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PDF SP7612 Data sheet ( Hoja de datos )
| Número de pieza | SP7612 | |
| Descripción | Low Dropout Linear LED Driver | |
| Fabricantes | Exar | |
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SP7612 SP7614
Low Dropout Linear LED Driver
FEATURES
LED Drivers for parallel connected LEDs
No EMI, no switching noise
Integrated current matching
PWM and Analog brightness control
Enable/Shutdown control
Shutdown current < 0.01µA
Tiny, RoHS Compliant Lead-Free
Packages: SC-70
Part #
SP7612
SP7614
Channels
3
2
Maximum Steady
State Current per LED
40mA
80mA
N/C VLED1 CTRL
3 21
SSPP7766114A4
6 Pin SC70
4 56
GND
VLED2 ON/OFF
Pin outs for SP7611A and SP7612A on page 3
APPLICATIONS
Ultra low cost Handsets
PDA, DSC, MP3 players
Handheld Computers
LCD Display Modules
Keyboard Backlight
LCD Backlight
DESCRIPTION
The SP7612/4 provides a simple solution for a matched current source for any color LED. The current in the
LEDs can be programmed by an external resistor. The SP7612 is capable of driving three LEDs, while the
SP7614 can drive two LEDs. LED1 should always be connected to an LED and never left open in order to
have the other LEDs driven with a matched current to LED1. The SP7612 and SP7614 feature Enable pins
for flexible on/off control and PWM dimming. SP7612/4 has extremely low (0.01uA typical) shutdown current,
prolonging the battery life and giving the longest standby period possible in today's modern design. It is
available in a small footprint 6-pin SC-70 package.
TYPICAL APPLICATION SCHEMATIC
Jan 09 -08 RevT
SP7612 Typical application
SP7612/7614 Low Dropout Linear LED driver
Page 1
© 2008 EXAR Corporation
1 page  
SP7612 SP7614
SP7612 TYPICAL PERFORMANCE CHARACTERISTICS
Iset vs Control pin voltage
LED current vs Enable voltage
Iset at .5V VLED(cathode voltage)
Jan 09 -08 RevT
SP7612/7614 Low Dropout Linear LED driver
Page 5
© 2008 EXAR Corporation
5 Page 
When using white or blue low VF LEDs, and
utilizing the driver's low voltage drop, only 3.4V VIN
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.
VDROP < 0.3V. This is the dropout voltage for the
SP7611A.
- VF = 3.1V. Low VF white LED forward voltage
drop
- VIN (at 20mA) needs to be greater than
(VDROP+VF)
3.1V+.3V= 3.4V
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 VF white or blue LEDs from existing
bus ~ 4.0V to 5.5V
High VF LEDs have a forward voltage drop in the
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 VF white
or blue LEDs with its ultra-low dropout feature.
The VIN needs to be only 300mV higher than the
highest VF in the circuit.
- VDROP < 0.3V. Dropout voltage of the SP7611A
- VF (at 20mA) < 3.3V to 4.0V (High VF)
- VIN (at 20mA) = VDROP + VF = 3.6V to 4.3V
- VIN (at 5mA typical) ~ 3.3V
Where VIN = Existing bus = 3.3V to 4.3V
SP7612 SP7614
Key Advantages
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
The SP7612/4 LED Drivers feature analog and
PWM controls to give designers flexible
brightness control. To determine the value of
RSET , use the "ISET vs. VCRTL" graph under
the Typical Performance Characteristics.
1. SP7612/4
- Analog using VCONTROL
Set VCONTROL and RSET for LED current
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
- PWM using Enable
- Set VCONTROL and RSET for LED current
SETTING THE LED CURRENT – page 6
ENABLE = PWM
-Amplitude has no effect on current
-Pulse width controls current between 0 and
maximum LED set current
Jan 09 -08 RevT
SP7612/7614 Low Dropout Linear LED driver
Page 11
© 2008 EXAR Corporation
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet SP7612.PDF ] | |
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