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Número de pieza | PAM2842 | |
Descripción | HIGH POWER LED DRIVER | |
Fabricantes | Diodes | |
Logotipo | ||
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No Preview Available ! A Product Line of
Diodes Incorporated
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 TSSOP-20 packages.
Pin Assignments
Features
• Output Power up to 30W
• Chip Enable with Soft-start
• Analog and PWM Dimming
• Peak Efficiency up to 97%
• Low Quiescent Current
• Switching Frequency Adjustable
• Support Buck/Boost/Sepic Toplogy
• Over Current Protection
• Over Voltage Protection
• Thermal Protection
• UVLO
• Tiny Pb-Free Packages: 40-Pin QFN6x6 and TSSOP-20
Applications
• Home Lighting
• Automotive Lighting
• Monitor Backlighting
PAM2842
Document number: DSxxxxx Rev. 1 - 2
1 of 17
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October 2012
© Diodes Incorporated
1 page A Product Line of
Diodes Incorporated
PAM2842
Electrical Characteristics (cont.) (@TA = +25°C, VEN = VDD = 24V, 1W x 10 LEDs, unless otherwise specified.)
Parameter
Test Conditions
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
Switch Stage
Switch RDS(ON)
VDD_5V = 5V
Switch Current Limit
Switch Leakage Current
RT Voltage
RRT = 71kΩ
RRT = 30kΩ
Switching Frequency (Note 2)
RRT = 71kΩ
RRT = 180kΩ
FSW = 1MHz
Min Duty Cycle
FSW = 500kHz
Max Duty Cycle
FSW = 200kHz
Low Side Sense
High Side Sense
VC Source Current
Feedback Voltage = 0
VC Sink Current
Feedback Voltage = 0
Fault Protection
OV Threshold Voltage
OV Hysteresis
Thermal Shutdown
Thermal Shutdown Hysteresis
Control Interface
EN High
EN Low
Note:
1012
2. Switching frequency FSW = 24x(RRT + 12k) , reference value.
Min Typ Max
4.5 5 5.5
14 74 90
3.7 4.0 4.3
200
4.5 5 5.5
14 50 90
3.7 4.0 4.3
0.1
3.5
50
1.1 1.2 1.3
800k 1M 1.2M
400 500 600
160 200 240
10
5
2.5
95
100
30
30
1.1 1.2 1.3
70
150
30
1.5
0.4
Units
V
mA
V
mV
V
mA
V
Ω
A
µA
V
Hz
kHz
kHz
%
%
%
%
%
µA
µA
V
mV
°C
°C
V
V
PAM2842
Document number: DSxxxxx Rev. 1 - 2
5 of 17
www.diodes.com
October 2012
© Diodes Incorporated
5 Page A Product Line of
Diodes Incorporated
Also, the recommended PWM frequency is between 100Hz and 200Hz.
PAM2842
Application Information (cont.)
● Method 2: LED Current Setting with PWM Signal Using COMP Pin (cont.)
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%).
It maybe generate the audible noise in this dimming condition.
● 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.
Figure 2. PWM Dimming Use Sense Pin in Low Side Current Sense
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.
Setting the Output Limit Voltage
The OV pin is connected to the center tap of a resistive voltage divider from the high-voltage output to ground (see application schematic).
VOUT−LIMIT
=
VOV (1 +
RUP )
RDOWN
The recommend procedure is to choose R3 = 360K and R4 = 12K to set VOUT_LIMIT = 37.2V.
In boost and sepic circuit, when LED open or no load, the circuit will have no feedback, if no other measure be taken the switch voltage will be
very high and damage the switch, so this OV pin must be set carefully.
In buck circuit, the switch voltage is always small than input voltage, so the OV pin setting is not important in this condition.
This OV pin is used to limit output voltage to avoid breakdown of the switch other than to regulate output voltage. The setting value must keep
the switch voltage below 40V.
In sepic circuit, one must notice that the switch voltage equals VIN +VO.
This OV pin has a hysteresis voltage detect function, not latch-up function, so output voltage will have a overshoot when no load or load working
voltage is high than setting limit voltage. If the component parameter not match appropriately, the overshoot voltage will be too high and can
demage the switch.
PAM2842
Document number: DSxxxxx Rev. 1 - 2
11 of 17
www.diodes.com
October 2012
© Diodes Incorporated
11 Page |
Páginas | Total 17 Páginas | |
PDF Descargar | [ Datasheet PAM2842.PDF ] |
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