MP24183 1A, 55V, Programmable Frequency White LED Driver The Future of Analog IC Technology FEATURES DESCRIPTION The MP24183 is a 55V, 1A, white LED driver suitable for either step-down or inverting step-up/down applications. It achieves 1A peak 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, input over voltage protection, open strings protection and output short circuit protection. The MP24183 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 MP24183 requires a minimum number of readily available standard external components and is available in a 10-pin 3mm x 3mm QFN package. 1A Maximum Output Current Unique Step-up/down Operation (BuckBoost Mode) Wide 4.5V to 55V Operating Input Range for Step-Down Applications (Buck Mode) 0.28Ω Internal Power MOSFET Switch Adjustable Switching Frequency Analog and PWM Dimming 0.198V Reference Voltage 5μA Shutdown Mode No minimum LED required Stable with Low ESR Output Ceramic Capacitors Cycle-by-Cycle Over Current Protection Thermal Shutdown Protection Open Strings Protection Input Over Voltage Protection Output Short Circuit Protection Available in 10-Pin 3x3 QFN Package APPLICATIONS General LED Illuminations LCD Backlight Panels Handheld Computers Automotive Internal Lighting Portable Multimedia Players Portable GPS Devices “MPS” and “The Future of Analog IC Technology” are Trademarks of Monolithic Power Systems, Inc. TYPICAL APPLICATION VIN 4.5V<VIN<55V OFF ON DC or PWM Input VDD C1 10 OVP MP24183 R4 C3 100nF R3 L1 4.7 SW D1 B360A EN/DIM INGND C4 1nF C2 2.2 FB VSS COMP MP24183 Rev. 1.0 8/28/2008 BST R2 RSET C5 1nF R1 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 1 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER ORDERING INFORMATION Part Number* MP24183DQ Package 3x3 QFN10 Top Marking 9M Free Air Temperature (TA) -40C to +85C * For Tape & Reel, add suffix –Z (e.g. MP24183DQ–Z). For RoHS compliant packaging, add suffix –LF (e.g. MP24183DQ–LF–Z) PACKAGE REFERENCE TOP VIEW VDD 1 10 SW VSS 2 9 BST OVP 3 8 INGND FB 4 7 EN/DIM COMP 5 6 RSET ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply Voltage VDD – VSS............................. 60V VSW – VSS .............................. -0.3V to VIN + 0.3V VBST ...................................................... VSW + 6V VOVP – VSS .......................................-0.3V to +6V VEN – VINGND.....................................-0.3V to +6V VDIM – VINGND....................................-0.3V to +6V VINGND – VSS ..................................... -0.3V to 60V (2) Continuous Power Dissipation (TA = +25°C) ………………………………………………....2.5W Junction Temperature ...............................150C Lead Temperature ....................................260C Storage Temperature ............... -65C to +150C 3x3 QFN10 .............................. 50 ...... 12 ... 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 Junct. Temp (TJ)..... -40C to +125C MP24183 Rev. 1.0 8/28/2008 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 2 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER ELECTRICAL CHARACTERISTICES VIN = 12V, TA = +25C, 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 Symbol Condition VFB 4.5V VIN 55V IFB VFB = 0.22V RDS(ON) VEN = 0V, VSW = 0V fSW Default 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 fSW_default VFB = 0.19V, Rset=100kΩ VFB = 0.19V, Rset open VFB = 0V, VOVP=0V VFB = 0.19V Min 0.188 -50 VOVP VOVP th 2.0 Units V nA mΩ μA A 0.5 MHz 1 1.05 3 IQ Ioff Max 0.208 50 280 tON VEN = 2V VEN Falling VEN Rising VFB = 0V VFB = 0.2V VEN = 2V, VFB = 1V VEN=0V Typ 0.198 1.35 250 90 100 3.3 100 2.1 1.65 3.6 0.4 0.6 1.25 1.1 hys 0.7 1.4 0.8 3.4 150 1.2 60 0.6 0.8 1.5 1.0 15 1.3 MHz kHz % ns V mV μA V V V V mA μA °C V mV Notes: 5) Guaranteed by design. MP24183 Rev. 1.0 8/28/2008 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 3 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER PIN FUNCTIONS Pin # 1 2 3 4 5 6 7 8 9 10 Name Description Supply Voltage. The MP24183 operates from a +4.5V to +55V unregulated input (with respect to VSS). C1 is needed to prevent large voltage spikes from appearing at the input. Power Return Pin. Connect to the lowest potential in the circuit, which is typically the anode of the Schottky rectifier. This pin is the voltage reference for the regulated output voltage. VSS For this reason care must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to prevent switching current spikes from inducing voltage noise into the part. The exposed pad is also connected to this pin. Over Voltage Protection Pin. Use a voltage divider to program OVP threshold. When the OVP pin voltage reaches the shutdown threshold 1.2V, the switch will be turned off and will recover when OVP voltage decreases sufficiently. When the OVP pin voltage (with respect OVP to VSS) is lower than 0.4V and FB pin voltage is lower than 0.1V, the chip reecognizes this as short circuit condition and the operating frequency will be folded back. Program the OVP pin voltage from 0.4V to 1.2V for normal operation. LED Current Feedback Input. MP24183 regulates the voltage across the current sensing resistor between FB and VSS. Connect the current sensing resistor from the bottom of the FB LED strings to VSS. The FB pin is connected to the bottom of the LED strings. The regulation voltage is 0.198V. Output of error amplifier. Connect a 1nF or larger capacitor on COMP to improve the COMP stability and to provide a soft on at start up and PWM dimming. Frequency Set Pin. Connect a resistor to VSS to set the switching frequency and an 1nF RSET capacitor to VSS to bypass the noise. Leaving this pin open gets a default operating frequency 1.35MHz. On/Off Control Input and Dimming Command Input. A voltage greater than 0.6V will turn on the chip. Both DC and PWM dimming are implemented on this pin. When the EN/DIM pin EN/DIM voltage (with respect to INGND) rises from 0.7V to 1.4V, the LED current will change from 0% to 100% of the maximum LED current. To use PWM dimming, apply a 100Hz to 2kHz square wave signal with amplitude greater than 1.4V to this pin. INGND Input Ground Reference. This pin is the reference for the EN/DIM signal. Bootstrap. A capacitor is connected between SW and BST pin to form a floating supply BST across the power switch driver. A 100nF or larger ceramic capacitor is recommended to provide sufficient energy to drive the power switch’s gate above the supply voltage. Switch Output. SW is the source of the internal MOSFET switch. Connect this pin to the SW power inductor and the cathode of the Schottky rectifier. Exposed pad should be connected to VSS in step up/down mode. VDD MP24183 Rev. 1.0 8/28/2008 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 4 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS VIN=20V, ILED=0.7A, two 3W LED in series, step down application, unless otherwise noted. WLED Current vs VEN Efficiency 800 100 700 700 90 600 80 600 500 400 300 200 100 0 0 EFFICIENCY(%) 800 WLED CURRENT(mA) WLED CURRENT(mA) WLED current vs Dimming Duty 500 400 300 200 100 0.2 0.4 0.6 0.8 DIMMING DUTY MP24183 Rev. 1.0 8/28/2008 1 1.2 3WLED, 710mA 70 1WLED, 710mA 60 50 40 30 20 0 -100 0 2WLED, 710mA 10 0 400 800 1200 1600 0 10 VEN(mV) www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 20 30 40 50 INPUT VOLTAGE(V) 60 5 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN=20V, ILED=0.7A, two 3W LED in series, step down application, unless otherwise noted. PWM Dimming Steady State PWM 5V/div. VIN 10V/div. SW 10V/div. SW 10V/div. IINDUCTOR 500mA/div. IINDUCTOR 500mA/div. IWLED 500mA/div. 400ns/div. IWLED 500A/div. EN 5V/div. SW 10V/div. IINDUCTOR 500mA/div. IWLED 500mA/div. 2ms/div. 40us/div. VDD-VSS OVP Protection Open LED Protection EN off EN 5V/div. SW 50V/div. SW 10V/div. SW 10V/div. OVP 1V/div. IINDUCTOR 500mA/div. VDD 20V/div. VLED+ 5V/div. VOUT 5V/div. IWLED 500mA/div. 4us/div. MP24183 Rev. 1.0 8/28/2008 EN on IINDUCTOR 1A/div. IINDUCTOR 500mA/div. 20ms/div. www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 2us/div. 6 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER FUNCTIONAL BLOCK DIAGRAM Figure 1—Functional Block Diagram MP24183 Rev. 1.0 8/28/2008 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 7 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER OPERATION The MP24183 is a current mode regulator. The EA output voltage is proportional to the peak inductor current. At the beginning of a cycle, M1 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 1.35MHz CLK signal sets the RS Flip-Flop. Its output turns on M1 thus connecting the SW pin and inductor to the input supply. The increasing inductor current is sensed and amplified by the Current Sense Amplifier. Ramp compensation is summed to the Current Sense Amplifier output and compared to the Error Amplifier output by the PWM Comparator. When the sum of the Current Sense Amplifier output and the Slope Compensation signal exceeds the EA output voltage, the RS FlipFlop is reset and M1 is turned off. The external Schottky rectifier diode (D1) conducts the inductor current. If the sum of the Current Sense Amplifier output and the Slope Compensation signal does not exceed the EA output for a whole cycle, then the falling edge of the CLK resets the Flip-Flop. The output of the Error Amplifier integrates the voltage difference between the feedback and the 0.198V reference. The polarity is a FB pin voltage lower than 0.198V increases the EA output voltage. Since the EA output voltage is proportional to the peak inductor current, an increase in its voltage also increases the current delivered to the output. Open LED Protection If the LED is open, there is no voltage on the FB pin. The duty cycle will increase until V(VDD)-V(VSS) reaches 55V or OVP-VSS reaches the shutdown threshold set by the external resistor divider. The top switch will turn off till the voltage V(VDD)-V(VSS) and OVPVSS decreases sufficiently. MP24183 Rev. 1.0 8/28/2008 Dimming Control The MP24183 allows both DC and PWM dimming. When the voltage on EN is less than 0.6V, the chip is turned off. For analog dimming, when the voltage on EN is from 0.7V to 1.4V, the LED current will change from 0% to 100% of the maximum LED current. If the voltage on EN pin is higher than 1.4V, maximum LED current will be generated. For PWM dimming, its amplitude (VDIM – VINGND) must exceed 1.4V. The PWM frequency is recommended in range of 100Hz to 2kHz to get a good dimming linearity. Output Short Circuit Protection The MP24183 integrates output short circuit protection. When the output is shorted to VSS, the voltage on OVP pin which detects the output voltage gets smaller than 0.4V, and FB pin senses no voltage (<0.1V) as no current goes through the WLED. At this condition, the operating frequency is folded back to decrease the power consumption. In Buck-boost application, when there is possibility that the LED+ short circuit to VSS, it is recommended to add a diode from VSS to INGND to protect the IC, as shown in below Figure 2 . Figure 2—Buck-boost Application When LED+ Possibly Short to VSS www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 8 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER Setting the LED Current The external resistor is used to set the maximum LED current (see the schematic on front page) through the use of the equation: Choose the inductor ripple current to be 30% of the maximum load current. The maximum inductor peak current is calculated from: E S N E S V 8 D 9 E 1 IL . 0 Where ΔIL is the inductor ripple current. R APPLICATION INFORMATION Setting the Operating Frequency The resistor on Rset pin is used to set the operating frequency. A 1nF capacitor is recommended to bypass this pin to GND. The relationship between the operating frequency and the Rest resistor is as the following curve. A 20kΩ to 200kΩ Rset resistor is recommended, which sets the operating frequency from around 1.3MHz to 250kHz. Leaving the RSET pin open will set the operating frequency to the default operating frequency 1.35MHz. Frequency vs. RSET FREQUENCY (kHz) 1400 1200 1000 800 Series1 600 400 200 0 0 50 100 150 200 250 Selecting the Inductor (Step-Down Applications, see Figure 3) A 1μH to 47μH inductor with a DC current rating of at least 25% percent higher than the maximum load current is recommended for most applications. For high efficiency, the inductor’s DC resistance should be less than 200mΩ. Refer to Table 2 for suggested surface mount inductors. For most designs, the required inductance value can be derived from the following equation. L MP24183 Rev. 1.0 8/28/2008 IL(MAX ) ILOAD I L 2 Under light load conditions below 100mA, a larger inductance is recommended for improved efficiency. Also note that the maximum recommended load current is 2A if the duty cycle exceeds 35%. Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. The input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current from passing through the input. Ceramic capacitors with X5R or X7R dielectrics are highly recommended because of their low ESR and small temperature coefficients. For most applications, a 4.7μF capacitor is sufficient. Selecting the Output Capacitor The output capacitor keeps the output voltage ripple small and ensures feedback loop stable. The output capacitor impedance should be low at the switching frequency. Ceramic capacitors with X5R or X7R dielectrics are recommended for their low ESR characteristics. For most applications, a 2.2μF ceramic capacitor will be sufficient. PC Board Layout The high current paths (VSS, VDD and SW) should be placed very close to the device with short, direct and wide traces. The input capacitor needs to be as close as possible to the VDD and VSS pins. The external feedback resistors should be placed next to the FB pin. Keep the switch node traces short and away from the feedback network. VOUT ( VIN VOUT ) VIN IL f SW www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 9 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER Table 2—Suggested Surface Mount Inductors Manufacturer Part Number Inductance(μH) Max DCR(Ω) Toko Sumida Wurth Electronics A921CY-4R7M CDRH4D28C/LD 7440530047 4.7 4.7 4.7 0.027 0.036 0.038 Current Rating (A) 1.66 1.5 2.0 Dimensions L x W x H (mm3) 6 x 6.3 x 3 5.1 x 5.1 x 3 5.8 x 5.8 x 2.8 TYPICAL APPLICATION CIRCUITS Figure 3—Step-Down White LED Driver Application Figure 4— Step-up/down White LED Driver Application MP24183 Rev. 1.0 8/28/2008 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 10 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER Figure 5— Step-up White LED Driver Application MP24183 Rev. 1.0 8/28/2008 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 11 MP24183 – 1A, 55V, PROGRAMABLE FREQUENCY WHITE LED DRIVER PACKAGE INFORMATION 3mm x 3mm QFN10 2.90 3.10 0.30 0.50 PIN 1 ID MARKING 0.18 0.30 2.90 3.10 PIN 1 ID INDEX AREA 1.45 1.75 PIN 1 ID SEE DETAIL A 10 1 2.25 2.55 0.50 BSC 5 6 TOP VIEW BOTTOM VIEW PIN 1 ID OPTION A R0.20 TYP. PIN 1 ID OPTION B R0.20 TYP. 0.80 1.00 0.20 REF 0.00 0.05 SIDE VIEW DETAIL A NOTE: 2.90 0.70 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH. 3) LEAD COPLANARITY SHALL BE 0.10 MILLIMETER MAX. 4) DRAWING CONFORMS TO JEDEC MO-229, VARIATION VEED-5. 5) DRAWING IS NOT TO SCALE. 1.70 0.25 2.50 0.50 RECOMMENDED LAND PATTERN NOTICE: The information in this document is subject to change without notice. Users should warrant and guarantee that third party Intellectual Property rights are not infringed upon when integrating MPS products into any application. MPS will not assume any legal responsibility for any said applications. MP24183 Rev. 1.0 8/28/2008 www.MonolithicPower.com MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 12