MP24833GN-Z

MP24833 3A, 55V White LED Driver The Future of Analog IC Technology DESCRIPTION FEATURES The MP24833 is a 55V, 3A, white LED driver suitable for step-down, inverting step-up/down and step-up applications. It achieves 3A output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. Fault condition protection includes thermal shutdown, cycle-by-cycle peak current limiting, open strings protection and output short circuit protection.   3A Maximum Output Current Unique Step-Up/Down Operation (BuckBoost Mode) Wide 4.5V-to-55V Operating Input Range for Step-Down Applications (Buck Mode) 0.19Ω Internal Power MOSFET Switch Fixed 200kHz Switching Frequency Analog and PWM Dimming 0.198V Reference Voltage 6μA Shutdown Mode No Minimum Number of LEDs Required Stable with Low ESR Output Ceramic Capacitors Cycle-by-Cycle Over-Current Protection Thermal Shutdown Protection Open Strings Protection Output Short-Circuit Protection Available in an SOIC8E Package         The MP24833 incorporates both DC and PWM dimming onto a single control pin. The separate input reference ground pin allows for direct enable and/or dimming control for a positive to negative power conversion.      The MP24833 requires a minimal number of readily-available standard external components and is available in an SOIC8E package. APPLICATIONS       General LED Illumination LCD Backlight Panels Notebook Computers Automotive Internal Lighting Portable Multimedia Players Portable GPS Devices All MPS parts are lead-free, halogen free, and adhere to the RoHS directive. For MPS green status, please visit MPS website under Quality Assurance. “MPS” and “The Future of Analog IC Technology” are Registered Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION OVP BST CIN SW EN/DIM 5 7 CBST 8 L EN/DIM D ON OFF DC or PWM Input 6 INGND FB VSS Co LEDs VDD R OVP1 VIN R OVP2 3 1 4 R FB 2 MP24833 Rev. 1.03 www.MonolithicPower.com 05/05/2010 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 1 MP24833 – 3A, 55V WHITE LED DRIVER ORDERING INFORMATION Part Number* Package Top Marking MP24833GN SOIC-8 EP MP24833 * For Tape & Reel, add suffix –Z (e.g. MP24833GN–Z). PACKAGE REFERENCE SOIC8E ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply Voltage VDD - VSS ............................. 60V VSW - VSS ...............................-0.3V to VIN + 0.3V VBST ...................................................... VSW + 6V VEN/Dim - VINGND.................................-0.3V to +6V VINGND - VSS .....................................-0.3V to 60V Other pins - VSS ...............................-0.3V to +6V (2) Continuous Power Dissipation (TA = +25°C) SOIC8E...................................................... 2.5W Junction Temperature ...............................150°C Lead Temperature ....................................260°C Storage Temperature............... -65°C to +150°C SOIC-8 EP ..............................50 ...... 10 ... °C/W Recommended Operating Conditions (3) (4) θJA θJC Notes: 1) Exceeding these ratings may damage the device. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-toambient thermal resistance θJA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX)-TA)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. Internal thermal shutdown circuitry protects the device from permanent damage. 3) The device function is not guaranteed outside of the recommended operating conditions. 4) Measured on JESD51-7, 4-layer PCB. Supply Voltage VDD - VSS .................4.5V to 55V Operating Junction Temp. (TJ). -40°C to +125°C MP24833 Rev. 1.03 www.MonolithicPower.com 05/05/2010 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 2 MP24833 – 3A, 55V WHITE LED DRIVER ELECTRICAL CHARACTERISTICS VIN = 12V, TA = 25°C, all voltages with respect to VSS, unless otherwise noted. Parameters Feedback Voltage Feedback Current Switch-On Resistance (5) Switch Leakage Current Limit (5) Oscillator Frequency Fold-back Frequency Maximum Duty Cycle Minimum On-Time (5) Under Voltage Lockout Threshold Rising Under Voltage Lockout Threshold Hysteresis EN Input Current EN OFF Threshold (w/Respect to INGND) EN ON Threshold (w/Respect to INGND) Minimum EN Dimming Threshold Maximum EN Dimming Threshold Supply Current (Quiescent) Supply Current (Quiescent) at EN Off Thermal Shutdown (5) Open LED OV Threshold Open LED OV Hysteresis Symbol Condition VFB 4.5V  VIN  55V IFB VFB = 0.22V RDS(ON) VEN = 0V, VSW = 0V Duty=0 fSW VFB = 0V, VOVP=0V VFB = 0.19V tON Min 0.188 -50 IQ Ioff VOVP_ th VOVP_ hys Max 0.208 50 190 1 3 VEN = 2V VEN Falling VEN Rising VFB = 0V VFB = 0.2V VEN = 2V, VFB = 1V VEN=0V Typ 0.198 5 200 36 91 100 3.3 200 3.6 2.1 0.4 0.6 1.25 1.1 0.67 1.36 0.6 6 150 1.2 60 0.6 0.75 1.47 0.8 12 1.3 Units V nA mΩ μA A kHz kHz % ns V mV μA V V V V mA μA °C V mV Notes: 5) Guaranteed by design. MP24833 Rev. 1.03 www.MonolithicPower.com 05/05/2010 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 3 MP24833 – 3A, 55V WHITE LED DRIVER TYPICAL CHARACTERISTICS MP24833 Rev. 1.03 www.MonolithicPower.com 05/05/2010 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 4 MP24833 – 3A, 55V WHITE LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS Performance waveforms are tested on the evaluation board of the Design Example section. VIN = 36V, ILED = 1A, 7WLEDs in series, L = 68µH, TA = 25°C, Buck Application, unless otherwise noted. MP24833 Rev. 1.03 www.MonolithicPower.com 05/05/2010 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 5 MP24833 – 3A, 55V WHITE LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS (continued) Performance waveforms are tested on the evaluation board of the Design Example section. VIN = 24V, ILED = 1A, 7WLEDs in series, L = 68µH, TA = 25°C, Buck-boost Application, Refer to INGND, unless otherwise noted. MP24833 Rev. 1.03 www.MonolithicPower.com 05/05/2010 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 6 MP24833 – 3A, 55V WHITE LED DRIVER PIN FUNCTIONS Pin # 1 2 3 4 5 6 7 8 Name Description Supply Voltage. The MP24833 operates from a 4.5V to 55V unregulated input (with respect to VSS). Input capacitor is needed to prevent large voltage spikes from appearing at the input. VSS, Power Return. Connect to the lowest potential in the circuit, which is typically the anode of the exposed Schottky rectifier. This pin is the voltage reference for the regulated output voltage, and thus pad requires extra care in layout. The exposed pad is also connected to this pin Over-Voltage Protection. Use a voltage divider to program the OVP threshold. When the OVP pin voltage reaches the shutdown threshold of 1.2V, the switch turns off and will recover when the OVP voltage drops to normal operating range. When the voltage (with respect to OVP VSS) drops below 0.2V and the FB pin voltage is less than 0.1V, the chip treats this as a short circuit and the operating frequency folds back. Program the OVP pin voltage from 0.2V to 1.2V for normal operation. LED Current Feedback Input. Senses the current across the sensing resistor between FB and FB VSS. Connect the current sensing resistor from the bottom of the LED strings to VSS. The FB pin is connected to the bottom of the LED strings. The regulation voltage is 0.198V. On/Off Control Input and Dimming Command Input. A voltage greater than 0.67V will turn on the chip. This pin implements both DC and PWM dimming. When the EN/DIM pin voltage (with respect to INGND) rises from 0.67V to 1.36V, the LED current will change from 0% to EN/DIM 100% of the maximum LED current. To use PWM dimming, apply a 100Hz-to-2kHz square wave signal with amplitude greater than 1.5V to this pin. For combined analog and PWM dimming, apply a 100HZ to 2kHz square wave signal with amplitude from 0.67V to 1.36V. INGND Input Ground Reference. This pin is the reference for the EN/DIM signal. Bootstrap. Connect a capacitor between SW and BST pin to form a floating supply for the BST power switch driver. Use a 100nF or larger ceramic capacitor to provide sufficient energy to drive the power switch with this supply voltage. Switch Output. Source of the internal MOSFET. Connect this pin to the power inductor and SW the cathode of the rectifier diode. VDD MP24833 Rev. 1.03 www.MonolithicPower.com 05/05/2010 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 7 MP24833 – 3A, 55V WHITE LED DRIVER FUNCTIONAL BLOCK DIAGRAM 0.198V Figure 1: Functional Block Diagram MP24833 Rev. 1.03 www.MonolithicPower.com 05/05/2010 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2016 MPS. All Rights Reserved. 8 MP24833 – 3A, 55V WHITE LED DRIVER OPERATION The MP24833 is a current-mode regulator. The error amplifier (EA) output voltage is proportional to the peak inductor current. At the beginning of a cycle, the MOSFET is off. The EA output voltage is higher than the current sense amplifier output, and the current comparator’s output is low. The rising edge of the CLK signal (its frequency is the operating frequency) sets the RS flip-flop. Its output turns on the MOSFET that connects the SW pin and inductor to the input supply. The current sense amplifier detects and amplifies the rising inductor current. The PWM comparator compares the output of the EA against the sum of the ramp compensator and the current sense amplifier. When the sum of the current sense amplifier output and the slope compensation signal exceeds the EA output voltage, the RS flip-flop resets and the MOSFET turns off. The external Schottky rectifier diode (D) conducts the inductor current. If the sum of the current sense amplifier output and the slope compensation signal does not exceed the EA output throughout the cycle, then the falling edge of the CLK resets the flipflop. The output of the EA integrates the voltage difference between the feedback and the 0.198V reference. The EA output will increase when the FB pin voltage less than 0.198V. Since the EA output voltage is proportional to the peak inductor current, The increase in EA output voltage also increases the current delivered to the output. Soft Start When the MP24833 is enabled and VDD exceeds the UVLO threshold, the switching begins. The soft-start is not active when VFBVSS is lower than 1/2 of VREF, which is helpful to charge the output cap quickly. At the same time, the current limit is folded to half. extend slowly to limit the current overshoot at start-up. When the internal reference input of the EA rises up to around VREF+100mV, the soft-start ends and the reference input of the EA is connected to full scale of VREF (0.198V). Open LED Protection The OVP pin is used for open LED protection. It monitors the output voltage through a voltage divider. If the LED is open, there is no voltage on the FB pin. The duty cycle will increase until VOVP-VSS reaches the protection threshold set by the external resistor divider. The top switch turns off until VOVP-VSS decreases sufficiently. Dimming Control The MP24833 allows both DC and PWM dimming. When the voltage on EN (reference to INGND) is less than 0.6V, the chip turns off. For analog dimming, the LED current is linearly dependent on the EN voltage range between 0.67V and 1.36V, from 0% to 100%. EN voltage higher than 1.36V results in the maximum LED current generated. For PWM dimming, (VDIM VINGND) must exceed 1.5V. Use a PWM frequency in the range of 100Hz to 2kHz for good dimming linearity. For combined analog and PWM dimming, apply a PWM signal with amplitude from 0.67V to 1.36V to EN pin. Output Short Circuit Protection The MP24833 features output short-circuit protection. When the output is shorted to VSS, the voltage on OVP pin drops below 0.2V, and the FB pin senses no voltage (