Supertex inc. HV9919B Hysteretic, Buck, High Brightness LED Driver with High-Side Current Sensing Features General Description The HV9919B is a PWM controller IC designed to drive high brightness LEDs using a buck topology. It operates from an input voltage of 4.5 to 40VDC and employs hysteretic control with a high-side current sense resistor to set the constant output current. Hysteretic control with high-side current sensing Wide input voltage range: 4.5 to 40V >90% Efficiency Typical 5% LED current accuracy Up to 2.0MHz switching frequency Adjustable constant LED current Analog or PWM control signal for PWM dimming Over-temperature protection -40C to +125C operating temperature range The operating frequency range can be set by selecting the proper inductor. Operation at high switching frequency is possible since the hysteretic control maintains accuracy even at high frequencies. This permits the use of small inductors and capacitors minimizing space and cost in the overall system. Applications LED brightness control is achieved with PWM dimming from an analog or PWM input signal. Unique PWM circuitry allows true constant color with a high dimming range. The dimming frequency is programmed using a single external capacitor. Low voltage industrial and architectural lighting General purpose constant current source Signage and decorative LED lighting Indicator and emergency lighting The HV9919B comes in a small, 8-Lead DFN package and is ideal for industrial and general lighting applications. Typical Application Circuit RSENSE L CIN CS RAMP 0 - 2.0V ADIM DIM VIN VDD GATE GND HV9919B Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: 408-222-8888 www.supertex.com HV9919B Pin Description Ordering Information Package Options Device CS 1 VIN 2 8-Lead DFN 3.00x3.00mm body, 0.80mm height (max), 0.65mm pitch HV9919B 8 GATE 7 GND GND HV9919BK7-G -G indicates package is RoHS compliant (`Green') RAMP 3 6 VDD ADIM 4 5 DIM 8-Lead DFN (K7) (top view) Product Marking Parameter Value VIN, CS to GND -0.3 to +45V VDD, GATE, RAMP, DIM, ADIM to GND -0.3 to +6.0V CS to VIN -1.0 to +0.3V Continuous power dissipation, (TA = +25C) Operating temperature range 8-Lead DFN (K7) Thermal Resistance 1.6W -40C to +125C Junction temperature +150C Storage temperature range Y = Last Digit of Year Sealed W = Code for Week Sealed L = Lot Number = "Green" Packaging 9919 YWLL Absolute Maximum Ratings Package ja 8-Lead DFN (K7) 60OC/W Mounted on FR-4 board, 25mm x 25mm x 1.57mm -65C to +150C Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Electrical Characteristics (VIN = 12V, VDIM = VDD, VRAMP = GND, CVDD = 1.0F, RCS = 0.5, TA = TJ = -40OC to +125OC* unless otherwise noted) Sym Description Min Typ Max Units VIN Input DC supply voltage range 4.5 VDD Internally regulated voltage - 40 V DC input voltage 4.5 - 5.5 V VIN = 6.0 to 40V Supply current - - 1.5 mA GATE open IIN, SDN Shutdown supply current - - 900 A DIM < 0.7V IIN, LIM Current limit - 30 - - 8.0 - Oscillator frequency - - 2.0 MHz UVLO VDD Undervoltage lockout threshold - - 4.5 V VDD rising UVLO VDD Undervoltage lockout hysteresis - 500 - mV VDD falling IIN fOSC mA Conditions VIN = 4.5V, VDD = 0V VIN = 4.5V, VDD = 4.0V --- * Guaranteed by design and characterization, 100% tested at TA = 25 C. Typical characteristics are given at TA = 25OC. O Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: 408-222-8888 www.supertex.com 2 HV9919B Electrical Characteristics (VIN = 12V, VDIM = VDD, VRAMP = GND, CVDD = 1.0F, RCS = 0.5, TA = TJ = -40OC to +125OC* unless otherwise noted) Sym Description Min Typ Max Units Conditions Sense Comparator VCS(HI) Sense voltage threshold high 213 230 246 mV (VIN - VCS) rising VCS(LO) Sense voltage threshold low 158 170 182 mV (VIN - VCS) falling tDPDH Propagation delay to output high - 70 - ns Falling edge of (VIN - VCS) = VRS(LO) - 70mV tDPDL Propagation delay to output low - 70 - ns Rising edge of (VIN - VCS) = VRS(HI) + 70mV Current-sense input current - - 1.0 A (VIN - VCS) = 200mV Current-sense threshold hysteresis - 56 70 mV --- ICS ICS(HYS) DIM Input VIH Pin DIM input high voltage 2.2 - - V --- VIL Pin DIM input low voltage - - 0.7 V --- tON Turn-on time - 100 - ns DIM rising edge to VGATE = 0.5 x VDD, CGATE = 2.0nF tOFF Turn-off time - 100 - ns DIM falling edge to VGATE = 0.5 x VDD, CGATE =2.0nF GATE current, source 0.3 0.5 - A VGATE = GND GATE current, sink 0.7 1.0 - A VGATE = VDD Gate Driver IGATE TRISE GATE output rise time - 40 55 ns CGATE= 2.0nF TFALL GATE output fall time - 17 25 ns CGATE= 2.0nF VGATE(HI) GATE high output voltage VDD -0.5 - - V IGATE = 10mA VGATE(LO) GATE low output voltage - - 0.5 V IGATE = -10mA 128 140 - C --- - 60 - C --- 130 - 300 550 - 1250 Over-Temperature Protection TOT THYST Over temperature trip limit Temperature hysteresis Analog Control of PWM Dimming Hz CRAMP = 47nF fRAMP Dimming frequency VLOW RAMP threshold, Low - 0.1 - V --- VHiGH RAMP threshold, High 1.8 - 2.1 V --- VOS ADIM offset voltage -35 - +35 mV --- CRAMP = 10nF * Guaranteed by design and characterization, 100% tested at TA = 25 C. Typical characteristics are given at TA = 25OC. Guaranteed by design and characterization. O Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: 408-222-8888 www.supertex.com 3 HV9919B Block Diagram VIN VDD REGULATOR + - CS GATE DRIVER CURRENT SENSE COMPARATOR BANDGAP REF GATE + DIM UVLO COMPARATOR GND PWM RAMP 0.1~1.9V RAMP + ADIM Application Information General Description The HV9919B is a step-down, constant current, high-brightness LED (HB LED) driver. The device operates from a 4.5 to 40V input voltage range and provides the gate drive output to an external N-channel MOSFET. A high-side current sense resistor sets the output current and a dedicated PWM dimming input (DIM) allows for a wide range of diming duty ratios. The PWM dimming could also be achieved by applying a DC voltage between 0 and 2.0V to the analog dimming input (ADIM). In this case, the dimming frequency can be programmed using a single capacitor at the RAMP pin. The high-side current setting and sensing scheme minimizes the number of external components while delivering LED current with a 8% accuracy, using a 1% sense resistor. HV9919B DIM Input The HV9919B allows dimming with a PWM signal at the DIM input. A logic level below 0.7V at DIM forces the GATEOUTPUT low, turning off the LED current. To turn the LED current on, the logic level at DIM must be at least 2.2V. ADIM and RAMP Inputs The PWM dimming scheme can be also implemented by applying an analog control signal to ADIM pin. If an analog control signal of 0~2.0V is applied to ADIM, the device compares this analog input to a voltage ramp to pulse-width-modulate the LED current. Connecting an external capacitor to RAMP programs the PWM dimming ramp frequency. fPWM = 1 CRAMP * 120k Undervoltage Lockout (UVLO) The HV9919B includes a 3.7V under-voltage lockout (UVLO) with 500mV hysteresis. When VIN falls below 3.7V, GATE goes low, turning off the external n-channel MOSFET. GATE goes high once VIN is 4.5V or higher. DIM and ADIM inputs can be used simultaneously. In such case, fPWM(MAX) must be selected lower than the frequency of the dimming signal at DIM. The smaller dimming duty cycle of ADIM and DIM will determine the GATE signal. 5.0V Regulator VDD is the output of a 5.0V regulator capable of sourcing 8.0mA. Bypass VDD to GND with a 1.0F capacitor. When the analog control of PWM dimming feature is not used, RAMP must be wired to GND, and ADIM should be connected to VDD. Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: 408-222-8888 www.supertex.com 4 HV9919B One possible application of the ADIM feature of the HV9919B may include protection of the LED load from over-temperature by connecting an NTC thermistor at ADIM, as shown in Figure 1. VDD HV9919B ADIM input comparator with hysteresis (Figure 2). As the current through the inductor ramps up and the voltage across the sense resistor reaches the upper threshold, the voltage at GATE goes low, turning off the external MOSFET. The MOSFET turns on again when the inductor current ramps down through the freewheeling diode until the voltage across the sense resistor equals the lower threshold. Use the following equation to determine the inductor value for a desired value of operating frequency fS: NTC L= GND Figure 1 where: Setting LED Current with External Resistor RSENSE The output current in the LED is determined by the external current sense resistor (RSENSE) connected between VIN and CS. Disregarding the effect of the propagation delays, the sense resistor can be calculated as: 1 (VRS(HI) + VRS(LO) ) 200mV RSENSE * = ILED ILED 2 Selecting Buck Inductor L The HV9919B regulates the LED output current using an VRS(HI) RSENSE ILED VRS(LO) RSENSE (VIN - VOUT )VOUT (VIN - VOUT )tDPDL VOUT tDPDH fSVINIO IO IO tDPDL IO = VRS(HI) - VRS(LO) RSENSE and tDPDL, tDPDH are the propagation delays. Note, that the current ripple I in the inductor L is greater than IO. This ripple can be calculated from the following equation: (VIN - VOUT)tDPDL VOUTtDPDH I = IO + + L L For the purpose of the proper inductor selection, note that the maximum switching frequency occurs at the highest VIN and VOUT = VIN/2. TS = 1/fS tDPDH I IO t VDIM t Figure 2 Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: 408-222-8888 www.supertex.com 5 HV9919B MOSFET Selection MOSFET selection is based on the maximum input operating voltage VIN, output current ILED, and operating switching frequency. Choose a MOSFET that has a higher breakdown voltage than the maximum operation voltage, low RDS(ON), and low total charge for better efficiency. MOSFET threshold voltage must be adequate if operated at the low end of the input-voltage operating range. Freewheeling Diode Selection The forward voltage of the freewheeling diode should be as low as possible for better efficiency. A Schottky diode is a good choice as long as the breakdown voltage is high enough to withstand the maximum operating voltage. The forward current rating of the diode must be at least equal to the maximum LED current. LED Current Ripple The LED current ripple is equal to the inductor current ripple. In cases when a lower LED current ripple is needed, a capacitor can be placed across the LED terminals. PCB Layout Guidelines Careful PCB layout is critical to achieve low switching losses and stable operation. Use a multilayer board whenever possible for better noise immunity. Minimize ground noise by connecting high-current ground returns, the input bypass capacitor ground lead, and the output filter ground lead to a single point (star ground configuration). The fast di/dt loop is formed by the input capacitor CIN, the free-wheeling diode and the MOSFET. To minimize noise interaction, this loop area should be as small as possible. Place RSENSE as close as possible to the input filter and VIN. For better noise immunity, a Kelvin connection is strongly recommended between CS and RSENSE. Connect the exposed tab of the IC to a largearea ground plane for improved power dissipation. Pin Description Pin # Pin Description 1 CS Current sense input. Senses LED string current. 2 VIN Input voltage 4.5 to 40V DC. 3 RAMP Analog PWM dimming ramp output. 4 ADIM Analog 0~2.0V signal input for analog control of PWM dimming. 5 DIM PWM signal input. 6 VDD Internally regulated supply voltage. Connect a capacitor from VDD to ground. 7 GND Device ground. 8 GATE Drives gate of external MOSFET. TAB GND Must be wired to pin 7 on PCB. Supertex inc. 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: 408-222-8888 www.supertex.com 6 HV9919B 8-Lead DFN Package Outline (K7) 3.00x3.00mm body, 0.80mm height (max), 0.65mm pitch D2 D 8 8 E E2 Note 1 (Index Area D/2 x E/2) Note 1 (Index Area D/2 x E/2) 1 1 Top View Bottom View View B Note 3 A A3 e b A1 L Seating Plane L1 Note 2 View B Side View Notes: 1. A Pin 1 identifier must be located in the index area indicated. The Pin 1 identifier can be: a molded mark/identifier; an embedded metal marker; or a printed indicator. 2. Depending on the method of manufacturing, a maximum of 0.15mm pullback (L1) may be present. 3. The inner tip of the lead may be either rounded or square. Symbol Dimension (mm) A A1 MIN 0.70 0.00 NOM 0.75 0.02 MAX 0.80 0.05 A3 0.20 REF b D D2 E E2 e 0.25 2.85* 1.60 2.85* 1.35 0.30 3.00 - 3.00 - 0.35 3.15* 2.50 3.15* 1.75 0.65 BSC L L1 0.30 0.00* 0O 0.40 - - 0.50 0.15 14O JEDEC Registration MO-229, Variation WEEC-2, Issue C, Aug. 2003. * This dimension is not specified in the JEDEC drawing. Drawings not to scale. Supertex Doc. #: DSPD-8DFNK73X3P065, Version C041009. (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to http://www.supertex.com/packaging.html.) Supertex inc. does not recommend the use of its products in life support applications, and will not knowingly sell them for use in such applications unless it receives an adequate "product liability indemnification insurance agreement." Supertex inc. does not assume responsibility for use of devices described, and limits its liability to the replacement of the devices determined defective due to workmanship. No responsibility is assumed for possible omissions and inaccuracies. Circuitry and specifications are subject to change without notice. For the latest product specifications refer to the Supertex inc. (website: http//www.supertex.com) Supertex inc. (c)2011 Supertex inc. All rights reserved. Unauthorized use or reproduction is prohibited. Doc.# DSFP-HV9919B B082911 1235 Bordeaux Drive, Sunnyvale, CA 94089 Tel: 408-222-8888 www.supertex.com 7