AL8821

AL8821
40V, 2A BOOST LED DRIVER
Pin Assignments
(Top View)
The AL8821 is a boost converter that delivers an accurate constant
current for MR16 and similar LED Lamps. With proprietary control
scheme, the LED driver is compatible with many commonly used
electronic transformers and provides designs with High Power Factor
(PF) and low Total Harmonic Distortion (THD) for these applications.
The operation frequency is up to 1MHz that allows the use of small
size inductor. With the package of SO-8EP, the AL8821 has small
thermal resistance and can be used for wide range of output power.
The driver can be used for dimmable MR16 application and can be
compatible with leading-edge dimmer and trailing-edge dimmer.
8
NC
7
VCC
3
6
VIN
4
5
NC
SW
1
CS
2
FB
COMP
EP
Features
SO-8EP

Wide Input Voltage Range: 5V to 36V

Internal 40V NDMOS Switches

Continuous Conduction Mode (CCM) Operation

Up to 1MHz Switching Frequency

High PF > 0.9 and Low THD < 30% and low Ripple < 20%

Compatible With Leading-edge Dimmer And Trailing-edge
Dimmer
Applications

Internal Protections


Under Voltage Lock Out (UVLO)

Output Open

Over Temperature Protection (OTP)
Pb-free SO-8EP

Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)

Halogen and Antimony Free. “Green” Device (Note 3)
Notes:



Non-dimmable MR16 Lamps
Dimmable MR16 Lamps
General Illumination Lamps
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 <900ppm bromine, <900ppm chlorine (<1500ppm total Br + Cl) and
<1000ppm antimony compounds.
Typical Applications Circuit
L
D1
Vac
D2
D5
D3
D4
CO
RSET
RHYS
SW
CS
VCC
C3
C4
AL8821
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VIN
AL8821
NEW PRODUCT
Description
FB
RFB
COMP
(Exposed Pad)
January 2015
© Diodes Incorporated
AL8821
Pin Descriptions
Pin Name
1
SW
Integrated MOS Drain
2
CS
Input Current Sense Pin
3
FB
LED Output Current Feedback Pin
4
COMP
5
NC
Not Connected
6
VIN
IC Input Voltage, Adding from Boost Output Voltage
7
VCC
Supply Voltage For Internal Circuit
8
NC
9
Exposed Pad
NEW PRODUCT
Pin Number
Function
Control Loop Compensation Pin
Not Connected
Connected to Ground
Functional Block Diagram
VIN
VCC
6
7
VCC
Internal
Regulator
VREF
VBG
UVLO
Chip_EN
VBG
Bandgap
VIN
OVP
PWM1
OVP
9
LOGIC
Exposed
Pad
2
IHYS
OTP
VFB
CS
CS1
OTP
VCS1
1
VCC
SW
Driver
COMPARATOR
3
FB
PWM1
EA
IHYS
VBG
4
COMP
AL8821
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AL8821
Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified. Note 4)
Symbol
Parameter
NEW PRODUCT
Unit
VIN
VIN Pin Voltage
-0.3 to 40
V
VSW
SW Pin Voltage
-0.3 to 40
V
COMP Pin Voltage
-0.3 to 6
V
VCS
CS Pin Voltage
-0.3 to 6
V
VFB
FB Pin Voltage
-0.3 to 6
V
VCC
VCC Pin Voltage
-0.3 to 6
V
+150
ºC
-65 to +150
ºC
66
°C/W
Lead Temperature (Soldering, 10sec)
+300
ºC
–
ESD (Machine Model)
200
V
–
ESD (Human Body Model)
2000
V
VCOMP
TJ
Operating Junction Temperature
TSTG
Storage Temperature
θJA
Thermal Resistance (Junction to Ambient) (Note 5)
TLEAD
Notes:
Rating
4. Stresses greater than those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only and
functional operation of the device at these or any other conditions beyond those indicated under “Recommended Operating Conditions” is not implied.
Exposure to “Absolute Maximum Ratings” for extended periods may affect device reliability.
5. Device mounted on FR-4 PCB (51mm x 51mm) 2oz copper, minimum recommended pad layout on top layer and thermal vias to bottom layer ground
plane. For better thermal performance, larger copper pad for heat-sink is needed.
Recommended Operating Conditions
Symbol
Parameter
VIN
VIN Pin Voltage
TA
Ambient Temperature
Electrical Characteristics
Symbol
Min
Max
Unit
5
36
V
-40
+105
°C
(@TA = +25°C, unless otherwise specified.)
Parameters
Conditions
Min
Typ
Max
Unit
Input Supply
VIN
VIN Pin Voltage
–
5
–
36
V
IQ
Quiescent Current
No Switching
–
1
–
mA
VUVLO
Under-Voltage Lockout
Voltage
VIN Rising
–
4.2
–
V
VHYS
UVLO Hysteresis
–
–
500
–
mV
VCC Pin Voltage
–
4.5
5
5.5
V
–
Source Current Capability
VCC = 5V
10
–
–
mA
–
Load Regulation
–
–
4
–
%
VCC Regulator
VCC
AL8821
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AL8821
Electrical Characteristics
Symbol
(Cont. @TA = +25°C, unless otherwise specified.)
Parameters
Conditions
Min
Typ
Max
Unit
NEW PRODUCT
Integrated NMOS_BOOST
VDS
MOS Voltage Stress (Note 6)
–
–
40
–
V
IDS
MOS Current Stress (Note 6)
–
–
2
–
A
MOS RDSON
–
–
250
–
mΩ
RDSON
Compensation and Soft Start (COMP Pin)
GEA
Error Amplifier Transconductance
–
–
1000
–
µA/V
IO-H
Sourcing Current
VCOMP = 0.5V
–
68
–
µA
IO-L
Sinking Current
VCOMP = 4.5V
–
68
–
µA
VFB
FB Pin Voltage
–
–
444
–
mV
Boost Sense Voltage Low
Level
VCOMP = 0V
–
-90
–
mV
Hysteresis Current
–
85
100
115
µA
TOTSD
Thermal Shutdown (Note 6)
–
–
+160
–
ºC
THYS
Thermal Shutdown
Hysteresis (Note 6)
–
–
+40
–
ºC
Hysteresis Competitor
VCS_MIN
IHYS
Over-Temperature Protection
Note 6:
These parameters, although guaranteed by design, are not 100% tested in production.
AL8821
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AL8821
Performance Characteristics
Quiescent Current vs. VIN Pin Voltage
Quiescent Current vs. Ambient Temperature
1.2
Quiescent Current (mA)
Quiescent Current (mA)
1.0
0.9
0.8
1.2
1.0
VIN = 12V
0.8
0.7
0.6
0.6
4
8
12
16
20
24
28
32
36
-45
-30
-15
VIN Pin Voltage (V)
0
15
30
45
60
75
90
105
o
Ambient Temperature ( C)
VCC Pin Voltage vs. VIN Pin Voltage
VCC Pin Voltage vs. Ambient Temperature
5.5
5.2
5.4
VIN = 12V
VCC Pin Voltage (V)
VCC Pin Voltage (V)
5.1
5.0
4.9
4.8
4.7
5.3
5.2
5.1
5.0
4.9
4.6
4.5
4
8
12
16
20
24
28
32
4.8
-45
36
-30
-15
VIN Pin Voltage (V)
0
15
30
45
60
75
90
105
o
Ambient Temperature ( C)
FB Pin Voltage vs.VIN Pin Voltage
FB Pin Voltage vs. Ambient Temperature
0.50
0.50
0.48
0.48
FB Pin Voltage (V)
FB Pin Voltage (V)
NEW PRODUCT
1.4
1.1
0.46
0.44
0.42
0.46
0.44
VIN = 12V
0.42
0.40
4
8
12
16
20
24
28
32
36
VIN Pin Voltage (V)
AL8821
Document number: DS37671 Rev. 1 - 2
0.40
-45
-30
-15
0
15
30
45
60
75
90
105
o
Ambient Temperature ( C)
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AL8821
Performance Characteristics (Cont.)
Boost Sense Voltage Low Level vs.
VIN Pin Voltage
Boost Sense Voltage Low Level vs.
Ambient Temperature
-80
Boost Sense Voltage Low Level (mV)
Boost Sense Voltage Low Level (mV)
-82
-84
-86
-88
4
8
12
16
20
24
28
32
-82
-84
-86
36
VIN = 12V
-88
-90
-45
-90
-30
-15
0
15
30
45
60
75
90
105
o
VIN Pin Voltage (V)
Ambient Temperature ( C)
Hysteresis Current vs. VIN Pin Voltage
Hysteresis Current vs. Ambient Temperature
116
114
114
112
Hysteresis Current (A)
VIN = 12V
Hysteresis Current (A)
NEW PRODUCT
-80
112
110
108
110
108
106
104
106
104
4
8
12
16
20
24
28
32
36
102
-45
AL8821
Document number: DS37671 Rev. 1 - 2
-30
-15
0
15
30
45
60
75
90
105
o
VIN Pin Voltage (V)
Ambient Temperature ( C)
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AL8821
Application Information
AL8821 Operation
The AL8821 is a boost converter that delivers an accurate constant current for driving LEDS. With hysteretic control scheme, the LED driver is
compatible with most of commonly used electronic transformers. The driver can be compatible with leading-edge dimmer and trailing-edge dimmer.
L
D1
Vac
D2
D5
D4
NEW PRODUCT
D3
CO
RSET
RHYS
SW
VCC
C3
AL8821
VIN
CS
FB
RFB
COMP
C4
(Exposed Pad)
Figure 1. Typical Application Circuit
LED Current Control
The LED current is controlled by the resistor RFB in Figure 1.
Connected between FB pin and Ground, the nominal average output current in the LED(s) is defined as:
ILED 
0.444
RFB
RSET and RHYS Setting
The Boost converter of the AL8821 operates at continuous conduction mode and is based on hysteresis schematic which has lower threshold and
upper threshold. Refer to Figure 2 depicting the inductor current waveform.
IL
Peak or Upper Threshold
IL
IL(peak)
IL(ave)
IL(val)
Valley or Lower Threshold
tON
tOFF
Time
Figure 2. Inductor Current
When switch SW is turned on, the inductor current flows through R SET and ramps up linearly. The rising current produces a voltage ramp across
RSET. When the voltage across RSET reaches the upper threshold, switch SW is turned off. The inductor current continues to flow through R SET but
decays. The decaying current produces a falling voltage at RSET. When the voltage across RSET falls to the lower threshold, switch SW is turned
on again.
The lower threshold voltage VLT depends on the voltage VCOMP at COMP pin that varies with the input voltage and output load. The equation is
shown as below.
AL8821
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AL8821
Application Information (Cont.)
VLT
 (VCOMP  1.5)  0.6  1.4
mV ,1.5V  VCOMP  5V


16

88mV , 0V  VCOMP  1.5V
The range of VCOMP is from 0V to 5V.
NEW PRODUCT
The upper threshold depends on the lower threshold and the hysteresis value. The hysteresis value is set by external resister RHYS. It is defined as
below.
VHYS  RHYS 100 A
According to the operation principle , the peak to peak current ∆IL and the valley current IL(val) can be obtained by the below equations.
I L ( val) 
I L 
VLT
RSET
VHYS
RSET
Where:
∆IL is the peak to peak current of inductor.
IL(val) is the valley current of inductor.
From the Figure 2, the relationship between IL(peak), IL(val), IL(ave) and ∆IL can be obtained as below.
I L ( peak )  I L ( val)  I L
1
I L ( ave)  I L ( val)   I L
2
Where:
IL(peak) is the peak current of inductor.
IL(ave) is the average current of inductor.
As we know the average current IL(ave) depends on the output power, rated input voltage VIN1 of step-up converter and total efficiency η. So the
average current IL(ave) can be obtained by the following equation.
I L ( ave) 
(VLED  0.444 )  I LED
  VIN1
Where: VLED is the voltage in LEDs.
Set ratio of ∆IL to IL(peak) as K.
AL8821
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AL8821
Application Information (Cont.)
I L
K
I L ( peak )
NEW PRODUCT
RSET and RHYS can be obtained from above equations:
 ((VCOMP  1.5)  0.6  1.4)  (2  K )   VIN 1 103
1.5V  VCOMP  5V

32  (VLED  0.444)  I LED (1-K)

RSET = 
3
 44  (2  K )   VIN 1 10 , 0V  V
COMP  1.5V
 (VLED  0.444)  I LED (1-K)
RHYS =
2  (VLED  0.444)  I LED  K  RSET 104
 VIN 1  (2  K )
When the value of K, η and VCOMP are provided, the value of resister RSET and RHYS can be calculated according to these above equations. In
order to get appropriate efficiency and Electronic Transformer (ET) compatibility, generally K is set between 0.4 and 0.8. Due to the range of
VCOMP is from 0V to 5V, in order to get output voltage regulation, generally VCOMP is set as 3V at rated input voltage.
Inductor Selection
Because of the using of the hysteretic control scheme, the switching frequency in a boost configuration can be adjusted in accordance to the value
of the inductor being used. The value of the inductor can be determined on the desired switching frequency by using the following equation:
L
[VIN1  ( RSET  RL  RDSON )  I L ( ave) ]  [VLED  0.444  VIN1  VF  ( RL  RSET )  I L ( ave) ]
I L [VLED  0.444  VF  (2RSET  2RL  RDSON )  I L ( ave) ]  f SW
Where:
L is the coil inductance.
RL is the coil resistance.
RDSON is the switch SW resistance.
VIN1 is the rated input voltage.
VF is the diode forward voltage.
fSW is the desired switching frequency. Generally 500kHz to 800kHz switching frequency is suggested. Low switching frequency can decrease the
switching loss but need to choose higher inductor values that will result in larger size in order to meet the saturation current. For example the
relationship between switching frequency and inductor value is shown as below Table 1 in the same application system. Considering these factors,
500kHz switching frequency is recommend in typical application.
Inductance Value of L @ Vac = 12Vac, VIN = 22V
VLED = 28V, ILED = 180mA
Operation Frequency of SW at Peak Voltage Of Vac
10µH
840kHz
15µH
800kHz
22µH
680kHz
33µH
465kHZ
Table 1
AL8821
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AL8821
Application Information (Cont.)
VIN OVP Protection
AL8821 has an internal over voltage protection to protect IC from excessive input voltage. When the voltage applied at VIN pin exceeds 39V, it will
turn off the power switch SW. The power switch SW will be turned on again once the voltage at VIN drops below 34V.
NEW PRODUCT
VCC Regulator
The VCC pin requires a capacitor C3 for stable operation and to store the charge for the large GATE switching currents. Choose a 10V rated low
ESR, X7R or X5R, ceramic capacitor for best performance. A 4.7µF capacitor will be adequate for many applications. Place the capacitor close to
the IC to minimize the trace length to the VCC pin and to the IC ground.
An internal current limit on the VCC output protects the excessive on-chip power dissipation. The VCC pin has set the output to 5V (typ.) to protect
the internal FETs from excessive power dissipation caused by not being fully enhanced. If the VCC pin is used to drive extra circuits beside the
AL8821, the extra loads should be limited to less than 8mA.
Output Capacitor CO
The capacitor CO is used to hold the bus voltage and reduce the ripple of LED current when the electronic transformer has no output. For most
applications, it is recommended to use an aluminum electrolytic capacitor with greater than 220µF capacitance.
Compensation Capacitor C4
In applications powered by electronic transformer, the input voltage can change roughly in one cycle of AC power frequency. A 1µF ceramic
capacitor C4 connected from COMP pin to ground help to stabilize the control loop of the regulator.
Diode Selection
For maximum efficiency and performance, the rectifiers (D5) should be fast low capacitance Schottky diodes with low reverse leakage at
maximum operating voltage and temperature. With its low power dissipation, the Schottky diode outperforms other silicon diodes and increases
overall efficiency.
Over Temperature Protection
A over temperature protection feature is to protect the AL8821 from excessive heat damage. When the junction temperature exceeds +160ºC, the
internal FET will be turned off. When junction temperature drops below +120ºC, IC will turn on both FETs and return to normal operation.
AL8821
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AL8821
Ordering Information
NEW PRODUCT
AL8821 XX - XX
Package
Packing
SP : SO-8EP
13 :13" Tape & Reel
Part Number
Package Code
Package
AL8821SP-13
SP
SO-8EP
13” Tape and Reel
Quantity
Part Number Suffix
2500/Tape & Reel
-13
Marking Information
(Top View)
8
7
6
5
Logo
Part Number
AL8821
YY WW X X E
YY : Year : 08, 09, 10~
WW : Week : 01~52; 52
Represents 52 and 53 Week
X X : Internal Code
E : SO-8EP
1
AL8821
Document number: DS37671 Rev. 1 - 2
2
3
4
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AL8821
Package Outline Dimensions (All dimensions in mm(inch).)
(1)
Package Type: SO-8EP
3.800(0.150)
4.000(0.157)
2.110(0.083)
2.750(0.108)
3.402(0.134)
NEW PRODUCT
2.710(0.107)
1.270(0.050)
TYP
4.700(0.185)
5.100(0.201)
0.300(0.012)
0.510(0.020)
5.800(0.228)
6.200(0.244)
0.050(0.002)
0.150(0.006)
1.350(0.053)
1.550(0.061)
0°
8°
0.400(0.016)
1.270(0.050)
0.150(0.006)
0.250(0.010)
Note: Eject hole, oriented hole and mold mark is optional.
AL8821
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AL8821
Suggested Pad Layout
Package Type: SO-8EP
NEW PRODUCT
(1)
Y1
G
Z
X1
Y
E
X
Dimensions
Z
(mm)/(inch)
G
(mm)/(inch)
X
(mm)/(inch)
Y
(mm)/(inch)
X1
(mm)/(inch)
Y1
(mm)/(inch)
E
(mm)/(inch)
Value
6.900/0.272
3.900/0.154
0.650/0.026
1.500/0.059
3.600/0.142
2.700/0.106
1.270/0.050
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AL8821
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INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
(AND THEIR EQUIVALENTS UNDER THE LAWS OF ANY JURISDICTION).
NEW PRODUCT
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Diodes Incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express
written approval of the Chief Executive Officer of Diodes Incorporated. As used herein:
A. Life support devices or systems are devices or systems which:
1. are intended to implant into the body, or
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failure of the life support device or to affect its safety or effectiveness.
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Copyright © 2015, Diodes Incorporated
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AL8821
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