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PDF RT9284B Data sheet ( Hoja de datos )
| Número de pieza | RT9284B | |
| Descripción | Constant Current Switching Regulator | |
| Fabricantes | Richtek Technology | |
| Logotipo |  |
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RT9284A/B
Tiny Package, High Performance, Constant Current
Switching Regulator for White LED
General Description
Features
The RT9284A/B is a compact, high efficient and high
integration LED driver. Internal 22V MOSFET can support
2 to 5 White LEDs for backlighting and camera flashing.
Highly integration and internal compensation network
minimizes as 5 external component counts. Optimized
operation frequency can meet the requirement of small
LC filters value and low operation current with high
efficiency. Internal soft start function can reduce the inrush
current. Tiny package type of TSOT-23-5 and TSOT-23-6
packages provide the best solution for PCB space saving
and total BOM cost.
z VIN Operating Range : 2.7V to 5.5V
z Maximum Output Voltage up to 20V
z Dimming with Zero-inrush and Wide Frequency
Range of 100 to 100kHz
z Over Voltage Protection
z Output Current up to 100mA at VOUT = 12V.
z Zero Shutdown Supply Current
z Minimize the External Component
z Small LC Filter
z Internal Soft Start
z RoHS Compliant and 100% Lead (Pb)-Free
Ordering Information
RT9284 (- )
Package Type
J5 : TSOT-23-5
J6 : TSOT-23-6
Applications
z Camera Flash White LED
z Mobile Phone, Smart Phone LED Backlight
z PDA LED Backlight
z Digital Still Camera
Operating Temperature Range
z Camcorder
P : Pb Free with Commercial Standard
G : Green (Halogen Free with
Commercial Standard)
Pin Configurations
OVP Voltage
15 : 15V
20 : 20V
TOP VIEW
VDD
EN
FB Voltage
A : 1.235V
B : 0.25V
54
12 3
Note :
Richtek Pb-free and Green 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.
`100% matte tin (Sn) plating.
LX GND FB
TSOT-23-5
VDD OVP EN
654
Marking Information
For marking information, contact our sales representative
directly or through a Richtek distributor located in your
area, otherwise visit our website for detail.
123
LX GND FB
TSOT-23-6
Note : There is no pin1 indicator on top mark for TSOT-23-6
type, and pin 1 will be lower left pin when reading top mark
from left to right.
DS9w28w4Aw/B.-D05ataASughueset t240U07.com
www.richtek.com
1
1 page  
RT9284A/B
Parameter
MOSFET
On Resistance of MOSFET
Protection
OVP Threshold
OVP Sink Current
OCP
Shut Down Voltage
Enable Voltage
Symbol
Test Condition
Min
RDS(ON)
--
VOVP
VEN
VEN
for 2,3,4 WLEDs application
for 5 WLED application
14
19
--
--
--
1.5
Typ Max Units
0.75
--
Ω
15 16 V
20 21 V
5 -- μA
750 -- mA
-- 0.4 V
-- -- V
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. Devices are ESD sensitive. Handling precaution recommended.
Note 3. The device is not guaranteed to function outside its operating conditions.
Note 4. θJA is measured in the natural convection at TA = 25°C on a low effective thermal conductivity test board of
JEDEC 51-3 thermal measurement standard.
Note 5. Floating the OVP pin to disable OVP function.
DS9284A/B-05 August 2007
www.richtek.com
5
5 Page 
RT9284A/B
L1
VIN C1 4.7uH to 22uH
2.7V to 5.5V
D1
SS0520
VEN > 1.5V
VEN < 0.4V
RT9284A
6 VDD LX 1
4 EN OVP 5
2
GND
FB 3
C2
R2
10k
R3
10k
ILED
R1
110
RDC
3k
2.8V
0V
PWM Signal
CDC
1uF
Figure 7. Filtered PWM Signal for LED Dimming Control
of RT9284A
The LED current can be calculated by the following
equation.
ILED
VFB
=
−
R2
×
(VPWM ×Duty
R3 + RDC
−
VFB
)
R1
20
18
16
14
12
10
8
6
4
2
0
0
10 20
30 40 50 60 70
PWM Duty (%)
80 90 100
Figure 8
Capacitor Selection
Input and output ceramic capacitors of 1μF are
recommended for RT9284A/B applications. For better
voltage filtering, ceramic capacitors with low ESR are
recommended. X5R and X7R types are suitable because
of their wider voltage and temperature ranges.
Diode Selection
Schottky diode is a good choice for RT9284A/B because
of its low forward voltage drop and fast reverse recovery.
Using Schottky diode can get better efficiency. The high-
speed rectification is also a good characteristic of
Schottky diode for high switching frequency. Current rating
of the diode must meet the root mean square of the peak
current and output average current multiplication as
following :
ID (RMS) ≈ (IOUT × IPEAK )
The diode’ s reverse breakdown voltage should be larger
than the output voltage. SS0520 is recommended Schottky
diode for rectifier.
Layout Guide
z A full GND plane without gap break.
z VCC to GND noise bypass–Short and wide connection
for the 1μF MLCC capacitor between Pin6 and Pin2.
z Minimized LX node copper area to reduce EMI.
z Minimized FB node copper area and keep far away from
noise sources.
Inductor Selection
The recommended value of inductor for 3 to 5 WLEDs
applications are 4.7 to 22μH. Small size and better
efficiency are the major concerns for portable device, such
as RT9284A/B used for mobile phone. The inductor should
have low core loss at 1.2MHz and low DCR for better
efficiency. To avoid inductor saturation current rating should
be considered.
Figure 9. Top Layer
DS9284A/B-05 August 2007
www.richtek.com
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet RT9284B.PDF ] | |
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