PS1313 [PICSEMI]
High Efficiency, High Power White-LED Driver; 高效率，高功率白光LED驱动器
| 型号： | PS1313 |
| 厂家： | 
POWER IC LTD. |
| 描述： | High Efficiency, High Power White-LED Driver |
| 文件： | 总9页 (文件大小：175K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
PS1313
High Efficiency, High Power
White-LED Driver
FEATURES
DESCRIPTION
On Board Power MOSFET
The PS1313 is a step up converter designed for
driving up to 4 branches with 4 white LEDs in series
in each branch, providing backlight in cell phones,
PDAs, and other hand-held devices. The PS1313
uses current mode, fixed frequency architecture to
regulate the LED current, which is measured
through an external current sense resistor. Its low
100mV feedback voltage reduces power loss and
improves efficiency. The OV pin monitors the output
voltage and turns off the converter if an over-
voltage condition is present due to an open circuit
condition.
Drives up to 4 strings of parallel LEDs
Up to 87% Efficiency
1.4MHz Fixed Switching Frequency
Open Load Shutdown
Low 100mV Feedback Voltage
Soft Start
PWM Dimming Control
UVLO, Thermal Shutdown
Internal Circuit Limit
Available in SOT26 Package
APPLICATIONS
WLED Backlight
Cell Phones
Handheld Computers and PDAs
Digital Cameras
Small LCD Displays
LED Module
The PS1313 includes under-voltage lockout, current
limiting and thermal overload protection preventing
damage in the event of an output overload. The
PS1313 is available in small 6-pin SOT26 Package.
Game Devices
TYPICAL APPLICATION CIRCUIT
Fig: Typical Application Circuit with 20mA Output
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PS1313
Fig: PS1313 for Innolux 8” Panel LED Back light unit
PIN CONFIGURATION
PIN DESIGNATOR
Name
SW
GND
FB
Pin
1
2
3
4
Type
Switch
Ground
Function
Connect inductor between SW and IN.
Ground pin
Feedback
Enable input.
Over voltage
input.
Adjustable feedback input, connect to resistor voltage divider.
EN=High: normal operation. (Supports both TTL and CMOS Logic).
EN
OVP
IN
5
6
Measures the output voltage for over voltage protection.
Boost regulator input.
Battery input.
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PS1313
BLOCK DIAGRAM
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PS1313
ABSOLUTE MAXIMUM RATINGS
Symbol
VSW
VEN
Parameter
DC Voltage at Pin 1
Value
-0.5 to +28
-0.3 to +6.0
Internally limited
-65 to +150
235
Unit
V
V
W
°C
°C /W
°C
°C
Enable Input Voltage at Pin 2
Continuous Power Dissipation
Storage Temperature Range
Thermal Resistance, Junction-To-Air
Operating Junction Temperature
Lead Temperature (Soldering, 5sec)
ESD Capability, HBM model
PD
TSTG
RθJA
TJ,MAX
TL
-40 to +125
260
ESD
2.0
kV
RECOMMENDED OPERATING CONDITIONS
Symbol
VIN
VEN
Parameter
Value
+2.5 to 6
0 to VIN
Unit
V
V
DC Supply Voltage at Pin 1
Enable Input Voltage at Pin 2
Operating Junction Temperature
TJ
-40 to +125
°C
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PS1313
ELECTRICAL CHARACTERISTICS
( Vin = 2.5V, TA = +25°C, unless otherwise noted. Typical values are at TA = +25°C.)
Symbol
Parameter
Test Condition
Min
Typ
Max
Units
2.5
VIN
Operating Input
Voltage
5.5
V
UVLO
Under Voltage
Lock-out
Vin going Lo.
2.05
2.15
2.25
V
UVLO Hysteresis
80
mV
235
IG
Supply Current
(quiescent)
No Switching
(Vin=5V, VFB=
270mV)
240
μA
Supply Current
Switching FB=0
VEN =0
1935
μA
μA
ISH
Supply Current (shut-
down)
Operation Frequency
0.15
1.5
FOSC
DMAX
VFB
1.3
90
1.4
94
MHz
%
Maximum Duty Cycle
Feedback Voltage
mV
μA
100
110
1.5
Feedback Input Bias
Current
VFB=270mV
RDS(ON)
MOSFET ON
resistance
Current Limit
Enable Threshold
0.63
1.18
Ω
ILIM
VEN
Vin=3
A
V
V
Turn ON
Turn OFF
VEN =0, 5V
1
0.4
6
IEN
Enable Input Bias
Current
μA
Thermal Shut-down
160
18
C
V
VOV
Over Voltage
Threshold
VOV rising
OV Hysteresis
2.6
V
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PS1313
OPERATION DESCRIPTION
Under Voltage Lockout:
The PS1313 is a high efficiency, fixed frequency, peak
current mode boost regulator. It has the architecture to
regulate the voltage at the feedback pin, so that a
regulated fixed current is achieved to drive white LEDs.
The power MOS is turned ON through the control
circuitry, at the start of each oscillator cycle and thus the
charging phase is initiated. The error amplifier, consisting
of a voltage comparator and current sense amplifier, is
basically, a PWM comparator. The voltage comparator
amplifies the difference between the reference and feed
back voltage. When the output of the current sense
amplifier, reaches the output of the voltage comparator,
the POWER MOS is turned OFF and thus the charging
phase is terminated. To prevent sub-harmonic oscillations
at duty cycles greater than 50 percent, a stabilizing ramp
is added to the current sense signal. In this way the peak
current level keeps the output in regulation. The PS1313
has internal soft start mechanism, to limit the inrush
current at startup and to limit the amount of overshoot
on the output, also. An internal blanking time is provided
during start up, to prevent the start of switching before
all the circuitry become ready for operation. The current
limit is increased by a fourth every 60µs giving a total
soft start time of 240µs.
When the input supply goes too low (below 2.15V)
the PS1313 produces an internal UVLO (under
voltage lockout) signal that shuts down the chip.
This mechanism protects the chip from producing
false logic due to low input supply.
Thermal Overload Protection:
Thermal-overload protection limits total power
dissipation in the PS1313. When the junction
temperature exceeds Tj= +160°C, the thermal
sensor signals the shutdown logic and turning off
most of the internal circuitry. The thermal sensor
turns internal circuitry on again after the IC’s
junction temperature drops by 20°C. The regulator
then starts functioning in the required mode based
on the supply voltage.
Thermal-Overload protection is designed to protect
the PS1313 in the event of a fault condition. For
continual operation, do not exceed the absolute
maximum junction temperature rating of Tj =
+150°C.
Setting the LED current :
Open Load Protection:
The LED current can be set, according to the
requirement, by feedback to ground resistor, R1.
The current through the LEDs is selected by the
following equation:
Open load protection in PS1313, protects the chip
from destruction, due to excessive high voltage.
When, in any case, one or more LEDs in the LED
string fails, the feedback pin is pulled down to zero.
As a result, the chip runs at maximum duty cycle,
boosting the output voltage higher and higher. The
open load protection mechanism, checks this
condition, if OV pin is tied to the top of the LED
string. If the output voltage exceeds the OV
threshold (18V) and persists there for a certain
span of time (15µS), the switching stops, allowing
the output to discharge. The open load protection
mechanism includes a hysteretic comparator. The
switching is enabled again, when the output voltage
has fallen to a certain level. Because the chip
doesn’t turn OFF fully, no power recycling is
necessary, when this condition takes place. But it’s
highly recommended, not to use the chip in that
mode of operation for longer span of time.
ILED=100mV/R1
Current Limit :
The PS1313 includes a current limiter. It monitors
the peak current through the inductor and controls
gate of the power device.
Enable Input :
The PS1313 features an active-high Enable input
(EN) pin that allows on/off control of the regulator.
The PS1313 bias current reduces to less than
microampere when it is shutdown. The output
remains at a schottky forward voltage lower than
the SW pin, if a schottky diode is connected
between SW and OV pin, at shut. The Enable input
is TTL/CMOS compatible.
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PS1313
Dimming Control:
LED is a current driven device. Hence, current
through the LED needs to be controlled to have
dimming control. Different ways are there to control
dimming for PS1313, in the normal mode of
operation. In the first way, the feedback voltage is
controlled using an external voltage source. As
shown in the figure-8, current starts flowing down
R1, R2 and R3, as the external voltage increases.
The loop will continue to regulate the feedback
voltage to 100mV, and as a result, the current
through the LEDs has to decrease as the same
amount of that being injected from the external
source. With the external voltage from 0 to 2V, the
resistor values shown for R2 and R3 can control
LED current from 0 to 20mA.
Dimming can also be achieved using logic signal to
EN pin. As shown in Figure-9, the PWM signal can
be applied to the EN pin of PS1313. The LEDs will
switch between full load to completely shut down
state. The average current through the LEDs will be
proportional to the duty cycle of PWM. The PWM
signal in figure-9 should be of 1 KHz or less,
because of the presence of the soft-start
mechanism.
PS1313
Figure 9: PWM dimming control using
Logic signal
PS1313
Figure 8: Dimming control using a DC
voltage
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PS1313
PACKAGE INFORMATION
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PS1313
DISCLAIMERS
LIFE SUPPORT
Power IC’s products are NOT designed to be used as components in devices intended to support or sustain
human life. The use of Power IC’s products in components intended for surgical implants into the body or other
applications, in which failure of Power IC’s products could create a situation where personal death or injury
may occur, is NOT authorized without the express written approval of Power IC’s Chief Executive Officer.
Power IC will NOT be held liable for any damages or claims resulting from the use of its products in medical
applications.
MILITARY
Power IC’s products are NOT designed for use in military applications. The use of Power IC’s products in
military applications is NOT authorized without the express written approval of Power IC’s Chief Executive
Officer. Power IC will NOT be held liable for any damages or claims resulting from the use of its products in
military applications.
RIGHT TO MAKE CHANGES
Power IC reserves the right to change this document and/or this product without notice. Customers are
advised to consult their Power IC sales representative before ordering.
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