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PDF PAM2842 Data sheet ( Hoja de datos )
| Número de pieza | PAM2842 | |
| Descripción | High Power LED Driver | |
| Fabricantes | Power Analog Micoelectronics | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de PAM2842 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
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Features
n Output Power up to 30W
n Chip Enable with Soft-start
n Analog and PWM Dimming
n Peak Efficiency up to 97%
n Low Quiescent Current
n Switching Frequency Adjustable
n Support Buck/Boost/Sepic Topology
n Over Current Protection
n Over Voltage Protection
n Thermal Protection
n UVLO
n Tiny Pb-Free Packages :
40-Pin QFN6x6 and TSSOP-20
Applications
n Home Lighting
n Automotive Lighting
n Monitor Backlighting
PAM2842
High Power LED Driver
Description
The PAM2842 is a high power LED driver,
capable of driving up to 10 high power LEDs in
series. The PAM2842 supports buck, boost and
sepic topology.
The PAM2842 features over current protection,
over voltage protection, under voltage lockout
and over temperature protection, which prevent
the device from damage.
LED dimming can be done by using a PWM signal
to the COMP pin.
The PAM2842 is available in 40-Pin QFN6x6 and
TSSOP-20 packages.
Typical Application Circuit
Boost with Low Side Current Sense
Vin L1
33μH
1μF
PGND
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PGND
SW
SW
HVIN
OV
10μF
EN VDD-5V
PAM2842
VDD-DR
COMP
1μF RT
130kΩ
AGND
Sense+
Sense-
430kΩ
1μF
15kΩ
1kΩ 10nF
Boost with High Side Current Sense
Vin L1
33μH
1μF
10μF
0.14Ω
PGND
SW
PGND
SW
HVIN
OV
EN VDD-5V
PAM2842
VDD-DR
COMP
1μF RT
130kΩ
AGND
Sense+
Sense-
430kΩ
1μF
15kΩ
1kΩ 10nF
0.14Ω
Power Analog Microelectronics,Inc
www.poweranalog.com
1
09/2008 Rev 1.1
1 page  
PAM2842
High Power LED Driver
Absolute Maximum Ratings
These are stress ratings only and functional operation is not implied. Exposure to absolute
maximum ratings for prolonged time periods may affect device reliability. All voltages are with
respect to ground.
Supply Voltage.............................................40V
Output Current................................................1A
I/O Pin Voltage Range.........GND-0.3V to VDD+0.3V
Storage Temperature.....................-40OC to 125OC
Maximum Junction Temperature..................150OC
Soldering Temperature.......................300OC, 5sec
Recommended Operating Conditions
Supply Voltage Range.........................5.5V to 40V Junction Temperature Range..........-40OC to 150OC
Operation Temperature Range..........-40OC to 85OC
Thermal Information
Parameter
Thermal Resistance
(Junction to Case)
Thermal Resistance
(Junction to Ambient)
Symbol
θJC
θJA
Package
TSSOP
QFN 6mm*6mm
TSSOP
QFN 6mm*6mm
*The Exposed PAD must be soldered to a thermal land on the PCB.
Maximum
20
7.6*
90
18.1*
U nit
°C /W
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Power Analog Microelectronics,Inc
www.poweranalog.com
5
09/2008 Rev 1.1
5 Page 
PAM2842
High Power LED Driver
Chose
so
DIL
=
VINVO
LF(VIN + VO )
ΔIL=0.4IL1
L = 2.5VI2N
FIO(VIN + VO )
Capacitor Selection
An input capacitor is required to reduce the input
ripple and noise for proper operation of the
PAM2842. For good input decoupling, Low ESR
(equivalent series resistance) capacitors should
be used at the input. At least 10μF input capacitor
is recommended for most applications. And close
the IC Vin-Pin we should add a bypass capacitor,
usually use a 1μF capacitor.
A minimum output capacitor value of 10μF is
recommended under normal operating
conditions, while a 22μF or higher capacitor may
be required for higher power LED current. A
reasonable value of the output capacitor depends
on the LED current. The total output voltage ripple
has two components: the capacitive ripple caused
by the charging and discharging on the output
capacitor, and the ohmic ripple due to the
capacitor's equivalent series resistance. The ESR
of the output capacitor is the important parameter
to determine the output voltage ripple of the
converter, so low ESR capacitors should be used
at the output to reduce the output voltage ripple.
The voltage rating and temperature
characteristics of the Output capacitor must also
w wbwe. Dcaont asSidheeredt 4. US.oc oamvalue of 10μF, 50V voltage
rating capacitor is chosen.
Consider from discharge aspect: IxΔt=CxΔV
In
boost
and
sepic
topology,
CO
=
IOD
FVRIPPLE
In buck topology,
CO
= IO(1- D)
FVRIPPLE
V :RIPPLE Output voltage allowable ripple.
Consider from equivalent series resistance:
V =I xCripple-esr co.ripple
oesr
In sepic topology, there is a series capacitor Cs
between L1 and L2 (see application schematic), it
flows the current:
ICs(RMS) = IO
VO
VIN
The ripple voltage is
DVCs
=
IOD
FCS
The voltage rating must be higher than input
voltage.
Because the Cs capacitor will flow the large RMS
current, so this topology is suitable for small
power application.
Diode Selection
PAM2842 is a high switching frequency converter
which demands high speed rectifier. It's
indispensable to use a Schottky diode rated at 3A,
40V with the PAM2842. Using a Schottky diode
with a lower forward voltage drop is better to
improve the power LED efficiency.
In boost topology, the voltage rating should be
higher than Vout and in buck topology, the voltage
rating higher than Vin, the peak current is
IDMAX
= IL
+
DIL
2
in sepic topology, the voltage rating should be
higher than Vin+Vout, the peak current is
I =I +IDMAX L1peak L2peak
The average current of the diode equals to Io.
Work frequency selection
PAM2842 working frequency is decided by
resistor connect to the RT pin, it can be calculated
by follow equation:
FSW
=
1012 (Hz)
24 ´ (RT + 12K)
From the equations, we can see when working
frequency is high, the inductance can be small.
It's important in some size limit application. But
we should know when the working frequency is
higher, the switching loss is higher too. We must
pay attention to thermal dissipation in this
application.
Methods for Setting LED Current
There are two methods for setting and adjusting
the LED current:
1) Rsense only
2) PWM signal with external components
a) Use the COMP pin
b) Use the Sense pin
Power Analog Microelectronics,Inc
www.poweranalog.com
11
09/2008 Rev 1.1
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet PAM2842.PDF ] | |
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