TECHNICAL DATA
HIGH-POWER LED DRIVER
IK2804
FEATURES
4 constant-current output channels
Constant output current invariant to load voltage
change
Maximum output constant current per channel:
240mA
Excellent output current accuracy:
between channels: <±3% (max.), and
between ICs: <±6% (max.)
Output current adjusted through an external
resistor
Schmitt trigger input
5V supply voltage
Package type: Pb-free SOP8 with thermal pad
Small Outline Package
SOP8
ORDERING INFORMATION
Device
IK2804DT
Operating
Temperature Range
ТА = - 40 ... + 85 С
Current Accuracy
Between Channels
Between ICs
<±3%
<±6%
Package
Shipping
SOP-8
Tape& Reel
Conditions
IOUT = 40 ~ 240 mA
PRODUCT DESCRIPTION
IK2804 is an instant On/Off LED driver for high power LED applications and exploits to enhance
its output characteristics. At IK2804 output stage, four regulated current ports are designed to provide
uniform and constant current sinks for driving LEDs within a large range of VF variations.
IK2804 provides users 4-channel constant current ports. Users may adjust the output current
from 40 mA up to 240mA through an external resistor, Rext, which gives users flexibility in controlling
the light intensity of LEDs. In addition, users can precisely adjust LED brightness from 0% to 100%
via output enable
with Pulse Width Modulation.
Additionally, to ensure the system reliability, IK2804 is built with TP (Thermal Protection) function
and thermal pad. The TP function protects IC from over temperature (165°C). Also, the thermal pad
enhances the power dissipation. As a result, a large amount of current can be handled safely in one
package.
APPLICATIONS
High-flux LED lighting
Automotive interior lighting
LCD backlight
Photocopier
Scanner
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2011, February Ver. 03
IK2804
TYPICAL APPLICATION CIRCUIT
Figure 1
FUNCTIONAL DIAGRAM
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2011, February Ver. 03
IK2804
PIN CONFIGURATION
PIN DESCRIPTION
Pin No.
Pin Name
1
GND
3,4,5,6
OUT0~OUT3
7
OE
2
R-EXT
8
VDD
-
Thermal Pad
Function
Ground terminal for control logic and current sink
Constant current output terminals
Output enable terminal
When OE is active (low), the output pins are enabled; when OE is
inactive (high), all output pins are turned OFF (blanked).
Terminal used to connected an external resistor (Rext) for setting up
output current for all output channels
5V supply voltage terminal
Power dissipation terminals connected to GND*
*To eliminate the noise influence, the thermal pad is suggested to be connected to GND on PCB.
In addition, desired thermal conductivity will be improved, if a heat-conducting copper foil on PCB is soldered
with thermal pad.
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2011, February Ver. 03
IK2804
MAXIMUM RATINGS
Characteristic
Symbol
Rating
Unit
Supply Voltage
VDD
0~7.0
V
Input Voltage
VIN
-0.4~VDD + 0.4
V
Output Current
IOUT
320*
mA
Sustaining Voltage
VDS
27.0
V
GND Terminal Current
IGND
1000
mA
PD
0.8
W
Power Dissipation*
(On PCB, Ta=25 ºC)
Thermal Resistance**
(By simulation)
Empirical Thermal Resistance*
(On PCB, Ta=25 ºC)
Operating Junction Temperature
SOP8
33.39
ºC/W
Rth(j-a)
125
Tj,max
125
ºC
Operating Temperature
Topr
-40~+85
ºC
Storage Temperature
Tstg
-55~+150
ºC
*Users must notice that the power dissipation (almost equaling to I OUT x VDS) should be within the Safe
Operation Area shown in Figure 7.
** Provided by factory.
*** Stresses beyond those listed under “absolute maximum ratings” may cause permanent damage to the device.
These are stress ratings only and functional operation of the device at these or any other conditions beyond those
indicated under “recommended operating conditions” is not implied.
Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
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2011, February Ver. 03
IK2804
ELECTRICAL CHARACTERISTICS
Characteristics
Symbol
Condition
Min.
Typ.
Max.
Unit
Supply Voltage
VDD
·
4.5
5.0
5.5
V
Sustaining Voltage at OUT pin
VDS
OUT0~OUT15
·
·
27.0
V
Output Current
IOUT
DC Test Circuit
40
·
240*
mA
“H” level
VIH
Ta=-40~85 ºC
1.6
VDD
V
“L” level
VIL
Ta=-40~85 ºC
GND
0.6
V
IOH
VOH=27V
·
·
0.5
uA
Input Voltage
Output Leakage Current
Output Current 1
IOUT1
VDS=0.6V
Rext=2.4kOhm
·
120
·
mA
Current Skew 1
dIOUT/IOUT
IOL=120mA
VDS=0.6V
Rext=2.4kOhm
·
±1
±3
%
Output Current 2
IOUT2
VDS=0.8V
Rext=1.3kOhm
·
220
·
mA
Current Skew 2
dIOUT/IOUT
IOL=220mA
VDS=0.8V
Rext=1.3kOhm
·
±1
±3
%
Regulation of Output Current
vs. Sustaining Voltage
Regulation of Output Current
vs. Supply Voltage
Pull-up Resistor
Thermal Shutdown temperature
%/dVDS
VDS within 1.0V and 3.0V
·
±0.1
·
%/V
%/dVDD
VDD within 4.5V and 5.5V
·
±1
·
%/V
RN(up)
OE
300
700
800
kOhm
TXI
Shutdown
Temp.increasing
·
165
·
ºC
TXD
Reset
Temp.decreasing
·
150
·
ºC
·
5
9
·
7
10
·
8
12
·
4
10
·
5
10
IDD(off) 1
“OFF”
Supply
Current
IDD(off) 2
IDD(off) 3
“ON”
IDD(on) 1
IDD(on) 2
Rext=Open,
OUT0~OUT15=Off
Rext=2.4kOhm,
OUT0~OUT15=Off
Rext=1.3kOhm,
OUT0~OUT15=Off
Rext=2.4kOhm,
OUT0~OUT15=On
Rext=1.3kOhm,
OUT0~OUT15=On
mA
* Each output current, IOUT, can be driven up to 240mA, but the total output current should be smaller than 1A.
TEST CIRCUIT FOR ELECTRICAL CHARACTERISTICS
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2011, February Ver. 03
IK2804
Figure 2
SWITCHING CHARACTERISTICS
Characteristics
Propagation Delay
Time(“L” to “H”)
Propagation Delay
Time(“H” to “L”)
Pulse width
Symbol
Condition
OE-OUTn
tpLH
OE-OUTn
tpHL
VDD=5.0V
VDS=1.0V
VIH=VDD
VIL=GND
Rext=1226Ohm
(IOUTn=240mA)
VL=4.0V
RL=12.5Ohm
CL=10pF
OE
tw(OE)
Output Rise Time of OUT (turn off)
tor
Output Rise Time of OUT (turn on)
tof
Min.
Typ.
Max.
Unit
0.3
0.5
1
us
0.3
0.5
1
us
1
-
-
us
0.3
0.5
1
us
0.3
0.5
1
us
TEST CIRCUIT FOR SWITCHING CHARACTERISTICS
Figure 3
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2011, February Ver. 03
IK2804
APPLICATION CIRCUITS
(a) IK2804 application circuit, where VLED and VDD share a single voltage source.
(b) IK2804 application circuit with dimming control by PWM signal, where V LED and VDD use voltage sources
separately.
Figure 4
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2011, February Ver. 03
IK2804
Constant Current
In LED lighting applications, IK2804 provides nearly no variation in current from channel to channel and from
IC to IC. This can be achieved by:
1) The maximum current variation between channels is less than ±3%, and that between ICs is less than
± 6%.
2) In addition, the current characteristic of output stage is flat and users can refer to the figure as shown
below. The output current can be kept constant regardless of the variations of LED forward voltages (VF).
This guarantees LED to be performed on the same brightness as user’s specification.
Iout versus Vds
Iout (ma)
280
240
7,73k
200
3,72k
160
2,44k
120
1,82k
80
1,44k
40
1,19k
0
0
0,5
1
1,5
2
2,5
3
Vds (V)
Figure 5
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2011, February Ver. 03
IK2804
Setting Output Current
The output current of each channel (Iout) is set by an external resistor, Rext. The relationship between Iout
and Rext is shown in the following figure and Table.
Iout versus Rext
Iout (ma)
280
240
200
160
120
80
40
0
0
1
2
3
4
5
6
7
8
Rext (kOhm)
Figure 6
Iout
ma
Rext
kOhm
240
1,19
200
1,44
160
1,82
120
2,44
80
3,72
40
7,73
The output current can be calculated from the equation:
VR-EXT = 1.24V;
Rext = (VR-EXT / Iout) × 236 = (1.24V / Iout) × 236,
Iout = (VR-EXR / Rext) × 236 = (1.24V / Rext) × 236 within ± 6% chip skew
Where Rext is the resistance of the external resistor connected to R-EXT terminal and VR-EXT is the voltage of
R-EXT terminal. The magnitude of current (as a function of Rext) is around 225mA at 1.3kΩ and 122mA at
2.4kΩ.
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2011, February Ver. 03
IK2804
Package Power Dissipation (PD)
The maximum power dissipation, PD(max) = (Tj,max – Ta) / Rth(j-a), decreases as the ambient temperature
increases.
Figure 7
The maximum allowable package power dissipation is determined as PD(max) = (Tj,max – Ta) / Rth(j-a). When 4
output channels are turned on simultaneously, the actual package power dissipation is:
PD(act) = (IDD x VDD) + (IOUT x Duty x VDS x 4).
Therefore, to keep PD(act) ≤ PD(max), the allowable maximum output current as a function of duty cycle is:
IOUT = { [(Tj – Ta) / Rth(j-a) ] – (IDD x VDD) } / VDS / Duty / 4,
where Tj = 125°C;
Duty= tON / T;
tON: the time of LEDs turning on; T:
signal period
*Note: The empirical thermal resistor Rth(j-a) =125 °C/W is based on the following structure.
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2011, February Ver. 03
IK2804
TP Function (Thermal Protection)
Thermal protection turns off the output current when the junction temperature rises to approximately 165°C,
allowing the device to cool. When the junction temperature cools to approximately 150°C, the output current
is turned on again. Depending on power dissipation, thermal resistance, and ambient temperature, the
thermal protection circuit may cycle on and off. This limits the dissipation of the driver, protecting it from
damage due to overheating.
Load Supply Voltage (VLED)
IK2804 is designed to operate with adequate VDS to achieve constant current. VDS together with IOUT should
not exceed the package power dissipation limit, PD(max).
As in Figure 8, VDS = VLED – VF, and VLED is the load supply voltage. PD(act) will be greater than PD(max), if VDS
drops too much voltage on the driver. In this case, it is recommended to use the lowest possible supply
voltage or to set an external voltage reducer, VDROP.
A voltage reducer lets VDS = (VLED –VF) – VDROP.
Resistors can be used in the applications as shown in Figure 8.
Figure 8
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2011, February Ver. 03
IK2804
PACKAGE DIMENSIONS
SOP 8
Note: The unit for the outline drawing is mm.
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2011, February Ver. 03