Supertex inc. HV9910BDB3 Low Voltage, High Current, LED Driver Demoboard General Description Specifications The HV9910BDB3 demoboard is a high current LED driver Parameter Value designed to drive one LED or two LEDs in series at currents Input voltage 10 - 30VDC up to 1.0A from a 10 30VDC input. The demoboard uses Supertexs HV9910B Universal LED driver IC to drive a Output voltage - 2.0 - 4.5V buck converter. constant frequency mode Output voltage - The HV9910BDB3 can be configured to operate in either a 4.0 - 8.0V constant off-time mode constant frequency mode (for driving a single LED) or in a Maximum output current 1.0A 10% constant off-time mode (for driving two LEDs). Output current ripple (typ) 20% (peak-peak) The output current can be adjusted in two ways either 86% (for one LED) with linear dimming using the onboard potentiometer or Efficiency ( 12V input) with PWM dimming by applying a TTL compatible square 93% (for two LEDs) wave signal at the PWMD terminal. Using linear dimming, Open LED protection yes the output current of the HV9910DB1 can be lowered to Output short circuit protection no about 0.01A (note: zero output current can be obtained only by PWM dimming). Dimensions 48.2mm X 29.0mm Connection Diagram + - + Short for constant Short for frequency mode constant off-time mode Connections 3. PWM Dimming Connection 1. Input Connection - Connect the input DC voltage between VIN and GND terminals of connector J1 as shown a. If no PWM dimming is required, short PWMD and in the connection diagram. VDD terminals of connector J3. 2. Output Connection - Connect the LEDs between b. If PWM dimming is required, connect the TTL- LED+ (anode of LED string) and LED- (cathode of LED compatible PWM sourc between PWMD and GND string) of connector J2. terminals of connector J3. The recommended PWM dimming frequency is 1.0kHz. a. If the load is one LED, short the RT and FREQ terminals of connector J4 using a jumper. b. If the load is two LEDs, short the RT and OFFT terminals of connector J4 using a jumper. Doc. DSDB-HV9910BDB3 Supertex inc. A032813 www.supertex.comHV9910BDB3 Frequently Asked Questions 1. Why does the demoboard have two operating 2. If the minimum input voltage in my application is high- modes er (say 20V), does that mean I can drive a 9V LED string in the constant frequency mode or an 16V LED string in Constant frequency mode limits the maximum output the constant off-time mode using the demoboard voltage to less then 50% of the minimum input voltage. So, in this case, if we use only the constant frequency Although a larger LED string can be driven using the mode, the maximum output voltage will have to be less demoboard in these conditions, the demoboard will not than 5V. Constant off-time mode removes this limita- be able to drive the LED at 1A. tion and allows the output voltage become higher. How- The HV9910B is a constant peak current controller. The ever, in order to achieve reasonable noise immunity and average LED current is equal to the peak current set to limit the switching frequency variation over the input (using the sense resistor) minus one-half of the ripple voltage range, it is not recommended to operate the current in the inductor. HV9910DB3 with the output voltage exceeding 80% of the input voltage, even in the constant off-time mode. Higher output voltages lead to larger ripple current val- Please refer to application note AN-H50 on the Supertex ues, which will reduce the maximum LED current the website for more details. board can deliver. 3. How can I compute the maximum LED current the demoboard can deliver if I use a higher input voltage and a higher LED string voltage See table below: Parameters = V Minimum input voltage IN,MIN = V Maximum LED string voltage O,MAX = f (100kHz) Switching frequency (constant frequency mode) S = T (5.1s) Off-Time (constant off-time mode) OFF = V (0.25V) HV9910B CS threshold voltage CS = R (0.22) Sense Resistor CS = L (220H) Inductor Constant Off-Time Mode Constant Frequency Mode V T O,MAX OFF l = L V O, MAX V 1 O,MAX V IN,MIN V l CS l = I = LED L f R 2 S CS V V l CS O, MAX I = 1 LED V R 2 CS IN,MIN Maximum Switching Frequency = T OFF Doc. DSDB-HV9910BDB3 Supertex inc. A032813 2 www.supertex.com