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RT8470 Schematic ( PDF Datasheet ) - Richtek

Teilenummer RT8470
Beschreibung High Brightness LED Driver
Hersteller Richtek
Logo Richtek Logo 




Gesamt 13 Seiten
RT8470 Datasheet, Funktion
RT8470
1.2A/1A, Hysteretic, High Brightness LED Driver with
Internal Switch
General Description
The RT8470 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
30V and employs hysteretic control with a high side current
sense resistor to set the constant output current.
The RT8470 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 RT8470 is available in a small TSOT-23-5 package or
a more thermal efficient SOP-8 (Exposed Pad) package.
Ordering Information
RT8470
Package Type
J5 : TSOT-23-5
SP : SOP-8 (Exposed Pad-Option 1)
Lead Plating System
G : Green (Halogen Free and Pb Free)
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.
Marking Information
RT8470GJ5
BS=DNN
BS= : Product Code
DNN : Date Code
RT8470GSP
RT8470
GSPYMDNN
RT8470GSP : Product Number
YMDNN : Date Code
Features
z 7V to 30V Input Voltage Range
z Hysteretic Control with High Side Current Sensing
z Internal N-MOSFETs with 350mΩ Low RDS(ON)
z 1A Output Current (For TSOT-23-5 Only)
z 1.2A Output Current (For SOP-8 (Exposed Pad) Only)
z Up to 97% Efficiency
z Typical ±5% LED Current Accuracy
z Analog or PWM Control Signal for LED Dimming
z 300Hz On-Board Ramp Generator
z Input Under Voltage Lockout
z Thermal Shutdown Protection
z RoHS Compliant and Halogen Free
Applications
z Automotive LED Lighting
z High Power LED Lighting
z Indicator and Emergency Lighting
z Architectural Lighting
z Low Voltage Industrial Lighting
z Signage and Decorative LED Lighting
Pin Configurations
(TOP VIEW)
VIN SENSE
54
23
LX GND ADJ
TSOT-23-5
VIN
SENSE
GND
ADJ
8
27
GND
36
9
45
GND
LX
NC
NC
SOP-8 (Exposed Pad)
DS8470-04 August 2011
www.richtek.com
1






RT8470 Datasheet, Funktion
RT8470
Output Current vs. Input Voltage
1.04
ILED = 1A, L = 33μH
8 LED
1.03
1.02
1.01 1 LED
2 LED
1
3 LED
4 LED
5 LED
0.99 6 LED
7 LED
0.98
0
5 10 15 20 25 30 35
Input Voltage (V)
Switching Frequency vs. Input Voltage
800
ILED = 1A, L = 33μH
700
600
500
400
300
200
100
0
0
1 LED
2 LED
3 LED
4 LED
5 LED
6 LED
7 LED
5
8 LED
10 15 20 25
Input Voltage (V)
30
35
Quiescent Input Current vs. Input Voltage
470
465
460
455
450
5
VADJ = 0V
10 15 20 25
Input Voltage (V)
30
www.richtek.com
6
Output Current Deviation vs. Input Voltage
4%4 ILED = 1A, L = 33μH
3%3
8 LED
2%2
1%1
0%0 1 LED
-1-%1 2 LED
3 LED
-2-%2 4 LED
5 LED
-3-%3 6 LED
7 LED
-4-%4
0 5 10 15 20 25 30 35
Input Voltage (V)
Duty Cycle vs. Input Voltage
10100%0 ILED = 1A, L = 33μH
909%0
8 LED
808%0
707%0
606%0
505%0
404%0
303%0
202%0
101%0
0%0
0
1 LED
2 LED
3 LED
4 LED
5 LED
6 LED
7 LED
5
10 15 20 25
Input Voltage (V)
30
35
Quiescent Input Current vs. Input Voltage
1000
900
800
700
600
500
400
300
200
100
0
5
VADJ = 2V
10 15 20 25
Input Voltage (V)
30
DS8470-04 August 2011

6 Page









RT8470 pdf, datenblatt
RT8470
Outline Dimension
EXPOSED THERMAL PAD
(Bottom of Package)
J
A
Y
XB
H
M
F
C
I
D
Symbol
A
B
C
D
F
H
I
J
M
Option 1
Option 2
X
Y
X
Y
Dimensions In Millimeters Dimensions In Inches
Min
4.801
3.810
1.346
0.330
Max
5.004
4.000
1.753
0.510
Min
0.189
0.150
0.053
0.013
Max
0.197
0.157
0.069
0.020
1.194
0.170
1.346
0.254
0.047
0.007
0.053
0.010
0.000
5.791
0.152
6.200
0.000
0.228
0.006
0.244
0.406
2.000
2.000
1.270
2.300
2.300
0.016
0.079
0.079
0.050
0.091
0.091
2.100
3.000
2.500
3.500
0.083
0.118
0.098
0.138
8-Lead SOP (Exposed Pad) Plastic Package
www.richtek.com
12
DS8470-04 August 2011

12 Page





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