LM3508 Datasheet, PDF (8/14 Pages) National Semiconductor (TI) – Synchronous Magnetic Constant Current White LED Driver

Over-Voltage Protection Function
Line-Step Response
VIN = 3.6V, V_OUT = 18.86V
Channel 1: V_OUT (1V/div)
Channel 4: I_IN (500mA/div)
Time Base: 400µs/div
30004237
Output Short-Circuit Response
V_IN = 3.6V, 4 LEDs
Channel 1: V_OUT (AC Copupled, 1V/div)
Channel 3: V_IN (AC Coupled, 500mV/div)
Channel 4: I_LED (DC Coupled, 5mA/div)
Time Base: 200µs/div
30004255
Typical Operating Waveforms (DIM High)
V_IN = 3.6V, I_LED = 30mA
Channel 1: V_OUT (10V/div)
Channel 2: I_IN (100mA/div)
Time Base: 200µs/div
30004256
V_IN = 3.6V, 4 LEDs, I_LED = 30mA, V_OUT = 15.8V
Channel 1: V_OUT (AC Coupled, 100mV/div)
Channel 2: V_SW (DC Coupled, 10V/div)
Channel 4: I_L (DC Coupled, 100mA/div)
Time Base: 400ns/div
30004229
Typical Operating Waveforms (DIM With 20kHz Square
Wave)
DIM Operation (I_LED changing from 30mA to 15mA)
V_IN = 3.6V, 4 LEDs, I_LED = 15mA
Channel 1: V_OUT (AC Coupled, 200mV/div)
Channel 3: V_IN (AC Coupled, 100mV/div)
Channel 2: I_L (DC Coupled, 100mA/div)
Channel 4: DIM (DC Coupled, 2V/div)
Time Base: 10µs/div
30004230
www.national.com
30004238
V_IN = 3.6V
Channel 4: I_LED (DC Coupled, 10mA/div)
Channel 2: V_OUT (AC Coupled, 2V/div)
Channel 1: DIM (DC Coupled, 2V/div, 20kHz, 50% duty cycle)
Channel 3: I_IN (DC Coupled, 200mA/div)
Time Base: 400µs/div
8