LP55281RLX/NOPB National Semiconductor, LP55281RLX/NOPB Datasheet - Page 24

• Manufacturer Part Number: LP55281RLX/NOPB
• Description: IC LED DRIVER RGB 36-USMD
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: RGB LED Driverr

Specifications of LP55281RLX/NOPB

• Constant Current: Yes
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 12
• Internal Driver: Yes
• Type - Primary: Light Management Unit (LMU)
• Type - Secondary: Color, RGB
• Frequency: 1MHz ~ 2MHz
• Voltage - Supply: 3 V ~ 5.5 V
• Voltage - Output: 4 V ~ 5.3 V
• Mounting Type: Surface Mount
• Package / Case: 36-MicroSMDxt
• Operating Temperature: -30°C ~ 85°C
• Current - Output / Channel: 300mA
• Internal Switch(s): Yes
• Efficiency: 88%
• For Use With: LP55281RLEV - BOARD EVAL FOR LP5528 RGB DRIVER
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LP55281RLX

www.national.com
Recommended External
Components
OUTPUT CAPACITOR, C
The output capacitor C
the output ripple voltage. In general, the higher the value of
C
ramic capacitors with low ESR are the best choice. At the
lighter loads, the low ESR ceramics offer a much lower
V
At the higher loads, the ceramics offer a slightly lower V
ripple magnitude than the tantalums of the same value. How-
ever, the dv/dt of the V
lower than the tantalums under all load conditions. Capacitor
voltage rating must be sufficient, 10V or greater is recom-
mended.
Some ceramic capacitors, espesically those in small pack-
ages, exhibit a strong capacitance reduction with the in-
creased applied voltage. The capacitance value can fall to
below half of the nominal capacitance. Too low output capac-
itance will increase the noise and it can make the boost
converter unstable.
INPUT CAPACITOR, C
The input capacitor C
input ripple voltage and to a lesser degree the V
higher value C
rating must be sufficient, 10V or greater is recommended.
LIST OF RECOMMENDED EXTERNAL COMPONENTS
OUT
OUT
, the lower the output ripple magnitude. Multilayer ce-
Symbol
ripple than the higher ESR tantalums of the same value.
L
C
C
C
LEDs
C
C
C
C
R
C
BOOST
R
C
VREF
D
V
V
V
V
V
OUT
RGB
ASE
RT
DDIO
DDIO
DDA
IN
DD1
DD2
1
IN
will give a lower V
C between battery voltage and GND
L between SW and VBAT at 2 MHz
C between Audio input and ASEx
Rectifying Diode (V
IN
C between VREF and GND
C between V
C between V
R between IRGB and GND
OUT
OUT
C between V
C between V
C between V
IN
directly affects the magnitude of the
R between IRT and GND
C between FB and GND
:
Symbol explanation
OUT
directly affects the magnitude of
ripple with the ceramics is much
:
IN
ripple. Capacitor voltage
DDIO
DDIO
DDA
DD1
DD2
f
and GND
and GND
and GND
and GND
and GND
@ maxload)
OUT
ripple. A
OUT
Value
100
100
100
100
100
100
4.7
8.2
0.3
10
10
82
24
1
OUTPUT DIODE, D
A Schottky diode should be used for the output diode. To
maintain high efficiency the average current rating of the
schottky diode shoulde be larger than the peak inductor cur-
rent (1A). Schottky diodes with a low forward drop and fast
switching speeds are ideal for increasing efficiency in portable
applications. Choose a reverse breakdown of the schottky
diode larger than the output voltage. Do not use ordinary rec-
tifier diodes, since slow switching speeds and long recovery
times cause the efficiency and the load regulation to suffer.
INDUCTOR, L:
The LP55281's high switching frequency enables the use of
the small surface mount inductor. A 4.7 µH shielded inductor
is suggested for 2 MHz operation, 10 µH should be used at 1
MHz. The inductor should have a saturation current rating
higher than the peak current it will experience during circuit
operation (~1A). Less than 300 mΩ ESR is suggested for high
efficiency. Open core inductors cause flux linkage with circuit
components and interfere with the normal operation of the
circuit. This should be avoided. For high efficiency, choose an
inductor with a high frequency core material such as ferrite to
reduce the core losses. To minimize radiated noise, use a
toroid, pot core or shielded core inductor. The inductor should
be connected to the SW pin as close to the IC as possible.
Recommended inductors are LPS3015 and LPS4012 from
Coilcraft and VLF4012 from TDK.
Unit
µH
kΩ
kΩ
nF
nF
nF
µF
µF
µF
nF
nF
nF
V
User defined
1
:
Shielded, low ESR, I
Ceramic, X7R/X5R
Ceramic, X7R/X5R
Ceramic, X7R/X5R
Ceramic, X7R/X5R
Ceramic, X7R/X5R
Ceramic, X7R/X5R
Ceramic, X7R/X5R
Schottky diode
Ceramic, X7R
Ceramic, X7R
Type
±1%
±1%
SAT
1A