Motore di ricerca datesheet componenti elettronici
  Italian  ▼
ALLDATASHEETIT.COM

X  

LM3520_0509 Scheda tecnica(PDF) 11 Page - National Semiconductor (TI)

[Old version datasheet] Texas Instruments acquired National semiconductor.
Il numero della parte LM3520_0509
Spiegazioni elettronici  Integrated White LED Driver with Organic LED Display Power Supply
Download  14 Pages
Scroll/Zoom Zoom In 100%  Zoom Out
Produttore elettronici  NSC [National Semiconductor (TI)]
Homepage  http://www.national.com
Logo NSC - National Semiconductor (TI)

LM3520_0509 Scheda tecnica(HTML) 11 Page - National Semiconductor (TI)

Back Button LM3520_0509 Datasheet HTML 6Page - National Semiconductor (TI) LM3520_0509 Datasheet HTML 7Page - National Semiconductor (TI) LM3520_0509 Datasheet HTML 8Page - National Semiconductor (TI) LM3520_0509 Datasheet HTML 9Page - National Semiconductor (TI) LM3520_0509 Datasheet HTML 10Page - National Semiconductor (TI) LM3520_0509 Datasheet HTML 11Page - National Semiconductor (TI) LM3520_0509 Datasheet HTML 12Page - National Semiconductor (TI) LM3520_0509 Datasheet HTML 13Page - National Semiconductor (TI) LM3520_0509 Datasheet HTML 14Page - National Semiconductor (TI)  
Zoom Inzoom in Zoom Outzoom out
 11 / 14 page
background image
Circuit Description
The LM3520 is designed for White LED & OLED backlighting
in mobile phone applications. It has a main display loop
which can drive up to 5 white LEDS in series and a sub
display loop which is designed to drive OLED up to 20V/50
mA. The main display loop employs a fixed frequency cur-
rent mode scheme to regulate the LED current. The sub
display loop employs a fixed frequency gated oscillator
scheme to regulate the output voltage. The device has two
independent control pins to enable the Main or Sub displays.
Note that both displays can not be ON at the same time.
PWM Operation
The LM3520 utilizes a synchronous Current Mode PWM
control scheme to regulate the feedback voltage over all load
and line conditions for the main display. The LM3520 is
internally compensated preventing the need for external
compensation components yielding a compact solution. The
operation can best be understood referring to the functional
block diagram. The LM3520 operates as follows: During the
first cycle, the oscillator sets the driver logic and turns on the
NMOS power device conducting current through the inductor
and reverse biases the external diode isolating the output
from the V
SW node.
The LED current is supplied by the output capacitor when
the NMOS power device is active. During this cycle, the
output voltage of the EAMP controls the current through the
inductor. This voltage will increase for larger loads and de-
crease for smaller loads limiting the peak current in the
inductor. The sum of the EAMP voltage and voltage ramp is
compared with the sensed switch voltage. Once these volt-
ages are equal, the PWM COMP will then reset the logic
turning off the NMOS power device and forward biasing the
external diode to the white LED load and flows through the
diode to the white LED load and output capacitor. The induc-
tor current recharges the output capacitor and supplies the
current for the white LED branches. The oscillator then sets
the driver logic again repeating the process.
PFM Operation
The LM3520 utilizes a gated oscillator control scheme for the
sub-display. There is a hysteresis window to regulate the
output voltage. The oscillator frequency is the same as the
frequency in PWM control. The Duty cycle of the oscillator
signal is always set to maximum. During the first part of each
switching cycle, the internal NMOS switch is turned on until
the PFM current limit is reached. When the NMOS is off, the
voltage of the inductor reverses and forces current through
the diode to the output capacitor. This process continues
until the upper comparator hysteresis is reached at which
point the NMOS is disabled until the lower comparator
threshold is reached and the process repeats again.
Current Limit Protection
The LM3520 has current limiting protection to prevent exces-
sive stress on itself and external components during over-
load conditions. The internal current limit comparator will
disable the NMOS power device at a typical switch peak
current limit of 700 mA.
Output Over-Voltage Protection
The LM3520 contains dedicated circuitry for monitoring the
output voltage. In the event that the primary LED network is
disconnected the output will increase and be limited to 23.2V
(typ.). There is a ~1V hysteresis associated with this cir-
cuitry, which will turn the NMOS off when the output voltage
is at 24.2V(max.) until the output voltage reach 22.5V(typ.)
or lower. The 23.5V limit allows the use of 25V 1 µF ceramic
output capacitors creating an overall small solution for white
LED applications.
Under Voltage Protection
The LM3520 has an UVP comparator to turn the NMOS
power device off in case the input voltage or battery voltage
is too low preventing an on state of the power device con-
ducting large amounts of current.
Reliability and Thermal Shutdown
The LM3520 has an internal thermal shutdown function to
protect the die from excessive temperatures. The thermal
shutdown trip point is typically 160˚C, Normal operation re-
sumes when the temperature drops below 140˚C.
Startup
The LM3520 does not include a power on reset circuit and
relies on external signal to monitor enable signal. In the
event of under voltage condition, the device enable pin must
be brought low until the input voltage is above the minimum
guarantee voltage (2.7V).
Application Information
SETTING LED CURRENT
The White LED current is set using the following equation:
For main display:
(1)
PWM CONTROL
The LED current can be controlled using a PWM signal on
the enable pin with frequencies in the range of 100 Hz to
1 kHz. LM3520 LED current can be controlled with PWM
signal frequencies above 1 kHz but LED current is not
linearly porportional to the duty cycle. The maximum LED
current would be achieved using the equation above with
100% duty cycle, ie. The enable pin is always high.
SETTING SUB VOLTAGE
Sub-display voltage is be set by choosing R
SUB1 and RSUB2
as illustrated in Figure 4.V
SUB is calculated as follow:
(2)
www.national.com
11


Codice articolo simile - LM3520_0509

Produttore elettroniciIl numero della parteScheda tecnicaSpiegazioni elettronici
logo
National Semiconductor ...
LM3520 NSC-LM3520 Datasheet
963Kb / 14P
   Integrated White LED Driver with Organic LED Display Power Supply
More results

Descrizione simile - LM3520_0509

Produttore elettroniciIl numero della parteScheda tecnicaSpiegazioni elettronici
logo
Sipex Corporation
SP6415 SIPEX-SP6415 Datasheet
1Mb / 12P
   Integrated White LED Driver With Organic LED Display Power Supply
logo
National Semiconductor ...
LM3520 NSC-LM3520 Datasheet
963Kb / 14P
   Integrated White LED Driver with Organic LED Display Power Supply
logo
Analog Microelectronics
AME5136 AME-AME5136 Datasheet
391Kb / 15P
   Integrated White LED Driver With Organic LED Display Power Supply
logo
Linear Technology
LT3591 LINER-LT3591_15 Datasheet
298Kb / 16P
   White LED Driver with Integrated Schottky
logo
Global Mixed-mode Techn...
G2500 GMT-G2500 Datasheet
130Kb / 2P
   Integrated Power Supply for TFT-LCD Panels with 1-Channel White LED Driver
G5524A GMT-G5524A Datasheet
136Kb / 2P
   Integrated Power Supply for TFT-LCD Panels with 4-Channel White LED Driver
logo
FSP TECHNOLOGY INC.
FSP102-3FS01 FSP-FSP102-3FS01 Datasheet
204Kb / 1P
   Power supply with LED Driver
logo
STMicroelectronics
STLD40D STMICROELECTRONICS-STLD40D Datasheet
306Kb / 14P
   White led power supply for large display backlight
STLD40D STMICROELECTRONICS-STLD40D_V01 Datasheet
345Kb / 16P
   White LED power supply for large display backlight
May 2011 Rev 7
logo
Freescale Semiconductor...
MC34844 FREESCALE-MC34844 Datasheet
1Mb / 37P
   10 Channel LED Backlight Driver with Integrated Power Supply
More results


Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14


Scheda tecnica Scarica

Go To PDF Page


Link URL




Privacy Policy
ALLDATASHEETIT.COM
Lei ha avuto il aiuto da alldatasheet?  [ DONATE ] 

Di alldatasheet   |   Richest di pubblicita   |   contatti   |   Privacy Policy   |   scambio Link   |   Ricerca produttore
All Rights Reserved©Alldatasheet.com


Mirror Sites
English : Alldatasheet.com  |   English : Alldatasheet.net  |   Chinese : Alldatasheetcn.com  |   German : Alldatasheetde.com  |   Japanese : Alldatasheet.jp
Russian : Alldatasheetru.com  |   Korean : Alldatasheet.co.kr  |   Spanish : Alldatasheet.es  |   French : Alldatasheet.fr  |   Italian : Alldatasheetit.com
Portuguese : Alldatasheetpt.com  |   Polish : Alldatasheet.pl  |   Vietnamese : Alldatasheet.vn
Indian : Alldatasheet.in  |   Mexican : Alldatasheet.com.mx  |   British : Alldatasheet.co.uk  |   New Zealand : Alldatasheet.co.nz
Family Site : ic2ic.com  |   icmetro.com