G5121 GMT | Alldatasheet
Document overview
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Technical content
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
Applications
White LED Backlight Display for PDA Pocket PC Smart Phones Handheld Devices Cellular Phones General Description The G5121 is a step-up DC/DC converter specifically designed to drive up to 5 series white LEDs with con- stant 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 ex- ternal components. A low 0.254V feedback voltage minimizes power loss in the current setting resistor for high efficiency. The OVP pin monitors the output volt- age and turns off the converter whenever the LEDs are open. The G5121 is available in low profile SOT-23-6 pack- age.
Ordering Information
NUMBER MARKING TEMP. RANGE PACKAGE (Pb free) G5121TB1U 5121x -40°C ~ +85°C SOT-23-6 Note: TB : SOT23-6 U: Tape & Reel Pin Configuration Typical Application Circuit VCC SHDN SOT-23-6 G5121 1SW GND FB
5 OVP
2.7V to 4.2V OVP
5 LEDs
4.7µF/6.3V 4.7µH 1µF/25V C1:TAIYO YUDEN, JMK212BJ475KD C2:TAIYO YUDEN, TMK316BJ105KD VCC SHDN SOT-23-6 G5121 1SW GND FB 2.7V to 4.2V OVP 4.7µF/6.3V 4.7µH 1µF/25V VCC SHDN SOT-23-6 G5121 1SW GND FB 2.7V to 4.2V OVP 4.7µF/6.3V 4.7µH 1µF/25V C1:TAIYO YUDEN, JMK212BJ475KD C2:TAIYO YUDEN, TMK316BJ105KD
Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw G5121Global Mixed-mode Technology Inc. Absolute Maximum Ratings 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 CONDITIONS MIN TYP MAX UNITS Input Voltage Range 2.5 --- 6 V Input Voltage UVLO 1.7 2.0 2.3 V Over Voltage Protection Threshold trigger 18.5 19.5 21 V Over Voltage Protection Threshold release 13.5 15 16.5 V OVP Pin Input Current V ovp = 16V --- 40 60 µA VFB = 0.3V (no switching) --- 80 120 µA VFB = 0.2V (switching) --- --- 2 mA Quiescent Current V SHDN = 0V --- 0.1 1 µA Initial Accuracy 244 254 264 mV FB Comparator Trip Point Temperature Coefficient --- 100 --- ppm/°C Switching Frequency V FB = 0.2V 0.8 1.0 1.2 MHz Maximum Duty 85 --- --- % Switch RDS(ON) I SW = 150mA --- 0.7 1.0 Ω Switch Leakage Current V SW = 20V --- 0.1 10 µA Switch Current Limit 500 600 700 mA Soft Start Time --- 120 --- µs SHDN Pin Voltage High 2 --- --- V SHDN Pin Voltage Low --- --- 0.8 V
Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw G5121Global Mixed-mode Technology Inc. Typical Performance Characteristics (VCC= +3.6V, V SHDN = +3.6V, L=4.7µH, TA=25°C, unless otherwise noted.) Stability for Driving 5 WLEDs Stability for Driving 4 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 G5121Global Mixed-mode Technology Inc. Typical Performance Characteristics (continued) 0 5 10 15 20 25 Load Current (mA) Efficiency (%) 5LEDs, CO=1µF VIN=4.2VVIN=2.7V VIN=3.6V 0 5 10 15 20 25 Load Current (mA) Efficiency (%) VIN=4.2V VIN=3.6V VIN=2.7V 4LEDs, CO=1µF Efficiency vs. Load Current Efficiency vs. Load Current Inrush Current for Driving 3 WLEDs Inrush Current for Driving 2 WLEDs OVP Waveform Dimming Control for Driving 4 WLEDs
Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw G5121Global Mixed-mode Technology Inc. Typical Performance Characteristics (continued) 0 5 10 15 20 25 Load Current (mA) Efficiency (%) VIN=3.6V 3LEDs, CO=1µF VIN=4.2VVIN=2.7V 0 5 10 15 20 25 Load Current (mA) Efficiency (%) VIN=4.2VVIN=3.6VVIN=2.7V 2LEDs, CO=1µF 100 110 120 130 22 . 533 . 544 . 555 . 56 Input Voltage (V) IQ_NoSW (uA) 100 -40 -20 0 20 40 60 80 100 Temperature (°C) IQ_NoSW (uA) 0.7 0.75 0.8 0.85 0.9 0.95 2 2.5 3 3.5 4 4.5 5 5.5 6 Input Voltage (V) Frequency (MHz) 0.7 0.75 0.8 0.85 0.9 0.95 1.05 1.1 -40 -20 0 20 40 60 80 100 Temperature (°C) Frequency (MHz) Efficiency vs. Load Current Efficiency vs. Load Current IQ_NoSW vs. Input Voltage IQ_NoSW vs. Temperature Frequency vs. Input Voltage Frequency vs. Temperature
Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw G5121Global Mixed-mode Technology Inc. Typical Performance Characteristics (continued) 17.5 18.5 19.5 20.5 2 2.5 3 3.5 4 4.5 5 5.5 6 Input Voltage (V) OVP Trigger Threshold (V) 17.5 18.5 19.5 20.5 - 4 0 - 2 00 2 04 06 08 0 1 0 0 Temperature (°C) OVP Trigger Threshold (V) 13.5 14.5 15.5 16.5 2 2.5 3 3.5 4 4.5 5 5.5 6 Input Voltage (V) OVP Release Threshold (V) 13.5 14.5 15.5 16.5 - 4 0 - 2 00 2 04 06 08 0 1 0 0 Temperature (°C) OVP Release Threshold (V) 22 . 533 . 544 . 555 . 56 Input Voltage (V) OVP Pin Input Current (uA) - 4 0 - 2 00 2 04 06 08 0 1 0 0 Temperature (°C) OVP Pin Input Current (uA) OVP Trigger Threshold vs. Input Voltage OVP Trigger Threshold vs. Temperature OVP Release Threshold vs. Input Voltage OVP Release Threshold vs. Temperature OVP Pin Input Current vs. Input Voltage OVP Pin Input Current vs. Temperature
Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw G5121Global Mixed-mode Technology Inc. Recommended Minimum Footprint SOT-23-6 Block Diagram VREF SWFB 0.254V GND CONTROL DRIVER OC OVP SHDN R S Q 1MHz OSCILLATOR VCC COMPENSATION COMPARATOR A2+ RAMP GENERATOR VREF SWFB 0.254V GND CONTROL DRIVER OC OVP SHDN R S Q 1MHz OSCILLATOR VCC COMPENSATION COMPARATOR A2+ RAMP GENERATOR
Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw G5121Global Mixed-mode Technology Inc. Pin Description PIN NAME FUNCTION 1 SW Switch Pin. The drain of the internal NMOS power switch. Connect this pin to inductor. 2 GND Ground Pin. 3 FB Feedback Pin. Connect current setting resistor Rs from th is pin to ground. The LED current is set a s 0.254V/ Rs. 4 SHDN Active Low Shutdown Pin. 5 OVP Over Voltage Protection Sense Pin. 6 VCC Input Supply Pin. Bypass this pin with a capacitor as close to the device as possible. 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 dia- gram. 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 feed- back 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 de- livered 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 in- creased 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.
Application Information
A 4.7µF inductor is recommended for G5121 applica- tions. Small size and high efficiency are the major concerns for most G5121 applications. Inductor with low core losses and small DCR (cooper wire resis- tance) at 1MHz are good choice for G5121 applica- tions. Since the G5121 is designed to operate in discontinu- ous 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 300 Ω resistor across the inductor, although this will degrade efficiency. Capacitor Selection The small size of ceramic capacitors makes them suit- able 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 in- put/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 (C T or C D) repre- sents 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 suffi- cient for most G5121 applications.
Ver: 1.1 Nov 17, 2005 TEL: 886-3-5788833 http://www.gmt.com.tw G5121Global Mixed-mode Technology Inc.
Package Information
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 θ1 1º 5º 9º 1º 5º 9º Taping Specification PACKAGE Q’TY/REEL SOT-23-6 3,000 ea 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. E D H L C b A e E D H L C b A e Feed Direction Feed Direction