FP6745S6C [FITIPOWER]
High-Efficiency, 40V White LED Driver with Dimming Control;
| 型号： | FP6745S6C |
| 厂家： | 
Fitipower |
| 描述： | High-Efficiency, 40V White LED Driver with Dimming Control |
| 文件： | 总11页 (文件大小：633K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
fitipower integrated technology lnc.
High-Efficiency, 40V White LED Driver
with Dimming Control
Description
Features
The FP6745 is
a
step-up DC/DC converter
Wide Range for PWM Dimming, Ranging from
100Hz to 50kHz
High Efficiency: 87%
specifically designed for driving WLEDs with a
constant current. The FP6745 can drive up 10
white LEDs in series from a Lithium Lon battery.
Series connection of LEDs provides identical LED
current for uniform brightness and minimizes the
number of traces to the LEDs. The FP6745 uses
current mode, fixed frequency of approximately
1.3MHz architecture to regulate the LED current
through an external current sense resistor. The low
feedback voltage of 195mV can minimize power
dissipation.
Drives up to 10 WLEDs
Fast 1.3MHz Switching Frequency
Low 195mV Feedback Voltage
Over Voltage Protection
Low Profile TSOT-23-5 ,TSOT-23-6 and SOT-23-6
Packages
RoHS Compliant
Applications
Other features include current limit protection,
thermal shutdown protection, under-voltage lockout
(UVLO), and over-voltage function, which can shut
off the device if output voltage reaches above 41V.
The FP6745 is available in space saving TSOT-23-5,
TSOT-23-6 and SOT-23-6 packages.
Cellular Phone
Digital Camera
LCD Panel Backlight
GPS Receiver
PDA, Handheld Computer
Pin Assignments
Ordering Information
FP6745□□□
S8 Package (TSOT-23-5)
TR: Tape / Reel
Blank: Tube
EN
4
VIN
5
1
G: Green
C: Green
(Marking)
2
3
Package Type
S8: TSOT-23-5
S9: TSOT-23-6
S6: SOT-23-6
GND FB
SW
S9 Package (TSOT-23-6)
VIN NC EN
TSOT-23-5 Marking
6
1
5
4
3
Part Number
Product Code
P4=
(Marking)
2
FP6745S8G
SW GND FB
TSOT-23-6 Marking
Part Number
Product Code
P5=
S6 Package (SOT-23-6)
VIN NC EN
FP6745S9G
SOT-23-6 Marking
Part Number
6
1
5
4
3
(Marking)
Product Code
A8G
2
FP6745S6C
SW GND FB
Figure 1. Pin Assignment of FP6745
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Typical Application Circuit
L1
D1
VIN
6.8μH
2.7V-5.5V
CIN
10μF
LED1
VIN
SW
COUT
0.47μF
EN FP6745
LED10
Enable/
Dimming Control
GND
FB
RFB
Figure 2. Typical Application Circuit of FP6745
Functional Pin Description
Pin No.
(TSOT-23-6)
(SOT-23-6)
Pin
Name
Pin No.
(TSOT-23-5)
Pin Function
Switch Pin. Connect inductor/diode here. Minimize trace area at this node to reduce
EMI.
SW
GND
FB
1
2
3
1
2
3
Ground Pin. Connect directly to local ground plane.
Feedback Pin. Reference voltage is 195mV. Connect cathode of the lowest LED and
resistor here. Calculate resistor value according to the formula: RFB=VFB/ILED
Enable and dimming control
1. Enable: Logic high enables the device; logic low forces the device into shutdown
mode.
2. Analog dimming control: apply 0.7V to 1.4V DC voltage signal.
3. Digital dimming control: apply external 100Hz to 50kHz PWM pulse signal with
amplitude greater than 1.5V.
EN
4
4
NC
5
6
-
No connection.
VIN
5
Input Supply Pin. Must be locally bypassed.
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Block Diagram
PWM/PFM
CONTROL
ENABLE&
DIMMING
CONTROL
EN
SW
OVP
42V
195mV
VREF
DRIVER
PWM
COMPARATOR
M1
CONTROL
LOGIC
ERROR
AMP.
FB
SLOPE
1.3MHz
COMPENSATION
OSCILLATOR
RC
CURRENT AMP.
CC
RS
Internal
Soft Start
GND
Figure 3. Block Diagram of FP6745
Absolute Maximum Ratings
● VIN ------------------------------------------------------------------------------------------------------------------- +6V
● SW Voltage --------------------------------------------------------------------------------------------------------- +43V
● FB Voltage ---------------------------------------------------------------------------------------------------------- +6V
●EN Voltage ---------------------------------------------------------------------------------------------------------- +6V
● Maximum Junction Temperature (TJ) ------------------------------------------------------------------------ +150ºC
● Power Dissipation @TA=25ºC, (PD)
TSOT-23-5/TSOT-23-6/SOT-23-6 --------------------------------------------------------------- +0.5W
● Package Thermal Resistance, (θJA)
TSOT-23-5/TSOT-23-6/SOT-23-6 --------------------------------------------------------------- +250ºC/W
● Storage Temperature Range (TS) ----------------------------------------------------------------------------- -65ºC to +150ºC
● Lead Temperature (Soldering, 10 sec.) (TLEAD) ------------------------------------------------------------ +260ºC
Note 1：Stresses beyond those listed under “Absolute Maximum Ratings" may cause permanent damage to the device.
Recommended Operating Conditions
● Input Voltage (VIN) ------------------------------------------------------------------------------------------------ +2.5 to +5.5V
● Operating Temperature Range -------------------------------------------------------------------------------- -40ºC to +85ºC
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Electrical Characteristics
(VIN=VEN=5V, TA=+25ºC, unless otherwise noted)
Parameter
Symbol
VIN
Conditions
Min
Typ
Max
5.5
8
Unit
V
Operating Input Voltage
2.5
ISD
VEN=0V
4
μA
μA
MHz
%
Operation Current
IQ
VFB=0.2V
430
1.3
550
1.5
Switching Frequency
Maximum Duty Cycle
Under Voltage Lockout
VIN Under Voltage Lockout
Under Voltage Lockout Hysteresis
Open Lamp Shutdown Threshold
Enable
fSW
1.0
92
Duty
VFB=0V
UVLO
VOV
VIN Rising
VSW Rising
2.25
92
2.45
V
mV
V
41
42
EN OFF Threshold
VEN Falling
VEN Rising
VFB=0V
0.4
V
V
EN ON Threshold
0.6
Minimum EN Dimming Threshold
Maximum EN Dimming Threshold
Dimming On Time
0.7
1.4
V
VFB=195mV
VIN=5V
V
TON
1.5
μs
Feedback
FB Voltage
VFB
IFB
VEN=1.5V
VFB=0.1V
185
195
205
mV
nA
FB Input Bias Current
Output Switch
-300
SW ON-Resistance (Note 2)
SW Current Limit (Note 2)
Thermal Shutdown (Note 2)
RON
ILM
0.5
1.33
150
Ω
A
TSD
°C
Note 2：The specification is guaranteed by design, not production tested.
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Typical Performance Curves
VSW
VSW
VFB
VEN
VOUT
VIN=5V, 3S9P WLEDs
CIN=1μF, COUT=1μF
VOUT
ILED
IL
VIN=5V, 3S9P WLEDs
CIN=1μF, COUT=1μF
Figure 4. Switch waveforms
Figure 5. Enable Startup Response Waveforms
VSW
VSW
VEN
VEN
VOUT
VOUT
VIN=5V, 3S9P WLEDs
CIN=1μF, COUT=1μF
ILED
VIN=5V, 3S9P WLEDs
CIN=1μF, COUT=1μF
ILED
Figure 7. PWM Dimming Response Waveforms at a
frequency of 25kHz
Figure 6. Enable Shutdown Response Waveforms
VSW
VEN
VSW
VEN
VOUT
VIN=3.3V, 3S10P WLEDs
CIN=1μF, COUT=1μF
ILED
VIN=5.0V
CIN=1μF, COUT=1μF
VOUT
Figure 8. PWM Dimming Response Waveforms at a
frequency of 1kHz
Figure 9. Open load Protection Waveforms
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Typical Performance Curves (Continued)
200
150
100
50
VIN=3V, 10S1P WLEDs
25
20
15
10
5
VIN=5V, 10S1P WLEDs
20KHz
100KHz
50KHz
100Hz
1KHz
0
0
0.6
0.8
1.0
1.2
EN Pin Voltage (V)
1.4
1.6
0
20
40
60
80
100
PWM Duty Cycle (%)
Figure10. LED Current vs. Duty Cycle
Figure11. Feedback Voltage vs. EN Voltage
220
VIN=5V, 3S1P WLEDs
1600
1500
1400
1300
1200
1100
VIN=5V, 3S1P WLEDs
210
200
190
180
170
160
150
-40
-20
0
20
40
60
80
-40
-20
0
20
40
60
80
Temperature (oC)
Temperature (oC)
Figure12. Operating frequency vs. Temperature.
Figure13. Feedback Voltage vs. Temperature.
95
ILED=19.5mA/string
3S9P
90
85
80
75
70
65
6S1P
8S1P
10S1P
CIN=1uF, COUT=1uF
L=10uH (SLF7045T100M1R3, DCR=36mohm)
3.5 4.0 4.5 5.0 5.5
3.0
6.0
Input Voltage (V)
Figure14. Efficiency vs. Input Voltage.
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Applications Information
Operation
Over Voltage Protection
The FP6745 is designed in a current mode,
fixed-frequency pulse-width modulation (PWM)
step-up converter to drive up 10 series-connected
WLEDs. The FP6745 operates well with a variety of
external components. See the following sections to
optimize external components for a particular
application.
The FP6745 has an internal open-lamp protection
circuit. In the cases of output open circuit, when
the LEDs are disconnected from the circuit or the
LEDs fail open circuit, the over-voltage function will
monitor the output voltage through SW pin to
protect the converter. The LED strings open will
cause N-MOS to switch with a maximum duty cycle
and come out output over-voltage. This may
cause the SW voltage exceed its maximum rating
then damage built-in N-MOS. In the state, the
OVP protection circuitry will be triggered if output
voltage exceeds 42V (typ.). The FP6745 will then
stop switching and latch off. The FP6745 will
automatically recover normal operation until EN
input is recycled or the VIN is re-started.
Inductor Selection
For most applications, a 4.7μH to 15Μh inductor is
recommended for general use.
The inductor
parameters, current rating, DCR and physical size,
should be considered. The DCR of inductor affects
the efficiency of the converter. The inductor with
lowest DCR is chosen for highest efficiency. The
saturation current rating of inductor must be greater
than the switch peak current, typically 1.33A.
These factors affect the efficiency, output load
capability, output voltage ripple and cost.
Dimming Control
There are two different types of dimming control
circuits.
The LED current can be set by
modulating the EN pin with a DC voltage or a PWM
signal.
The inductor selection depends on the switching
frequency and current ripple by the following formula:
(1) DC Voltage
ꢂꢃꢄ
ꢂꢃꢄ
The dimming control uses a DC voltage ranging
from 0.7V to 1.4V which results in regulating FB
voltage from 0V to 195mV respectively.
ꢀ
ꢀꢁ
ꢊꢋ
ꢅꢆꢇꢈꢉꢃꢀ
ꢂꢌꢍT
Where fSW is the 1.3MHz switching frequency.
ꢉIL is the inductor ripple current.
(2) PWM Signal
Changing the LED forward current not only changes
the intensity of the LEDs but also the color.
Controlling the intensity of the LEDs with a direct
PWM signal allows dimming of the LEDs without
changing the color.
Capacitor Selection
The ceramic capacitor is ideal for FP6745
application. X5R or X7R types are recommended
because they hold their capacitance over wide
voltage and temperature ranges better than other
Y5V or Z5U types. The input capacitor can reduced
peak current and noise at power source. The
output capacitor is typically selected based on the
Dimming the LEDs via a PWM signal essentially
involves turning the LED on and off. The LEDs
operate at either zero or full current.
The
amplitude of the PWM signal should be higher than
the minimum EN dimming voltage (typically 1.4V).
The LED average current increases proportionally
with the duty cycle of the PWM signal. The color
of the LEDs remains unchanged since the LED
current value is either zero or a constant value.
The dimming frequency of the PWM signal can up
to 50kHz and still retain well linearity. To avoid
audio noise, dimming frequency greater than 20kHz
is recommended. The PWM dimming on time
(TON) must be greater than 1.5μs. For example,
when dimming frequency is 40KHz, the cycle period
output voltage ripple requirements.
applications, a 10μF input capacitors with a 0.47μF
output capacitor are sufficient for general use.
higher or lower capacitance may be used depending
on the acceptable noise level.
For most
A
LED Current Setting
The LED current is specified by resistor from the FB
pin to ground. In order to have accurate LED
current, precision resistors are preferred (1% is
recommended). The LED current can be
programmed by: ILED=195mV/RFB
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Applications Information (Continued)
will be 25μs. The PWM signal’s duty cycle (D) must
be greater than 6% to set TON greater than 1.5μs.
Tꢌꢄ
ꢎꢏ
Period
TON
PWM Signal
Period
Layout Consideration
The proper PCB layout and component placement
are critical for all switching regulators. The careful
attention should be taken to the high-frequency and
high current loops to prevent electromagnetic
interference (EMI) problems.
Here are some
suggestions to the layout of FP6745 design.
a. The input capacitor should be located as close to
the VIN and GND pin as possible.
b. Minimize the distance of all traces connected to
the SW node. The external components, COUT
,
L1 and D1 should be placed as close to the
device as possible with short and wide route to
obtain optimum efficiency.
c. Keep the noise-sensitive feedback circuitry away
from the switching node.
Place feedback
resistor as close to FB pin as possible.
d. The ground terminal of COUT must be located as
closed to GND pin as possible. Place COUT next
to Schottky diode.
In Backlight application, the system engineers
usually place the COUT close to the LED connector.
The far COUT of the FP6745 may result in variable
VFB. It’s recommended to add one more COUT
close to FP6745.
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Outline Information
TSOT-23-5 Package (Unit: mm)
DIMENSION IN MILLIMETER
SYMBOLS
UNIT
MIN
MAX
A
0.70
0.90
A1
A2
B
0.00
0.70
0.30
2.80
2.60
1.50
0.90
1.80
0.30
0.10
1.00
0.50
3.00
3.00
1.70
1.00
2.00
0.60
D
E
E1
e
e1
L
Carrier Dimensions
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Outline Information (Continued)
TSOT-23-6 Package (Unit: mm)
DIMENSION IN MILLIMETER
SYMBOLS
UNIT
MIN
0.70
0.00
0.70
0.30
2.80
2.60
1.50
0.90
1.80
0.30
MAX
0.90
0.10
1.00
0.50
3.00
3.00
1.70
1.00
2.00
0.60
A
A1
A2
B
D
E
E1
e
e1
L
Carrier Dimensions
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Outline Information (Continued)
SOT-23-6 Package (Unit: mm)
DIMENSION IN MILLIMETER
SYMBOLS
UNIT
MIN
0.90
0.00
0.90
0.30
2.80
2.60
1.50
0.90
1.80
0.30
MAX
1.45
0.15
1.30
0.50
3.00
3.00
1.70
1.00
2.00
0.60
A
A1
A2
B
D
E
E1
e
e1
L
Note：Followed From JEDEC MO-178-C.
Carrier Dimensions
Life Support Policy
Fitipower’s products are not authorized for use as critical components in life support devices or other medical systems.
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