25 3.10 0.004 0.106 0.006 0.114 0.010 0.122 E e 1.40 ----- 1.60 0.95 1.80 ----- 0.055 ----- 0.063 0.037 0.071 ----- e1 ----- 1.90(TYP) ----- ----- 0.075(TYP) ----- H L θ1 2.60 0.37 2.80 ------ 3.00 ----- 0.102 0.015 0.110 ----- 0.118 ----- 1° 5° 9° 1° 5° 9° SYMBOL Taping Specification PACKAGE Q’TY/REEL SOT-23-6 3,000 ea 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. TEL: 886-3-5788833 http://www.gmt.com.tw Ver: 0.5 Jan 11, 2008 8