LD-B4-20 2-12Amp 20mm constant current LED flashlight driver

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Datasheet (17mm version) download: LD-x4 datasheet v1.1

LD-A4/B4-20  2-12A constant current („PWM-less“) LED drivers are next generation of LD driver series. Based on completely re-designed hardware and improved firmware, these drivers are optimized for single-cell (4.2V) flashlights, and offer some new  features compared to LD-3, like hardware (real) direct drive mode option, 1-wire temperature sensor support, integrated moonlight with 3 levels (2.5mA, 5.0mA, 7.5mA) adjustable via user interface, and low current bleeding support for illuminated tailcap modules like ILC-1. Typical bleeding current is just 1mA, which is 5-10 times lower than conventional resistor bleeding. This enables significantly longer run times on moonlight modes.

LD-A4-20 is standard type of linear driver with all components on PCB, designed for power dissipation 2W -6W@60C. Recommended applications are single Li-ion cell LED flashlights with single LED.

LD-B4-20 is designed to work with external power MOSFET (source of heat) for much higher power dissipation – up to 15W@60C, which is more than enough for any triple or quad LED setup. “MOSLED” high performance metal core PCBs have space for MOSFET and NTC sensor, which makes triple or quad LED builds fast and easy, and more important – reliable because of real constant current driving/limiting.

Because current on all modes is regulated, LD-x4-20 driver series is ideal solution for driving modern LEDs with very low Vf like Nichia 219C,319AT, Cree XP-L2,XP-G3, Luxeon V and Luminus SST-40 from 1S li-ion battery cells/pack.

Hardware features:
  • True PWM-less constant current (all modes)
  • Available as 3, 6, 9 and 12Amps version – 2-12Amps possible by adjusting current in UI
  • Completely silent – no acoustical or EMI noise („whining“)
  • Longer run-times on lower modes compared to PWM drivers
  • Higher overall lm/W efficiency on lower modes compared to PWM drivers
  • Lower losses in springs, wires, switch compared to PWM drivers
  • Very low internal resistance comparable to best DD drivers
  • Hardware DD mode option on high mode without current limit
  • Calibrated internal voltage reference and temp. sensor
  • Dual over-temperature protection (internal, and external [NTC] sensor) – single wire NTC connection
  • Integrated moonlight with UI selectable 2.5mA – 7.5mA current
  • Low sleep current
  • Improved Off-time mode memory circuit
  • Low current (1mA) bleeding support for illuminated tailcaps
  • Single-sided PCB with large (9mm) spring pad on bottom side
  • 4-layer gold plated PCB
  • Lead free
User interface features:
  • 2-level depth configuration menu with back/cancel option – possibility to change many settings without leaving configuration mode
  • Adjustable current (without any resistor change):                                                                                                                                                                                                                                                     0.125Amp steps (3A version) down to 2A;                                                                                                                                                                                                                                                            0.250Amp steps (6A and 9A version) down to 4A (6A version) and                                                                                                                                                                                                                                 7A (9A version):0.500Amp steps (12A version) down to 8A
  • 1-5 modes mode – groups
  • Mode memory Enable/Disable
  • CC/DD Enable/Disable for high. mode (Constant current/Hardware Direct Drive)
  • Mode order Forward/Backward
  • 2x or 3x tap special function – Tactical strobe/High mode/Disable
  • External over-temperature(OTP) threshold setting – Factory/Custom/ Disable
  • Configuration mode password Enable/Disable
  • Factory reset
Electrical characteristics:
  • Input voltage: 2.8V-4.35V
  • Output current: 2-12 Amperes (3A,6A,9A,12A default options)
  • Switch type supported: reverse clicky switch
  • Internal resistance: 5mΩ@3.7V
  • Average efficiency(Vf=3V):      85%
  •                                 ( Vf=3.4V):  90%
  • Sleep/off current: 20uA typ. (40uA typ. with ext. NTC sensor) /1mA with low current bleeding
  • Active state (operating) current: 1.6mA typ. (2.6mA typ. with low current bleeding)
  • Tailcap bleeding current consumption: 1.0mA typ.
  • Driver internal OTP protection threshold: ~105°C
  • Default external sensor OTP threshold: ~65°C
  • Step 1 LVP threshold: 3.0V (restricted power)
  • Step 2 LVP threshold: 2.8V (shutdown)
  • Configuration menu level 1 (main menu) current: 350mA (175mA for 3A version)
  • Configuration menu level 2 (sub-menus) current: 90mA   (45mA for 3A version)
Mechanical characteristics:
  • Driver diameter: 20.00±0.15mm
  • Thickness: 2.4±0.15mm
  • LED wire pads hole diameter: 1.4mm
  • Spring pad diameter: 9.15mm
  • Number of el. components on PCB (top side only): 26
Signal wires option explanation:

LD-A4 – 1x 10cm 30AWG silicone wire (white color) for NTC external overtemp. protection sensor (optional feature)

LD-B4 -3x 10cm 30AWG silicone wires:

  1. White color – for NTC external overtemp. protection sensor (optional feature)
  2. Yellow or blue color – for Gate signal connection between LD-B4 pcb and MOSLED MCPCB (mandatory)
  3. Red color – for moonlight mode signal connection between LD-B4 pcb and MOSLED MCPCB(optional, needed if moonlight mode is enabled)


Additional information

Weight 2.5 g