MP24893 Step Down White LED Driver with Wide 6V-to-36V Input Voltage The Future of Analog IC Technology DESCRIPTION FEATURES The MP24893 is a high efficiency step-down converter designed in continuous current mode for driving the high brightness LEDs from wide input voltage of 6V to 36V. • • • • • • • • • The MP24893 employs hysteretic control architecture to regulate a highly accurate LED current, which is measured through an external high-side current-sense resistor. Moreover, this control scheme provides optimal circuit stabilization and a very quick response time without loop compensation. Its low 200mV average feedback voltage reduces power loss and improves the converter efficiency. Internal 36V MOSFET Wide 6V-to-36V Input Range 1A Output Current High Efficiency Hysteretic Control PWM and Analog Dimming 1000:1 PWM Dimming Resolution UVLO, Thermal Shutdown Available in TSOT23-5 and QFN6 Packages APPLICATIONS • • • • • The MP24893 implements PWM and analog dimming together through the DIM pin. The MP24893 includes under-voltage lockout, thermal overload protection to prevent damage in the event of an output overload. Low-Voltage Halogen Replacement Low-Voltage General Illumination Automotive/Decorative LED Lighting Signs/Emergency Lighting LED Backlighting All MPS parts are lead-free and adhere to the RoHS directive. For MPS green status, please visit MPS website under Products, Quality Assurance page. “MPS” and “The Future of Analog IC Technology” are registered trademarks of Monolithic Power Systems, Inc. The MP24893 is available in TSOT23-5 and QFN6 packages. TYPICAL APPLICATION D1 VIN 6V - 36V RSENSE CIN IN RS L1 MP24893 EN/DIM GND SW MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 1 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V-TO-36V INPUT VOLTAGE ORDERING INFORMATION Part Number Package TSOT23-5 QFN6 (3x3mm) MP24893DJ* MP24893DQ** Top Marking ABD ABD * For Tape & Reel, add suffix –Z (e.g. MP24893DJ–Z); For RoHS Compliant Packaging, add suffix –LF (e.g. MP24893DJ–LF–Z) * *For Tape & Reel, add suffix –Z (e.g. MP24893DQ–Z); For RoHS Compliant Packaging, add suffix –LF (e.g. MP24893DQ–LF–Z) PACKAGE REFERENCE TSOT23-5 QFN6 (3x3mm) (4) ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance VIN, VSW .........................................-0.3V to +40V VRS ..................................................VIN-5V to VIN All Other Pins ...............................-0.3V to +6.3V Continuous Power Dissipation (TA = +25°C) (2) TSOT23-5 .................................................. 1.1W QFN6 (3x3mm) .......................................... 2.5W Junction Temperature ...............................150°C Lead Temperature ....................................260°C Storage Temperature............... -65°C to +150°C TSOT23-5 .............................110 ..... 55 ... °C/W QFN6 (3x3mm) ......................50 ...... 14 ... °C/W Recommended Operating Conditions (3) Supply Voltage VIN ..............................6V to 36V Operating Junction Temp. (TJ). -40°C to +125°C 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 is not guaranteed to function outside of its operation conditions. 4) Measured on JESD51-7 4-layer board. MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 2 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V-TO-36V INPUT VOLTAGE ELECTRICAL CHARACTERISTICS VIN = 24V, TA = +25°C, unless otherwise noted. Parameter Input Voltage IN Under-Voltage Lockout Under-Voltage Lockout Hysteresis Shutdown Supply Current Quiescent Supply Current Feedback Reference Voltage Peak (with respect to VIN) Feedback Reference Voltage Valley (with respect to VIN) EN/DIM Max. Dimming Voltage(5) EN/DIM Min. Dimming Voltage(5) EN/DIM Enable High Voltage EN/DIM Enable Hysterisis EN/DIM Pull-Up Resistor Internal Reference Voltage Switch On Resistance Minimum On Time(5) Minimum Off Time(5) Recommended Duty Cycle Range Symbol VIN VIN_UVLO Condition Min 6 VIN Rising No Switching VIN-VRS VEN/DIM = 5V 220 VIN-VRS VEN/DIM = 5V 160 VEN Rising 120 1 Units V V mV µA mA 230 240 mV 170 180 mV 5.3 700 100 0.7 ISD IQ VDIM_MAX VDIM_MIN VEN_HIGH VEN_HYS REN VREF RDS_ON3 tON_MIN tOFF_MIN D Typ 0.2 20 Max 36 5.9 2.56 0.3 0.25 50 45 1.275 0.2 100 100 30 0.3 80 70 V V V mV kΩ V Ω ns ns % Notes: 5) Guaranteed by design MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 3 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V-TO-36V INPUT VOLTAGE PIN FUNCTIONS TSOT23-5 Pin# QFN6 (3x3mm) Pin# 1 1 SW 2 2 GND Name Description Drain of Internal MOSFET. Connect the inductor common terminal and Schottky anode to this pin. Ground. Enable/Dimming Command Input. For PWM dimming, apply a square wave signal to this pin. For analog dimming, apply a 0.3V-to-2.5V DC voltage to EN/DIM linearly control the LED current range from 25% to 200%. Turn off the output current when pulling this pin below 0.2V. Leave it open for normal operation (VEN/DIM=1.28V). 3 5 4 4 RS LED Current Sense Input. Connect a current-sense resistor to program the LED average current to IN pin. 5 3 IN Input Supply Pin. Connect an appropriate decoupling capacitor from the IN pin to GND. 6 N/C Not Connected. MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 4 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V-TO-36V INPUT VOLTAGE TYPICAL PERFORMANCE CHARACTERISTICS VIN=24V, 3 LEDS in series, IOUT=1A, unless otherwise noted. Efficiency vs. Input Voltage Analog Dimming Curve 1200 95 1000 LED CURRENT(mA) EFFICIENCY (%) 94 93 92 91 90 15 20 25 30 35 VSW 10V/div. VEN 1V/div. VPWM 5V/div. IOUT 500mA/div. 200 0 0.2 0.4 0.6 0.8 VIN Startup 1 1.2 1.4 VEN Startup VSW 20V/div. VSW 10V/div. VIN 10V/div. IL 500mA/div. 400 ANALOG DIMMING LEVEL(V) Steady State VEN 1V/div. 600 0 40 INPUT VOLTAGE (V) VSW 10V/div. 800 VEN 1V/div. VEN 1V/div. VIN 10V/div. IOUT 1A/div. VIN 20V/div. IOUT 1A/div. PWM Dimming Open LED Protection Short LED Protection fPWM = 200Hz, DPWM = 50% Open LEDs at working Short LEDs at working VSW 10V/div. VSW 10V/div. VLED+ 10V/div. IOUT 500mA/div. VLED10V/div. IOUT 500mA/div. MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 5 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V-TO-36V INPUT VOLTAGE FUNCTION DIAGRAM D VIN Rsense CIN IN RS HV Regulator 5V 1.275V Reference High Side Current Sense L SW 0.2V Enable + DIM EN /DIM Filter PWM + Driver R1 R2 GND Figure 1: MP24893 Functional Block Diagram MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 6 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V-TO-36V INPUT VOLTAGE OPERATION Steady State The MP24893 is a hysteretic-controlled, stepdown LED driver that is easily configured for various applications with an input range from 6V to 36V. The converter employs a high-side current-sense resistor to detect and regulate the LED current. The voltage across the currentsense resistor is measured and regulated to within 202mV±30mV. The internal 1.275V reference voltage provides a 0.2V reference to enable the part and a 1.275V pull-up voltage as current reference. When VEN>0.2V, the output of the comparator goes high and the other blocks are enabled. A high-side resistor, RSENSE, senses the output current. When the switch is on, R2 is shorted and R1 sets the output current upper-threshold. When the switch is off, R1 and R2 set the output current lower-threshold, and the ratio of R1 and R2 determines the current hysteresis. Enable Control Once Input voltage is applied, the internal 1.275V reference is connected to EN/DIM pin through pull up resistor. If the EN/DIM pin is left open, the IC will automatically start up to the maximum brightness. Adding a capacitor to this pin can hereby program a soft-start time. Applying an external voltage range from 0.2V to 1.25V to the EN/DIM pin linearly controls the current-sense voltage reference from 0mV to 202mV for analog dimming. Applying an external PWM voltage with an amplitude of 1.25V to the EN/DIM pin achieves PWM dimming. For additional information on the flexible external PWM dimming method, please refer to the “Selecting Dimming Control Mode” section. System Soft Start The voltage on the EN/DIM pin is the inductor current reference. An external capacitor from the EN/DIM pin to ground provides a soft-start delay. When VIN starts, internal voltage source charges the capacitor from 0V to 1.25V for soft-start. Dimming Control MP24893 provides two dimming methods: PWM dimming and DC analog dimming. To use PWM dimming, apply a square wave to the EN/DIM pin. To use analog dimming, apply a 0.3V-to-2.5V DC voltage to this pin. MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 7 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V-TO-36V INPUT VOLTAGE APPLICATION INFORMATION Setting the LED Current The LED current is set by the current-setting resistor between the IN and RS pins, where: RSET=202mV/ILED For RSET=0.36Ω, the LED current is set to 550mA Selecting the Inductor Lower values of the inductor result in higher switching frequencies, leading to larger switch loss. For most applications, select a switching frequency between 200kHz and 600kHz. Estimate the inductor value based on the desired switching frequency, where: V (1- OUT ) × VOUT VIN L= 0.3 × ILED × fSW For higher efficiency, use inductors with low DC resistance. Selecting the Diode The output diode supplies current to the inductor when the internal MOSFET is off. To reduce losses due to the diode forward voltage and recovery time, use a Schottky diode. Select a diode rated with a reverse voltage greater than the input voltage. The average current rating must be exceed the maximum expected load current, and the peak current rating must exceed the peak inductor current. Selecting the Input Capacitor The input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. Select capacitor value between 10µF and 22µF for most applications. The voltage rating should exceed the input voltage. Use a low-ESR capacitor input decoupling. Selecting the Output Capacitor For most applications, an output capacitor is not necessary. But if the peak-to-peak ripple LED current must be less than 30% of the average current, add a capacitor across the LEDs, where a higher capacitor value leads to a proportionally lower ripple. A 2.2µF capacitor will meet most requirements. Selecting Soft-Start Capacitor The delay time with the soft-start capacitor can be estimated by 0.2ms/nF. In PWM dimming, select a C<2.2nF to eliminate its effect on the average LED current. Selecting Dimming Control Mode MP24893 provides two dimming methods: DC analog dimming and PWM dimming. 1. DC analog dimming mode Apply a 0.3V-to-2.5V DC voltage to the EN/DIM pin. The voltage from 0.3V to 2.5V changes the inductor current reference directly and linearly controls the inductor current range from 25% to 200% (see Figure 2). VIN IN TP4 MP24893 R6 EN/DIM EN/DIM 0 C5 1nF GND Figure 2: Analog Dimming External Circuit 2. PWM dimming mode Apply a 100Hz-to-2kHz square waveform to the EN/DIM pin. The average LED current is proportional to the PWM duty cycle. Add an NPNtransistor on/off circuit to separate the PWM signal from the current reference (see Figure 3) because this pin is pulled up by the 1.25V internal source as the inductor current reference. The minimum PWM amplitude is 1.5V. VIN IN TP4 EN/DIM MP24893 R6 NC R4 1k EN/DIM Q1 R5 NS C5 82pF GND Figure 3: PWM Dimming External Circuit MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 8 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V-TO-36V INPUT VOLTAGE Circuit Layout Consideration Pay careful attention to the PCB board layout and components placement. RSENSE should be placed close to the IN pin and RS pin to minimize set current error. The input loop—including the input capacitor, Schottky diode, and internal MOSFET—should be as short as possible. MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 9 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V~36V INPUT VOLTAGE TYPICAL APPLICATION CIRCUIT D1 B260 R1 VIN LED+ 0.4 C2 R2 C1 C4 NC 0.4 R3 IN Q1 NC R5 NC C5 1nF U1 MP24893 SW 1 2 NC EN/DIM L1 GND 0 R4 3 AGND RS 4 5 C3 NC R6 EN/DIM LED- NC PGND AGND PGND Figure 4: Drive 3 LEDs in Series, 1A Current Output MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 10 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V~36V INPUT VOLTAGE PACKAGE INFORMATION TSOT23-5 0.95 BSC 0.60 TYP 2.80 3.00 5 4 1.20 TYP 1.50 1.70 1 2.60 3.00 2.60 TYP 3 TOP VIEW RECOMMENDED LAND PATTERN 0.84 0.90 1.00 MAX 0.09 0.20 SEATING PLANE 0.30 0.50 0.95 BSC 0.00 0.10 SEE DETAIL "A" FRONT VIEW SIDE VIEW NOTE: GAUGE PLANE 0.25 BSC 0o-8o DETAIL 揂 0.30 0.50 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH , PROTRUSION OR GATE BURR. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSION. 4) LEAD COPLANARITY(BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.10 MILLIMETERS MAX. 5) DRAWING CONFORMS TO JEDEC MO-193, VARIATION AA. 6) DRAWING IS NOT TO SCALE. MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 11 MP24893 – STEP DOWN WLED DRIVER WITH WIDE 6V~36V INPUT VOLTAGE QFN6 (3x3mm) 2.90 3.10 0.35 0.55 PIN 1 ID MARKING 0.35 0.45 1.40 1.60 PIN 1 ID SEE DETAIL A 1 6 2.90 3.10 PIN 1 ID INDEX AREA 2.20 2.40 0.95 BSC 3 4 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 0.80 1) 2) 3) 4) 5) 1.50 0.40 ALL DIMENSIONS ARE IN MILLIMETERS. EXPOSED PADDLE SIZE DOES NOT INCLUDE MOLD FLASH. LEAD COPLANARITY SHALL BE0.10 MILLIMETER MAX. JEDEC REFERENCE IS MO-229, VARIATION VEEA-2. DRAWING IS NOT TO SCALE. 2.30 0.95 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. MP24893 Rev.1.02 www.MonolithicPower.com 12/7/2012 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2012 MPS. All Rights Reserved. 12