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  Richtek Technology Electronic Components Datasheet  

RT9272 Datasheet

Constant Current LED Driver

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Preliminary
RT9272
High Performance, Constant Current LED Driver
for Dual Panel Mobile Phone
General Description
The RT9272 is a high efficiency step-up DC-DC converter
specifically designed for dual panel mobile phone
applications.
According to SP status, RT9272 can either regulates output
current flowing through series-connected LEDs for main
panel or for sub panel with a common output LC filter. This
along with compact VDFN-10L 3x3 package and high
switching frequency allows less part count and smaller
external components for space and cost saving.
Pulling low EN pin shuts down the chip and reduces the
supply current to less than 1μA. The EN pin also accepts
PWM signal for LED brightness dimming control. The
averaged LED current is well proportional to the duty cycle
of the PWM signal. The internal soft start reduces inrush
current during EN turning on or PWM dimming control.
Other features include OVP, OCP and OTP. OVP prevents
the damages in case of feedback loop open.
Ordering Information
RT9272
Package Type
QV : VDFN-10L 3x3 (V-Type)
Operating Temperature Range
P : Pb Free with Commercial Standard
Note :
RichTek Pb-free 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.
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.
Features
z Low VIN Operating Range : 2.7V to 4.5V
z Maximum Output Voltage up to 16V
z Small LC filter by 1.1MHz Operation Frequency
z Share One Set of Inductor and Schottky Diode for
2 Channels
z Programmable Dimming Function by EN Pin with
100Hz to 1kHz
z 40μA Quiescent Current (Switch-Off)
z Internal Soft-Start Function to Avoid PWM Dimming
Noise.
z Zero Shut Down Supply Current
z Complete Protection : OVP, OCP, OTP and SS
z RoHS Compliant and 100% Lead (Pb)-Free
Applications
z Dual panel mobile phone, with LED backlight
Pin Configurations
(TOP VIEW)
GND 1
FB2 2
CH2 3
VCC 4
CH1 5
10 LX
9 SP
8 OVP
7 EN
6 FB1
VDFN-10L 3x3
Typical Application Circuit
CIN
2.2uF
L SS0520
4.7uF DSH
VIN
4 10
VCC LX
Chip Enable
7
9
EN
SP
RT9272
OVP
CH1
CH2
8
5
3
R1 6 FB1
FB2 2 R2
GND
1
COUT
1uF
Sub-Panel
Main Panel
Figure 1. 2LEDs for Sub panel and 3LEDs for Main panel
DS9272-06 November 2005
www.richtek.com
1


  Richtek Technology Electronic Components Datasheet  

RT9272 Datasheet

Constant Current LED Driver

No Preview Available !

RT9272
Preliminary
CIN
2.2uF
L SS0520
4.7uF DSH
VIN
4 10
VCC LX
Chip Enable
7
9
EN
SP
RT9272
OVP
CH1
CH2
8
5
3
R1 6 FB1
FB2 2 R2
GND
1
COUT
1uF
Sub-Panel
Main Panel
Figure 1. 2LEDs for Sub panel and 4LEDs for Main panel
Note:
L : Measured by Murate LQH32C_53 series 4.7μH with DCR = 0.15Ω
Functional Pin Description
Pin Name
Function
1 GND Ground
2 FB2 Feedback 2. Internal feedback voltage to set FB current of Ch2 as SP pin pull high
3 CH2 Channel 2. Internal FB loop. Connect the cathode of LED to this pin.
4 VCC Voltage Input Pin. Bypass a 2.2uF capacitor to GND to reduce the input noise.
5 CH1 Channel 1. Internal FB loop. Connect the cathode of LED to this pin.
6 FB1 Feedback 1. Internal feedback voltage to set FB current of Ch1 as SP pin pull low
7 EN Chip Enable Pin. Pull low or floating this pin to disable the system. Using a PWM signal on
CE pin can achieve the dimming control.
8 OVP Over Voltage Protection. Detect over voltage condition and latch system until SP, EN or
UVLO reset. Connect directly to the output capacitor.
Selection Pin. Internal MOSFET selection. Pull low to turn on the internal Ch1. Pull high to
9 SP turn on Ch2. As SP input signal change, internal MOSFET of LX pin will turn off 1ms to
prevent the over voltage damage by the output voltage instant change
Switch Pin. Connect this pin to inductor and schottky diode. Minimize the track area to reduce
10 LX
EMI
www.richtek.com
2
DS9272-06 November 2005


Part Number RT9272
Description Constant Current LED Driver
Maker Richtek
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RT9272 Datasheet PDF






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