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LM3520SDX/NOPB Datasheet

Download or read online National Semiconductor LM3520SDX/NOPB IC LED DRVR WT/OLED BCKLGT 14LLP pdf datasheet.



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LM3520
Integrated White LED Driver with Organic LED Display
Power Supply
General Description
The LM3520 is a dual step-up DC/DC converter, designed to
drive up to 5 white LEDs with a constant current and to
power an organic LED display with a constant voltage.
A single external resistor is used to set the maximum LED
current. The LED current can be adjusted by applying a
PWM signal to the EN pin. For higher efficiency the LM3520
operates with pulse frequency modulation (PFM) control
scheme when the sub-display is enabled. When Main dis-
play is enabled, the device is operating in PWM mode.
Overvoltage protection circuitry and a 1MHz switching fre-
quency allow for the use of small, low cost external compo-
nents.
Additional features include a low-side NFET switch that can
turn off the LED string with no DC current path to ground.
The LM3520 is available in a small 14-pin thermally-
enchanced LLP package.
Typical Applications
© 2005 National Semiconductor Corporation
Features
n Integrated OLED and white-LED driver
n 80% efficiency
n Drives up to 5 LEDs at 20mA/3.6V and 4 LEDs at
30mA/3.6V for main-display
n Up to 20V
@
n True shutdown isolation
n Small External Components
n 1 MHz Switching Frequency
n 23V OverVoltage Protection
n Wide Input Voltage Range: 2.7V to 5.5V
n Cycle-By-Cycle Current Limit
n PWM Dimming Control
n Low Profile 14-Pin LLP(3mm x 4mm x 0.8mm)
Applications
n Flip-phones/Clam-shell Cellular Phones
n Handheld Devices
n High-fashion cellular phones
n White LED Backlighting
n Digital Cameras
Main Display with OLED Sub Display
DS201288
September 2005
50mA/3.6V for sub-display
20128803
www.national.com
Specifications of National Semiconductor LM3520SDX/NOPB
Constant Current:
Yes
Constant Voltage:
Yes
Current - Output / Channel:
20mA, 30mA
Efficiency:
80%
Frequency:
800kHz ~ 1.4MHz
Internal Driver:
Yes
Internal Switch(s):
Yes
Mounting Type:
Surface Mount
Number Of Outputs:
2
Operating Temperature:
-40°C ~ 85°C
Package / Case:
14-LLP
Series:
-
Topology:
PWM, Step-Up (Boost)
Type:
Backlight, OLED, White LED
Type - Primary:
Backlight
Type - Secondary:
OLED, White LED
Voltage - Output:
22.5 V ~ 23.2 V
Voltage - Supply:
2.7 V ~ 5.5 V
Other Names:
LM3520SDX

Summary of Contents

Page 1

... LED string with no DC current path to ground. The LM3520 is available in a small 14-pin thermally- enchanced LLP package. Typical Applications © 2005 National Semiconductor Corporation Features n Integrated OLED and white-LED driver n 80% efficiency n Drives LEDs at 20mA/3.6V and 4 LEDs at 30mA/3 ...

Page 2

Functional Block Diagram www.national.com FIGURE 1. Functional Block Diagram 2 20128802 ...

Page 3

Pin Descriptions Pin # Pin Name AGND MAIN_EN 6 SUB_EN 7 PFM_EN 8 SUB_FB 9 V SUB 10 V O_MAIN 11 MAIN_FB 12 MAIN_RTN 13 DGND 14 NC Ordering Information ...

Page 4

Operation Modes LM3520 has two operating modes; Figure 2 shows main display in PWM current mode operation, the appropriate selection of R resistor in series with four white LEDs set FB Note: The current I is very small and ...

Page 5

... Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications O_MAIN V SW Main_FB, Main_RTN MAIN_EN, PFM_EN & SUB_EN(Note 2) Continuous Power Dissipation (Note 3) Maximum Junction Temperature (T ) J-MAX Storage Temperature Range Maximum Lead Temperature ...

Page 6

Electrical Characteristics type apply over the full operating junction temperature range (40C ≤ apply to the LM3520 3.6V, V(En) IN Symbol Parameter OVP Output Over-Voltage Protection (Main & Sub Displays) UVP Input Under-Voltage Protection I V ...

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Typical Performance Characteristics CMMSHI-40 10µ 1µ OUT Switching Quiescent Current vs. Vin (Disconnected LEDs from VO_Main & Rsub1 from Vsub) Close Loop Duty Cycle vs. Load Current (PWM at Main_EN 3.6V ...

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Typical Performance Characteristics CMMSHI-40 10µ 1µ OUT Shutdown Current vs. Vin Feedback Voltage vs. Vin (3 LEDs) Main Display Efficiency (4 LEDs) www.national.com Typical Application circuit Figure 25C , Unless ...

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Typical Performance Characteristics CMMSHI-40 10µ 1µ OUT Main Display Efficiency (2 LEDs) Vsub Efficiency vs. Load (Vsub 18V) Typical PWM Switching Waveform (Vin 3.6V at 30mA LED Current) Typical Application circuit ...

Page 10

Typical Performance Characteristics CMMSHI-40 10µ 1µ OUT Typical PFM Switching Waveform (Vin 3.6V, at 30mA Load Current) www.national.com Typical Application circuit Figure 25C , Unless otherwise Stated. (Continued) A ...

Page 11

Circuit Description The LM3520 is designed for White LED & OLED backlighting in mobile phone applications. It has a main display loop which can drive white LEDS in series and a sub display loop which is designed ...

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Application Information FIGURE 4. The above equation to solve for R SUB1 SUB1 SUB SUB_FB The LM3520 is optimized for 20V over the input voltage range, for higher output current up to 50mA ...

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Application Information tor is sufficient for the main-display. A minimum of 4.7µF output capacitor is recommended for V output capacitor can be used to reduce ripple voltage. The LM3520 has a maximum OVP of 24.2V, a 25V minimum rated capacitor ...

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... BANNED SUBSTANCE COMPLIANCE National Semiconductor manufactures products and uses packing materials that meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no Banned Substances as defined in CSP-9-111S2. ...

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