high voltage low-side N-channel MOSFET controller

www.DataSheet4U.com LM3430 Boost Controller for LED Backlighting January 2007 LM3430 Boost Controller for LED Backlighting General Description The LM3430 is a high voltage low-side N-channel MOSFET controller. Ideal for use in a boost regulator, the LM3430 can power the LED backlight in LCD panels, such as in notebook PCs. It contains all of the features needed to implement single ended primary topologies. Output voltage regulation is based on current-mode control, which eases the design of loop compensation while providing inherent input voltage feed-forward. The LM3430 includes a start-up regulator that operates over a wide input range of 6V to 40V. The PWM controller is designed for high speed capability including an oscillator frequency range up to 2 MHz and total propagation delays less than 100 ns. Additional features include an error amplifier, precision reference, line under-voltage lockout, cycle-by-cycle current limit, slope compensation, soft-start, external synchronization capability and thermal shutdown. The LM3430 is available in the LLP-12 package. Features ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Internal 40V Startup Regulator 1A Peak MOSFET Gate Driver VIN Range 6V to 40V Duty Cycle Limit in Excess of 90% Programmable UVLO with Hysteresis Cycle-by-Cycle Current Limit External Synchronizable (AC-coupled) Single Resistor Oscillator Frequency Set Slope Compensation Adjustable Soft-start LLP-12 (3mm x 3mm) Applications ■ LED Backlight Driver (companion to LM3432) ■ Boost Converter ■ SEPIC Converter Typical Application 20209601 © 2007 National Semiconductor Corporation 202096 www.national.com www.DataSheet4U.com LM3430 Connection Diagram 20209602 12-Lead LLP Package NS Package Number SDF12A Ordering Information Part Number LM3430SD LM3430SDX NS Package Drawing SDF12A SDF12A Supplied As 1000 Units on Tape and Reel 4500 Units on Tape and Reel Pin Descriptions Pin(s) 1 2 3 Name VDHC VIN FB Description Proprietary control input from LM3432 Source input voltage Feedback pin Error amplifier output and PWM comparator input Application Information This pin accepts a control signal from LM3432 to adjust the output voltage in real time. Input to the start-up regulator. Operates from 6V to 40V. Inverting input to the internal voltage error amplifier. The noninverting input of the error amplifier connects to a 1.25V reference. The control loop compensation components connect between this pin and the FB pin. 4 5 6 7 8 COMP VCC OUT GND UVLO Output of the internal, high voltage linear This pin should be bypassed to the GND pin with a ceramic regulator. capacitor. Output of gate driver System ground Input Under-Voltage Lock-out Current Sense input Set the start-up and shutdown levels by connecting this pin to the input voltage through a resistor divider. A 20 µA current source provides hysteresis. Input for the switch current sensing used for current mode control and for current limiting. An external resistor connected from this pin to GND sets the oscillator frequency. This pin can also accept an ac-coupled input for synchronization from an external clock. An external capacitor placed from this pin to ground will be charged by a 10 µA current source, creating a ramp voltage to control the regulator start-up. Leave this pin open-circuit. Thermal connection pad, connect to GND. Connect this pin to the gate of the external MOSFET. The gate driver has a 1A peak current capability. 9 CS 10 RT/SYNC Oscillator frequency adjust pin and synchronization input 11 12 DAP SS NC EP Soft-start pin No-connect Exposed Pad www.national.com 2 www.DataSheet4U.com LM3430 Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. VIN to GND VCC to GND RT/SYNC to GND OUT to GND All other pins to GND Power Dissipation Junction Temperature -0.3V to 45V -0.3V to 16V -0.3V to 5.5V -1.5V for < 100 ns -0.3V to 7V Internally Limited 150°C Storage Temperature Soldering Information Vapor Phase (60 sec.) Infrared (15 sec.) ESD Rating Human Body Model (Note 2) -65°C to +150°C 215°C 220°C 2 kV Operating Ranges Supply Voltage External Volatge at VCC Junction Temperature Range (Note 4) 6V to 40V 7.5V to 14V -40°C to +125°C Limits in standard type are for TJ = 25°C only; limits in boldface type apply over the junction temperature (TJ) range of -40°C to +125°C. Minimum and Maximum limits are guaranteed through test, design, or statistical correlation. Typical values represent the most likely parametric norm at TJ = 25°C, and are provided for reference purposes only. VIN = 18V and RT = 27.4 kΩ unless otherwise indicated. (Note 3) Symbol VFB Parameter FB Pin Voltage Conditions -40°C ≤ TJ ≤ 125°C 9V ≤ VIN ≤ 40V, ICC = 1 mA 6V ≤ VIN < 9V, VCC Pin Open Circuit OUT Pin Capacitance = 0 VCC = 10V VCC = 0V, (Note 4, 6) ICC = 0 mA, fSW < 200 kHz 6V ≤ VIN ≤ 8.5V VIN increasing VIN Decreasing VIN = 6.0V VIN = 8.0V VIN = 18.0V 15 Min 1.225 6.6 5 3.5 35 200 8.7 260 58 53 1.1 5 300 VIN = 40V VUVLO = 0V, VCC = Open Circuit 150 350 4 75 VFB = 1.5V VCOMP = 1V 5 17 500 450 V mV µA µA MHz dB mA Ω 4 Typ 1.250 7 Max 1.275 7.4 V Units V SYSTEM PARAMETERS START-UP REGULATOR VCC Regulation VCC VCC Regulation Supply Current VCC Current Limit Dropout Voltage Across Bypass Switch Bypass Switch Turn-off Threshold Bypass Switch Threshold Hysteresis VCC Pin Output Impedance 0 mA ≤ ICC ≤ 5 mA VCC Pin UVLO Rising Threshold VCC Pin UVLO Falling Hysteresis Start-up Regulator Leakage Shutdown Current Gain Bandwidth DC Gain COMP Pin Current Sink Capability Electrical Characteristics ICC ICC-LIM VIN - VCC VBYP-HI VBYP-HYS ZVCC VCC-HI VCC-HYS IVIN IIN-SD GBW ADC ICOMP UVLO VSD ISD-HYS CURRENT LIMIT tLIM-DLY VCS tBLK RCS mA mA mV V mV ERROR AMPLIFIER Shutdown Threshold Shutdown Hysteresis Current Source CS steps from 0V to 0.6V OUT transitions to 90% of VCC 1.22 16 1.25 20 1.28 24 V µA Delay from ILIM to Output Current Limit Threshold Voltage Leading Edge Blanking Time CS Pin Sink Impedance 30 0.45 0.5 65 40 0.55 75 ns V ns Ω Blanking active 3 www.national.com www.DataSheet4U.com LM3430 Symbol SOFT-START ISS VSS-OFF OSCILLATOR Parameter Soft-start Current Source Soft-start to COMP Offset RT to GND = 84.5 kΩ Conditions Min 7 0.35 Typ 10 0.55 200 600 990 Max 13 0.75 230 675 1115 Units µA V kHz kHz kHz V (Note 5) (Note 5) (Note 5) 170 525 865 3.8 fSW VSYNC-HI RT to GND = 27.4 kΩ RT to GND = 16.2 kΩ Synchronization Rising Threshold PWM COMPARATOR tCOMP-DLY DMIN DMAX APWM VCOMP-OC ICOMP-SC VSLOPE MOSFET DRIVER VSAT-HI VSAT-LO tRISE tFALL TSD TSD-HYS θJA Output High Saturation Voltage (VCC – VOUT) Output Low Saturation Voltage (VOUT) OUT Pin Rise Time OUT Pin Fall Time Thermal Shutdown Threshold Thermal Shutdown Hysteresis Junction to Ambient Thermal Resistance SDF-12A Package IOUT = 50 mA IOUT = 100 mA OUT Pin load = 1 nF OUT Pin load = 1 nF 0.25 0.25 18 15 165 25 122 0.75 0.75 V V ns ns °C °C °C/W Delay from COMP to OUT Transition Minimum Duty Cycle Maximum Duty Cycle COMP to PWM Comparator Gain COMP Pin Open Circuit Voltage COMP Pin Short Circuit Current Slope Compensation Amplitude VFB = 0V VCOMP = 0V, VFB = 1.5V 4.3 0.6 80 VCOMP = 2V CS stepped from 0V to 0.4V VCOMP = 0V 90 95 0.33 5.2 1.1 105 6.1 1.5 130 25 0 ns % % V/V V mA mV SLOPE COMPENSATION THERMAL CHARACTERISTICS Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. The Recommended Operating Limits define the conditions within which the device is intended to be functional. For guaranteed specifications and test conditions, see the Electrical Characteristics. Note 2: The human body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin. Note 3: Min and Max limits are 100% production tested at 25°C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods. Limits are used to calculate National’s Average Outgoing Quality Level (AOQL). Note 4: Device thermal limitations may limit usable range. Note 5: Specification applies to the oscillator frequency. Note 6: VCC provides bias for the internal gate drive and control circuits. www.national.com 4 www.DataSheet4U.com LM3430 Typical Performance Characteristics Efficiency, VO = 40V VFB vs. Temp (VIN = 18V) 20209654 20209603 VFB vs. VIN (TA = 25°C) VCC vs. VIN (TA = 25°C) 20209604 20209605 Max Duty Cycle vs. fSW (TA = 25°C) fSW vs. Temperature (RT = 16.2 kΩ) 20209606 20209607 5 www.national.com www.DataSheet4U.com LM3430 RT vs. fSW (TA = 25°C) SS vs. Temperature 20209608 20209609 OUT Pin tR vs. Gate Capacitance OUT Pin tF vs. Gate Capacitance 20209610 20209611 www.national.com 6 www.DataSheet4U.com LM3430 Block Diagram 20209612 7 www.national.com www.DataSheet4U.com LM3430 Example Circuit: LM3430 and LM3432 20209613 FIGURE 1. LM3430 with LM3432 Application Parameters for Various LED Configurations Input Voltage Maximum Output Voltage LED Configuration Switching Frequency L1 Co 8V to 21V 33V 8 LEDs x 6 Strings, 20 mA per string 1 MHz 22 µH 10 µF, 50V 8V to 21V 50V 12 LEDs x 6 Strings, 20 mA per string 1 MHz 22 µH 20 µF, 100V 8V to 18V 33V 8 LEDs x 6 Strings, 20 mA per string 2 MHz 4.7 µH 10 µF, 50V www.national.com 8 www.DataSheet4U.com LM3430 Cin Cinx Css Rt Rfb1 Rfb2 Ruv1 Ruv2 Control Loop Compensation C1 R1 C2 VDHC Rdhc Slope Compensation Rs1 Rs2 Current Sensing Rsns Csns 10 µF, 50V 100 nF 1 nF 16.5 kΩ 4.64 kΩ 118 kΩ 10 kΩ 49.9 kΩ 12 pF 75 kΩ 220 nF 30 kΩ 4.02 kΩ 301Ω 0.2Ω (1W) 1 nF 10 µF, 50V 100 nF 1 nF 16.5 kΩ 3.01 kΩ 118 kΩ 10 kΩ 49.9 kΩ 12 pF 118 kΩ 47 nF 9.09 kΩ 4.02 kΩ 301Ω 0.2Ω (1W) 1 nF 10 µF, 50V 100 nF 1 nF 8.25 kΩ 16.5 kΩ 422 kΩ 10 kΩ 49.9 kΩ 39 pF 150 kΩ 4.7 nF 60.4 k�