PAM2804
1A Step-Down Constant Current, High Efficiency LED Driver
Features
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Efficiency up to 93%
180
μ
A(TYP.) Quiescent Current
Output Current: Up to 1A
Internal Synchronous Rectifier
1.5MHz Switching Frequency
Soft Start
Under-Voltage Lockout
Short LED Protection
Open LED Protection
Thermal Shutdown
5-pin Small SOT23-5 Packages
Pb-Free Package
General Description
The PAM2804 is a step-down constant current
LED driver. When the input voltage down to lower
than LED forward voltage, then PAM2804 run into
LDO mode.
The PAM2804 supports a range of input voltages
from 2.5V to 6.0V, allowing the use of a single
Li+/Li-polymer cell, 3AA or 4AA cell, USB, and
other standard power sources.
The FB voltage is only 0.1V to achieve high
efficiency.
PAM2804 employ internal power switch and
synchronous rectifier to minimize external part
count and realize high efficiency.
During shutdown, the input is disconnected from
the output and the shutdown current is less than
1
μ
A. Other key features include under-voltage
lockout to prevent deep battery discharge of the
Li+ battery.
.
Applications
n
3AA or 4AA Batteries Powered Flashlight
n
1 Cell Li-Ion Battery Powered Flashlight
Typical Application
1 Cell Li-Ion Battery
3AA or 4AA Batteries
V
IN
C
IN
10µF
L
4.7
µH
VIN
GND
SW
1~5W
WLED
FB
Rs
Co
10µF
EN
ILED =0.1/Rs
Power Analog Microelectronics
,
Inc
www.poweranalog.com
10/2010 Rev1.0
1
PAM2804
1A Step-Down Constant Current, High Efficiency LED Driver
Block Diagram
1.5M
OSC
SLOPE
COMP
+
IAMP
-
VIN
FB
FREQ
SHIFT
OSC
S Q
R Q
-
EA
VIN
RS LATCH
+
COMP
SWITCHING
LOGIC
AND
BLANKING
CIRCUIT
MAIN
SWITCH
(
PCH
)
ANTI
-
SHOOT
-
THRU
SW
SYNCHRONOUS
RECTIFIER
(
NCH
)
EN
0.6VREF
SHUTDOWN
+
IRCMP
-
GND
Pin Configuration & Marking Information
Top View
SOT23
-
5
EN 1
GND 2
SW 3
4
VIN
5
FB
EE: Product Code
of PAM2804
X: Internal Code
Y: Year
W: Week
Pin Description
Nam e
VIN
GND
EN
FB
SW
Chip main power supply pin
Ground
Enable cont rol input. Force this pin voltage above 1. 5V, enables the chip, and below
0.3V shuts down the device.
Feedback voltage to intern al error amplifier, the threshold voltage is 0.1V.
The drains of t he int ernal main and synchronous p ower MOSFET.
Func tion
Power Analog Microelectronics
,
Inc
www.poweranalog.com
10/2010 Rev1.0
2
PAM2804
1A Step-Down Constant Current, High Efficiency 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
.
Input Voltage..................................-0.3V to 6.5V
EN, FB Pin Voltage...........................- 0.3V to V
IN
SW Pi n Voltage.....................-0.3V to
(
V
IN
+0.3V
)
Junction Temperature................................150°
C
Storage Temperature Range........-65° to 150°
C
C
Soldering Temperature......................300°
,
5sec
C
Recommended Operating Conditions
Supply Voltage................................2.5V to 6.0V
Operation Temperature Range.........-40 ° to 85 °
C
C
Junction Temperature Range........-40 ° to 125 °
C
C
Thermal Information
Parameter
Thermal Resistance
(Junc tion to Case)
Thermal Resistance
(Junction to Ambient)
Internal Power Dissipation
Package
SOT23-5
Note
Symbol
θ
C
J
θ
JA
P
D
Maximum
130
Unit
°
C/W
SOT23-5
SOT23-5
250
400
mW
Note:
The maximun output current for SOT23-5 package is limited by internal power dissipation capacity as
described in Application Information herein after.
Power Analog Microelectronics
,
Inc
www.poweranalog.com
10/2010 Rev1.0
3
PAM2804
1A Step-Down Constant Current, High Efficiency LED Driver
Electrical Characteristic
T
A
=25 ° , V
IN
=4.2V, Real WLED load, C
IN
=10µF, C
O
=10µF, L=4.7µH, unless otherwise noted.
C
PARAMETER
Input Voltage Range
Regulated Feedback Voltage
Peak Induc tor Current
Quiescent Current
Shutdown Current
Oscillator Frequency
Drain-Source On-State Resis tance
SW Leakage Current
High Effic iency
EN Threshold High
EN Threshold Low
EN Leakage Current
Over Temperature Protection
OTP
Hysteresis
SYMBOL
V
IN
V
FB
I
PK
I
Q
I
SD
f
OSC
R
DS (ON)
I
LSW
η
V
EH
V
EL
I
EN
OTP
OTH
±0.01
150
30
1.5
0.3
V
IN
=5V
No load
V
EN
= 0V
V
O
= 100%
I
DS
=100mA
P MOSFET
N MOSFET
1.2
1.5
0.3
0.35
±0.01
93
Test Conditions
MIN
2.5
0.095
0.1
1.5
180
1
1.8
0.45
0.5
1
TYP
MAX
6.0
0.105
UNITS
V
V
A
µA
µA
MHz
Ω
Ω
µA
%
V
V
µA
°
C
°
C
Power Analog Microelectronics
,
Inc
www.poweranalog.com
10/2010 Rev1.0
4
PAM2804
1A Step-Down Constant Current, High Efficiency LED Driver
Typical Performance Characteristics
T
A
=25 ° , C
IN
=10
μ
F, C
O
=10
μ
F, L=4.7
μ
H, unless otherwise noted.
C
Eifficiency VS Input Voltage
96%
94%
92%
90%
88%
86%
84%
82%
3
3.5
4
4. 5
5
5.5
6
Input Volt age (V)
330m A
750m A
1A
350
300
250
200
150
100
50
0
2.5
Output Current VS Input Voltage
Rcs=0.3ohm
3
3.5
4
4.5
Vin(V)
5
5.5
6
Output Current VS Input Voltage
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
3
3.5
4
4.5
5
5.5
6
Input Voltage (V)
200
800
600
400
1200
1000
Output Current VS Input Voltage
Rcs=0.135ohm
0
2.5
3
3.5
4
4.5
Vin(V)
Rcs=0.1ohm
5
5.5
6
R dson VS Input Voltage
0.4
0.35
0.3
0.25
0.2
0.15
0.1
2
3
4
Input Voltage
5
6
Rdson VS Temperature
0.6
0.5
0.4
0.3
0.2
0.1
0
20
70
Temperature(℃)
120
Vin =4.2V
Vin =3.6V
Vin =2.7V
Vin=3.6V
Power Analog Microelectronics
,
Inc
www.poweranalog.com
10/2010 Rev1.0
5
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