MP3398A Step up, 4 strings, Max. 350mA/string Analog and PWM dimming, White LED Controller The Future of Analog IC Technology DESCRIPTION FEATURES The MP3398A is a step-up controller with 4 current channels, which is designed to drive WLED arrays for large-size LCD-panel backlighting applications. It is flexible to expand the number of LED channels by two or more ICs in parallel sharing a single inductive power source. * * * 4-String, Max 350mA/String WLED Driver 5V to 28V Input Voltage Range 2.5% Current Matching Accuracy Between Strings Programmable Switching Frequency PWM and Analog Dimming Mode Cascading Capability with a Single Power Source LED Open and Short LED Protection Programmable Over-Voltage Protection Recoverable Thermal Shutdown Protection Over Current Protection Inductor/Diode short Protection Under-Voltage Lockout SOIC16, TSSOP16-EP and SOIC20 Packages * * * The MP3398A uses peak-current mode with fixed switching frequency. The frequency is programmable by an external setting resistor. The MP3398A drives an external MOSFET to boost up the output voltage from a 5V to 28V input supply. It regulates the current in each LED string to the value set by an external current-setting resistor. * * * * * * * The MP3398A applies 4 internal current sources for current balance. The current matching can achieve 2.5% regulation accuracy between strings. Its low regulation voltage on LED current sources reduces power loss. APPLICATIONS * * * The MP3398A can support both analog and PWM dimming independently to meet the different dimming-mode request. In addition, rich protection modes are also integrated including OCP, OTP, UVP, OVP, LED short/open protection, inductor/diode short protection. Desktop LCD Flat Panel Displays Flat Panel Video Displays 2D/3D LCD TVs and Monitors 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. The MP3398A is available in SOIC16, TSSOP16-EP and SOIC20 packages. TYPICAL APPLICATION L1 VOUT D1 VIN C2 C1 GND R1 GATE 14 R4 2 C4 5 R5 7 COMP EN MP3398A GND OVP OSC LED1 ADIM LED2 PWM LED3 ISET LED4 3 6 13 R2 4 12 11 String 4 ISENSE VCC 1 String 3 16 String 2 VIN String 1 15 C3 10 9 8 R3 MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 1 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER ORDERING INFORMATION Part Number MP3398AGS* MP3398AGF** MP3398AGY*** Package SOIC16 TSSOP16-EP SOIC20 Top Marking MP3398A MP3398A MP3398A * For Tape & Reel, add suffix -Z (e.g. MP3398AGS-Z); ** For Tape & Reel, add suffix -Z (e.g. MP3398AGF-Z); *** For Tape & Reel, add suffix -Z (e.g. MP3398AGY-Z); PACKAGE REFERENCE TOP VIEW TOP VIEW TOP VIEW COMP 1 20 VCC EN 2 19 VIN PWM 3 18 GATE 4 17 ISENSE 5 16 NC NC 6 15 NC 1 16 VCC COMP 1 16 VCC 2 15 VIN EN 2 15 VIN PWM 3 14 GATE PWM 3 14 GATE GND 4 13 ISENSE GND 4 13 I SENSE OSC 5 12 OVP O SC 5 12 OVP ISET 6 11 LED1 ISET 6 11 LED1 OSC 7 14 OVP ADIM 7 10 LED2 LED2 ISET 8 13 LED1 8 9 LED3 ADIM 9 12 LED2 LED4 10 11 LED3 COMP EN LED4 ADIM LED4 Exposed Pad Connect to GND 7 10 8 SOIC16 9 LED3 NC GND TSSOP16-EP SOIC20 ABSOLUTE MAXIMUM RATINGS (1) Thermal Resistance VIN .............................................. -0.3V to +30V VGATE ........................................... -0.3V to +6.5V VCC ............................................ -0.3V to +6.8V VLED1 to VLED4 .................................. -1V to +55V VISENSE ......................................... -0.5V to +6.5V All Other Pins............................... -0.3V to VCC (2) Continuous Power Dissipation (TA = 25C) SOIC16.................................................... 1.56W TSSOP16-EP....................................2.78W SOIC20 ....................................... 1.74W Junction Temperature .............................. 150C Lead Temperature ................................... 260C ESD Capability Human Body Mode (all pins) ................................................................. 3.5kV SOIC16.................................80......35....C/W TSSOP16-EP........................45.......10....C/W ........................72 ...... 30 ... C/W SOIC20 Recommended Operating Conditions (3) (4) JA JC Notes: 1) Exceeding these ratings may damage the device. The voltage is measured with a 20MHz bandwidth limited oscilloscope. 2) The maximum allowable power dissipation is a function of the maximum junction temperature TJ (MAX), the junction-toambient thermal resistance JA, and the ambient temperature TA. The maximum allowable continuous power dissipation at any ambient temperature is calculated by PD (MAX) = (TJ (MAX)-TA)/JA. 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 PCB. Supply Voltage VIN ............................. 5V to 28V LED Current (Backlight) ...........10mA to 350mA Operating Junction Temp. (TJ). -40C to +125C MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 2 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER ELECTRICAL CHARACTERISTICS (5) VIN =12V, VEN = 5V, TA = 25C, unless otherwise noted. Parameters Symbol Condition Operating Input Voltage VIN Supply Current (Quiescent) IQ Supply Current (Operation) IOP VIN=12V, VEN=5V, no load without switching VIN=12V, VEN=5V, no load with switching Supply Current (Shutdown) IST VEN=0V, VIN=12V LDO Output Voltage VCC VCC UVLO Threshold VIN_UVLO Min Max Units 28 V 1.35 1,5 mA 3 5.5 mA 0.01 0.5 A 5.4 6 6.6 V 3.6 4 4.4 V 5 VEN=5V, 7V<VIN<28V, 0<IVCC<10mA Rising Edge 1.2 VCC UVLO Hysteresis 200 EN High Voltage VEN_HIGH VEN Rising EN Low Voltage VEN_LOW VEN Falling STEP-UP CONVERTER Gate Driver Impedance (Sourcing) Gate Driver Impedance (Sinking) Switching Frequency Typ fSW mV 1.8 V 0.6 V VCC=6V,VGATE=6V 4.5 7 VCC=6V,IGATE=10mA 2.5 5 ROSC= 115k 459 540 621 kHz ROSC= 374k 150 180 210 kHz 1.20 1.23 1.26 V OSC Voltage VOSC Maximum Duty Cycle Cycle By Cycle ISENSE Current Limit COMP Source Current Limit DMAX ICOMP SOLI 1V<COMP<1.9V 70 A COMP Sink Current Limit ICOMP SILI 1V<COMP<1.9V 17 A ICOMP=10A 400 A/V COMP Trans-conductance 93 Max Duty Cycle GCOMP 145 180 % 215 mV CURRENT DIMMING PWM Input Low Threshold VPWM_LO VPWM Falling PWM Input High Threshold Analog Dimming Input Low Threshold Analog Dimming Input High Threshold LED CURRENT REGULATION VPWM_HI VPWM Rising Adim_L RISET=9.72k ISET Voltage LEDX Average Current Current Matching V 1.25 V 0.38 0.41 0.44 V Adim_H 1.44 1.49 1.54 V VISET 1.195 1.22 1.245 V 31.3 32.3 33.3 mA 2.5 % 100 mA ILED (5) VCC Max Current Limit LED FET Resistance 0.75 RISET=30.5k ILED=33.2mA Icc_Limit R_LED 50 ILED=10mA 75 1.7 MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 3 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER ELECTRICAL CHARACTERISTICS (continued) VIN =12V, VEN = 5V, TA = 25C, unless otherwise noted. Parameters LEDX Regulation Voltage PROTECTION OVP(Over Voltage Protection) Threshold OVP(Over Voltage Protection) Threshold HYS OVP UVLO threshold LEDX UVLO Threshold LEDX Over Voltage Threshold Symbol VLEDX VOVP_OV Condition ILED=60mA 285 mV Rising Edge Step-up Converter Fails Latch-Off Current Limit VLMT Thermal Protection Threshold TST Units mV VOVP UV VLEDX_UV T_LED_OV Max 800 HYS LED Short Fault Cycles Typ ILED=330mA VOVP_HYS VLEDX_OV Min 1.20 1.23 1.26 80 V mV 30 120 75 200 120 280 mV mV 5.8 6.3 6.8 V 720 mV 4096 560 Thermal Protection Hysteresis 640 150 C 25 C Notes: 5) Matching is defined as the difference of the maximum to minimum current divided by 2 times average currents. MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 4 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER TYPICAL CHARACTERISTICS MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 5 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER TYPICAL PERFORMANCE CHARACTERISTICS VIN = 12V, VOUT = 30V, L = 33H, ILED=120mA/String, 4 strings, TA = 25C, unless otherwise noted. 98 96 94 92 90 88 86 84 82 80 0 5 10 15 20 25 30 MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 6 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER TYPICAL PERFORMANCE CHARACTERISTICS (continued) VIN = 12V, VOUT = 30V, L = 33H, TA = 25C, unless otherwise noted. Steady State VIN Power On VSW 20V/div. VSW 20V/div. VOUT 20V/div. VOUT 10V/div. ILED 500mA/div. VSW 20V/div. VSW 20V/div. VADIM 2V/div. VPWM1 5V/div. IL 1A/div. ILED 200mA/div. VSW 20V/div. VEN 5V/div. IL 1A/div. IL 1A/div. ILED 500mA/div. EN Power On IL 1A/div. ILED 500mA/div. VSW 20V/div. VOUT 20V/div. IL 1A/div. IL 1A/div. ILED 500mA/div. ILED 500mA/div. Short Inductor Protection VSW 20V/div. VLED1 20V/div. IL 1A/div. ILED 500mA/div. VSW 20V/div. VSENSE 500mV/div. IL 10A/div. ILED 1A/div. Short Diode Protection VSW 20V/div. VCOMP 1V/div. IL 5A/div. ILED 500mA/div. MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 7 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER PIN FUNCTIONS TSSOP16-EP SOIC20 &SOIC16 Pin # Pin # Name 1 1 COMP 2 2 EN 3 3 PWM Description Step-up Converter Compensation Pin. This pin compensates the regulation control loop. Connect a ceramic capacitor from COMP to GND. Enable Control Input. A voltage greater than 1.8V will turn the part on and less than 0.6 V will turn the part off. Do not let this pin float. Input Signal for PWM Brightness Control. By applying a PWM signal on this pin, the LED current can be chopped and the average current is equal to Iset*D_dim (I_set is the LED current value set by a resistor connected to PIN 6; D_dim is the duty cycle of the PWM dimming duty cycle). Make sure the PWM amplitude voltage level > VPWM_HI and the low level voltage < VPWM_HI. The input PWM signal frequency mainly determines the LED current dimming ratio. Lower dimming frequency, smaller dimming current can be gotten. In general, 200Hz to 2kHz can be used to cover most of the customers' LED current dimming requests. Internally weakly pulled to GND if this pin is floated. If PWM dimming is not voltage(1.25V<Vpwm<5V), 4 5 GND 5 7 OSC 6 8 ISET 7 9 ADIM 8 10 LED4 9 11 LED3 10 12 LED2 11 13 LED1 12 14 OVP required, pulling this pin to high Ground. Switching Frequency Set. Connect a resistor between OSC and GND to set the step-up converter switching frequency. The voltage at this pin is regulated to 1.23V. The clock frequency is proportional to the current sourced from this pin. LED Current Set. Tie a current-setting resistor from this pin to ground to program the current in each LED string. This pin voltage is regulated to 1.225V. The LED current is proportional to the current through the ISET resistor. Signal Input for Analog Brightness Control. The LED current amplitude is determined by this pin and the input signal can be either a PWM signal or a DC voltage signal. An internal RC filter (10Mohm resistor and 100pF capacitor) is integrated to this pin. So, if a PWM signal applied to this pin, >20kHz frequency is recommended to get a better PWM signal filtering performance and make sure the amplitude voltage is higher than 1.5V and low level voltage is less than 0.4V. For DC signal input, please apply a DC input signal range from 0.4V to 1.5V to linearly set the LED current from 0% to 100%. Internally weakly pulled to GND if this pin is floated. If Analog dimming is not required, pulling this pin to high voltage(1.54V<Vpwm<5V), LED String 4 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 4 cathode to this pin. LED String 3 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 3 cathode to this pin. LED String 2 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 2 cathode to this pin. LED String 1 Current Input. This pin is the open-drain output of an internal dimming control switch. Connect the LED String 1 cathode to this pin. Over-Voltage Protection Input. Connect a resistor divider from output to this pin to program the OVP threshold. When this pin voltage reaches 1.23V, the MP3398A triggers Over Voltage Protection mode. MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 8 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER PIN FUNCTIONS (continued) TSSOP16-EP SOIC20 &SOIC16 Pin # Pin # Name Description Current Sense Input. During normal operation, this pin senses the voltage across the external-inductor current-sensing resistor (RSENSE) ISENSE for peak-current-mode control and also to limit the inductor current during every switching cycle. If this pin is not used for cascading applications, tie this pin to GND; do not let this pin float. 13 17 14 18 GATE 15 19 VIN 16 20 VCC 4, 6, 15, 16 NC Step-up Converter Power Switch Gate Output. This pin drives the external power N-MOS device. Supply Input. VIN supplies the power to the chip, as well as the step-up converter switch. Drive VIN with a 5V to 28V power source. Must be locally bypassed. The Internal 6V Linear Regulator Output. VCC provides power supply for the external MOSFET switch gate driver and the internal control circuitry. Bypass VCC to GND with a ceramic capacitor. No Connect. MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 9 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER BLOCK DIAGRAM VCC VIN Regulator GND - Control Logic + GATE PWM Comparator Current Sense Amplifier + 200 ns Blank Time ISENSE - OV Comparator - 100ns Blanking + COMP PWM STOP - UP_CLAMP - 1.23V + ILIMIT Short String Protection OVP + Oscillator OSC 6.3V + Max - Min EA Feedback Control + Ref EN Enable Control LED1 + 1.225V - ISET Current Control ADIM PWM LED4 Figure 1--Functional Block Diagram MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 10 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER OPERATION The MP3398A is a step-up converter with peakcurrent mode. It employs 4 channels of current sources to drive up to 4 strings of white LEDs. Internal 6V Regulator The MP3398A includes an internal linear regulator (VCC). When VIN is greater than 6.5V, this regulator outputs a 6V power supply to the external MOSFET switch gate driver and the internal control circuitry. The VCC voltage drops to 0V when the chip shuts down. The MP3398A features under-voltage lockout (UVLO). The chip is disabled until VCC exceeds the UVLO threshold. The UVLO hysteresis is approximately 200mV. System Startup When enabled, the MP3398A checks the topology connection first. The chip monitors the over-voltage protection (OVP) pin to see if the Schottky diode is not connected or if the boost output is shorted to GND. An OVP voltage of less than 75mV will disable the chip. The MP3398A also checks other safety limits, including UVLO and over-temperature protection (OTP), over-current protection after passing the OVP test. If all the protection tests pass, the chip then starts boosting the step-up converter with an internal soft-start. It is recommended that the enable signal occurs after the establishment of the input voltage and PWM dimming signal during the start-up sequence to avoid large inrush current. Step-Up Converter The converter operating frequency is programmable (from 100kHz to 500kHz) with a external resistor connected to the OSC pin. This helps to optimize the size of external components and the efficiency. At the beginning of each switching cycle, the internal clock turns on the external MOSFET (In normal operation, the minimum turn on time is 200ns). A stabilizing ramp added to the output of the current sense amplifier prevents subharmonic oscillations for duty cycles greater than 50 percent. This result is fed into the PWM comparator. When this resulting voltage reaches the output voltage of the error amplifier (VCOMP) the external MOSFET turns off. The output voltage of the internal error amplifier is an amplified signal of the difference between the reference voltage and the feedback voltage. The converter automatically chooses the lowest active LEDX pin voltage to provide a highenough bus voltage to power all the LED arrays. If the feedback voltage drops below the reference, the output of the error amplifier increases. This results in more current flowing through the MOSFET, thus increasing the power delivered to the output. This forms a closed loop that regulates the output voltage. Under light-load operation, especially in the case of VOUT VIN, the converter runs in pulse-skipping mode where the MOSFET turns on for a minimum on-time of approximately 200ns, and then the converter discharges the power to the output for the remaining period. The external MOSFET remains off until the output voltage needs to be boosted again. Dimming Control The MP3398A provides two dimming methods: PWM or analog dimming mode. For PWM dimming, apply a PWM signal to PWM pin. The LED current is chopped by this PWM signal and the average LED current is equal to Iset*D_dim where D_dim is the duty cycle of PWM dimming signal and Iset is the LED current amplitude. For analog dimming, either a PWM signal or DC signal can be applied to ADIM pin. When a PWM signal is applied to ADIM pin, this signal will be filtered by the internal RC filter. The LED current amplitude is equal to Iset*D_Dim where D_dim is the duty cycle of PWM dimming signal and Iset is the LED current amplitude. 20KHz or higher PWM signal is recommended to get the better filtering performance. MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 11 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER When a DC signal is applied to ADIM pin, the voltage range in 0.4V to 1.5V directly sets the LED current linearly from 0% to 100%. Open String Protection Open string protection is achieved through the OVP pin and the LED(1 to 4) pins. If one or more strings are open, the respective LEDX pins are pulled to ground and the IC keeps charging the output voltage until it reaches the over-voltage protection (OVP) threshold. If the OVP point has been triggered for >4us, the chip stops switching and marks the strings which have an LEDX pin voltage lower than 196mV. Once marked, the remaining LED strings force the output voltage back into tight regulation. The string with the largest voltage drop determines the output regulation. The MP3398A will always attempt to light at least one string. If all strings are open, the MP3398A shuts down the step-up converter. The strings will remain in this marked state until the chip reset. Short String Protection The MP3398A monitors the LEDX pin voltages to determine if a short string fault has occurred. If one or more strings are shorted, the respective LEDX pins tolerate high voltage stress. If an LEDX pin voltage is higher than 6.3V, this condition triggers the detection of a short string. When a short string faults (LEDX over-voltage fault) keeps for 4096 switching clocks, the fault string is marked OFF and disabled. Once a string is marked OFF, it disconnects from the output voltage loop. The marked LED strings shut off completely until the part restarts. In order to prevent mis-triggering short LED protection when open LED string or sharp ADIM, the short LED protection function is disabled when Vledx of all used LED channels are higher than 1.5V. Inductor/Diode short Protection To prevent the IC and external MOSFET damage when external inductor is shorted, MP3398A has the protection mode in two following methods. When inductor is shorted, the output can not maintain enough energy to load the LED and the output voltage will drop. Thus, the COMP (the error amplifier output) voltage tends to rise till be clamped high, when it lasts longer than 512 switching cycles the IC turns off and latches. In some cases that the COMP voltage can not be clamped to high when inductor is shorted, the IC also provides the protection mode by detecting the current flowing through power MOSFET. In this mode, when the current sense voltage across sense resistor (connected between MOSFET and GND) hits VLMT limit value and lasts for 4 switching cycles, the IC turns off and latches. Thermal Shutdown Protection To prevent the IC operate at exceedingly high temperature, thermal shutdown is implemented in this chip by detecting the silicon die temperature. When the die temperature exceeds the upper threshold TST, the IC shutdowns and recovers to normal operation when die temperature drops below lower threshold. Typically, the hysteresis value is 25C. MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 12 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER APPLICATION INFORMATION Selecting the Switching Frequency The switching frequency of the step-up converter is recommended from 100kHz to 500kHz for most of application. An oscillator resistor on OSC pin sets the internal oscillator frequency for the step-up converter according to the below equation: FSW(kHz) = Choose an inductor that does not saturate under the worst-case load conditions. Select the minimum inductor value to ensure that the boost converter works in continuous conduction mode with high efficiency and good EMI performance. Calculate the required inductance value using the equation: L 67320 ROSC (k ) D = 1- For ROSC=374k, the switching frequency is set to 180kHz. ILED (mA) = 810 x 1.22V R k ISET For RSET=8.2k, the LED current is set to 120mA. Please do not leave ISET pin open. 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 the high-frequency switching current from passing through to the input. Use ceramic capacitors with X5R or X7R dielectrics for their low ESR and small temperature coefficients. For most applications, use a 4.7F ceramic capacitor in parallel with a 220F electrolytic capacitor. Selecting the Inductor and Current Sensing Resistor The MP3398A requires an inductor to supply a higher output voltage while being driven by the input voltage. A larger value inductor results in less ripple current, resulting in lower peak inductor current and reducing stress on the Nchannel MOSFET. However, the larger value inductor has a larger physical size, higher series resistance, and lower saturation current. VIN VOUT Where VIN and VOUT are the input and output voltages, fSW is the switching frequency, ILOAD is the LED load current, and is the efficiency. The switching current is usually used for the peak current mode control. In order to avoid hitting the current limit, the voltage across the sensing resistor RSENSE must measure less than 80% of the worst-case current-limit voltage, VSENSE. RSENSE = IL(PEAK) = 0.8 x VSENSE IL(PEAK) VOUT x ILOAD VIN x (VOUT - VIN ) + VIN 2 x L x FSW x VOUT Where IL(PEAK) is the peak value of the inductor current. VSENSE is shown in Figure 2. Vsense vs.Duty Cycle 450 400 350 VSENSE (mV) Setting the LED Current The LED each string current can be set through the current setting resistor on the ISET pin. x VOUT x D x (1- D)2 2 x fSW x ILOAD 300 250 200 150 100 50 0 0 10 20 30 40 50 60 70 80 90 100 Figure 2--VSENSE vs Duty Cycle MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 13 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER Selecting the Power MOSFET The MP3398A is capable of driving a wide variety of N-channel power MOSFETS. The critical parameters of selection of a MOSFET are: 1. Maximum drain-to-source voltage, VDS(MAX) 2. Maximum current, ID(MAX) 3. On-resistance, RDS(ON) 4. Gate source charge QGS and gate drain charge QGD 5. Total gate charge, QG Ideally, the off-state voltage across the MOSFET is equal to the output voltage. Considering the voltage spike when it turns off, VDS(MAX) should be greater than 1.5 times of the output voltage. The maximum current through the power MOSFET occurs at the minimum input voltage and the maximum output power. The maximum RMS current through the MOSFET is given by IRMS(MAX) = IIN(MAX) x DMAX , where: DMAX VOUT - VIN(MIN) VOUT The current rating of the MOSFET should be greater than 1.5xIRMS The ON resistance of the MOSFET determines the conduction loss, which is given by: Pcond = IRMS 2 x R DS (on) x k Where k is the temperature coefficient of the MOSFET. The switching loss is related to QGD and QGS1 which determine the commutation time. QGS1 is the charge between the threshold voltage and the plateau voltage when a driver charges the gate, which can be read in the chart of VGS vs. QG of the MOSFET datasheet. QGD is the charge during the plateau voltage. These two parameters are needed to estimate the turn-on and turn-off losses. PSW = Q GS1 x R G x VDS x IIN x f SW + VDR - VTH Q GD x R G x VDS x IIN x f SW VDR - VPLT Where VTH is the threshold voltage, VPLT is the plateau voltage, RG is the gate resistance, and VDS is the drain-source voltage. Please note that calculating the switching loss is the most difficult part in the loss estimation. The formula above provides a simplified equation. For more accurate estimates, the equation becomes much more complex. The total gate charge, QG, is used to calculate the gate drive loss. The expression is PDR = Q G x VDR x f SW Where VDR is the drive voltage. Selecting the Output Capacitor The output capacitor keeps the output voltage ripple small and ensures feedback loop stability. The output capacitor impedance must be low at the switching frequency. Ceramic capacitors with X7R dielectrics are recommended for their low ESR characteristics. For most applications, a 4.7F ceramic capacitor in parallel with a 22F electrolytic capacitor will suffice. Setting the Over Voltage Protection The open string protection is achieved through the detection of the voltage on the OVP pin. In some cases, an LED string failure results in the feedback voltage always zero. The part then keeps boosting the output voltage higher and higher. If the output voltage reaches the programmed OVP threshold, the protection will be triggered. To ensure the chip functions properly, select the resistor values for the OVP resistor divider to provide an appropriate set voltage. The recommended OVP point is about 1.1 to 1.2 times higher than the output voltage for normal operation. VOVP = 1.23 x (1 + RHIGH ) RLOW Selecting Dimming Control Mode The MP3398A provides two different dimming methods. 1. Direct PWM Dimming An external PWM dimming signal is employed to achieve PWM dimming control. Apply a PWM dimming signal (in the range of 100Hz to 20kHz) to the PWM pin. The minimum recommended MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 14 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER amplitude of the PWM signal is 1.5V and the low level should be less than 0.4V. Table 1--The Range of PWM Dimming Duty fPWM(Hz) 100<f200 200<f500 500<f1k 1k<f2k 2k<f5k 5k<f10k 10k<f20k Dmin 0.30% 0.75% 1.50% 3.00% 7.50% 15.00% 30.00% Dmax 100% 100% 100% 100% 100% 100% 100% 2. Analog Dimming For analog dimming, apply a PWM signal or a DC voltage signal to ADIM pin. An internal RC filter (10Mohm resistor and 100pF capacitor) is integrated to this pin. So, if a PWM signal applied to this pin, >20kHz frequency is recommended to get a better PWM signal filtering performance and make sure the amplitude voltage is higher than 1.5V and low level voltage is less than 0.4V with >15mV/ns slope rate for falling/rising edge. For DC signal input, please apply a DC input signal range from 0.4V to 1.5V to linearly set the LED current from 0% to 100%. Expanding LED Channels The MP3398A can expand the number of LED channels by using two or three MP3398A in parallel. To connect two MP3398A for a total of 8 LED strings, tie the VCC pins of the master IC and the slave IC together to power the slave IC internal logic circuitry. Tie the COMP pins of the slave IC and the master IC together to regulate the voltage of all 8 strings LEDs. The slave IC MOSFET driving signals are not used; the boost converter can be only driven by the master IC. Do not leave the ISENSE pin of the slave IC floating; tie it to ground. Apply the EN and DIM signals to both ICs. Layout Considerations The circuit layout for the MP3398A requires special attention to reduce EMI noise. The loop from the external MOSFET (M1), through the output diode (D1) and the output capacitor (C2, C3) carry a high-frequency pulse current and must be as small and short as possible (See Figure 3). Figure 3--Layout Consideration All logic signals refer to the signal ground. in order to reduce the noise affection, it is recommend to separate the power ground(PGND) and signal ground(GND), then connect PGND and GND together. MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 15 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER TYPICAL APPLICATION CIRCUITS 8V-28V VIN C4 F1 C5 C1 C2 D1 L1 0V NC C3 00V 00V 12S 4P 120mA/string LED B360 NC C7 100V/4A 10 GND R1 M1 R3 15 R4 C9 C10 EN R8 2k 16 R7 270 1 470nF R10 R11 C11 330k 100k NC 100pF C12 A-DIM R20 2k R14 2 GATE VCC ISENSE COMP GND EN OVP 14 7 3 6 OSC LED1 ADIM LED2 PWM LED3 ISET LED4 R19 0 4 12 11 10 9 8 C8 100pF LED1 LED2 LED3 LED4 R6 0.05 13 MP3398AGS 5 10k 10 VIN C6 NC R5 U1 R2 357k C14 NC R21 2k R9 0 R12 0 R13 0 R15 0 100k PWM-DIM R16 2k C13 NC R18 100k R17 8.45k C15 100pF Figure 4: 4 string, 12 LED in series, 120mA/string application (Some components are reasonably adjustable based on real case) MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 16 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER PACKAGE INFORMATION SOIC16 0.386( 9.80) 0.394(10.00) 0.024(0.61) 9 16 0.063 (1.60) 0.150 (3.80) 0.157 (4.00) PIN 1 ID 0.050(1.27) 0.228 (5.80) 0.244 (6.20) 0.213 (5.40) 8 1 TOP VIEW RECOMMENDED LAND PATTERN 0.053(1.35) 0.069(1.75) SEATING PLANE 0.050(1.27) BSC 0.013(0.33) 0.020(0.51) 0.004(0.10) 0.010(0.25) 0.0075(0.19) 0.0098(0.25) SEE DETAIL "A" SIDE VIEW FRONT VIEW NOTE: 0.010(0.25) x 45o 0.020(0.50) GAUGE PLANE 0.010(0.25) BSC 0o-8o 0.016(0.41) 0.050(1.27) 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 AC. 6) DRAWING IS NOT TO SCALE. DETAIL "A" MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 17 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER TSSOP16-EPwith external thermal pad PIN 1 ID TOP VIEW RECOMMENDED LAND PATTERN SEE DETAIL "A" FRONT VIEW SIDE VIEW DETAIL "A" NOTE: BOTTOM VIEW 1) ALL DIMENSIONS ARE IN MILLIMETERS. 2) PACKAGE LENGTH DOES NOT INCLUDE MOLD FLASH, PROTRUSION OR GATE BURR. 3) PACKAGE WITDH 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-153, VARIATION ABT. 6) DRAWING IS NOT TO SCALE. MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 18 STEP UP, 4 STRINGS, MAX. 350MA/STRING ANALOG AND PWM DIMMING, WHITE LED CONTROLLER SOIC20 0.024 (0.61) 0.496(12.60) 0.512(13.00) 20 11 0.050 (1.27) 0.079 (2.00) 0.291 (7.40) 0.299 (7.60) 0.394 (10.00) 0.418 (10.60) 0.370 (9.40) PIN 1 ID 1 10 TOP VIEW RECOMMENDED LAND PATTERN 0.093(2.35) 0.104(2.65) SEATING PLANE 0.050(1.27) 0.004(0.10) BSC 0.012(0.30) 0.013(0.33) 0.020(0.51) FRONT VIEW 0.010(0.25) x 45o 0.030(0.75) GAUGE PLANE 0.010(0.25) BSC 0o-8o 0.016(0.41) 0.050(1.27) DETAIL "A" 0.009(0.23) 0.013(0.33) SEE DETAIL "A" SIDE VIEW NOTE: 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 0.10 MILLIMETERS MAX. 5) DRAWING CONFORMS TO JEDEC MS-013, VARIATION AC. 6) DRAWING IS NOT TO SCALE. NOTICE: The information in this document is subject to change without notice. Please contact MPS for current specifications. 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. MP3398A Rev. 1.03 www.MonolithicPower.com 5/27/2015 MPS Proprietary Information. Patent Protected. Unauthorized Photocopy and Duplication Prohibited. (c) 2015 MPS. All Rights Reserved. 19 Mouser Electronics Authorized Distributor Click to View Pricing, Inventory, Delivery & Lifecycle Information: Monolithic Power Systems (MPS): MP3398AGF-Z MP3398AGY-Z MP3398AGS MP3398AGF MP3398AGY MP3398AGS-Z