Using the MAX15005 Supply and Driver for an LED Application

Mar 14 2023

The reference design below provides a reference design for an automotive LED application. The MAX15005 is used to boost a standard, 8V to 16V car battery to 21V in order to drive a string of 6 to 8 LEDs. Key specifications for this reference design are listed below, along with a detailed schematic (Figure 1) and the bill of materials (Table 1) needed for this application.

Specifications

  • VIN: 8V to 16V (Continuous), 40V (Transient)
  • VLED+ Supply Voltage: 21V ±5% at 80mA (max)
  • VLED+ Load Range: 10V to 20V at 70mA
  • ILED: 70mA ±5%
  • Dimming Input: 400Hz, 50Ω, Open Collector
  • Dimming Resolution: 3µs
  • Switching Frequency: 385kHz
  • Operating Temperature: -40°C to +125°C

Figure 1. MAX15005 reference design

Figure 1. MAX15005 reference design

Table 1. Bill of Materials
Designator Value Description Part Footprint Manufacturer Quantity
C1, C5, C6, C8, C10 1µF/50V Capacitors GCM31MR71H105KA55L 1206 Murata 5
C2 200pF/100V Capacitor GRM2165C2A201JA01D 0805 Murata 1
C3, C13, C14 100pF/50V Capacitors GRM2165C1H101JA01D 0805 Murata 3
C4, C7, C9 100pF/50V Capacitors GRM2165C1H101JA01D 0805 Murata 3
C11 10nF/50V Capacitor GRM216R71H103KA01D 0805 Murata 3
C12 10µF/50V Capacitor UUD1H100MCL1GS SMD Nichocon 1
D1 1A/400V Diode S1G SMA Fairchild 1
D2 200mA/100V Schottky Diode BAD41ZFILM SOD123 STM 1
D3 200mA/30V Schottky Diode STM SOT23 STM 1
L1 470µF/0.86A Inductor MSD1260-474 SMD Coilcraft 1
Q1 1A/100V n-FET ZXMN10A07Z SOT89 Zetex 1
Q2 2A/55V n-FET IRLL014NTRPBF SOT223 International Rectifier 1
Q3 220mA/50V n-FET BSS138 SOT23 Fairchild 1
R1 22.1kΩ Resistor SMD, 1%, 0.125W 0805 Vishay 1
R2, R4, R6 100kΩ Resistors SMD, 1%, 0.125W 0805 Vishay 3
R5 6.19kΩ Resistor SMD, 1%, 0.125W 0805 Vishay 1
R7 3.65kΩ Resistor SMD, 1%, 0.125W 0805 Vishay 1
R8 210kΩ Resistor SMD, 1%, 0.125W 0805 Vishay 1
R3 26.7kΩ Resistor SMD, 1%, 0.125W 0805 Vishay 1
R9, R16 2kΩ Resistors SMD, 1%, 0.125W 0805 Vishay 2
R10 10Ω Resistor SMD, 1%, 0.125W 0805 Vishay 1
R11 100Ω Resistor SMD, 1%, 0.125W 0805 Vishay 1
R12 8.66kΩ Resistor SMD, 1%, 0.125W 0805 Vishay 1
R13 .051kΩ Resistor SMD, 1%, 0.125W 0805 Vishay 1
R14 1.4kΩ Resistor SMD, 1%, 0.125W 0805 Vishay 1
R15 100Ω Resistor SMD, 1%, 0.125W 0805 Vishay 1
R17 10Ω Resistor SMD, 1%, 0.205W 1206 Vishay 1
IC1 MAX15005A Boost Controller MAX15005AAUE+ 16-TSSOP-EP Maxim 1
IC2 MAX4400 Single Op-Amp MAX4400AXK+ 5-SC70 Maxim 1

The oscilloscope photos in Figures 2, 3, and 4 show the switching waveforms for this reference design at three different dimming conditions.

Figure 2. Waveform measurements for ILED at VIN = 14V with dimming at 50.0%

Figure 2. Waveform measurements for ILED at VIN = 14V with dimming at 50.0%

Figure 3. Waveform measurements for ILED at VIN = 14V with dimming at 0.1%

Figure 3. Waveform measurements for ILED at VIN = 14V with dimming at 0.1%

Figure 4. Waveform measurements for ILED at VIN = 14V with dimming at 99.9%

Figure 4. Waveform measurements for ILED at VIN = 14V with dimming at 99.9%

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