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PDF RT8471 Data sheet ( Hoja de datos )
| Número de pieza | RT8471 | |
| Descripción | High Brightness LED Driver | |
| Fabricantes | Richtek | |
| Logotipo |  |
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®
RT8471
1.2A/1A, Hysteretic, High Brightness LED Driver with
Internal Switch
General Description
The RT8471 is a high efficiency, continuous mode inductive
step-down converter, designed for driving single or multiple
series connected LEDs from a voltage source higher than
the LED voltage. It operates from an input voltage of 7V to
36V and employs hysteretic control with a high side current
sense resistor to set the constant output current.
The RT8471 includes an output switch and a high side
output current sensing circuit, which uses an external
resistor to set the nominal average output current. LED
brightness control is achieved with PWM dimming from
an analog or PWM input signal.
The RT8471 is available in a small TSOT-23-5 package or
a more thermal efficient SOP-8 (Exposed Pad) and MSOP-
8 (Exposed Pad) packages.
Ordering Information
RT8471
Package Type
J5 : TSOT-23-5
SP : SOP-8 (Exposed Pad-Option 1)
FP : MSOP-8 (Exposed Pad)
Lead Plating System
G : Green (Halogen Free and Pb Free)
(for MSOP-8 (Exposed Pad) and
TSOT-23-5 )
Z : ECO (Ecological Element with
Halogen Free and Pb free)
(for SOP-8 (Exposed Pad) Only)
Note :
Richtek products are :
RoHS compliant and compatible with the current require-
ments of IPC/JEDEC J-STD-020.
Suitable for use in SnPb or Pb-free soldering processes.
Features
7V to 36V Input Voltage Range
Hysteretic Control with High Side Current Sensing
Internal N-MOSFET with 350mΩ Low RDS(ON)
1A Output Current (For TSOT-23-5 Only)
1.2A Output Current (For SOP-8 (Exposed Pad) and
MSOP-8 (Exposed Pad) Only)
Up to 97% Efficiency
Typical ±5% LED Current Accuracy
Analog or PWM Control Signal for LED Dimming
300Hz On-Board Ramp Generator
Input Under Voltage Lockout
Thermal Shutdown Protection
RoHS Compliant and Halogen Free
Applications
Automotive LED Lighting
High Power LED Lighting
Indicator and Emergency Lighting
Architectural Lighting
Low Voltage Industrial Lighting
Signage and Decorative LED Lighting
Marking Information
RT8471GJ5
01=DNN
01= : Product Code
DNN : Date Code
RT8471ZSP
RT8471
ZSPYMDNN
RT8471ZSP : Product Number
YMDNN : Date Code
RT8471GFP
0D=YM
DNN
0D= : Product Code
YMDNN : Date Code
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8471-02 December 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
1
1 page  
RT8471
Electrical Characteristics
(VIN = 12V, TA = 25°C, unless otherwise specified)
Parameter
Symbol
Mean Current Sense Threshold
Voltage
VSENSE
Sense Threshold Hysteresis
Low Side Switch On-Resistance
Low Side Switch Leakage Current
Under Voltage Lockout Threshold
Under Voltage Lockout Threshold
Hyster esi s
V SE NS E
RDS(ON)
VUVLO
VUVLO
Ramp Frequency
ADJ Input Threshold Logic-High
Voltage
Lo gi c-Lo w
Analog Dimming Range
fRAMP
VADJ, H
VADJ, L
Analog Dimming Logic-High
Threshold Voltage Logic-Low
Test Conditions
Measure on SENSE Pin with
Respecting to VIN. ADJ is
F loating.
VLX = 12V, VADJ = 0V
VIN Rising
Min Typ Max Unit
95 100 105 mV
-- ±15 --
%
-- 350 500 m
-- 0.01 10 A
-- 5.2 --
V
-- 400 -- mV
-- 300 -- Hz
1.4
--
--
--
--
0.2
V
0.3 -- 1.3 V
-- 1.2 1.3
0.3 0.4
--
V
Minimum Switch On-Time
Minimum Switch Off-Time
Quiescent Input Current with
Output Off
Quiescent Input Current with
Output Switching
Internal Propagation Delay
Sense Pin Input Current
Thermal Shutdown
Thermal Shutdown Hysteresis
tON(MIN)
tOFF(MIN)
IVIN, Off
IVIN, On
tPD
ISE NS E
TS D
T SD
LX Switch On
LX Switch Off
VADJ = 0V
ADJ is Floating, fSW = 250kHz,
VIN = 8V
VSENSE = VIN 0.1V
-- 210 --
-- 170 --
-- 450 --
-- 1000 --
-- 25 --
-- 300 --
-- 150 --
-- 30 --
ns
ns
A
A
ns
nA
C
C
Note 1. Stresses beyond those listed “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 in
the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions may
affect device reliability.
Note 2. θJA is measured in natural convection at TA = 25°C on a two-layer and four-layer test board of JEDEC 51 thermal
measurement standard. For SOP-8 (Exposed Pad) and MSOP-8 (Exposed Pad) the measurement case position of θJC
is on the exposed pad of the package. For TSOT-23-5, the measurement case position of θJC is on the lead of the
package.
Note 3. Devices are ESD sensitive. Handling precaution is recommended.
Note 4. The device is not guaranteed to function outside its operating conditions.
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8471-02 December 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
5
5 Page 
RT8471
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
where TJ(MAX) is the maximum junction temperature, TA is
the ambient temperature, and θJA is the junction to ambient
thermal resistance.
For recommended operating condition specifications, the
maximum junction temperature is 125°C. The junction to
ambient thermal resistance, θJA, is layout dependent. For
TSOT-23-5 packages, the thermal resistance, θJA, is
264.4°C/W on a standard JEDEC 51-3 two-layer thermal
test board and 230.6°C/W on a standard JEDEC 51-7 four-
layer thermal test board. For SOP-8 (Exposed pad)
package, the thermal resistance, θJA, is 42.5°C/W on a
standard JEDEC 51-7 two-layer thermal test board, and
30.6°C/W on a standard JEDEC 51-7 four-layer thermal
test board. For MSOP-8 (Exposed pad) package, the
thermal resistance, θJA, is 72°C/W on a standard JEDEC
51-7 two-layer thermal test board, and 47.4°C/W on a
standard JEDEC 51-7 four-layer thermal test board. The
maximum power dissipation at TA= 25°C can be calculated
by the following formulas :
PD(MAX) = (125°C − 25°C) / (264.4°C/W) = 0.37W for
TSOT-23-5 package (Two-Layer PCB)
PD(MAX) = (125°C − 25°C) / (230.6°C/W) = 0.43W for
TSOT-23-5 package (Four-Layer PCB)
PD(MAX) = (125°C − 25°C) / (42.5°C/W) = 2.35W for
SOP-8 (Exposed pad, Two-Layer PCB) package
PD(MAX) = (125°C − 25°C) / (30.6°C/W) = 3.26W for
SOP-8 (Exposed pad, Four-Layer PCB) package
PD(MAX) = (125°C − 25°C) / (72°C/W) = 1.38W for
MSOP-8 (Exposed pad, Two-Layer PCB) package
PD(MAX) = (125°C − 25°C) / (47.4°C/W) = 2.1W for
MSOP-8 (Exposed pad, Four-Layer PCB) package
The maximum power dissipation depends on the operating
ambient temperature for fixed TJ(MAX) and thermal
resistance, θJA. The derating curves in Figure 2 allow the
designer to see the effect of rising ambient temperature
on the maximum power dissipation.
4.0 SOP-8 (Exposed Pad, Four-Layer PCB)
3.5
SOP-8 (Exposed Pad, Two-Layer PCB)
MSOP-8 (Exposed Pad, Four-Layer PCB)
3.0
MSOP-8 (Exposed Pad, Two-Layer PCB)
TSOT23-5 (Four-Layer PCB)
2.5 TSOT23-5 (Two-Layer PCB)
2.0
1.5
1.0
0.5
0.0
0
25 50 75 100
Ambient Temperature (°C)
125
Figure 2. Derating Curves of Maximum Power
Dissipation
Copyright ©2013 Richtek Technology Corporation. All rights reserved.
DS8471-02 December 2013
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet RT8471.PDF ] | |
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