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PAM2842 Schematic ( PDF Datasheet ) - Power Analog Micoelectronics

Teilenummer PAM2842
Beschreibung High Power LED Driver
Hersteller Power Analog Micoelectronics
Logo Power Analog Micoelectronics Logo 




Gesamt 17 Seiten
PAM2842 Datasheet, Funktion
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






PAM2842 Datasheet, Funktion
PAM2842
High Power LED Driver
Electrical Characteristic
VEN=VDD=24V, 1Wx10 LEDs, TA=25°C, unless otherwise noted.
PARAMETER
Conditions
Input Voltage Range
ENA=high (no switching)
ENA =high (1M switching frequency)
Quiescent Current
ENA =high (500k switching frequency)
ENA =high (200k switching frequency)
ENA =low
Feedback Voltage, Low Side
Feedback Voltage, High Side
LED Current Line Regulation
LED Current Load Regulation
VFB=VSENSE+ -AGND, VSENSE-=AGND
VFB =VSENSE+ - VSENS E-
IO=350mA
LDO Stage
VDD_5V
No switching
VDD_5V current_limit
No switching
VDD_5V UVLO Threshold
No switching
VDD_5V UVLO Hysteresis
No switching
VDD_DR
No switching
VDD_DR current_limit
No switching
VDD_DR UVLO Threshold
No switching
VDD_DR UVLO Hysteresis
No switching
Switch Stage
Switch Rdson
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Switch Current Limit
VDD_5V=5V
Switch Leakage Current
RT Voltage
Switching Frequency*
Min Duty Cycle
Max Duty Cycle
R RT =71kΩ
R RT =30kΩ
R RT =71kΩ
R RT =180kΩ
FSW=1MHz
FSW=500kHz
FSW=200kHz
Low Side Sense
High Side Sense
Vc Source Current
Feedback voltage=0
Vc Sink Current
Feedback voltage=0
( )* Switching Frequency FSW
=
24 ´
1012
RRT +12k
, reference value
Power Analog Microelectronics,Inc
www.poweranalog.com
6
Min Typ Max Units
5.5 40 V
1 2 mA
6 mA
3 mA
1.6 mA
5 10 μA
95 100 105 mV
95 100 105 mV
0.02
%/V
1.0 %
4.5 5 5.5 V
14 74 90 mA
3.7 4.0 4.3
V
200 mV
4.5 5 5.5 V
14 50 90 mA
3.7 4.0 4.3
V
200 mV
0.1 Ω
3.5 A
50 μA
1.1 1.2 1.3
V
800k 1M 1.2M Hz
400 500 600 kHz
160 200 240 kHz
10 %
5%
2.5 %
95 %
100 %
30 μA
30 μA
09/2008 Rev 1.1

6 Page









PAM2842 pdf, datenblatt
PAM2842
High Power LED Driver
l Method 1: LED Current Setting with Resistor
Rsense
The most basic means of setting the LED current
is connecting a resistor between Rsense+ and
Rsense-. The LED current is decided by ISET
Resistor Rsense.
ILED =0.1/ Rsense
For flowing the large current, must pay attention
to power dissipation on the resistor.
Rsense has two position to select: high side
current sense and low side current sense. In buck
topology it just has high side current sense. In
other topology we recommend use low side
current sense for easier PCB layout.
l Method 2: LED Current Setting with PWM
Signal Using COMP Pin
This circuit uses resistor Rsense to set the on
state current and the average LED current, then
proportional to the percentage of off-time when
the COMP pin is logic high. Here use a invert
component 2N7002 (Q1) to isolate and invert the
PWM signal (See Figure 1).
PAM2842
COMP
Q1
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2N7002
PW M signal
Ton Toff
It maybe generate the audible noise in this
dimming condition.
l Method 3: LED Current Setting with PWM
Signal using Sense Pin
This method is turn PWM signal to DC voltage, the
output current can be adjusted. Because the LED
current is a adjustable DC value, it will cause LED
color drift.
Low side current sense and high side current
sense circuit is different. Please see Figure 2 and
3. It use the internal reference voltage, so PWM
dimming signal voltage is not considered, just
meet the request of the MOSFET driving voltage.
VDD_5V
R1
D1
Q1
PWM-DIM
R2
C1
Sense+
RTN
R3 R4
C2 RSense
Figure 2. PWM Dimming Use Sense Pin in Low
Side Current Sense
VDD_5V
Sense+
R1
D1
Vo
RSense
R3
Sense-
Q2
Figure 1. PWM Dimming Use COMP Pin
Average LED current is approximately equal to:
IAVG
=
TOFFILED
TON + TOFF
Also, the recommended PWM frequency is
between 100Hz and 200Hz.
Frequency <100Hz can cause the LEDs to blink
visibly. As the COMP pin connects to a capacitor,
it needs rise time. If frequency >200Hz, the
average LED current will have a large error when
duty cycle is small (<50%).
Q1
PWM-DIM
R5 C1 R4
Figure 3. PWM Dimming Use Sense Pin in High
Side Current Sense
The RC filter (R1,R2,C1,C2) value is decided by
dimming frequency, the divider resistor (R3,R4) is
decided by dimming range.
Because final adjusted is a DC value, this method
can avoid audible noise effectively and achieve
better EMI performance than the second method.
Power Analog Microelectronics,Inc
www.poweranalog.com
12
09/2008 Rev 1.1

12 Page





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