MP4689 100V Input, 1A High Power LED Driver The Future of Analog IC Technology DESCRIPTION FEATURES The MP4689 is a high voltage input step-down switching regulator to deliver a constant current of up to 1A to high power LEDs. It integrates a high-side high voltage power MOSFET with a current limit of 2.5A (typical value). The wide 4.5V to 100V input range accommodates a variety of step-down applications, making it ideal for automotive, industrial and general lighting applications. Hysteresis current mode control is applied for very fast response, which makes the 20kHz dimming frequency possible. MPS’s proprietary feedback control scheme minimizes the number of external components while delivering a LED current with typical ±3% accuracy. • • • • • • • • • • • • • • The switching frequency is up to 1MHz, thus allowing for small component size. The thermal shut down, short circuit protection, and optional output voltage limitation provide reliable, fault tolerant operations. A 170µA quiescent current allows its use in battery-powered applications. Wide 4.5V to 100V Operating Input Range No Output Capacitor Required ±3% LED Current Accuracy Hysteretic Control: No Compensation Up to 1MHz Switching Frequency Up to 20kHz Dimming Frequency Dedicated PWM Dimming Control Input Short circuit protection with integrated high side MOSFET Optional Output Voltage Limitation Thermal shut down 200mV reference voltage for high efficiency Up to 95% Efficiency 170µA Quiescent Current Available in SOIC8 with Exposed Pad Packages APPLICATIONS • • • The MP4689 is available in SOIC8 with exposed pad packages. High Power LED Driver Automotive, Industry and General Lighting Constant Current Source 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 PWM Enable DIM EN VIN VIN BST 4.5V to 100V CBST SW FB MP4689 Rev. 1.0 4/29/2011 D1 CIN LO VOUT GND www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 1 MP4689 – 100V INPUT, 1A HIGH POWER LED DRIVER ORDERING INFORMATION Part Number* Package Top Marking Free Air Temperature (TA) MP4689DN SOIC8E MP4689 -40°C to +85°C * For Tape & Reel, add suffix –Z (e.g. MP4689DN–Z); For RoHS compliant packaging, add suffix –LF (e.g. MP4689DN–LF–Z) PACKAGE REFERENCE (4) ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance Supply Voltage (VIN)....................-0.3V to +100V Switch Voltage (VSW)............. -0.5V to VIN + 0.5V BST to SW ......................................-0.3V to +6V All Other Pins ..................................-0.3V to +6V Junction Temperature ...............................150°C Continuous Power Dissipation (TA = +25°C) (2) ............................................................. 2.5W Lead Temperature ....................................260°C Storage Temperature ............... -65°C to +150°C SOIC8E (Exposed Pad) .......... 50 ...... 10 ... °C/W Recommended Operating Conditions (3) Supply Voltage VIN ........................... 4.5V to 95V EN and DIM Voltages ........................... 0V to 5V Maximum Junction Temp. (TJ) ............... +125°C MP4689 Rev. 1.0 4/29/2011 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 operating conditions. 4) Measured on JESD51-7 4-layer board. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 2 MP4689 – 100V INPUT, 1A HIGH POWER LED DRIVER ELECTRICAL CHARACTERISTICS VIN = 60V, TA= +25°C, unless otherwise noted. Specifications over temperature are guaranteed by design and characterization. Parameter Symbol Condition VIN UVLO Threshold VIN UVLO Hysteresis Shutdown Supply Current Quiescent Supply Current Upper Switch On Resistance (5) Upper Switch Leakage Current Current Limit EN Up Threshold EN Threshold Hysteresis EN Input Current EN Sinking Current DIM Up Threshold DIM Threshold Hysteresis DIM Input Current RDS(ON) ISWLK IPK VENH VENHY IENI IENS VDIMH VDIMHY IDIM DIM On Propagation Delay TDIMDH DIM Off Propagation Delay TDIMDL Feedback Voltage Threshold High (5) VFBH Feedback Voltage Threshold Low (5) VFBL FB Pin Input Current IFB FB Propagation Delay to Output High TFBDH FB Propagation Delay to Output High TFBDL Thermal Shutdown VEN = 0V No load, VFB = 250mV VBST – VSW = 5V VEN = 0V, VSW = 0V VFB = 0.15V Min Typ Max Units 3.6 4.0 0.4 2 170 500 0.01 2.5 1.55 320 0.01 2 1.15 300 4.35 V V µA µA mΩ µA A V mV µA µA V mV µA 1.7 1.4 VEN =5V VEN =2V 0.8 VDIM =5V or 0V VFB=0V, VDIM Rising edge to VSW Rising Edge VFB=0V, VDIM Falling edge to VSW Falling Edge 4.5V < VIN < 95V, VFB rising from 0V until VSW < 30V 4.5V < VIN < 95V, VFB falling from 0.25V until VSW > 30V VFB=5V or 0V Falling edge of VFB from 0.25V to 0V to VSW rising edge Rising edge of VFB from 0V to 0.25V to VSW falling edge Hysteresis = 20°C -1 5 240 1 1.7 1 3 1.5 1 50 ns 50 ns 209 215 221 mV 179 185 191 mV 300 nA -300 100 ns 100 ns 150 °C Note: 5) Guaranteed by design. MP4689 Rev. 1.0 4/29/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 3 MP4689 – 100V INPUT, 1A HIGH POWER LED DRIVER PIN FUNCTIONS SOIC8E Pin # 1 2 3 4 5 6 7 8 Name Description Feedback. This is the input to hysteretic comparators. An external current sensing resistor is connected in series with the LEDs to GND. The feedback voltage is connected to this pin and is regulated at +200mV with 15% current ripple. N/C Not connected Input Supply. This supplies power to all the internal control circuitry, both BS regulators and VIN the high-side switch. A decoupling capacitor to ground must be placed close to this pin to minimize switching spikes. Bootstrap. This is the positive power supply for the internal floating high-side MOSFET BST driver. Connect a bypass capacitor between this pin and SW pin. Switch Node. This is the output from the high-side switch. A low VF Schottky rectifier to SW ground is required. The rectifier must be close to the SW pins to reduce switching spikes. PWM Dimming Input. Pulling this pin below the specified threshold for dimming off. Pulling it DIM up above the specified threshold for dimming on. If there is no need for dimming function, connect DIM and EN pins together. Enable Input. Pulling this pin below the specified threshold shuts the chip down. Pulling it up EN above the specified threshold or leaving it floating enables the chip. GND, Ground. It should be connected as close as possible to the output capacitor avoiding the Exposed high current switch paths. Connect exposed pad to GND plane for optimal thermal pad performance. FB MP4689 Rev. 1.0 4/29/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 4 MP4689 – 100V INPUT, 1A HIGH POWER LED DRIVER BLOCK DIAGRAM VIN IENS Reference UVLO EN Internal Regulators Control Logic and Protection Circuits DIM VFBH R FB BST IPK SW Q S VFBL 200mV Adaptive Threshold Adjustment Circuit GND VFBH VFBL Figure 1—Function Block Diagram MP4689 Rev. 1.0 4/29/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 5 MP4689 – 100V INPUT, 1A HIGH POWER LED DRIVER TYPICAL PERFORMANCE CHARACTERISTICS L=47µH, 1 LED Load, TA=25 oC, unless otherwise noted. 100 Efficiency vs. String Voltage 200.50 VIN=40V 95 200.40 94 200.30 20 LED 90 88 82 80 3 LED 75 70 VIN=50V 10 LED 85 0 20 40 VIN=70V 76 60 80 VIN VOLTAGE(V) 20 30 0.8 199.80 40 50 60 70 80 10 LED FPWM=0.2kHz 0.7 0.6 IOUT CURRENT (A) 0.0 3 LED -0.3 -0.6 50 60 70 80 199.70 90 100 0 10 20 30 40 50 60 70 V IN ( V ) 80 Enable Start Up VIN = 40V EN 5V/div. 0.6 10 LED 40 200.00 ILED vs. PWM Dimming Duty 0.9 -0.9 30 200.10 LED STRING VOLTAGE (V) ILED Load Regulation 0.3 200.20 199.90 VIN=80V 70 10 100 V FB ( mV ) 100 Efficiency vs. Input Voltage 0.5 FB 100mV/div. SW 20V/div. 0.4 0.3 0.2 0.1 0.0 ILED 500mA/div. 0 20 40 60 80 100 VIN VOLTAGE (V) Enable Shut Down PWM Dimming VIN = 40V VIN = 60V, 7LEDs PWM Dimming VIN = 60V, 7LEDs EN 5V/div. DIM 5V/div. DIM 5V/div. FB 100mV/div. SW 20V/div. FB 100mV/div. FB 100mV/div. SW 50V/div. ILED 200mA/div. SW 50V/div. ILED 200mA/div. ILED 500mA/div. MP4689 Rev. 1.0 4/29/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 6 MP4689 – 100V INPUT, 1A HIGH POWER LED DRIVER OPERATION Hysteresis Current Control with Adaptive Threshold Adjustment MP4689 operates in a hysteresis current control mode to regulate the LED current accurately. FB pin is the sensed voltage of LED current across the sensing resistor. The power MOSFET is turned on and remains on until FB pin rises to 215mV. The power MOSFET is turned off and remains off until FB pin falls to 185mV. The two thresholds of 215mV and 185mV are adaptive adjusted to compensate all the circuit delays so that the LED current is regulated very accurately with 200mV average value at FB pin. Enable Control The MP4689 has a dedicated enable control pin (EN) with the positive logic. Its falling threshold is a precision 1.2V, and its rising threshold is 1.5V (300mV higher). When floating, EN is pulled up to about 3.0V by an internal 1µA current source so it is enabled. To pull it down, over 1µA current capability is needed. Thermal Shutdown Thermal shutdown is implemented to prevent the chip from operating at exceedingly high temperatures. When the silicon die temperature is higher than its upper threshold, it shuts down the whole chip. When the temperature is lower than its lower threshold, the chip is enabled again. LED Short Protection The LED current is well regulated with FB pin voltage at 200mV. As long as the LED sensing resistor is not failed, the output current is within limitation. If the LED sensing resistor is failed or the output is shorted to GND directly, the FB pin voltage is low even the power MOSFET is turned on. The power MOSFET will be shut off if such failure time is longer than 10us. MP4689 will retry the operation after about 300µs delay. The power MOSFET current is also accurately sensed via a current sense MOSFET. If the current is over 2.5A, the IC is shut down. This offers extra protection under output short conditions. Floating Driver and Bootstrap Charging The floating power MOSFET driver is powered by an external bootstrap capacitor. This floating driver has its own UVLO protection. This UVLO’s rising threshold is 2.2V with a threshold of 150mV. The bootstrap capacitor is charged and regulated to about 5V by the dedicated internal bootstrap regulator. In case the internal circuit does not have sufficient voltage and the bootstrap capacitor is not well charged, extra external circuitry can be used to ensure the bootstrap voltage is in the normal operational region. Refer to External Bootstrap Diode in Application section. Under-Voltage Lockout (UVLO) Under-voltage lockout (UVLO) is implemented to protect the chip from operating at insufficient supply voltage. The UVLO rising threshold is about 4.0V while its falling threshold is a consistent 3.65V. MP4689 Rev. 1.0 4/29/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 7 MP4689 – 100V INPUT, 1A HIGH POWER LED DRIVER APPLICATION INFORMATION COMPONENT SELECTION Input Capacitor CIN Setting the LED Current The input current to the step-down converter is discontinuous, therefore a capacitor is required to supply the AC current to the step-down converter while maintaining the DC input voltage. Use low ESR capacitors for the best performance especially under high switching frequency applications. The LED current ILED is set using a sensing resistor RFB, which is in series with the LEDs and connected to GND. The voltage on the sensing resistor RFB is connected to FB pin. ILED = VFB RFB For example, for a 700mA LED current, RFB is 287mΩ. The RMS current through the input capacitor is about: ID = ILED ⋅ Inductor Selection and Frequency Setting The inductor LO is required to supply a constant current to the LED. The inductor value is related to the switching frequency fs setting: VOUT ⋅ (VIN − VOUT ) fs = VIN ⋅ (8 ⋅ 10−8 ⋅ VIN + L ⋅ 15% ⋅ ILED ) Where, VIN is the input voltage, VOUT is the output voltage to drive the LEDs. A larger value inductor will result in smaller switching frequency. The peak inductor current is about: ILP 4 ⋅ 10−8 ⋅ VIN = ILED ⋅ ( + 1.075) L ⋅ ILED Choose an inductor that will not saturate under the maximum inductor peak current and the switching frequency under 2MHz. Output Rectifier Diode The output rectifier diode supplies the current to the inductor when the high-side switch is off. To reduce losses due to the diode forward voltage and recovery times, use a Schottky diode. The RMS current through the diode is about: ID = ILED ⋅ 1 − VOUT VIN Choose a diode whose maximum reverse voltage rating is greater than the maximum input voltage, and whose current rating is greater than the maximum diode current. MP4689 Rev. 1.0 4/29/2011 VOUT ’ VIN With low ESR capacitors, the input voltage ripple can be estimated by: ∆VIN = ⎛ V V ⎞ ILED × OUT × ⎜ 1 − OUT ⎟ fs × CIN VIN ⎝ VIN ⎠ Choose the input capacitor with enough RMS current rating and enough capacitance for small input voltage ripple. When electrolytic or tantalum capacitors are applied, a small, high quality ceramic capacitor, i.e. 0.1µF, should be placed as close to the IC as possible. Output Capacitor COUT The output capacitor (COUT) is not necessary for MP4689. The LED current ripple (peak-to-peak value) is about 15% of the LED DC current. Output capacitor can be used to further reduce the LED current ripple. Low ESR capacitors are preferred to keep the output voltage ripple low so that the AC ripple current through the LEDs is small. The output voltage ripple can be estimated by: ∆VOUT = VOUT ⎛ V × ⎜ 1 − OUT fS × L O ⎝ VIN ⎞ ⎞ ⎛ 1 ⎟ ⎟ × ⎜ RESR + 8 × fS × COUT ⎠ ⎠ ⎝ Where RESR is the equivalent series resistance (ESR) value of the output capacitor. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 8 MP4689 – 100V INPUT, 1A HIGH POWER LED DRIVER External Bootstrap Diode Layout Consideration An external bootstrap diode may enhance the efficiency of the LED driver. In below cases, an external BST diode is recommended from the 5V to BST pin: It is essential to place the input decoupling capacitor, catch diode and the MP4689 (VIN pin, SW pin and PGND) as close as possible, with traces that are very short and fairly wide. This can help to greatly reduce the voltage spike on SW node, and lower the EMI noise level as well. z There is a 5V rail available in the system; z VIN is no greater than 5V; z VOUT is between 3.3V and 5V; This diode is also recommended for high duty cycle operation (when VOUT/VIN>65%) and very high frequency (over 1.5MHz) applications. The bootstrap diode can be a low cost one such as IN4148 or BAT54. 5V BS MP4560 MP4689 SW Figure 2—External Bootstrap Diode MP4689 Rev. 1.0 4/29/2011 Try to run the feedback trace as far from the inductor and noisy power traces as possible. It is often a good idea to run the feedback trace on the side of the PCB opposite of the inductor with a ground plane separating the two. To help to improve the thermal conduction, a grid of thermal vias can be created right under the exposed pad. It is recommended that they be small (15mil barrel diameter) so that the hole is essentially filled up during the plating process, thus aiding conduction to the other side. Too large a hole can cause ‘solder wicking’ problems during the reflow soldering process. The pitch (distance between the centers) of several such thermal vias in an area is typically 40mil. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2011 MPS. All Rights Reserved. 9 MP4689 – 100V INPUT, 1A HIGH POWER LED DRIVER PACKAGE INFORMATION SOIC8E (EXPOSED PAD) 0.189(4.80) 0.197(5.00) 0.124(3.15) 0.136(3.45) 8 5 0.150(3.80) 0.157(4.00) PIN 1 ID 1 0.228(5.80) 0.244(6.20) 0.089(2.26) 0.101(2.56) 4 TOP VIEW BOTTOM VIEW SEE DETAIL "A" 0.051(1.30) 0.067(1.70) SEATING PLANE 0.000(0.00) 0.006(0.15) 0.013(0.33) 0.020(0.51) 0.0075(0.19) 0.0098(0.25) SIDE VIEW 0.050(1.27) BSC FRONT VIEW 0.010(0.25) x 45o 0.020(0.50) GAUGE PLANE 0.010(0.25) BSC 0.050(1.27) 0.024(0.61) 0o-8o 0.016(0.41) 0.050(1.27) 0.063(1.60) DETAIL "A" 0.103(2.62) 0.213(5.40) NOTE: 0.138(3.51) RECOMMENDED LAND PATTERN 1) CONTROL DIMENSION IS IN INCHES. DIMENSION IN BRACKET IS IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. 3) PACKAGE WIDTH DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. 4) LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.004" INCHES MAX. 5) DRAWING CONFORMS TO JEDEC MS-012, VARIATION BA. 6) DRAWING IS NOT TO SCALE. 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. MP4689 Rev. 1.0 4/29/2011 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited @2011 MPS. All Rights Reserved. 10