sp7612ec6-l-tr Exar Corporation, sp7612ec6-l-tr Datasheet - Page 11

• Manufacturer Part Number: sp7612ec6-l-tr
• Description: Sp7614 -low Dropout Led Driver For Any Color Led With Active Shutdown
• Manufacturer: Exar Corporation

When using white or blue low V
utilizing the driver's low voltage drop, only 3.4V V
is needed for the full 20mA LED current. At 3.1V,
there is still 5mA of typical current available for the
LEDs.
The single cell Li-Ion battery is utilized in many
applications like cell phones or digital still
cameras. In most cases, the Li-Ion battery voltage
level only goes down to 3.0V, and not down to the
full discharge level (2.7V) before requesting the
charger.
V
SP7611A.
- V
drop
- V
(V
Key Advantages
1) No boost circuit needed for the LCD or
keyboard backlight.
2) Drivers directly connected to a Li-Ion battery.
3) No EMI, no switching noise, no boost converter
efficiency loss, 1 capacitor, and no inductor.
Example 2:
Drive high V
bus ~ 4.0V to 5.5V
High V
range of 3.2V to 4.0V. In order to drive these LEDs
with the maximum current of 20mA, enabling
maximum brightness usually requires a boost
circuit for a single cell Li-Ion power supply. The
SP761X series is capable of driving high V
or blue LEDs with its ultra-low dropout feature.
The V
highest V
- V
- V
- V
Where V
Jan 09 -08 RevT
- V
DROP
DROP
DROP
F
IN
F
IN
IN
(at 20mA) < 3.3V to 4.0V (High VF)
= 3.1V.
(at 20mA) = V
(at 5mA typical) ~ 3.3V
IN
F
+V
< 0.3V. This is the dropout voltage for the
(at 20mA) needs to be greater than
3.1V+.3V= 3.4V
< 0.3V. Dropout voltage of the SP7611A
IN
LEDs have a forward voltage drop in the
needs to be only 300mV higher than the
F
F
in the circuit.
= Existing bus = 3.3V to 4.3V
)
F
white or blue LEDs from existing
Low V
DROP
F
white LED forward voltage
+ V
F
= 3.6V to 4.3V
SP7612/7614 Low Dropout Linear LED driver
F
LEDs, and
F
white
IN
Page 11
1) No boost circuit needed for the LCD or
keyboard backlight.
2) Drivers utilize existing bus.
3) Ultra-low voltage drop provides the full 20mA
LED current at the lowest possible voltage level.
LED Brightness Control
Key Advantages
The SP7612/4 LED Drivers feature analog and
PWM controls to give designers flexible
brightness control. To determine the value of
R
the Typical Performance Characteristics.
1. SP7612/4
-
Set V
SETTING THE LED CURRENT – page 8
- PWM - Vcontrol
-Amplitude of PWM signal sets maximum LED
current
-Pulse width controls current between 0 and
maximum LED Set current
-
-
SETTING THE LED CURRENT – page 6
ENABLE = PWM
maximum LED set current
-Amplitude has no effect on current
-Pulse width controls current between 0 and
SET
Analog using V
PWM using Enable
Set V
CONTROL
, use the "I
SP7612 SP7614
CONTROL
© 2008 EXAR Corporation
and R
SET
and R
CONTROL
SET
vs. V
for LED current
SET
CRTL
for LED current
" graph under