FC1360 [FS]
1A LED Lighting Driver;
| 型号： | FC1360 |
| 厂家： | 
First Silicon Co., Ltd |
| 描述： | 1A LED Lighting Driver |
| 文件： | 总7页 (文件大小：149K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
SEMICONDUCTOR
FC1360
TECHNICAL DATA
1A LED Lighting Driver
Features
Applications
Built in thermal and over current protection
Internal 32V Power MOSFET Switch
1A output current
MR16 and general lighting
Automotive lighting
Low voltage industrial lighting
LED back lighting
Single pin on/off and dimming control using
DC voltage or PWM at ADJ pin.
Internal PWM filter
Illuminated signs
Typical Application circuit
Soft-start
High efficiency (up to 90%)
Wide input voltage range : 7V to 32V
40V transient capability
LX Output shutdown
Up to 1MHz switching frequency
Inherent open-circuit LED protection
Typical 5% output current accuracy
Ordering Information
Item
Package
Shipping
FC1360PRG
SOT-89-5
1,000pcs/reel & tape
General Description
The FC1360 is a continuous mode inductive step-down converter, designed for driving single or multiple series
connected LEDs efficiently from a voltage source higher than the LED voltage. The device operates from an input
supply between 7V and 30V and provides an externally adjustable output current of up to 1A. Depending upon
supply voltage and external components, this can provide up to 24 watts of output power.
The FC1360 includes the output switch and a high-side output current sensing circuit, which uses an external
resistor to set the nominal average output current. Output current can be adjusted above, or below the set value,
by applying an external control signal to the 'ADJ' pin.
The PWM filter provides a soft-start feature by controlling the rise of input/output current. The soft-start time can
be increased using an external capacitor from the ADJ pin to ground. Applying a voltage of 0.2V or lower to the
ADJ pin turns the output off and switches the device into a low current standby state.
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Revision No : 0
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FC1360
Pin Assignment
Pin Function
Pin No.
Pin Name
SOT-23-5
Description
1
2
3
4
5
LX
VSS
Switching Output
Ground
ADJ
Current Adjustment
Current Sense
Input
ISENSE
VIN
SOT-89-5
Marking Information
Block Diagram
SOT-89-5
Absolute Maximum Ratings
Parameter
Input Voltage
Symbol
VIN
Ratings
Units
V
30
1.25
LX Output Current
ILX
A
I/O Pin Voltage
VIO
VSS-0.3 ~ VIN+0.3
1
V
Power Dissipation SOT-89-5
Operation Ambient Temperature
Storage Temperature
Pd
W
Topr
Tstg
-40 ~ +125
-55 ~ +125
˚C
˚C
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FC1360
Electrical Characteristics
Test Condition: VIN = 12V DC, Ta = 25 oC
Ta=25 C
Typ
Parameter
Symbol
VIN
Conditions
Units
Min
7
Max
32
Input Voltage
Internal regulator start-up
threshold voltage
V
V
VSU
VIN rising from 0V until VADJ 1.25V
5.65
V
ADJ= 0V, VIN = 12V
55
65
90
130
Quiescent supply current
with LX output off
Quiescent supply current
with LX output switching
Mean current sense
IINQoff
IINQon
VSENSE
A
mA
mV
VADJ= 0V, VIN = 30V
V
SENSE = VIN & VIN – 0.125V at
1.9
5.2
frequency of 250 kHz, ADJ pin floating
Measured on ISENSE pin with respect
to VIN, ADJ pin floating
95
100
105
threshold voltage (1)
±15
1.25
Sense threshold hysteresis VSENSEHYS
%
V
Internal reference voltage
External control voltage
range on ADJ pin for dc
brightness control (2)
VREF
Measured on ADJ pin with pin floating 1.15
0.3
1.35
2.0
VADJ
V
LX switch On Resistance
LX switch Output Current
RLX
ILX
VSENSE = VIN = 12V, ADJ pin floating
1.3
3.5
1.25
Ohm
A
VSENSE = VIN = 12V, VADJ= 0V,
LX switch Leakage Current ILX_Leakage
5
A
V
LX = 30V
Note
(NOTE 1) VSENSE defines LED current setting accuracy
(NOTE 2) VADJ defines LED current. The LED light intensity will vary by varying the VADJ voltage from 0.3V to 2.0V. By applying VADJ < 0.2V, the
LED shall switch off.
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FC1360
Application Notes
Setting nominal average output current with external resistor RS
The nominal average output current in the LED(s) is determined by the value of the external
current sense resistor (RS) connected between VIN and ISENSE and is given by:
IOUT = 0.1/RS (A)
The table below gives values of nominal average output current for several preferred values of
current setting resistor (RS) in the typical application circuit:
RS (ohm)
0.1
Nominal Average Output Current (mA)
1000
760
0.13
0.15
667
The above values assume that the ADJ pin is floating and at a nominal voltage of VREF
(1.25V).Note that RS = 0.1 ohm is the minimum allowed value of sense resistor under these
conditions to maintain switch current below the specified maximum value.
Output current adjustment by external DC control voltage
The ADJ pin can be driven by an external dc voltage (VADJ), to adjust the output current to a
value above or below the nominal average value defined by RS.
The nominal average output current in this case is given by:
IOUTdc = (VADJ /1.25) x 100mV x RS (for 0.3< VADJ <2.5V)
Note that 100% brightness setting corresponds to VADJ = VREF. When driving the ADJ pin
above 1.25V, RS must be increased in proportion to prevent IOUTdc exceeding 1A maximum.
The input impedance of the ADJ pin is 200k_ ±25% for voltages below VREF and 20k_ ±25%
for voltages above VREF +100mV.
Inherent open-circuit LED protection
If the connection to the LED(s) is open-circuited, the coil is isolated from the LX pin of the
chip, so the device will not be damaged, unlike in many boost converters, where the back EMF
may damage the internal switch by forcing the drain above its breakdown voltage.
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FC1360
Capacitor selection
A low ESR capacitor should be used for input decoupling, as the ESR of this capacitor appears in
series with the supply source impedance and lowers overall efficiency. This capacitor has to
supply the relatively high peak current to the coil and smooth the current ripple on the input
supply. A minimum value of 4.7 uF is acceptable if the input source is close to the device, but
higher values will improve performance at lower input voltages, especially when the source
impedance is high. The input capacitor should be placed as close as possible to the IC.
Inductor selection
Recommended inductor values for the FC1360 are in the range 33 uH to 100 uH. Higher values
of inductance are recommended at higher supply voltages in order to minimize errors due to
switching delays, which result in increased ripple and lower efficiency. Higher values of
inductance also result in a smaller change in output current over the supply voltage range. The
inductor should be mounted as close to the device as possible with low resistance connections
to the LX and VIN pins.
Note that, in practice, the duty cycle and operating frequency will deviate from the calculated
values due to dynamic switching delays, switch rise/fall times and losses in the external
components.
Optimum performance will be achieved by setting the duty cycle close to 0.5 at the nominal
supply voltage. This helps to equalize the undershoot and overshoot and improves temperature
stability of the output current.
Diode selection
For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance
Schottky diode with low reverse leakage at the maximum operating voltage and temperature.
It is important to select parts with a peak current rating above the peak coil current and a
continuous current rating higher than the maximum output load current. It is very important to
consider the reverse leakage of the diode when operating above 85°C. Excess leakage will
increase the power dissipation in the device and if close to the load may create a thermal
runaway condition.
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FC1360
PCB layout issue
LX pin
The LX pin of the device is a fast switching node, so PCB tracks should be
kept as short as possible. To minimize ground 'bounce', the ground pin of the
device should be soldered directly to the ground plane.
Coil,
It is particularly important to mount the coil and the input decoupling
capacitor as close to the device pins as possible to minimize parasitic
resistance and inductance, which will degrade efficiency. It is also important
decoupling
capacitors,
current sense to minimize any track resistance in series with current sense resistor RS. Its
resistor
best to connect VIN directly to one end of RS and Isense directly to the
opposite end of RS with no other currents flowing in these tracks. It is
important that the cathode current of the Schottky diode does not flow in a
track between RS and VIN as this may give an apparent higher measure of
current than is actual because of track resistance.
ADJ pin
The ADJ pin is a high impedance input for voltages up to 1.35V so, when left
floating, PCB tracks to this pin should be as short as possible to reduce noise
pickup. A 100nF capacitor from the ADJ pin to ground will reduce frequency
modulation of the output under these conditions. An additional series 10k
resistor can also be used when driving the ADJ pin from an external circuit .
This resistor will provide filtering for low frequency noise and provide
protection against high voltage transients.
High voltage Avoid running any high voltage tracks close to the ADJ pin, to reduce the risk
tracks
of leakage currents due to board contamination. The ADJ pin is soft-clamped
for voltages above 1.35V to desensitize it to leakage that might raise the ADJ
pin voltage and cause excessive output current. However, a ground ring
placed around the ADJ pin is recommended to minimize changes in output
current under these conditions.
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FC1360
Package Information
SOT-89-5
DISCLAIMER:
First silicon reserves the rights to change the information and specifications without prior notice. The information presented
in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed
without notice. No liability will be accepted by the publisher for any consequence of its use.
2009. 07. 10
Revision No : 0
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