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PDF RT9362A Data sheet ( Hoja de datos )
| Número de pieza | RT9362A | |
| Descripción | White LED Driver | |
| Fabricantes | Richtek Technology | |
| Logotipo |  |
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heet4U.comWhite LED Driver (1w2i0thmCAuCrrheRanrTtg9Se3oP6uu2rmc/Aep)General Description
taSThe RT9362/A is a high efficiency charge pump white LED
adriver. It supports up to 4 white LEDs with regulated
.Dconstant current for uniform intensity. The RT9362/A
wmaintains the highest efficiency by utilizing a x1/x1.5/x2
wfractional charge pump and low dropout current regulators.
wUser can easily configure each LED current up 30mA by
Features
z Very High Efficiency Over 90% of Battery Life
z Support up to 4 WLEDs
z Support up to 120mA Output Current
z Soft Start Function
z Short Circuit Protection Function
z Three Charge Pump Mode: x1, x1.5, x2
an external resistor. Two digital inputs can be programm-
able to control white LED On/Off. LED dimming can be
machieved by applying a PWM signal to the digital control
osignals.
.cThe operating voltage range is 2.5V to 5.5V. Internal soft-
start circuitry effectively reduces the in-rush current both
Uwhile start-up and mode change. RT9362/A also provides
comprehensive protections such short circuit protection
t4and over-temperature protection. The load is disconnected
from VIN while shutdown and the shutdown current is less
ethan 1uA. RT9362/Ais available in a QFN-16L 3x3 package.
heOrdering Information
SRT9362/A
taPackage Type
QV : QFN-16L 3x3 (V-Type)
aOperating Temperature Range
P : Pb Free with Commercial Standard
.D250kHz
1MHz
wNote :
RichTek Pb-free products are :
w−RoHS compliant and compatible with the current require-
wments of IPC/JEDEC J-STD-020.
z 250k/1MHz Fixed Frequency Oscillator
z RoHS Compliant and 100% Lead (Pb)-Free
Applications
z Mobile Phone
z White LED Backlighting
z Camera Flash LED Lighting
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.
Pin Configurations
(TOP VIEW)
12 11 10 9
LED4 13
LED3 14
LED2 15
GND
LED1 16
1234
8 C1P
7 VIN
6 VOUT
5 ISET
−Suitable for use in SnPb or Pb-free soldering processes.
−100%matte tin (Sn) plating.
DS9362/A-06 September 2005
QFN-16L 3x3
.DataSheet4U.comwww.richtek.com
www 1
1 page  
Operation
The RT9362/A is a high efficiency charge pump white LED
driver. It provides 4 channels low drop-out voltage current
source to regulated 4 white LEDs current. For high
efficiency, the RT9362/A implements x1/x1.5/x2 mode
charge pump. An external RSET is used to set the current
of white LED. RT9362/A has an input current regulation to
reduce the input ripple.
Soft Start
The RT9362/A includes a soft start circuit to limit the inrush
current at power on and mode switching. Soft start circuit
holds the input current level long enough for output
capacitor COUT reaching a desired voltage level. When the
soft start off, the RT9362/A won’ t sink spike current from
VIN.
Mode Decision
The RT9362/A uses a smart mode decision method to
select the working mode for maximum efficiency. Mode
decision circuit senses the output and LED voltage for
up/down selection.
Dimming Control
CTRL0 and CTRL1 are used to control the on/off of White
LED. When an external PWM signal is connected to the
control pin, brightness of white LED is adjusted by the
duty cycle.
RT9362/A
LED Current Setting
The current of white LED connected to RT9362/A can be
set by RSET. Every current flows through the white LED is
440 times greater than the current of RSET. The white LED
can be estimated by following equation:
ILED
=
440
x
⎜⎛
⎝
VISET
RSET
⎟⎞
⎠
where VISET = 1.1V, and RSET is the resistance connected
from ISET to GND.
Thermal Shutdown
The RT9362/A provides a high current capability to drive 4
white LEDs. A thermal shutdown circuit is needed to
protect the chip from thermal damage. When the chip
reaches the shutdown temperature 150°C, the thermal
shutdown circuit turns off the chip to prevent the thermal
accumulation in the chip.
Overvoltage Protection
The RT9362/A regulates the output voltage by controlling
the input current. When the output voltage reaches the
designated level, the RT9362/A reduces the input current.
And then, the output voltage regulation also serves an
over-voltage protection.
Short Circuit Protection
A current limiting circuit is also included in the RT9362/A
for short circuit protection. Whenever output source a
dangerously high current, the current limiting circuit takes
over the output regulation circuit and reduces the output
current at an acceptable level.
Table 2
Control Inputs
CTRL 1
CTRL 0
00
01
10
11
LED 4
OFF
OFF
ON
OFF
Output Status
LED 3
LED 2
OFF
ON
ON ON
ON ON
OFF
OFF
LED 1
ON
ON
ON
OFF
DS9362/A-06 September 2005
www.richtek.com
5
5 Page 
Applications Information
Selecting Capacitors
To get the better performance of RT9362/A, the selecting
of peripherally appropriate capacitor and value is very
important. These capacitors determine some parameters
such as input and output ripple, power efficiency,
maximum supply current by charge pump, and start-up
time. To reduce the input and output ripple effectively, the
low ESR ceramic capacitors are recommended. Generally,
to reduce the output ripple, increasing the output
capacitance COUT is necessary. However, this will increase
the start-up time of output voltage.
For LED driver applications, the input voltage ripple is more
important than output ripple. Input ripple is controlled by
input capacitor CIN, increasing the value of input
capacitance can further reduce the ripple. Practically, the
input voltage ripple depends on the power supply’s
impedance. If a single input capacitor CIN cannot satisfy
the requirement of application, it is necessary to add a
low-pass filter as shows in Figure 1.
VIN
2.2uF
1
2.2uF
RT9362/A
VIN
Frgure1. C-R-C filter used to reduce input ripple
The flying capacitor C1 and C2 determine the supply current
capability of the charge pump and to influence the overall
efficiency of system. The lower value will improve
efficiency, but it will limit the LED’ s current at low input
voltage.
Setting the LED Current
The RT9362/A can be set a fixed LEDs current by a resister
RSET connected from ISET to GND. RSET establishes the
reference current and mirrors the current into LED1, LED2,
LED3, and LED4. The current into LED is about 440 times
of the current flows through the RSET, the approximate
setting formula is given as follows:
ILED
(A)
=
484
RSET
(V)
(Ω)
(1)
RT9362/A
Figure 2 shows the typical value of RSET versus average
LED current and Table 3 shows the values of RSET for a
fixed LED current.
100
90
80
70
60
50
40
30
20
10
0
0
5 10 15 20 25
LED average current (mA)
30
Figure 2. The typical curve of RSET vs. LED's average
current.
ILED
(mA)
5
10
15
20
25
30
Table 3. RSET Value Selection
RSET Nearest Standard Values for
(kΩ)
RSET (kΩ)
91.0 91.0
47.9 47.5
32.7 32.4
24.0 24.0
19.6 19.6
16.4 16.5
If maximum accuracy is required, a precision resister is
needed. Equation (2) shows how to calculate the error
ILED(ERR).
ILED(ERR) =
ILED(MEA) − ILED(SET)
ILED(SET)
× 100%
(2)
Where ILED(MEA) is practical LED current ILED(SET) is LED
current which is determined by the RSET.
DS9362/A-06 September 2005
www.richtek.com
11
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