The LM3405A is a 1-A constant current buck LED driver designed to provide a simple, high efficiency solution for driving high power LEDs. With a 0.205-V reference voltage feedback control to minimize power dissipation, an external resistor sets the current as needed for driving various types of LEDs. Switching frequency is internally set to 1.6 MHz, allowing small surface mount inductors and capacitors to be used. The LM3405A uses current-mode control and internal compensation offering ease of use and predictable, high performance regulation over a wide range of operating conditions. With a maximum input voltage of 22 V, the device can drive up to 5 High-Brightness LEDs in series at 1-A forward current, with the single LED forward voltage of approximately 3.7 V. Additional features include user accessible EN/DIM pin for enabling and PWM dimming of LEDs, thermal shutdown, cycle-by-cycle current limit and overcurrent protection.
PART NUMBER | PACKAGE | BODY SIZE (NOM) |
---|---|---|
LM3405A | SOT (6) | 2.90 mm × 1.60 mm |
MSOP-PowerPAD (8) | 3.00 mm × 3.00 mm |
Changes from C Revision (May 2013) to D Revision
Changes from B Revision (April 2013) to C Revision
PIN | I/O | DESCRIPTION | ||
---|---|---|---|---|
NAME | SOT | MSOP-PowerPAD | ||
BOOST | 1 | 4 | O | Boost voltage that drives the NMOS output switch. A bootstrap capacitor is connected between the BOOST and SW pins. |
GND | 2 | 2, 7 | — | Signal and power ground pin. Place the bottom resistor of the feedback network as close as possible to this pin. |
FB | 3 | 1 | I | Feedback pin. Connect FB to the LED string cathode and an external resistor to ground to set the LED current. |
EN/DIM | 4 | 8 | I | Enable control input. Logic high enables operation. Toggling this pin with a periodic logic square wave of varying duty cycle at different frequencies controls the brightness of LEDs. Do not allow this pin to float or be greater than VIN + 0.3 V. |
VIN | 5 | 6 | I | Input supply voltage. Connect a bypass capacitor locally from this pin to GND. |
SW | 6 | 5 | O | Switch pin. Connect this pin to the inductor, catch diode, and bootstrap capacitor. |
NC | — | 3 | — | No connection. |
DAP | N/A | — | — | Attach to power ground pin (GND). |