PAM2805 [PAM]
3-Modes/3W WLED Driver with 1 or 2 Cell Battery; 3模式/ 3W白光LED驱动器，带有1或2节电池
| 型号： | PAM2805 |
| 厂家： | 
POWER ANALOG MICOELECTRONICS |
| 描述： | 3-Modes/3W WLED Driver with 1 or 2 Cell Battery |
| 文件： | 总9页 (文件大小：382K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
PAM2805
3-Modes/3W WLED Driver with 1 or 2 Cell Battery
Features
General Description
n
3 Modes Cycling Function:
The PAM2805 is a step-up DC-DC WLED driver
Power Off
<5S
Power Off
w i t h
3
m o d e s c y c l i n g f u n c t i o n ( 1 0 0 %
<5S
Bright
Dimming
Blinking
brightness,25% brightness and 8.5Hz blinking).
Power Off
<5S
The unique
3 modes cycling function can
n
Reset to Bright mode if Power Off time
more than 5S
eliminate the needs of extra functional MCU or IC.
n
n
n
Adjustable Output Current: up to 750mA
8.5Hz Blinking Mode
Low Start-Up Voltage: 0.9V(Typ.)
The PAM2805 can deliver up to 750mA output
current by setting an external resistor.
n Low SW on Resistance: 100mΩ
The PAM2805 switches at a 1.0MHz constant
frequency, allowing for the use of small value
external inductor and ceramic capacitors.
n
n
n
n
Over Temperature Protection
Over Voltage Protection
SOT23-6 Package
Pb-Free Package
A low 95mV feedback voltage reduces the power
loss in the Rs for better efficiency. With its internal
2A, 100mΩ NMOS switch, the device can provide
high efficiency even at heavy load.
Applications
n
White LED Torch (Flashlight)
The PAM2805 is available in SOT23-6 package.
Typical Application
Block Diagram
SW
VOUT VIN
Comparator
95mV
Reference
+
A1
-
L
-
VIN
VOUT
PWM
Logic
2.2μH
A2
+
Rc
Cc
10uF
20uF
VIN
SW
FB
+
-
VOUT
Σ
PAM2805
BLK
FB
BLK
Ramp
1uF
Dimming
and
Blinking
Logic
Generator
Rs
GND
1.0MHz
Oscillator
PGND
ILED=95mV/Rs
Power Analog Microelectronics, Inc
www.poweranalog.com
11/2011 Rev1.0
1
PAM2805
3-Modes/3W WLED Driver with 1 or 2 Cell Battery
Pin Configuration& Marking Information
Top View
SOT23-6
X: Internal Code
Y: Year
1
6
VIN
SW
W: Weekly
2
3
5
4
GND
BLK
VOUT
FB
Pin Number
Name
VIN
Function
1
2
3
4
5
6
Input Voltage
GND
BLK
FB
Power Ground
Connect A1uF CAP for Blinking
Feedback
VOUT
SW
Output Voltage
Connected to an internal NMOS switch
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...............................................6V
Output Voltage...............................................6V
Storage Temperature Range......... –65C to 150C
Lead Temperature (Soldering, 5 sec) ...........300C
Recommended Operating Conditions
Junction Temperature...............-40C to 125C
Operating Temperature Range .......-40C to 85C
Thermal Information
Parameter
Package
Symbol
Maximum
Unit
Thermal Resistance
(Junction to Case)
Thermal Resistance
(Junction to Ambient)
SOT23-6
θJC
130
℃/W
SOT23-6
SOT23-6
θJA
250
400
Internal Power Dissipation
PD
mW
@TA=25℃
Power Analog Microelectronics, Inc
www.poweranalog.com
11/2011 Rev1.0
2
PAM2805
3-Modes/3W WLED Driver with 1 or 2 Cell Battery
Electrical Characteristic
TA =25℃ , L=2.2uH, CΙΝ=10uF, COUT=10uF, CBLK=1uF, VF=3.4V, unless
otherwise noted.
Parameter
Input Voltage Range
Feedback Voltage
Start-up Voltage
Symbol
VIN
Conditions
Min
0.9
90
Typ
Max
Unit
V
VF-0.2
(note 1)
VFB
95
100
mV
V
V : 0V→3V
IN
VSTART
0.9
ILED=200mA
V : 3V→0V
IN
Hold Voltage
VHO LD
0.7
V
ILED:750mA→100mA
Oscillator Frequency
Over Temperature Shutdown
Over Temperature Hysteresis
Maximum Output Current
Range
FO SC
OTS
OTH
0.85
750
1.0
150
30
1.15
MHz
℃
℃
IO(MAX) VIN =2.4V
mA
mA
ILED=0mA, VO=3.4V,
Quiescent Current
IQ
1
3
Device Switching at 1MHz
VO=3.4V
Switch on Resistance
Current Limit
RDSON
ILIM
0.1
Ω
A
VO=3.4V
2
7
Over VoltageProtection(VOUT)
Blinking Frequency
V
OVP
4.5
8.5
V
FBL K
CBL K=1uF
10
Hz
Note1: VF --- LED Forward Voltage
Power Analog Microelectronics, Inc
www.poweranalog.com
11/2011 Rev1.0
3
PAM2805
3-Modes/3W WLED Driver with 1 or 2 Cell Battery
Typical Performance Characteristics
TA =25℃ , L=2.2uH , CΙΝ=10uF, CΟUT=10uF, CBLK=1uF, unless otherwise noted.
1. LED Power Efficiency vs Input Voltage
2. LED Current vs Input Voltage
100
800
700
600
500
400
300
200
100
0
90
80
70
60
50
40
30
20
10
0
ILED=750mA(100% brightness)
ILED=350mA(100% brightness)
ILED=750mA(25% brightness)
ILED=350mA
ILED=750mA
ILED=350 mA(25% brightness)
3.1
2.8
2.5
2.2
1.9
1.6
1.3
1.0
0.7
3.1
2.8
2.5
2.2
1.9
1.6
1.3
1.0
0.7
Input Voltage(V)
Input Voltage(V)
3. DC Input Current vs Input Voltage
4. Feedback Voltage vs Input Voltage
2500
ILED=350mA(100% brightness)
100
90
80
70
60
50
40
30
20
10
0
2000
1500
1000
500
ILED=750mA(100% brightness)
ILED=750mA(100% brightness)
ILED=350mA(25% brightness)
ILED=750 mA(25% brightness)
ILED=350mA(100% brightness)
0
3.4 3.1
2.8
2.5 2.2 1.9
Input Voltage(V)
1.6
1.3 1.0
0.7
3.4
3.1
2.8 2.5
2.2
1.9
1.6
1.3
1.0 0.7
Input Voltage(V)
Power Analog Microelectronics, Inc
www.poweranalog.com
11/2011 Rev1.0
4
PAM2805
3-Modes/3W WLED Driver with 1 or 2 Cell Battery
Typical Performance Characteristics
TA =25℃ , L=2.2uH , CΙΝ=10uF, CΟUT=10uF, CBLK=1uF, unless otherwise noted.
5. 3 Modes Change
6. Start-Up Waveform
VIN
VIN
VOUT
ILED
IL
SW
7. Overvoltage Protection
8. Switching Waveform
VOUT
VOUT
IL
SW
IL
Power Analog Microelectronics, Inc
www.poweranalog.com
11/2011 Rev1.0
5
PAM2805
3-Modes/3W WLED Driver with 1 or 2 Cell Battery
Application Information
Inductor Selection
selection is shown as follows:
Rs(Ohm)=95mV/ILED(mA) at VIN=3V.
The PAM2805 can use small value inductors due
to its switching frequency of 1 MHz. The value of
inductor will focus in the range of 2.2uH to 4.7uH
for most PAM2805 applications. In typical high
c u r r e n t w h i t e L E D a p p l i c a t i o n s , i t i s
recommended to use a 4.7uH inductor. The
inductor should have low DCR (DC resistance) to
minimize the I2R power loss, and it requires a
current rating of 2A to handle the peak inductor
current without saturating.
Typically, for 1W(330mA) and 3W(750mA) LED
light applications, the Rs are 0.288ohm and
0.127Ohm respectively.
3 Modes Cycling
T h e PA M 2 8 0 5 h as t h re e m o de s : 1 0 0 %
brightness, 25% brightness and blinking(typical
8.5Hz).
Capacitor Selection
The mode change is triggered by power on/off
actions and cycles in the following sequence:
bright, dimming, blinking and back to bright
mode.
An input capacitor is required to reduce the input
ripple and noise for proper operation of the
PAM2805. For good input decoupling, Low ESR
(equivalent series resistance) capacitors should
be used at the input. At least 2.2uF input
capacitor is recommended for most applications.
The PAM2805 will reset to the bright mode after
being power off for more than 5 seconds.
Low Voltage Startup and Soft Start
A minimum output capacitor value of 6.8uF is
r e c o m m e n d e d u n d e r n o r m a l o p e r a t i n g
conditions, while a 10uF-22uF capacitor may be
required for higher power LED current. A
reasonable value of the output capacitor
depends on the LED current. 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 small size of ceramic capacitors is an
excellent choice for PAM2805 applications. The
X5R and X7R types are preferred because they
maintain capacitance over wide voltage and
temperature ranges.
The PAM2805 has a build-in low voltage startup
circuit for the best battery life solution. It can
start up at 0.9V VIN typically when the preset
LED current is 200mA.
The soft-start function is made by clamping the
output voltage of error amplifier with another
voltage source which increases slowly from zero
to near VIN during the soft-start period.
Therefore, the duty cycle of the PWM will be
increased from zero to maximum in this
period. The charging time of the inductor will be
limited by the smaller duty so that the inrush
current can be reduced to an acceptable
value.`
Diode Selection
Over Voltage Protection
It's indispensable to use a Schottky diode rated
at 2A with the PAM2805. Using a Schottky diode
with a lower forward voltage drop is better to
improve the power LED efficiency, and its voltage
rating should be greater than the output voltage.
SS22 is recommended Schottky diode for
rectifier.
The output voltage of PAM2805 is monitored by
Over Voltage Protection circuit. Once VOUT
goes over VOVP, typically 4.5V, the power NMOS
is turned off and SW pin stops switching.
Then, the VOUT is clamped to around VOVP.
LED Current Setting
The LED current is set by the single external Rs
resistor connected to the FB pin as shown in the
typical application circuit on page 1. The typical
FB reference is internally regulated to 95mV. The
LED current is 95mV/R1. It's recommended to
use a 1% or better precision resistor for the
better LED current accuracy. The formula for Rs
Power Analog Microelectronics, Inc
www.poweranalog.com
11/2011 Rev1.0
6
PAM2805
3-Modes/3W WLED Driver with 1 or 2 Cell Battery
Application Information
Over Current Protection
The inductor current during charging period is
detected by a current sensing circuit. When the
value is larger than current limiting ILIM, the power
NMOS is turned off so that the inductor will be
forced to leave charging stage and enter
discharging stage. Therefore, the inductor
peak current will not exceed ILIM, whose minimum
value is 2A.
PCB Layout Guidelines
As for all switching power supplies, the layout
and components placement of the PAM2805 is
an important step in the design; especially at
hi gh pea k c urren ts and hi gh s wi tc hi ng
frequencies.
The input capacitor and output capacitor should
be placed respectively as close as possible to
the input pin and output pin of the IC; the inductor
and schottky diode should be placed as close as
possible to the switch pin by using wide and short
traces for the main current path; the current
sense resistor should be placed as close as
possible between the ground pin and feedback
pin.
Power Analog Microelectronics, Inc
www.poweranalog.com
11/2011 Rev1.0
7
PAM2805
3-Modes/3W WLED Driver with 1 or 2 Cell Battery
Ordering Information
PAM2805 X X X X
Number of Pins: F(6)
Package Type: A
Part Number
Marking
Package Type
Standard Package
3,000Units/Tape&Reel
PAM2805AF
ECXYW
SOT23-6
Power Analog Microelectronics, Inc
www.poweranalog.com
11/2011 Rev1.0
8
PAM2805
3-Modes/3W WLED Driver with 1 or 2 Cell Battery
Outline Dimensions
θ
L REF.
L1 (REF.)
Millimeter
REF.
Min
Max
1.35
0.15
1.2
A
A1
A2
c
-
0.04
0.70
0.12REF.
D
2.70
2.60
1.40
0.45REF.
0.60REF.
0º
0.30
3.10
3.00
1.80
E
E1
L
L1
θ
b
10º
0.50
e
0.95REF.
1.90REF.
e1
Power Analog Microelectronics, Inc
www.poweranalog.com
11/2011 Rev1.0
9
相关型号：
©2020 ICPDF网 联系我们和版权申明