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PDF ADD5203 Data sheet ( Hoja de datos )
| Número de pieza | ADD5203 | |
| Descripción | White LED Driver with SMBus and PWM Input | |
| Fabricantes | Analog Devices | |
| Logotipo |  |
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8-String, White LED Driver with SMBus and
PWM Input for LCD Backlight Applications
ADD5203
FEATURES
White LED driver based on inductive boost converter
Integrated 50 V MOSFET with 2.9 A peak current limit
Input voltage range: 6 V to 21 V
Maximum output adjustable up to 45 V
350 kHz to 1 MHz adjustable operating frequency
Overvoltage protection (OVP) up to typical 47.5 V
Built-in soft start for boost converter
Drives up to eight LED current strings
LED current adjustable up to 30 mA for each channel
Headroom control to maximize efficiency
Adjustable dimming frequency: 200 Hz to 10 kHz
LED open and short fault protection
Selectable dimming control interface methods
PWM input
SMBus serial input
Selectable dimming modes
Fixed delay PWM dimming control with 8-bit resolution
No delay PWM dimming control with 8-bit resolution
Direct PWM dimming control
DC current dimming control with 8-bit resolution
General
Thermal shutdown
Undervoltage lockout
28-lead, 4 mm × 4 mm × 0.75 mm LFCSP_WQ
APPLICATIONS
Notebook PCs, UMPCs, and monitor displays
FUNCTIONAL BLOCK DIAGRAM
STEP-UP SWITCHING REGULATOR
EIGHT CURRENT SOURCES
PWM DUTY EXTRACTOR
8-BIT BRIGHTNESS CONTROL LOGIC
FIXED DELAY/NO DELAY DIRECT PWM/
DC CURRENT DIMMING CONTROL
WITH PWM AND/OR SMBus INTERFACE
UNDERVOLTAGE LOCKOUT
INTERNAL SOFT START
THERMAL PROTECTION
OVERVOLTAGE PROTECTION
AUTODISABLE FOR LED OPEN/SHORT
Figure 1.
GENERAL DESCRIPTION
The ADD5203 is a white LED driver for backlight applications
based on high efficiency, current-mode, step-up converter tech-
nology. It is designed with a 0.15 Ω, 2.9 A internal switch and a
pin-adjustable operating frequency between 350 kHz and 1 MHz.
The ADD5203 contains eight regulated current sources for
uniform brightness intensity. Each current source can be driven
up to 30 mA, and the LED driving current is pin adjustable by
an external resistor. The ADD5203 drives up to eight parallel
strings of multiple series connected LEDs with a ±1.5% current
matching between strings.
The ADD5203 provides various dimming modes. Each
dimming mode is selectable with an external dimming mode
selection pin. The LED dimming control interface can be
achieved through PWM input and/or SMBus. The device
provides adjustable output dimming frequency range from
200 Hz to 10 kHz by an external resistor and capacitor. The
ADD5203 operates over an input voltage range of 6 V to 21 V,
but the device can function with a voltage as low as 5.6 V.
The ADD5203 also has multiple safety protection features to
prevent damage during fault conditions. If any LED is open or
short, the device automatically disables the faulty current source.
The internal soft start prevents inrush current during startup.
Thermal shutdown protection prevents thermal damage.
The ADD5203 is available in a low profile, thermally enhanced,
4 mm × 4 mm × 0.75 mm, 28-lead, RoHS-compliant lead frame
chip scale package (LFCSP_WQ) and is specified over the
industrial temperature range of −25°C to +85°C.
Rev. 0
Information furnished by Analog Devices is believed to be accurate and reliable. However, no
responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other
rights of third parties that may result from its use. Specifications subject to change without notice. No
license is granted by implication or otherwise under any patent or patent rights of Analog Devices.
Trademarksandregisteredtrademarksarethepropertyoftheirrespectiveowners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781.329.4700
www.analog.com
Fax: 781.461.3113
©2010 Analog Devices, Inc. All rights reserved.
1 page  
ADD5203www.DataSheet4U.com
SMBUS SPECIFICATIONS
VIN = 12 V, SHDN = high, TA = −25°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.
Table 3.
Parameter1
SMBus INTERFACE
Data, Clock Input Low Level
Data, Clock Input High Level
Data, Clock Output Low Level
SMBus TIMING SPECIFICATIONS
Clock Frequency
Bus-Free Time Between Stop and Start Condition
Hold Time After Start Condition2
Repeated Start Condition Setup Time
Stop Condition Setup Time
Data Hold Time
Data Setup Time
Clock Low Period
Clock High Period
Clock/Data Fall Time
Clock/Data Rise Time
Symbol
VIL
VIH
VOL
fSMB
tBUF
tHD:STA
tSU:STA
tSU:STO
tHD:DAT
tSU:DAT
tLOW
tHIGH
tF
tR
Test Conditions
Min
2.1
10
4.7
4.0
4.7
4.0
300
250
4.7
4.0
1 These electrical specifications are guaranteed by design.
2 After this period, the first clock is generated.
Typ
Max
0.8
5.5
0.4
100
50
300
1
Unit
V
V
V
kHz
μs
μs
μs
μs
ns
ns
μs
μs
ns
us
Rev. 0 | Page 5 of 24
5 Page 
ADD5203www.DataSheet4U.com
THEORY OF OPERATION
CURRENT-MODE, STEP-UP SWITCHING REGULATOR
OPERATION
The ADD5203 uses a current-mode PWM boost regulator to
provide the minimal voltage needed to enable the LED string at
the programmed LED current. The current-mode regulation
system allows fast transient response while maintaining a stable
output voltage. By selecting the proper resistor-capacitor network
from COMP to GND, the regulator response can be optimized for
a wide range of input voltages, output voltages, and load conditions.
The ADD5203 can provide a 45 V maximum output voltage and
drive up to 13 LEDs (3.4 V/30 mA type of LEDs) for each channel.
INTERNAL 3.3 V REGULATOR
The ADD5203 contains a 3.3 V linear regulator. The regulator is
used for biasing internal circuitry. The internal regulator requires
a 1 μF bypass capacitor. Place this bypass capacitor between
VDDIO (Pin 4) and GND, as close as possible to Pin VDDIO.
BOOST CONVERTER SWITCHING FREQUENCY
The ADD5203 boost converter switching frequency is user
adjustable, between 350 kHz to 1 MHz, by using an external
resistor, RF. A frequency of 350 kHz is recommended to optimize
the regulator for high efficiency, and a frequency of 1 MHz is
recommended for small external components.
See Figure 14 for considerations when selecting a switching
frequency and an adjustment resistor (RF).
1100
1000
900
800
700
600
500
400
300
120
170 220 270 320 370 420
RF (kΩ)
Figure 14. Switching Frequency vs. RF
470
DIMMING FREQUENCY (fPWM)
The ADD5203 contains an internal oscillator to generate the
PWM dimming signal for LED brightness control. The LED
dimming frequency (fPWM) is adjustable, in the fPWM range of 200 Hz
to 10 kHz, by using an external resistor (RFPWM) and capacitor
(CFPWM). The RFPWM should be in the range of 13 kΩ to 110 kΩ,
and the CFPWM should be in the range of 20 pF to 390 pF.
Table 8. RFPWM and CFPWM Recommendation
Dimming Freq (fPWM)
RFPWM (kΩ)
200 Hz
110
500 Hz
75
1 kHz
50
5 kHz
18
10 kHz
13
CFPWM (pF)
390
200
150
47
20
CURRENT SOURCE
The ADD5203 contains eight current sources to provide accurate
current sinking for each LED string. String-to-string tolerance is
kept within ±1.5% at 20 mA. Each LED string current is adjusted
up to 30 mA by an external resistor.
The ADD5203 contains an LED open and short fault protection
circuit for each channel. If the headroom voltage of the current
source remains below 200 mV while the boost converter output
reaches the OVP level, the ADD5203 recognizes that the current
source has an open load fault for the current source, and the current
source is disabled. If the headroom voltage of the current source
goes above 7.2 V, the current source is disabled for short protection.
If an application requires four LED strings, each LED string
should be connected using FB1 to FB4. Tie the unused FB pins
(FB5 to FB8) to GND.
The ADD5203 contains hysteresis to prevent the LED current
change that is caused by a ±0.195% jitter of the PWM input.
Programming the LED Current
As shown in Figure 2, the ADD5203 has an LED current set pin
(ISET). A resistor (RSET) from this pin to ground adjusts the LED
current up to 30 mA. LED current level can be set with the
following equation:
ILED = 2831 (A)
RSET
DIMMING CONTROL INTERFACE
The ADD5203 dimming control interface method is selectable
between the SMBus serial input and/or the external PWM input.
The LED dimming modes supported by ADD5203 can be
controlled externally through these dimming control interfaces.
The SEL1 and SEL2 pins should be set based on the application
conditions (see Table 9).
Table 9. Brightness Control Mode Selection
SEL1 SEL2 Dimming Mode
High
High
Fixed delay PWM
Low No delay PWM
Open High
Fixed delay PWM
Low No delay PWM
Low
High
DC current
Open DC current
Low Direct PWM
Interface
SMBus
SMBus
PWM
PWM
SMBus
PWM
PWM
Rev. 0 | Page 11 of 24
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet ADD5203.PDF ] | |
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