MP3412EJ-LF-P

MP3412 1.1A, 1MHz Synchronous Boost WLED Driver with Output Disconnect DESCRIPTION FEATURES The MP3412 is a synchronous, fixed frequency, high efficiency step-up WLED driver with true output load disconnect function in a low profile 6-lead Thin-SOT23 package.     The MP3412 can startup from an input voltage as low as 0.8V and provides in-rush current limiting as well as output short circuit protection. The open load protection is also integrated   A switching frequency of 1MHz minimizes overall solution footprint by allowing the use of tiny, low profile inductors and ceramic capacitors. Current mode PWM control with internal compensation reduces external parts, thereby saving critical board space. The device also features low shutdown current of under 1µA. The true output disconnect feature allows the output to be completely discharged in shutdown. It also limits the inrush of current during start-up, minimizing surge current seen by the input supply. The MP3412 is available in 6-pin thin SOT23 package.         Input Range: 0.8V to 4.4V Output Range: 2.5V to 5.0V 0.8V Low Start-Up Voltage Internal Power MOSFET and Synchronous Rectifier 1MHz Fixed Switching Frequency Current Mode Control with Internal Compensation Up to 96% Efficiency (VIN+0.1V) and the FB pin is >130mV. Thermal Shutdown An internal temperature monitor will start to reduce the peak current limit if the die temperature exceeds 125ºC. And if the die temperature continues to rise and reaches 150ºC, the part will be thermal shutdown. All switches would be off and the soft-start capacitor would be discharged completely. The chip will be enabled again if the die temperature drops down. Output Disconnect and Inrush Limiting The MP3412 is designed to allow true output disconnect by eliminating body diode conduction of the internal PMOS rectifier. This makes VOUT to decrease to zero volts during shutdown. This feature is also convenient to limit the inrush current during start up. VOUT < VIN Operation The MP3412 will maintain current regulation even if the input voltage is above the output voltage. Since the PMOS no longer acts as a low impedance switch in this mode, there will be more power dissipation in IC, and the efficiency in this mode is low. The maximum output current should be limited in order to maintain an acceptable junction temperature. www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 8 MP3412 - 1.1A, 1MHz SYNCHRONOUS BOOST WLED DRIVER WITH OUTPUT DISCONNECT Open Load Protection Open load protection will shut down the MP3412. If the WLED is fail, the feedback voltage will always be zero, and the part will run at maximum duty cycle. The output voltage will be boosted very high. When the output voltage of SW exceeds 5.1V, the MP3412 will be shut down. And it does not switch again until the power is recycled. Short Circuit Protection Unlike most boost converters, the MP3412 allows their output to be short circuit due to the output disconnect feature. The device incorporates internal features such as current limit function, thermal regulation and thermal shutdown to protect the chip from burn out which is caused by an excessive overload or short circuit. In the event of a short circuit, the internal soft-star capacitor gets partially discharged. This, in turn, decreased the current limit threshold from 1.1A to a small value. In addition to this, a thermal regulation circuit starts to work to decrease the current limit farther if the die temperature rises above 125ºC. And if the die temperature still rises and reaches 150ºC, the chip will be shut down. MP3412 Rev. 1.0 3/22/2017 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 9 MP3412 - 1.1A, 1MHz SYNCHRONOUS BOOST WLED DRIVER WITH OUTPUT DISCONNECT APPLICATION INFORMATION Setting the LED Current Layout Considerations The regulated LED current is identical and set through the current sensing resistor through the use of the equation: Careful attention must be paid to the PCB board layout and components placement. Proper layout of the high frequency switching path is critical to prevent noise and electromagnetic interference problems. The loop of MP3412 SW to GND pin, SW to OUT pin, and output capacitor is flowing with high frequency pulse current. It must be as short as possible. The IN and OUT pin are both the power supply input for the internal MOSFET switch gate driver and the internal control circuitry. They must be locally bypassed. ILED = 0.2V / RSENSE For RSENSE=1Ω, the LED current is set to about 200mA. PWM Dimming Apply a typical 200Hz square waveform to the EN pin to implement PWM dimming of the LEDs. The minimum recommended amplitude of the PWM signal is 0.8V. Selecting the Inductor A 3.3μH to 10µH inductor with a DC current rating of at least 40% higher than the maximum input current is recommended for most applications at wide input range. For highest efficiency, the inductor’s DC resistance should be as small as possible. Output Capacitor OUT SW GND 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 or 10μF capacitor is sufficient. Figure 1- Layout Consideration Selecting the Output Capacitor The output capacitor keeps the output voltage ripple small and ensures feedback loop stability. The output capacitor impedance should be low at the switching frequency. Ceramic capacitors with X7R dielectrics are recommended for their low ESR characteristics. For most applications, a 2.2μF ceramic capacitor is sufficient. MP3412 Rev. 1.0 3/22/2017 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 10 MP3412 - 1.1A, 1MHz SYNCHRONOUS BOOST WLED DRIVER WITH OUTPUT DISCONNECT TYPICAL APPLICATION CIRCUIT Figure 2—Step-up White LED Driver Application MP3412 Rev. 1.0 3/22/2017 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 11 MP3412 - 1.1A, 1MHz SYNCHRONOUS BOOST WLED DRIVER WITH OUTPUT DISCONNECT PACKAGE INFORMATION TSOT23-6 0.95 BSC 0.60 TYP 2.80 3.00 6 4 1.20 TYP 1.50 1.70 1 2.60 TYP 2.60 3.00 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 “A” 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. 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. MP3412 Rev. 1.0 3/22/2017 www.MonolithicPower.com MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. © 2017 MPS. All Rights Reserved. 12