LT1937 LINER [Linear Technology], LT1937 Datasheet - Page 6

• Manufacturer Part Number: LT1937
• Description: 20mA LED Driver and OLED Driver with Integrated Schottky in 3mm x 2mm DFN
• Manufacturer: LINER [Linear Technology]

LT3498
TYPICAL PERFORMANCE CHARACTERISTICS
200mA/DIV
PIN FUNCTIONS
6
INDUCTOR
LED1 (Pin 1): Connection Point Between the Anode of the
Highest LED and the Sense Resistor. The LED current can
be programmed by:
CTRL1 (Pin 2): Dimming and Shutdown Pin. Connect this
pin below 75mV to disable the white LED driver. As the
pin voltage is ramped from 0V to 1.5V, the LED current
ramps from 0 to (I
GND1, 2 (Pins 3, 4): Ground. Tie directly to local ground
plane. GND1 and GND2 are connected internally.
10mV/DIV
50mV/DIV
COUPLED
CURRENT
VOLTAGE
10V/DIV
10V/DIV
100mA/
I
V
V
LED
SW2
OUT2
CAP1
V
DIV
AC
SW
I
L
1
OLED Switching Waveforms
with 4mA Load
V
V
V
FRONT PAGE APPLICATION
LED Switching Waveforms
IN
OUT2
IN
= 3.6V
= 3.6V
R
200
= 16V
SENSE
mV
1
LED1
500ns/DIV
2 s/DIV
= 200mV / R
3498 G22
3498 G19
SENSE1
AC COUPLED
200mA/DIV
INDUCTOR
10mV/DIV
CURRENT
VOLTAGE
10V/DIV
200mA/
V
5V/DIV
5V/DIV
V
V
CTRL1
CAP1
OUT2
SW2
).
DIV
I
L
V
FRONT PAGE APPLICATION
LED Transient Response
OLED Switching Waveforms
with 35mA Load
V
V
IN
IN
OUT2
= 3.6V
= 3.6V
= 16V
500ns/DIV
1ms/DIV
CTRL2 (Pin 5): Dimming and Shutdown Pin. Connect it
below 75mV to disable the low noise boost converter.
As the pin voltage is ramped from 0V to 1.5V, the output
ramps up to the programmed output voltage.
FB2 (Pin 6): Feedback Pin. Reference voltage is 1.215V.
There is an internal 182kΩ resistor from FB2 to GND. To
achieve desired output voltage, choose R
the following formula:
R
FB
2
182
T
3498 G20
3498 G23
A
= 25°C, unless otherwise specifi ed.
•
SW2 VOLTAGE
V
1 215
AC COUPLED
OUT
.
100mA/DIV
INDUCTOR
INDUCTOR
10mV/DIV
50mA/DIV
CURRENT
CURRENT
VOLTAGE
VOLTAGE
10V/DIV
5V/DIV
5V/DIV
V
CAP2
V
2
OUT2
OUT2
1
V
V
OLED Switching Waveforms
with No Load
OLED Switching Waveforms
During Start-Up
V
V
IN
OUT2
IN
OUT2
= 3.6V
= 3.6V
k
= 16V
= 16V
500 s/DIV
5 s/DIV
FB2
according to
3498 G21
3498 G24
3498f