NOT RECOMMENDED FOR NEW DESIGN
USE AP3019A
AL3050
SMALL PANEL BACKLIGHT LED DRIVER
Description
Pin Assignments
The AL3050 is a current mode Boost-type LED driver with
programmable brightness dimming control for portable devices. With
a 30V rated integrated MOSFET and power diode, the AL3050 can
support up to 8 LEDs in series. The small solution size, advanced
dimming features and high efficiency are suitable for LED backlight
solutions for single cell Li-ion based equipment. The boost converter
runs at 750kHz fixed switching frequency to reduce output ripple,
improve conversion efficiency, and allows for the use of small external
components.
The default LED current is adjustable by an external resister at FB pin
and the feedback voltage is regulated to 200mV typically. The
AL3050 provides PWM dimming mode and single wire digital dimming
mode for accurate LED current control from CTRL pin. In PWM
dimming mode, the feedback reference voltage is changed with the
PWM duty cycle proportionally and the available PWM frequency
range is from 20kHz to 100kHz. In single wire digital dimming mode, it
provides a programmable 32-step brightness dimming function with
the CTRL pin setting.
The AL3050 provides protection functions including Under Voltage
Lockout, Over Voltage Protection, Over Current Protection and Over
Temperature Protection to protect the circuit.
(Top View)
CTRL
1
VIN
2
VOUT
3
Thermal
Pad
6
SW
5
GND
4
FB
U-DFN2020-6 (Type S)
Applications
•
•
•
•
•
•
Feature Phones
Smart Phones
Portable Media Players
Ultra Mobile Devices
GPS Receivers
Backlight for Small and Media Form Factor LCD Display
The AL3050 is available in U-DFN2020-6 (Type S) packages.
Features
•
•
•
•
•
•
2.7V to 5.5V Input Voltage Range
28V Open LED Protection (Up to 8 LEDs)
Integrated 0.7A/30V Internal MOSFET and Power Diode
200mV Reference with ±3% Accuracy
750kHz Switching Frequency
Flexible Digital and PWM Brightness Control
Single Wire Control Interface
PWM Dimming Control Interface
•
•
•
•
•
•
•
•
Up to 100:1 PWM Dimming Ratio
Integrated Loop Compensation
Built-in Soft-Start
Built-in OTP
Built-in OCP
Tiny Package with U-DFN2020-6 (Type S) Package
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Notes:
AL3050
1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com/quality/lead_free.html for more information about Diodes Incorporated’s definitions of Halogen- and Antimony-free, "Green"
and Lead-free.
3. Halogen- and Antimony-free "Green” products are defined as those which contain 3.5ms
Shutdown
…
Startup
Delay
Duty*200mV
0mV
t1w_det>450μs
Program code
Program code
…
CTRL
t1w_win>3.5ms
tOFF>3.5ms
Shutdown
……
200mV
100mV
FB
0mV
Figure 1. Dimming Mode Detection and Soft Start
7. PWM Dimming Mode
When the CTRL pin is constantly high, the FB voltage is regulated to 200mV typically. However, the CTRL pin allows a PWM signal to reduce this
regulation voltage; therefore, it achieves LED brightness dimming. The relationship between the duty cycle and FB voltage is given by Equation 2.
VFB = Duty × 200mV
(2)
Where
Duty = duty cycle of the PWM signal
200mV = internal reference voltage
AL3050
Document number: DS38578 Rev. 3 - 3
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AL3050
Application Information (Cont.)
VBG
200mV
CTRL
Error
Amplifier
EA Output
FB
Figure 2. Block Diagram of Programmable FB Voltage in PWM Dimming Mode
As shown in Figure 2, the AL3050 chops up the internal 200mV reference voltage at the duty cycle of the PWM signal. The pulse signal is then
filtered by an internal low pass filter. The output of the filter is connected to the error amplifier as the reference voltage for the FB pin regulation.
Therefore, although a PWM signal is used for brightness dimming, only the LED DC current is modulated, which is often referred as analog
dimming. This eliminates the audible noise which often occurs when the LED current is pulsed in replica of the frequency and duty cycle of PWM
control.
For optimum performance, use the PWM dimming frequency in the range of 20kHz to 100kHz. Since the CTRL pin is logic only pin, adding an
external RC filter applied to the pin does not work.
The minimum dimming duty cycle the IC can support is 1% within the PWM dimming frequency range 20kHz to 100kHz.
8. Single Wire Digital Dimming Mode
The CTRL pin features a simple digital interface to allow digital brightness control. The digital dimming can save the processor power and battery
life as it does not require a PWM signal all the time, and the processor can enter idle mode if available.
The AL3050 adopts a single wire digital protocol for the digital dimming mode control, which can program the FB voltage to any of the 32 steps
with single command. The step increment increases with the voltage to produce pseudo logarithmic curve for the brightness step. See the Table 1
for the FB pin voltage steps. The default step is full scale when the device is first enabled (VFB = 200mV). The programmed reference voltage is
stored in an internal register. A power reset clears the register value and reset it to default.
AL3050
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AL3050
Application information (Cont.)
-
FB Voltage (mV)
D4
D3
D2
D1
D0
0
0
0
0
0
0
0
1
5
0
0
0
0
1
2
8
0
0
0
1
0
3
11
0
0
0
1
1
4
14
0
0
1
0
0
5
17
0
0
1
0
1
6
20
0
0
1
1
0
7
23
0
0
1
1
1
8
26
0
1
0
0
0
9
29
0
1
0
0
1
10
32
0
1
0
1
0
11
35
0
1
0
1
1
12
38
0
1
1
0
0
13
44
0
1
1
0
1
14
50
0
1
1
1
0
15
56
0
1
1
1
1
16
62
1
0
0
0
0
17
68
1
0
0
0
1
18
74
1
0
0
1
0
19
80
1
0
0
1
1
20
86
1
0
1
0
0
21
92
1
0
1
0
1
22
98
1
0
1
1
0
23
104
1
0
1
1
1
24
116
1
1
0
0
0
25
128
1
1
0
0
1
26
140
1
1
0
1
0
27
152
1
1
0
1
1
28
164
1
1
1
0
0
29
176
1
1
1
0
1
30
188
1
1
1
1
0
31
200
1
1
1
1
1
Table 1. 32-Step Digital Dimming Setting
The digital dimming interface is based on a master-slave structure, where the master is typically a microcontroller or application processor. Figure
3 and Table 2 give an overview of the protocol. The protocol consists of a device specific address byte and a data byte. The device specific
address byte is fixed to 58 hex. The data byte consists of five bits for information, two address bits ("00"), and the RFA bit. The RFA bit set to high
indicates the Request for Acknowledge condition. The Acknowledge condition is only applied if the protocol was received correctly. The advantage
of single wire digital dimming compared with other on pin interfaces is that its bit detection is in a large extent independent from the bit
transmission rate. It can automatically detect bit rates between 1.1kBit/sec and up to 100kBit/sec.
DATA IN
Device Address
DATABYTE
Start DA7 DA6 DA5 DA4 DA3 DA2 DA1 DA0 EOS Start RFA
1
0
0
1
0
1
0
1
A1
A0
D4
D3
D2
D1
D0
EOS
DATA OUT
ACK
Figure 3. Single Wire Digital Protocol Overview
AL3050
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AL3050
Application Information (Cont.)
Byte
Device Address Byte
72 Hex
Data Byte
-
Transmission
Direction
Bit Number
Name
7
DA7
0 (MSB Device Address)
6
DA6
1
5
DA5
0
4
DA4
3
DA3
2
DA2
0
1
DA1
0
0
DA0
0 (LSB Device Address)
7 (MSB)
RFA
Request for acknowledge. If high, acknowledge is applied by
device.
6
A1
0 (Address bit A1)
5
A0
0 (Address bit A0)
4
D4
3
D3
Data bit D3
2
D2
Data bit D2
1
D1
Data bit D1
0 (LSB)
D0
Data bit D0
-
ACK
IN
IN
OUT
Description
1
1
Data bit D4
Acknowledge condition active 0, this condition will only be
applied to case RFA bit is set. Open drain output, line needs to
be pulled high by the host with a pullup resistor. This feature can
only be used if the master has an open drain output stage. In
case of a push pull output stage, acknowledge condition may
not be requested!
Table 2. Single Wire Dimming Bit Description
All bits are transmitted MSB first and LSB last. Figure 4 shows the protocol without acknowledge request (Bit RFA = 0), Figure 5 with acknowledge
(Bit RFA = 1) request. Prior to both bytes, device address byte and data byte, a start condition must be applied. For this, the CTRL pin must be
pulled high for at least tSTART (3.5μs) before the bit transmission starts with the falling edge. If the CTRL pin is already at high level, no start
condition is needed prior to the device address byte. The transmission of each byte is closed with an End of Stream condition for at least tEOS
(3.5μs).
The bit detection is based on a Logic Detection scheme, where the criterion is the relation between tLOW and tHIGH (refer to Figure 6). It can be
simplified to:
High Bit: tHIGH > tLOW, but with tHIGH at least 2x tLOW.
Low Bit: tHIGH < tLOW, but with tLOW at least 2x tHIGH.
The bit detection starts with a falling edge on the CTRL pin and ends with the next falling edge. Depending on the relation between tHIGH and tLOW,
the logic 0 or 1 is detected.
The acknowledge condition is only applied if:
• Acknowledge is requested by setting RFA bit to 1.
• The transmitted device address matches with the device address of the device.
• Device address byte and data byte are received correctly.
AL3050
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AL3050
Application Information (Cont.)
If above conditions are met, after tVAL_ACKN (3.5μs) delay from the moment when the last falling edge of the protocol is detected, an internal
ACKN-MOSFET is turned on to pull the CTRL pin low for the time tACKN (900μs maximum), then the Acknowledge condition is valid. During the
tVAL_ACKN delay, the master controller keeps the line low; after the delay, it should release the line by outputting high impedance and then detect
the acknowledge condition. If it reads back a logic 0, it means the IC has received the command correctly. The CTRL pin can be used again by the
master when the acknowledge condition ends after tACKN time.
Note that the acknowledge condition may only be requested in case the master device has an open drain output. For a push-pull output stage, the
use a series resistor in the CRTL line to limit the current to 500μA is recommended to for such cases as:
• an accidentally requested acknowledge, or
• to protect the internal ACKN-MOSFET.
tSTART
tSTART Address Byte
DATA Byte
Static High
DATA IN
DA7
0
//
Static High
DA0
0
RFA
0
tEOS
//
DO
1
tEOS
Figure 4. Single Wire Digital Dimming Timing, without Acknowledge RFA=0
tSTART Address Byte
tSTART
DATA Byte
Static High
Static High
DATA IN
DA7
0
//
DA0
0
tEOS
RFA
1
//
DO
1 tvalACKN
ACKN
Controller needs to
Pullup Data Line via a
resistor to detect ACKN
DATA OUT
tACKN
Acknowledge
true, Data line
pulled down by
device
Acknowledge
false, no pull
down
Figure 5. Single Wire Digital Dimming Timing, with Acknowledge RFA=1
AL3050
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AL3050
Application Information (Cont.)
//
//
Low Bit
High Bit
Figure 6. Single Wire Digital Dimming - Bit Coding
9. Under Voltage Lockout
An under voltage lockout prevents operation of the device at input voltages below typical 2.2V. When the input voltage is below the under voltage
threshold, the device is shutdown and the internal switch is turned off. If the input voltage rises by under voltage lockout hysteresis, the IC restarts.
10. Thermal Shutdown
An internal thermal shutdown turns off the device when the typical junction temperature of +160°C is exceeded. The device is released from
shutdown automatically when the junction temperature decreases by +20°C.
Ordering Information
AL3050 X - X
Product Name
Package
Packing
FDC: U-DFN2020-6
(Type S)
7 : 7" Tape & Reel
Part Number
Package Code
Package
AL3050FDC-7
FDC
U-DFN2020-6 (Type S)
7” Tape and Reel
Quantity
Part Number Suffix
3000/Tape & Reel
-7
Marking Information
U-DFN2020-6 (Type S)
( Top View )
XX
YWX
AL3050
XX : Identification Code
Y : Year : 0~9
W : Week : A~Z : 1~26 week;
a~z : 27~52 week; z represents
52 and 53 week
X : Internal Code
Part Number
Package
Identification Code
AL3050FDC-7
U-DFN2020-6 (Type S)
Z9
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AL3050
Package Outline Dimensions
Please see http://www.diodes.com/package-outlines.html for the latest version.
U-DFN2020-6 (Type S)
A
A1
A3
Seating Plane
D
D2
Pin #1 ID
E
k
z1
E2
U-DFN2020-6
(Type S)
Dim
Min
Max Typ
A
0.51 0.61 0.56
A1
0.00 0.05 0.02
A3
--0.203
b
0.25 0.35 0.30
D
1.95 2.05 2.00
D2
1.55 1.75 1.65
E
1.95 2.05 2.00
E2
0.86 1.06 0.96
e
0.650 BSC
k
--0.22
L
0.25 0.35 0.30
z
--0.20
z1
--0.175
All Dimensions in mm
L
z
e
b
Suggested Pad Layout
Please see http://www.diodes.com/package-outlines.html for the latest version.
U-DFN2020-6 (Type S)
X2
C
Dimensions
G
C
G
X
X1
X2
Y
Y1
Y2
Y2 Y1
X1
Value
(in mm)
0.650
0.150
0.400
1.690
1.700
0.500
1.000
2.300
Y
X
AL3050
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AL3050
IMPORTANT NOTICE
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DIODES INCORPORATED AND ITS SUBSIDIARIES (“DIODES”) MAKE NO WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
WITH REGARDS TO ANY INFORMATION CONTAINED IN THIS DOCUMENT, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR NON-INFRINGEMENT OF THIRD PARTY
INTELLECTUAL PROPERTY RIGHTS (AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
2.
The Information contained herein is for informational purpose only and is provided only to illustrate the operation of Diodes products
described herein and application examples. Diodes does not assume any liability arising out of the application or use of this document or any
product described herein. This document is intended for skilled and technically trained engineering customers and users who design with Diodes
products. Diodes products may be used to facilitate safety-related applications; however, in all instances customers and users are responsible for
(a) selecting the appropriate Diodes products for their applications, (b) evaluating the suitability of the Diodes products for their intended
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products
are
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and
Conditions
of
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(https://www.diodes.com/about/company/terms-and-conditions/terms-and-conditions-of-sales/) or other applicable terms. This document does not
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AL3050
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