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RT9052
Single Channel LED Current Source Controller
General Description
Features
The RT9052 is a low cost, single channel LED current
source controller with a specific FAULT detector. The part
can drive an external NPN-BJT for various applications.
The RT9052 is operated with Vcc power ranging from 3.8V
to 13.5V. With such a topology, it's very flexible and cost
effective.
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The RT9052 comes in a small SOT-23-6 package.
3.8V to 13.5V Operation Voltage
Voltage Reference 0.8V with ±2% High Accuracy
FAULT Indicator with Delay
Dimming Control by PWM
Small Footprint Package SOT-23-6
RoHS Compliant and Halogen Free
Applications
z
Ordering Information
z
RT9052
z
Package Type
E : SOT-23-6
Lead Plating System
G : Green (Halogen Free and Pb Free)
LED Backlight applications
Current Source
Transistor Driver
Pin Configurations
(TOP VIEW)
Note :
VCC DRI FAULT
Richtek products are :
`
RoHS compliant and compatible with the current require-
6
5
4
2
3
ments of IPC/JEDEC J-STD-020.
`
Suitable for use in SnPb or Pb-free soldering processes.
DIM GND ISET
Marking Information
SOT-23-6
EU= : Product Code
EU=DNN
DNN : Date Code
Typical Application Circuit
VLED
WLED
RT9052
5V
R1
100k
6 VCC
12V
CIN
1µF
DRI 5
ISET 3
4
FAULT
GND 2
RB
RISET
1 DIM
DS9052-01 April 2011
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RT9052
Functional Pin Description
Pin No.
1
2
3
4
5
6
Pin Name
Pin Function
DIM
GND
ISET
PWM Dimming Control Input.
Ground.
Current Setting Input.
FAULT
DRI
VCC
FAULT Signal Open Drain Output.
Driver Output.
Power Supply Input.
Function Block Diagram
VCC
Reference
Voltage VREF
FAULT
0.9 x VREF
3ms
Delay
+
-
DIM
+
Driver
DRI
ISET
GND
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DS9052-01 April 2011
RT9052
Absolute Maximum Ratings
(Note 1)
Supply Input Voltage, VCC ---------------------------------------------------------------------------------------------DIM Voltage ---------------------------------------------------------------------------------------------------------------FAULT Output Voltage --------------------------------------------------------------------------------------------------Power Dissipation, PD @ TA = 25°C
SOT-23-6 -------------------------------------------------------------------------------------------------------------------Package Thermal Resistance (Note 2)
SOT-23-6, θJA -------------------------------------------------------------------------------------------------------------Lead Temperature (Soldering, 10 sec.) -----------------------------------------------------------------------------Junction Temperature ---------------------------------------------------------------------------------------------------Storage Temperature Range -------------------------------------------------------------------------------------------ESD Susceptibility (Note 3)
HBM (Human Body Mode) ---------------------------------------------------------------------------------------------MM (Machine Mode) -----------------------------------------------------------------------------------------------------
Recommended Operating Conditions
15V
7V
7V
0.4W
250°C/W
260°C
150°C
−65°C to 150°C
2kV
200V
(Note 4)
Supply Input Voltage, VCC ---------------------------------------------------------------------------------------------DIM Voltage ---------------------------------------------------------------------------------------------------------------Junction Temperature Range ------------------------------------------------------------------------------------------Ambient Temperature Range -------------------------------------------------------------------------------------------
3.8V to 13.5V
0V to 5.5V
−40°C to 125°C
−40°C to 85°C
Electrical Characteristics
(VCC = 5V/12V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Min
Typ
Max
Unit
3.15
3.4
3.65
V
0.1
0.2
0.3
V
VCC = 12V
--
0.3
0.8
mA
Driver Source Current
VCC = 12V, VDRI = 6V
5
--
--
mA
Driver Sink Current
VCC = 12V, VDRI = 6V
5
--
--
mA
VCC = 12V, VDRI = 5V
0.784
0.8
0.816
V
ISET Line Regulation
VCC = 4.5V to 13.5V
--
3
6
mV
Amplifier Voltage Gain
VCC = 12V, No Load
--
70
--
dB
FAULT Rising Threshold
VCC = 12V
85
90
95
%VREF
FAULT Hysteresis
VCC = 12V
--
15
--
%VREF
Sink Capability
VCC = 12V @ 1mA
--
0.2
0.4
V
VCC = 12V
1
3
10
ms
VCC = 12V
--
15
20
μs
VCC = 12V
--
0.7
1
V
VCC = 12V
--
30
--
mV
VCC = 12V, VDIM = 0V
--
--
5
μA
UVLO Threshold
Test Conditions
VCC Rising
UVLO Hysteresis
VCC Supply Current
ISET Reference Voltage
Delay Time
I CC
VREF
t DELAY
Falling Delay
DIM
DIM Rising Threshold
DIMth
DIM Hysteresis
Standby Current
DS9052-01 April 2011
I STANDBY
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RT9052
Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for
stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended
periods may remain possibility to affect device reliability.
Note 2. θJA is measured in natural convection at TA = 25°C on a low effective thermal conductivity test board of JEDEC 51-3
thermal measurement standard.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
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DS9052-01 April 2011
RT9052
Typical Operating Characteristics
Standby Current vs. VCC Input Voltage
1.0
VDIM = 0V
0.9
VDIM = 3V
0.9
0.8
Supply Current (mA)
Standby Current (μA)1
Supply Current vs. VCC Input Voltage
1.0
0.7
0.6
0.5
0.4
0.3
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.2
0.1
0.1
0.0
0.0
3.5
5.0
6.5
8.0
9.5
11.0
12.5
14.0
3.5
5.0
DIM Threshold Voltage (V)
Supply Current (mA)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
11.0
12.5
14.0
0.9
Rising
0.8
Falling
0.7
0.6
0.5
0.4
0.0
-50
-25
0
25
50
75
100
3.5
125
5.0
6.5
8.0
9.5
11.0
12.5
14.0
VCC Input Voltage (V)
Temperature (°C)
DIM Threshold Voltage vs. Temperature
1.0
ISET Voltage vs. VCC Input Voltage
0.820
VCC = 12V
VDIM = 3V
0.815
0.9
Rising
ISET Voltage (V)
DIM Threshold Voltage (V)
9.5
1.0
VDIM = 3V
0.9
8.0
DIM Threshold Voltage vs. VCC Input Voltage
Supply Current vs. Temperature
1.0
6.5
VCC Input Voltage (V)
VCC Input Voltage (V)
0.8
Falling
0.7
0.6
0.810
0.805
0.800
0.795
0.790
0.5
0.785
0.4
0.780
-50
-25
0
25
50
Temperature (°C)
DS9052-01 April 2011
75
100
125
3.5
5.0
6.5
8.0
9.5
11.0
12.5
14.0
VCC Input Voltage (V)
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RT9052
ISET Voltage vs. Temperature
DRI Source Current vs. DRI Voltage
0.820
55
0.815
53
DRI Source Current (mA)
ISET Voltage (V)
0.810
0.805
0.800
0.795
0.790
0.785
0.780
0.775
0.770
0.765
-50
-25
0
25
50
75
100
49
47
45
43
41
39
37
VCC = 12V
0.760
51
VCC = 12V, VISET 0.6V, VDIM = 3V
35
125
0
1
2
Temperature (°C)
4
5
6
7
DRI Voltage (V)
DRI Source Current vs. Temperature
DRI Sink Current vs. DRI Voltage
25
70
60
DRI Sink Current (mA)
DRI Source Current (mA)
3
50
40
30
20
20
15
10
5
10
VCC = 12V, VISET 0.6V, VDRI = 6V
0
-50
-25
0
25
50
75
100
VCC = 12V, VISET = 1V, VDIM = 3V
0
0
125
1
2
3
4
5
6
7
DRI Voltage (V)
Temperature (°C)
DIM PWM Dimming
LED Current vs. PWM Duty
180
8LEDs
160
LED Current (mA)
VDIM
(5V/Div)
VISET
(500mV/Div)
VLED
(2V/Div)
I LED
(100mA/Div)
140
120
100
80
60
40
VCC = 12V, RISET = 5.1Ω, VLED = 3V
VCC = 12V, RISET = 5.1Ω,
VDIM = 0 to 5V/250Hz
20
0
Time (1ms/Div)
0
10
20
30
40
50
60
70
80
90
100
PWM Duty (%)
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DS9052-01 April 2011
RT9052
Application Information
The RT9052 is a low cost single channel LED current
source controller with a specific FAULT indicating scheme.
This device can drive an external NPN-BJT for various
applications. The RT9052 is operated with VCC power
ranging from 3.8V to 13.5V. With such a topology, it is
very flexible and cost effective.
Capacitors Selection
Careful selection of the external capacitors for the RT9052
is necessary to maintain high stability and performance.
A capacitor ≥ 1μF must be connected between VCC and
ground to improve supply voltage stability for proper
operation.
The RT9052 has a FAULT function with delay. The FAULT
output is an open drain output. Connect a 100kΩ pull up
resistor to external 5V source to obtain an output voltage.
When the ISET voltage reaches 90% of normal value,
FAULT will become active and be pulled high by external
circuits with a typical 3ms delay.
LED Current Setting
The RT9052 includes a 0.8V reference voltage for easy
setting of the LED current source. As shown in application
circuit, the LED current is easily set via an RISET resistor.
ILED
Thermal Considerations
For continuous operation, do not exceed absolute
maximum junction temperature. The maximum power
dissipation depends on the thermal resistance of the IC
package, PCB layout, rate of surrounding airflow, and
difference between junction and ambient temperature. The
maximum power dissipation can be calculated by the
following formula :
PD(MAX) = (TJ(MAX) − TA) / θJA
FAULT Function
0.8 (V)
=
RISET (Ω)
selection, the following criteria Should be considered :
DC current gain hFE , threshold voltage VBE, collectoremitter voltage V CE, maximum collector current IC
package thermal resistance θ(JA).
( A)
PWM Dimming Operation
For controlling the LED brightness, the RT9052 can perform
dimming control by applying a PWM signal to the DIM
pin. The average LED current is proportional to the PWM
signal duty cycle. Note that the magnitude of the PWM
signal needs to be higher than the maximum dimming
voltage of the DIM pin, in order to have correct dimming
control.
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJAis the junction to ambient
thermal resistance.
For recommended operating condition specifications of
the RT9052, the maximum junction temperature is 125°C
and TA is the ambient temperature. The junction to ambient
thermal resistance, θ JA , is layout dependent. For
SOT-23-6 packages, the thermal resistance, θ JA, is
250°C/W on a standard JEDEC 51-3 single-layer thermal
test board. The maximum power dissipation at TA = 25°C
can be calculated by the following formula :
PD(MAX) = (125°C − 25°C) / (250°C/W) = 0.400W for
SOT-23-6 package
The maximum power dissipation depends on the operating
ambient temperature for fixed T J(MAX) and thermal
resistance, θJA. For the RT9052 package, the derating
curve in Figure 1 allows the designer to see the effect of
rising ambient temperature on the maximum power
dissipation.
NPN Transistor Selection
The RT9052 drives the NPN transistor via the DRI pin
(source Base current IB ). When making an NPN transistor
DS9052-01 April 2011
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RT9052
Maximum Power Dissipation (W)1
0.45
Layout Consideration
Single-Layer PCB
0.40
There are three critical layout considerations.
0.35
`
0.30
0.25
The current setting resistor should be located as close
as possible to the RT9052 to avoid inducing any noise.
` The input capacitor have to put at near the IC for improved
0.20
performance.
0.15
` The pass element operating under high power situation
0.10
may raise the junction temperature above the package
thermal resistance limit. (copper area can be added to
improve power dissipation.)
0.05
0.00
0
25
50
75
100
125
Ambient Temperature (°C)
Figure 1. Derating Curve for RT9052 Package
Place CIN near the
IC for improved
performance
VLED
WLED
DRI
DIM
RB
ISET node copper
area should be
minimized and kept far
away from noise
sources
CIN
6
VCC
VCC
GND
2
5
DRI
ISET
3
4
FAULT
RISET
GND
5V
R1
The GND plane
should be connected
to a strong ground
plane for heat sinking
and noise protection.
Figure 2. PCB Layout Guide
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DS9052-01 April 2011
RT9052
Outline Dimension
H
D
L
C
B
b
A
A1
e
Dimensions In Millimeters
Dimensions In Inches
Symbol
Min
Max
Min
Max
A
0.889
1.295
0.031
0.051
A1
0.000
0.152
0.000
0.006
B
1.397
1.803
0.055
0.071
b
0.250
0.560
0.010
0.022
C
2.591
2.997
0.102
0.118
D
2.692
3.099
0.106
0.122
e
0.838
1.041
0.033
0.041
H
0.080
0.254
0.003
0.010
L
0.300
0.610
0.012
0.024
SOT-23-6 Surface Mount Package
Richtek Technology Corporation
Richtek Technology Corporation
Headquarter
Taipei Office (Marketing)
5F, No. 20, Taiyuen Street, Chupei City
5F, No. 95, Minchiuan Road, Hsintien City
Hsinchu, Taiwan, R.O.C.
Taipei County, Taiwan, R.O.C.
Tel: (8863)5526789 Fax: (8863)5526611
Tel: (8862)86672399 Fax: (8862)86672377
Email: [email protected]
Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit
design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be
guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek.
DS9052-01 April 2011
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