AL9901

AL9901
UNIVERSAL HIGH VOLTAGE LED DRIVER
Description
Pin Assignments
The AL9901, high-voltage PWM LED driver provides an efficient
solution for offline, high-brightness LED lamps for rectified line
voltages ranging from 85VAC up to 305VAC. The AL9901 has an
internal MOSFET that allows switching frequencies up to 300kHz,
with the switching frequency determined by an external single
resistor. The AL9901 topology creates a constant current through the
LEDs providing constant light output. The output current is
programmed by one external resistor.
The LED brightness can be varied by both Linear and PWM dimming,
using the AL9901’s LD and PWM pins respectively. The PWM input
operates with a duty ratio of 0-100% and a frequency of up to several
kHz.
U-DFN6040-12
The AL9901 is available in the thermally enhanced U-DFN6040-12
and SO-16 packages. The SO-16 is compliant to high voltage spacing
rules for 230VAC mains applications.
Features
•
•
>90% Efficiency
Universal Rectified 85 to 305VAC Input Range
•
•
•
•
•
•
•
•
•
•
Internal MOSFET Up to 650V, 2A
High Switching Frequency Up to 300kHz
Internal Voltage Regulator Removes Start-Up Resistor
7.5V Regulated Output
Tighter Current Sense Tolerance Better Than 5%
LED Brightness Control with Linear and PWM Dimming
Internal Over-Temperature Protection (OTP)
U-DFN6040-12 and SO-16 Packages
Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)
Halogen and Antimony Free. “Green” Device (Note 3)
Notes:
SO-16
Applications
•
•
•
•
•
LED Offline Lamps
High Voltage DC-DC LED Driver
Signage and Decorative LED Lighting
Back Lighting of Flat Panel Displays
General Purpose Constant Current Source
1. No purposely added lead. Fully EU Directive 2002/95/EC (RoHS) & 2011/65/EU (RoHS 2) compliant.
2. See http://www.diodes.com 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
AL9901
Document number: DS37713 Rev. 1 - 2
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AL9901
Pin Descriptions
Pin Name
Gate
NC
PWM
U-DFN5040-10
1
2
3
VDD
4
LD
5
SO-16
Functions
14
Gate of Internal MOSFET switch.
1, 2, 4, 10,16 No connection
5
Low Frequency PWM Dimming pin, also Enable input. Internal 200kΩ pull-down to GND
Internally regulated supply voltage, 7.5V nominal.
Can supply up to 1 mA for external circuitry. A sufficient storage capacitor is used to provide
storage when the rectified AC input is near the zero crossing.
6
7
8
ROSC
6
VIN
CS
GND
7
9
8
9
DRV
10
11
12
13
SO
SW
EP1
11
12
EP1
EP2
EP2
15
3
NA
NA
Linear Dimming input. Changes the current limit threshold at current sense comparator and
changes the average LED current.
Oscillator control.
A resistor connected between this pin and ground puts the AL9901 into fixed frequency mode and
sets the switching frequency. A resistor connected between this pin and Gate pin puts the AL9901
into fixed off-time mode and determines the off-time.
Input voltage
Senses LED string and internal MOSFET switch current
Device ground
Gate driver output. Connect a resistor between this pin and ROSC pin to put the AL9901 into fixed
off time mode.
Source of the internal MOSFET Switch
Drain of the internal MOSFET switch.
Exposed Pad 1(bottom). Drain connection of internal power MOSFET.
Exposed Pad 2 (bottom). Substrate connection of control IC. Connect to GND directly underneath
the package and large PCB area to minimise junction to ambient thermal impedance.
Functional Block Diagram
AL9901
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AL9901
Absolute Maximum Ratings (Note 4) (@TA = +25°C, unless otherwise specified.)
Symbol
Parameter
Ratings
Unit
Maximum Input Voltage, VIN, to GND
-0.5 to +520
V
VCS
Maximum CS Input Pin voltage Relative to GND
-0.3 to +0.45
V
VLD
Maximum LD Input Pin Voltage Relative to GND
-0.3 to (VDD +0.3)
V
Maximum PWM_D input Pin Voltage Relative to GND
-0.3 to (VDD +0.3)
V
VIN(MAX)
VPWM_D
VSW
Maximum MOSFET Drain Pin Voltage Relative to GND
-0.5 to +650
V
VSO
Maximum MOSFET Source Pin Voltage Relative to GND
-0.5 to (VDD +0.3)
V
VGate
Maximum MOSFET GATE pin Voltage Relative to GND
-0.5 to (VDD +0.3)
V
8.1
V
VDD(MAX)
PDIS
Maximum VDD Pin Voltage Relative to GND
Continuous Power Dissipation (TA = +25°C)
U-DFN6040-12 (derate 10mW/°C above +25°C)
-
-
-
1,000
mW
TJ
Junction Temperature Range
+150
°C
TST
ESD HBM
Storage Temperature Range
-65 to +150
°C
2,000
V
Notes:
Human Body Model ESD Protection (Note 5)
4. Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional
operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
All voltages are with respect to Ground. Currents are positive into, negative out of the specified terminal.
5. Semiconductor devices are ESD sensitive and may be damaged by exposure to ESD events. Suitable ESD precautions should be taken when handling
and transporting these devices
Maximum Ratings of Internal MOSFET (@TA = +25°C, unless otherwise specified.)
Characteristic
Symbol
Value
Units
VDSS
650
V
VGSS
±30
V
ID
1.6
1
A
IDM
3
A
Avalanche Current (Note 7) VDD = 100V, VGS = 10V, L = 60mH
IAR
0.8
A
Repetitive Avalanche Energy (Note 7) VDD = 100V, VGS = 10V, L = 60mH
EAR
22
mJ
Peak Diode Recovery
dv/dt
5
V/ns
Drain-Source Voltage
Gate-Source Voltage
Continuous Drain Current (Note 5) VGS = 10V
Steady
State
TC = +25°C
TC = +100°C
Pulsed Drain Current (Note 6)
Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.)
Symbol
Min
Max
Input DC Supply Voltage Range
15
500
V
TA
Ambient Temperature Range (U-DFN6040-12)
-40
+105
°C
TA
Ambient Temperature Range (SO-16)
-40
+85
-
VINDC
Parameter
Unit
ISW
Switch Pin Output Current
-
0.4
A
VDD
Maximum Recommended Voltage Applied to VDD Pin (Note 6)
-
8.1
V
VEN(lo)
Pin PWM_D Input Low Voltage
0
1
VEN(hi)
Pin PWM_D Input High Voltage
2.4
VDD
Note:
V
6. When using the AL9901 in isolated LED lamps, an auxiliary winding might be used.
AL9901
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AL9901
Electrical Characteristics (@TA = +25°C, unless otherwise specified.)
Specifications apply to AL9901 unless otherwise specified
Symbol
Parameter
IInsd
Shut-Down Mode Supply Current
VDD
Internally Regulated Voltage
IDD(ext)
Conditions
Pin PWM_D to GND,
VIN = 15V
VIN = VIN(MIN) ~ 500V, (Note 8) lDD(ext) = 0,
Gate pin open
VDD Current Available for External Circuitry VIN = 15 to 100V (Note 7)
UVLO
VDD Under Voltage Lockout Threshold
∆UVLO
VDD Under Voltage Lockout Hysteresis
VDD falling
RPWM_D
PWM_D Pull-Down Resistance
VPWM_D= 5V
VT
MOSFET Threshold Voltage
VFD
MOSFET Diodes Forward Voltage
VDD rising
tDELAY
1
mA
7.2
7.5
8.1
V
-
-
1.0
mA
6.4
6.7
7.2
V
-
mV
kΩ
ISW = 0.5A
-
3
-
V
ID = 0.5A
-
0.85
-
V
-
VLD
0.5
250
TA = -40°C to +125°C
tBLANK
-
200
Drain-Source On-Resistance
Maximum Oscillator PWM Duty Cycle
Unit
500
Current Sense Threshold Voltage
DMAXhf
Max
-
VCS(hi)
Oscillator Frequency
Typ
150
RDS(ON)
fOSC
Min
-
4.4
-
Ω
237.5
250
262.5
mV
ROSC = 1MΩ
20
25
30
ROSC = 226kΩ
80
100
120
-
-
100
%
fPWMhf = 25kHz, at GATE, CS to GND.
kHz
Linear Dimming Pin Voltage Range
TA = <125°C, VIN = 15V
0
-
250
mV
Current Sense Blanking Interval
VCS = 0.45V, VLD = VDD
160
250
440
ns
Delay From CS Trip to GATE lo
VIN = 15V, VLD = 0.15,
VCS = 0 to 0.22V after TBLANK
-
-
300
ns
TSD
Thermal Shut-Down
-
-
+150
-
TSDH
Thermal Shut-Down Hysteresis
-
-
+50
-
-
65
-
°C/W
-
5
-
°C/W
-
100
-
°C/W
-
15
-
°C/W
θJA
Thermal Resistance Junction-to-Ambient
θJC
Thermal Resistance Junction-to-Case
θJA
Thermal Resistance Junction-to-Ambient SOIC-16
Thermal Resistance Junction-to-Case
θJC
Notes:
U-DFN6040-12 (Note 8)
°C
7. Also limited by package power dissipation capability, whichever is lower.
8. Device mounted on FR-4 PCB (25mm x 25mm 1oz copper, minimum recommended pad layout on top. For better thermal performance, larger
copper pad for heat-sink is needed.
AL9901
Document number: DS37713 Rev. 1 - 2
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AL9901
Internal MOSFET Characteristic
OFF CHARACTERISTICS (Note 9)
Symbol
Min
Typ
Max
Drain-Source Breakdown Voltage
BVDSS
Zero Gate Voltage Drain Current
IDSS
Gate-Source Leakage
Unit
Test Condition
650
—
—
V
VGS = 0V, ID = 250µA
—
—
1
µA
VDS = 650V, VGS = 0V
IGSS
—
—
±100
nA
VGS = ±30V, VDS = 0V
VGS(th)
3
—
5
V
VDS = VGS, ID = 250µA
RDS (ON)
—
4
5
Ω
VGS = 10V, ID = 1A
VSD
—
0.7
1
V
VGS = 0V, IS = 1A
Ciss
—
479
—
pF
Output Capacitance
Coss
—
29
—
pF
Reverse Transfer Capacitance
Crss
—
pF
Rg
—
1.9
2
—
Gate Resistance
—
Ω
Total Gate Charge
Qg
—
14
—
nC
Gate-Source Charge
Qgs
—
2.5
—
nC
nC
ON CHARACTERISTICS (Note 9)
Gate Threshold Voltage
Static Drain-Source On-Resistance
Diode Forward Voltage
DYNAMIC CHARACTERISTICS (Note 10)
Input Capacitance
Gate-Drain Charge
Qgd
—
7.3
—
Turn-On Delay Time
tD(on)
—
17
—
ns
Turn-On Rise Time
tr
—
33
—
ns
Turn-Off Delay Time
tD(off)
—
31
—
ns
Turn-Off Fall Time
tf
—
25
—
ns
Body Diode Reverse Recovery Time
trr
—
174
—
ns
—
884
—
nC
Body Diode Reverse Recovery Charge
Notes:
Qrr
VDS = 25V, VGS = 0V,
f = 1MHz
VDS = 0V, VGS = 0V, f = 1MHz
VDS = 520V, VGS = 10V,
ID = 2A
VDS = 325V, VGS = 10V,
RG = 25Ω, ID = 2.5A
VDS = 100V, IF = 2A,
di/dt = 100A/µs
9. Short duration pulse test used to minimize self-heating effect.
10. Guaranteed by design. Not subject to production testing.
AL9901
Document number: DS37713 Rev. 1 - 2
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AL9901
3.0
460
2.5
440
2.0
420
INPUT CURRENT (µA)
CURRENT SENSE THRESHOLD (mV)
Typical Characteristics
1.5
1.0
0.5
0.0
400
360
340
320
-1.0
300
-1.5
-40
280
-40
-15
10
35
60
AMBIENT TEMPERATURE (°C)
85
Input Current vs. Ambient Temperature
1.5
SHORT CIRCUIT OUTPUT CURRENT (mA)
450
1.0
CHANGE IN FREQUENCY (%)
V IN = 15V
380
-0.5
-15
10
35
60
85
AMBIENT TEMPERATURE (°C)
Change in Current Sense Threshold vs. Ambient Temperature
V IN = 400V
0.5
ROSC = 226kΩ
0.0
-0.5
ROSC = 1M Ω
-1.0
-1.5
-2.0
-40
-15
10
35
60
85
AMBIENT TEMPERATURE (°C)
Change in Oscillation Frequency vs. Ambient Temperature
ILED(NOM) = 180mA
400
350
300
250
200
150
85 105 125 145 165 185 205 225 245 265
INPUT VOLTAGE (VRMS )
180mA LED Driver Short Circuit Output Current vs. Input Voltage
100
ILED = 281mA
V IN = 264V
90
T A = 23.5C
80
IOUT MAX (%)
70
60
50
40
30
20
10
0
0
50
100
150
200
250
V LD DIMMING CONTROL (mV)
I OUT MAX vs. V LD Dimming Control
AL9901
Document number: DS37713 Rev. 1 - 2
300
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AL9901
Typical Characteristics (continued) measured using AL9901EV4
200
95
15 LEDs
14 LEDs
190
18 LE Ds
EFFICIENCY (%)
IOUT MAX (mA)
180
16 LEDs
170
17 LEDs
160
90
17 LE Ds
14 LEDs
16 LEDs
85
15 LEDs
150
18 LEDs
140
85
80
85
105 125
145 165 185 205 225 245 265
INPUT VOLTAGE (VRMS )
180mA LED Driver Output Current vs. Input Voltage
0.95
105 125
145 165 185 205 225 245 265
INPUT VOLTAGE (VRMS )
180mA LED Driver Efficiency vs. Input Voltage
12
17 LEDs
18 LEDs
18 LEDs
0.9
POWER (W)
POWER FACTOR
10
16 LEDs
0.85
17 LEDs
0.8
16 LEDs
8
15 LEDs
14 LEDs
15 LEDs
6
0.75
14 LEDs
0.7
85
105 125 145 165 185 205 225 245 265
IN PUT VOLTAGE (VRMS )
180mA LED Driver Power Factor vs. Input Voltage
AL9901
Document number: DS37713 Rev. 1 - 2
4
85
105 125 145 165 185 205 225 245 265
INPUT VOLTAGE (VRMS )
180mA LED Driver Input Power Dissipation vs. Input Voltage
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AL9901
Typical Characteristics (cont.) measured using internal MOSFET
2.0
VDS = 20V
VGS = 10V
VGS = 6.0V
1.4
1.2
1.0
1
ID, DRAIN CURRENT (A)
VGS = 8.0V
1.6
ID, DRAIN CURRENT (A)
10
VGS = 20V
1.8
VGS = 5.5V
0.8
0.6
0.1
TA = 150°C
0.4
TA = 85°C
0.2
0.0
0.001
0
1
2
3
4
5
6
7
8
9
VDS, DRAIN-SOURCE VOLTAGE (V)
Figure 1 Typical Output Characteristics
10
5
4.8
4.6
4.4
4.2
VGS = 10V
4
3.8
3.6
3.4
3.2
3
0
0.2
0.4 0.6 0.8
1
1.2 1.4 1.6 1.8
ID, DRAIN-SOURCE CURRENT (A)
Figure 3 Typical On-Resistance vs.
0
1
2
3
4
5
6
7
VGS, GATE-SOURCE VOLTAGE (V)
Figure
2 Typical Characteristics
Transfer Characteristics
Typical
Transfer
8
20
RDS(ON), DRAIN-SOURCE ON-RESISTANCE (Ω)
RDS(ON), DRAIN-SOURCE ON-RESISTANCE (Ω)
TA = -55°C
VGS = 5.0V
Typical Output Characteristics
18
16
14
ID = 1.0A
12
10
8
6
4
2
0
2
4
6
8
10
12
14
16
18
20
VGS, GATE-SOURCE VOLTAGE (V)
Figure 4 Typical Transfer Characteristics
Typical On-Resistance vs. Drain Current and
Gate Voltage
Typical Transfer Characteristics
15
3
VGS = 10V
12
RDS(ON), DRAIN-SOURCE
TA = 150°C
TA = 125°C
9
T A = 85°C
6
T A = 25°C
3
TA = -55°C
0
0
0.2
0.4
0.6 0.8
1
1.2 1.4 1.6
ID, DRAIN CURRENT (A)
1.8
Typical On-Resistance vs. Drain Current and
Temperature
AL9901
Document number: DS37713 Rev. 1 - 2
2
ON-RESISTANCE (NORMALIZED)
RDS(ON), DRAIN-SOURCE ON-RESISTANCE (Ω)
TA = 25°C
TA = 125°C
0.01
VGS = 20V
ID = 2A
2.5
2
VGS = 10 V
ID = 1A
1.5
1
0.5
0
-50
-25
0
25
50
75
100 125 150
TJ, JUNCTION TEMPERATURE (°C)
Figure 6 On-Resistance Variation with Temperature
On-Resistance Variation with Temperature
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AL9901
5
VGS(th), GATE THRESHOLD VOLTAGE (V)
RDS(ON), DRAIN-SOURCE ON-RESISTANCE (Ω)
15
12
VGS = 20V
ID = 2A
9
VGS = 10V
ID = 1A
6
3
0
-50
4.5
ID = 1mA
ID = 250µA
4
3.5
3
2.5
2
-25
0
25
50
75
100 125
TJ, JUNCTION TEMPERATURE (°C)
150
On-Resistance Variation with Temperature
-50
-25
0
25
50
75 100 125
TJ, JUNCTION TEMPERATURE (°C)
Gate Threshold Variation vs. Ambient Temperature
1000
2
Ciss
CT, JUNCTION CAPACITANCE (pF)
1.8
IS, SOURCE CURRENT (A)
1.6
1.4
TA = 150°C
1.2
T A = 25°C
1
TA = 125°C
0.8
TA = -55°C
0.6
TA = 85°C
0.4
100
Coss
10
Crss
0.2
0
150
f = 1MHz
0
0.3
0.6
0.9
1.2
VSD, SOURCE-DRAIN VOLTAGE (V)
1
1.5
0
Diode Forward Voltage vs. Current
5
10
15
20
25
30
35
VDS, DRAIN-SOURCE VOLTAGE (V)
40
Typical Junction Capacitance
10
10
8
ID, DRAIN CURRENT (A)
VGS GATE THRESHOLD VOLTAGE (V)
RDS(on)
Limited
6
VDS = 520V
ID = 2A
4
1
DC
PW = 1s
PW = 100ms
PW = 10ms
0.01
2
0
0
2
4
6
8
10
12
14
Qg, TOTAL GATE CHARGE (nC)
Figure
Gate Charge
Gate 11
Charge
AL9901
Document number: DS37713 Rev. 1 - 2
16
PW = 10s
0.1
0.001
1
TJ(max) = 150°C
TA = 25°C
VGS = 10V
Single Pulse
DUT on 1 * MRP Board
PW = 1ms
PW = 100µs
10
100
VDS, DRAIN-SOURCE VOLTAGE (V)
1000
SOA, Safe Operation Area
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AL9901
LED Current vs. Duty Cycle by PWM Dimming when VIN is
120Vac
AL9901
Document number: DS37713 Rev. 1 - 2
LED Current vs. Duty Cycle by PWM Dimming when VIN is
230Vac
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AL9901
Applications Information
The AL9901 is capable of operating in isolated or non-isolated topologies. It can also be made to operate in continuous as well as discontinuous
conduction mode.
Figure 1 Functional Block Diagram
The AL9901 contains a high voltage LDO (see figure 1) the output of the LDO provides a power rail to the internal circuitry including the gate
driver. A UVLO on the output of the LDO prevents incorrect operation at low input voltage to the VIN pin.
In a non-isolated Buck LED driver, when the gate pin goes high, the internal power MOSFET (Q1) is turned on causing current to flow through the
LEDs inductor (L1), and current sense resistor (RSENSE). When the voltage across RSENSE exceeds the current sense pin threshold, the internal
MOSFET Q1 is turned off. The energy stored in the inductor causes the current to continue to flow through the LEDs via diode D1.
The AL9901’s LDO provides all power to the rest of the IC including Gate drive, and this removes the need for large, high-power start-up resistors.
This means that during normal operation the AL9901 requires around 0.5mA from the high voltage power rail. The LDO can also be used to
supply up to 1mA to external circuits.
The AL9901 operates and regulates by limiting the peak current of the internal MOSFET; the peak current sense threshold is nominally set at
250mV. The AL9901 is capable of operating in a fixed frequency (PWM) mode and also variable frequency (fixed off-time) mode to regulate the
LED current.
The same basic operation is true for isolated topologies; however in these the energy stored in the transformer delivers energy to LEDs during the
off-cycle of the internal MOSFET.
The on-resistance of the AL9901’s internal power MOSFET means that it can drive up to 2A.
Design Parameters
Setting the LED Current
In the non-isolated buck converter topology, figure 1, the average LED current is not the peak current divided by two - however, there is a certain
error due to the difference between the peak and the average current in the inductor. The following equation accounts for this error:
R SENSE =
I LED
250mV
+ ( 0.5 * I RIPPLE )
AL9901
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AL9901
Applications Information (continued)
Setting Operating Frequency
The AL9901 is capable of operating between 25 and 450 kHz switching frequency range. The switching frequency is programmed by connecting
an external resistor between ROSC pin and ground. The corresponding oscillator period is:
tOSC =
R osc + 22
µs
25
with ROSC in kΩ
The switching frequency is the reciprocal of the oscillator period. Typical values for ROSC vary from 75kΩ to 1MΩ
In buck mode the duty cycle, D, is
VLEDs
; so when driving small numbers of LEDs from high input voltages the duty cycle will be reduced and
VIN
care should be taken to ensure that tON > tBLANK. The simplest way to do this is to reduce/limit the switching frequency by increasing the ROSC
value. Reducing the switching frequency will also improve the efficiency.
When operating in buck mode the designer must keep in mind that the input voltage must be maintained higher than two times the forward voltage
drop across the LEDs. This limitation is related to the output current instability that may develop when the AL9901 operates at a duty cycle greater
than 0.5. This instability reveals itself as an oscillation of the output current at a sub-harmonic (SBO) of the switching frequency.
Inductor Selection
The non-isolated buck circuit, Figure 1, is usually selected and it has two operation modes: continuous and discontinuous conduction modes. A
buck power stage can be designed to operate in continuous mode for load current above a certain level, usually 15% to 30% of full load. Usually,
the input voltage range, the output voltage and load current are defined by the power stage specification. This leaves the inductor value as the
only design parameter to maintain continuous conduction mode. The minimum value of inductor to maintain continuous conduction mode can be
determined by the following example.
The required inductor value is determined from the desired peak-to-peak LED ripple current in the inductor; typically around 30% of the nominal
LED current.
L=
(VIN − VLEDs ) × D
(0.3 × I LED ) × fOSC
Where, D is duty cycle
The next step is determining the total voltage drop across the LED string. For example, when the string consists of 10 High-Brightness LEDs and
each diode has a forward voltage drop of 3.0V at its nominal current; the total LED voltage VLEDS is 30V.
Dimming
The LED brightness can be dimmed either linearly (using the LD pin) or via pulse width modulation (using the PWM-D pin); or a combination of
both - depending on the application. Pulling the PWM_Dpin to ground will turn off the AL9901. When disabled, the AL9901’s quiescent current is
typically 0.5mA (0.65 for AL9901A). Reducing the LD voltage will reduce the LED current but it will not entirely turn off the external power
transistor and hence the LED current – this is due to the finite blanking period. Only the PWM_Dpin will turn off the power transistor.
Linear dimming is accomplished by applying a 45 to 250mV analog signal to the LD pin. This overrides the default 250mV threshold level of the
CS pin and reduces the output current. If an input voltage greater than 250mV is applied to the LD then the output current will not change.
The LD pin also provides a simple cost effective solution to soft start. By connecting a capacitor to the LD pin down to ground at initial power up,
the LD pin will be held low, causing the sense threshold to be low. As the capacitor charges up the current sense threshold will increase, thereby
causing the average LED current to increase.
PWM dimming is achieved by applying an external PWM signal to the PWM_D pin. The LED current is proportional to the PWM duty cycle and the
light output can be adjusted between 0 and 100%.The PWM signal enables and disables the AL9901 - modulating the LED current. The ultimate
accuracy of the PWM dimming method is limited only by the minimum gate pulse width, which is a fraction of a percentage of the low frequency
duty cycle. PWM dimming of the LED light can be achieved by turning on and off the converter with a low frequency 50Hz to 1000Hz TTL logic
level signal.
With both modes of dimming it is not possible to achieve average brightness levels higher than the one set by the current sense threshold level of
the AL9901. If a greater LED current is required, then a smaller sense resistor should be used.
AL9901
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AL9901
Applications Information (cont.)
Output Open Circuit Protection
The non-isolated buck LED driver topology provides inherent protection against an open circuit condition in the LED string due to the LEDs being
connected in series with the inductor. Should the LED string become open circuit then no switching occurs and the circuit can be permanently left
in this state with damage to the rest of the circuit.
AC/DC Off-Line LED Driver
The AL9901 is a cost-effective off-line buck LED driver-converter specifically designed for driving LED strings. It is suitable for being used with
either a rectified AC line or any DC voltage between 15-500V. See figure 3 for typical circuit.
Figure 2 Typical Application Circuit (without PFC)
Buck Design Equations:
D=
VLEDs
VIN
tON =
L≥
D
f osc
( VIN − VLEDs ) × t ON
0.3 × ILED
RSENSE =
0.25
Where ILED x 0.3 = IRIPPLE
ILED + (0.5 × (ILED × 0.3))
Design Example
For an AC line voltage of 120V the nominal rectified input voltage is VIN = 120V x 1.41 = 169V. From this and the LED chain voltage, the duty
cycle can be determined:
D = VLEDs /VIN = 30/169 = 0.177
From the switching frequency, for example fOSC = 50 kHz, the required on-time of the internal MOSFET can be calculated:
tON = D/fOSC = 3.5 µs
The value of the inductor is determined as follows:
L = (VIN - VLEDs) x tON / (0.3 x ILED) = 4.6mH
AL9901
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AL9901
Applications Information (cont.)
Input Bulk Capacitor
For offline lamps, an input bulk capacitor is required to ensure that the rectified AC voltage is held above twice the LED string voltage throughout
the AC line cycle. The value can be calculated from:
CIN ≥
Pin × (1 − D ch )
2 × VLine _ min × 2fL × ∆VDC _ max
Where:
Dch : Capacity charge work period, generally about 0.2~0.25
fL : Input frequency for full range (85~265VRMS)
∆VDC _ max Should be set 10~15% of
2 VLine _ min
If the capacitor has a 15% voltage ripple, then a simplified formula for the minimum value of the bulk input capacitor approximates to:
I
× VLEDs × 0.06
CMIN = LED
VIN 2
Power Factor Correction
If power factor improvement is required, then for the input power less than 25W, a simple method for improving the power factor can be
implemented by potential dividing down the rectified mains voltage (resistors R1 and R2 in Figure 4) and feeding it into the LD pin. The current
drawn from the supply voltage will follow an approximate half sine wave. A filter across the LEDs reduces the potential for flicker. This circuit also
significantly reduces the size of input capacitors.
Figure 3 Typical Application Circuit with Simple PFC
Passive power factor correction using three high voltage diodes and two identical capacitors can be implemented. For further design information,
please see AN75 from the Diodes website.
DC-DC Buck LED Driver
The design procedure for an AC input buck LED driver outlined in the previous chapters equally applies to DC input LED drivers.
AL9901
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Applications Information (cont.)
DC-DC Boost LED Driver
Due to the topology of the AL9901 LED driver-converter, it is capable of being used in boost configurations – at reduced accuracy. The accuracy
can be improved by measuring the LED current with an op amp and use the op amp’s output to drive the LD pin.
A Boost LED driver is used when the forward voltage drop of the LED string is higher than the input supply voltage. For example, the Boost
topology can be appropriate when input voltage is supplied by a 48V power supply and the LED string consists of twenty HB LEDs, as the case
may be for a street light.
Figure 4 Boost LED driver
In a Boost converter, when the internal MOSFET is ON the energy is stored in the inductor which is then delivered to the output when the internal
MOSFET switches OFF. If the energy stored in the inductor is not fully depleted by the next switching cycle (continuous conduction mode), the DC
conversion between input and output voltage is given by:
VOUT =
VIN
V
− VIN
D = OUT
1− D
VOUT
From the switching frequency, fOSC, the on-time of the MOSFET can be calculated:
t ON =
D
fOSC
From this the required inductor value can be determined by:
L=
VIN ∗ t ON
0 .3 ∗ ILED
The Boost topology LED driver requires an output capacitor to deliver current to the LED string during the time that the internal MOSFET is on.
In boost LED driver topologies, if the LEDs should become open circuit, damage may occur to the power switch and so some form of detection
should be present to provide overvoltage detection/protection.
AL9901
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AL9901
Ordering Information
Part Number
VCS Tolerance
Package Code
Packaging
AL9901FDF-13
AL9901S16-13
±5%
±5%
FDF
S16
U-DFN6040-12
SO-16
13” Tape and Reel
Quantity
Part Number Suffix
3,000/Tape & Reel
-13
2,500/Tape & Reel
-13
Marking Information
PKG
P/N
Marking Code
SOIC-16L
AL9901S16-13
AL9901
DFN6040-12
AL9901FDF-13
AL9901
AL9901
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AL9901
Package Outline Dimensions (All dimensions in mm.)
Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for the latest version.
(1)
U-DFN6040-12
A1
A3
A
U-DFN6040-12
Dim Min Max Typ
A 0.55 0.65 0.60
A1
0
0.05 0.02
A3
0.15
b 0.35 0.45 0.40
D 5.95 6.05 6.00
D1 1.95 2.15 2.05
D2 2.35 2.55 2.45
e
1.00
E 3.95 4.05 4.00
E1 2.10 2.30 2.20
E2 1.80 2.00 1.90
L 0.35 0.45 0.40
Z
0.30
All Dimensions in mm
Seating Plane
D
e
D2
D1
E
E2
E1
L
b
Z
(2)
SO-16
H
E
Gauge Plane
L
θ
Detail ‘A’
D
A
A2
B
AL9901
Document number: DS37713 Rev. 1 - 2
e
A1
SO-16
Dim
Min
Max
A
1.40
1.75
A1
0.10
0.25
A2
1.30
1.50
B
0.33
0.51
C
0.19
0.25
D
9.80
10.00
E
3.80
4.00
e
1.27 Typ
H
5.80
6.20
L
0.38
1.27
θ
0°
8°
All Dimensions in mm
C
Detail ‘A’
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Suggested Pad Layout
Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version.
(1)
U-DFN6040-12
X3
Dimensions
Y
C
G
Y1
X1
G1
X2
Y2
Y3
Pin1
C
G
G1
X
X1
X2
X3
Y
Y1
Y2
Y3
Value
(in mm)
0.500
0.650
0.350
0.250
1.075
1.275
2.750
0.400
1.150
1.000
2.300
X
(2)
SO-16
X1
Dimensions
C
X
X1
Y
Y1
Y1
Value
(in mm)
1.270
0.670
9.560
1.450
6.400
Y
Pin 1
X
C
Taping Orientation
The taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/ap02007.pdf.
(1)
U-DFN6040-12
(2)
SOIC-16
AL9901
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AL9901
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IMPORTANT NOTICE
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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).
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website, harmless against all damages.
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Should Customers purchase or use Diodes Incorporated products for any unintended or unauthorized application, Customers shall indemnify and
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This document is written in English but may be translated into multiple languages for reference. Only the English version of this document is the
final and determinative format released by Diodes Incorporated.
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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
2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the
labeling can be reasonably expected to result in significant injury to the user.
B. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the
failure of the life support device or to affect its safety or effectiveness.
Customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and
acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any
use of Diodes Incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related
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representatives against any damages arising out of the use of Diodes Incorporated products in such safety-critical, life support devices or systems.
Copyright © 2015, Diodes Incorporated
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