AL8807B

AL8807B
HIGH EFFICIENCY 36V 1.3A PWM DIMMABLE BUCK LED DRIVER
Description
Pin Assignments
The AL8807B is a step-down DC/DC converter designed to drive
LEDs with a constant current. The device can drive up to 9 LEDs,
depending on the forward voltage of the LEDs, in series from a
(Top View)
voltage source of 6V to 36V. Series connection of the LEDs provides
identical LED currents resulting in uniform brightness and eliminating
the need for ballast resistors. The AL8807B switches at frequency up
This
allows the use of small size external components, hence minimizing
the PCB area needed.
Maximum output current of AL8807B is set via an external resistor
connected between the VIN and SET input pins. Dimming is
SET
VIN
GND
N/C
GND
SW
CTRL
SW
MSOP-8EP
achieved by applying a PWM signal at the CTRL input pin. An input
voltage of 0.4V or lower at CTRL switches off the output MOSFET
simplifying PWM dimming.
Features
Applications

LED driving current up to 1.3A

MR16 lamps

Better than 5% accuracy

General illumination lamps

High efficiency up to 96%

12V powered LED Lamps

Optimally controlled switching speeds

24V powered LED Lamps

Operating input voltage from 6V to 36V

PWM input for dimming control

Open-Circuit LED protection

LED Chain Short Circuited

Over-Temperature Protection

MSOP-8EP Available in “Green” Molding Compound (No Br,
Sb) with lead Free Finish/ RoHS Compliant

Totally Lead-Free & Fully RoHS Compliant (Notes 1 & 2)

Halogen and Antimony Free. “Green” Device (Note 3)
Notes:
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 Application Circuit
VIN
AL88070B
Document number: DS36191 Rev. 1 - 2
AL8807B
SW
C1
GND
VIN:
6 ~ 36V
PWM Dimming
Input:
SET
R1
D1
CTRL
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to 1MHz with controlled rise and fall times to reduce EMI.
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L1
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AL8807B
Pin Descriptions
SET
GND
Pin
Number
1
2, 3
CTRL
4
SW
N/C
5, 6
7
VIN
8
EP
EP
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Pin Name
Function
Set Nominal Output Current Pin. Configure the output current of the device.
GND Pins
Dimming and On/Off Control Input.

Leave floating for normal operation.
(VCTRL = VREF = 2.5V giving nominal average output current IOUTnom = 0.1/RS)

Drive to voltage below 0.4V to turn off output current

A PWM signal ( 2.5V) allows the output current to be adjusted below the level set by the resistor
connected to SET input pin.
Switch Pin. Connect inductor/freewheeling diode here, minimizing track length at this pin to reduce EMI.
no connection
Input Supply Pin. Must be locally decoupled to GND with > 2.2µF X7R ceramic capacitor – see
applications section for more information.
Exposed pad/TAB connects to GND and thermal mass for enhanced thermal impedance. Should not be
used as electrical ground conduction path.
Functional Block Diagram
AL88070B
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AL8807B
Absolute Maximum Ratings
Symbol
ESD HBM
ESD MM
Ratings
2.5
200
Unit
kV
V
VIN
Continuous VIN Pin Voltage Relative to GND
-0.3 to +40
V
VSW
SW Voltage Relative to GND
-0.3 to +40
V
CTRL Pin Input Voltage
-0.3 to +6
V
1.6
A
VCTRL
ISW-RMS
ISW-PK
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Parameter
Human Body Model ESD Protection
Machine Model ESD Protection
DC or RMS Switch Current
MSOP-8EP
Peak Switch Current (<10%)
Junction Temperature
TJ
2.5
A
+150
°C
TLEAD
Lead Temperature Soldering
+300
°C
TST
Storage Temperature Range
-65 to +150
°C
Caution:
Stresses greater than the 'Absolute Maximum Ratings' specified above, may cause permanent damage to the device. These are stress ratings only;
functional operation of the device at these or any other conditions exceeding those indicated in this specification is not implied. Device reliability may be
affected by exposure to absolute maximum rating conditions for extended periods of time.
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.
Recommended Operating Conditions
Symbol
Min
Max
Unit
Operating Input Voltage Relative to GND
6.0
36
V
VCTRLH
Voltage High for PWM Dimming Relative to GND
2.5
5.5
V
VCTRLL
Voltage Low for PWM Dimming Relative to GND
0
0.4
V
fSW
Maximum Switching Frequency
—
1
MHz
ISW
Continuous Switch Current
—
1.3
A
TJ
Junction Temperature Range
-40
+125
°C
VIN
Parameter
MSOP-8EP
Electrical Characteristics (VIN = 12V, @TA = +25°C, unless otherwise specified.)
Symbol
Parameter
Conditions
VINSU
Internal Regulator Start Up Threshold
VINSH
Internal Regulator Hysteresis Threshold VIN falling
VIN rising
Min
Typ
Max
—
—
5.9
Unit
V
100
—
300
mV
—
—
350
µA
IQ
Quiescent Current
Output not switching (Note 4)
IS
Input Supply Current
CTRL pin floating f = 250kHz
—
1.8
5
mA
Set Current Threshold Voltage
—
95
100
105
mV
Set Threshold Hysteresis
—
—
±15
—
mV
SET Pin Input Current
VSET = VIN-0.1
—
16
22
µA
RCTRL
CTRL Pin Input Resistance
Referred to internal reference
—
50
—
kΩ
VREF
Internal Reference Voltage

—
2.5
—
V
On Resistance of SW MOSFET
ISW = 1A
—
0.25
0.4
Ω
tR
SW Rise Time
—
12
—
ns
tF
SW Fall Time
—
20
—
ns
—
155
—
°C
VTH
VTH-H
ISET
RDS(ON)
TOTP
Over-Temperature Shutdown
VSENSE = 100 ±20mV fSW = 250kHz
VSW = 0.1V~12V~0.1V CL = 15pF
—
TOTP-Hyst
Over-Temperature Hysteresis
—
—
55
—
°C
Switch Leakage Current
VIN =36V
—
—
0.5
μA
(Note 6)
—
69
—
°C/W
(Note 6)
—
4.3
—
—
ISW_Leakage
Thermal Resistance Junction-toAmbient (Note 5)
Thermal Resistance Junction-to-case
(Note 7)
θJA
θJC
Notes:
4. AL8807B does not have a low power standby mode but current consumption is reduced when output switch is inhibited: VSENSE = 0V. Parameter is
tested with VCTRL ≤ 2.5V.
5. Refer to figure 39 for the device derating curve.
6. Test condition for MSOP-8EP: Device mounted on FR-4 PCB (51mm x 51mm 2oz copper, minimum recommended pad layout on top layer and
thermal vias to bottom layer with maximum area ground plane. For better thermal performance, larger copper pad for heat-sink is needed.
7. Dominant conduction path is via exposed pad.
AL88070B
Document number: DS36191 Rev. 1 - 2
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AL8807B
Typical Performance Characteristics (@TA = +25°C, unless otherwise specified.)
400
80
350
60
300
40
ICTRL (µA)
IIN (µA)
250
200
20
0
150
-20
100
VCTRL = 0V
VSET = VIN
TA = 25°C
50
0
0
-40
-60
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.0
VCTRL (V)
9 12 15 18 21 24 27 30 33 36
VIN (V)
Figure 1. Supply Current (not switching) vs.
Input Voltage
3
6
Figure 2 ICTRL vs. VCTRL
3
2.52
VCTRL = Open
VSET = VIN = 12V
2.5
2.51
VCTRL (V)
VCTRL (V)
2
1.5
2.50
1
0
2.49
VCTRL = Open
VSET = VIN
T A = 25°C
0.5
0
3
2.48
-40
6
9 12 15 18 21 24 27 30 33 36
VIN (V)
Figure 3 VCTRL vs. Input Voltage
(CTRL Pin open circuit)
-15
10
35
60
85
AMBIENT TEMPERATURE (°C)
110
Figure 4 VCTRL vs. Temperature
400
300
270
350
240
RDS(ON) (m)
210
RDS(ON) (m)
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VSET = VIN = 12V
TA = 25°C
180
150
120
250
200
90
VCTRL = Open
VSET = VIN
TA = 25°C
60
30
0
300
6
9
12 15 18 21 24 27 30 33 36
VIN (V)
Figure 5 SW RDS(ON) vs. Input Voltage
AL88070B
Document number: DS36191 Rev. 1 - 2
VCTRL = Open
VSET = VIN = 12V
150
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100
-40
-15
10
35
60
85
110
Ambient Temperature (C)
Figure 6 SW RDS(ON) vs. Temperature
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AL8807B
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Typical Performance Characteristics (cont.) (@TA = +25°C, unless otherwise specified.)
Figure 8. Duty Cycle vs. Input Voltage
Figure 7 ILED vs. PWM Duty Cycle
Figure 9. Efficiency vs. Input Voltage
Figure 10. On-time vs. Input Voltage
Figure. 11 SW Output Rise Time
AL88070B
Document number: DS36191 Rev. 1 - 2
Figure. 12 SW Output Fall Time
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AL8807B
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Typical Performance Characteristics (670mA LED current) (@TA = +25°C, unless otherwise specified.)
Figure 13. LED Current Deviation vs. Input Voltage
Figure 15. LED Current Deviation vs. Input Voltage
Figure 17. LED Current Deviation vs. Input Voltage
AL88070B
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Figure 14. Switching Frequency vs. Input Voltage
Figure 16. Switching Frequency vs. Input Voltage
Figure 18. Switching Frequency vs. Input Voltage
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AL8807B
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Typical Performance Characteristics (1A LED currentMSOP-8EP) (@TA = +25°C, unless otherwise specified.)
Figure 19. LED Current Deviation vs. Input Voltage
Figure 20. Switching Frequency vs. Input Voltage
Figure 21. LED Current Deviation vs. Input Voltage
Figure 22. Switching Frequency vs. Input Voltage
Figure 23. LED Current Deviation vs. Input Voltage
Figure 24. Switching Frequency vs. Input Voltage
AL88070B
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AL8807B
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Typical Performance Characteristics (1.3A LED current MSOP-8EP) (@TA = +25°C, unless otherwise specified.)
Figure 25. LED Current Deviation vs. Input Voltage
Figure 26. Switching Frequency vs. Input Voltage
Figure 27. LED Current Deviation vs. Input Voltage
Figure 28. Switching Frequency vs. Input Voltage
Figure 29. LED Current Deviation vs. Input Voltage
Figure 30. Switching Frequency vs. Input Voltage
AL88070B
Document number: DS36191 Rev. 1 - 2
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AL8807B
Application Information
The AL8807B is a hysteretic (also known as equal ripple) LED driver with integrated power switch. It is available in two packages that provide a
PCB area-power dissipation capability compromise. It is recommended that at higher LED currents/smaller PCBs that the MSOP-8EP version is
used to maximize the allowable LED current over a wider ambient temperature range.
AL8807B Operation
In normal operation, when voltage is applied at +VIN, the AL8807B internal switch is turned on. Current starts to flow through sense resistor R1,
This rising current produces a voltage ramp across R1. The internal circuit of the AL8807B senses the voltage across R1 and applies a
proportional voltage to the input of the internal comparator.
When this voltage reaches an internally set upper threshold, the internal switch is turned off. The inductor current continues to flow through R1, L1,
the LEDs and the Schottky diode D1, and back to the supply rail, but it decays, with the rate of decay determined by the forward voltage drop of
the LEDs and the Schottky diode.
This decaying current produces a falling voltage at R1, which is sensed by the AL8807B. A voltage proportional to the sense voltage across R1 is
applied at the input of the internal comparator. When this voltage falls to the internally set lower threshold, the internal switch is turned on again.
This switch-on-and-off cycle continues to provide the average LED current set by the sense resistor R1.
LED Current Control
The LED current is controlled by the resistor R1 in Figure 31.
Ch4: LED Current
VIN
D1
SET
R1
PWM Dimming
Input:
VIN = 12V
TA =25ºC
2 LEDs
20ns/div
No C2
Ch2: 2V/div
Ch4: 100mA/div
AL8807B
SW
C1
GND
VIN:
6 ~ 36V
CTRL
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inductor L1, and the LEDs. The current ramps up linearly, and the ramp rate is determined by the input voltage +Vin and the inductor L1.
C2
L1
Ch2: SW Pin
Figure 31 Typical Application Circuit
Figure 32 Typical Operating Waveform (C2 not fitted)
Connected between VIN and SET the nominal average output current in the LED(s) is defined as:
ILED 
VTHD
R1
For example for a desired LED current of 660mA and a default voltage VCTRL=2.5V the resulting resistor is:
R1 
VTHD
0 .1

 150m
ILED
0.66
AL88070B
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AL8807B
Applications Information (cont.)
PWM Dimming
LED current can be adjusted digitally, by applying a low frequency Pulse Width Modulated (PWM) logic signal to the CTRL pin to turn the device
on and off.
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This will produce an average output current proportional to the duty cycle of the control signal. In particular, a PWM signal with a max resolution of
10bit can be applied to the CTRL pin to change the output current to a value below the nominal average value set by resistor RSET.
Figure 33 PWM Dimming waveforms (fPWM = 500Hz, 25% Duty Cycle fSW(NOM) = 530kHz)
While the PWM pin is high, the AL8807B switches as normal. When the PWM pin is brought low the output switch is turned off causing the SW pin
to go high (one Schottky voltage drop above VIN). It remains high (one Schottky voltage drop above VIN) until the current through the inductor falls
to zero. The time taken for the inductor current is dependent on the LED current, inductor value and LED chain voltage.
As the duty cycle gets smaller or PWM dimming frequency increases then fewer normal hysteretic switching cycles occur which will affect the
overall average LED current.
Figure 34 PWM Dimming waveforms (fPWM = 500Hz, 2% Duty Cycle fSW(NOM) = 530kHz)
To achieve high resolution the PWM frequency has to be much lower than the nominal switching frequency and the LED current output filter
capacitor across the LEDs must not be used. The figures above have an LED current output filter present.
AL88070B
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AL8807B
Applications Information (cont.)
Figures 35 and 36 show the PWM dimming performance of the AL8807B with a range of PWM frequencies with a nominal switching frequency of
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530kHz.
Figure 35 PWM Dimming at 530kHz nominal switching frequency
Looking at difference between duty cycle and percentage of full scale LED current yields a “Linearity Error”:
Figure 36 PWM Dimming Non-Linearity at 530kHz nominal switching frequency
The accuracy of the PWM dimming is affected by both the PWM frequency and also the switching frequency of the AL8807B. For best
accuracy/resolution the switching frequency should be increased while the PWM frequency should be reduced.
The CTRL pin is designed to be driven by both 3.3V and 5V logic levels directly from a logic output with either an open drain output or push pull
output stage.
AL88070B
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AL8807B
Applications Information (cont.)
Reducing Output Ripple
Peak to peak ripple current in the LED(s) can be reduced, if required, by shunting a capacitor C2 across the LED(s) as shown already in the circuit
schematic.
A value of 1μF will reduce the supply ripple current by a factor three (approx.). Proportionally lower ripple can be achieved with higher capacitor
values. Note that the capacitor will not affect operating frequency or efficiency, but it will increase start-up delay, by reducing the rate of rise of
LED voltage. By adding this capacitor the current waveform through the LED(s) changes from a triangular ramp to a more sinusoidal version
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without altering the mean current value.
Capacitor Selection
The small size of ceramic capacitors makes them ideal for AL8807B applications. X5R and X7R types are recommended because they retain their
capacitance over wider voltage and temperature ranges than other types such as Z5U.
A 2.2μF input capacitor is sufficient for most intended applications of AL8807B; however a 4.7μF input capacitor is suggested for input voltages
approaching 36V.
Diode Selection
For maximum efficiency and performance, the rectifier (D1) should be a fast low capacitance Schottky diode with low reverse leakage at the
maximum operating voltage and temperature. The Schottky diode also provides better efficiency than silicon PN diodes, due to a combination of
lower forward voltage and reduced recovery time.
It is important to select parts with a peak current rating above the peak coil current and a continuous current rating higher than the maximum
output load current. In particular, it is recommended to have a diode voltage rating at least 15% higher than the operating voltage to ensure safe
operation during the switching and a current rating at least 10% higher than the average diode current. The power rating is verified by calculating
the power loss through the diode.
Schottky diodes, e.g. B240 or B140, with their low forward voltage drop and fast reverse recovery, are the ideal choice for AL8807B applications.
Inductor Selection
Recommended inductor values for the AL8807B are in the range 33μH to 100μH.
Higher values of inductance are recommended at higher supply voltages in order to minimize errors due to switching delays, which result in
increased ripple and lower efficiency. Higher values of inductance also result in a smaller change in output current over the supply voltage range.
(See graphs).
Figure 37 Inductor value with input voltage and number of LEDs
The inductor should be mounted as close to the device as possible with low resistance/stray inductance connections to the SW pin.
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AL8807B
Applications Information (cont.)
Inductor Selection (cont.)
The chosen coil should have a saturation current higher than the peak output current and a continuous current rating above the required mean
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output current.
Suitable coils for use with the AL8807B are listed in the table below:
L
DCR
ISAT
Manufacturer
Part No.
(µH)
(V)
(A)
MSS1038-333
33
0.093
2.3
CoilCraft www.coilcraft.com
MSS1038-683
68
0.213
1.5
NPIS64D330MTRF
33
0.124
1.1
NIC www.niccomp.com
The inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' times over the supply voltage and load current range.
The following equations can be used as a guide, with reference to Figure 38 – typical switching waveforms.
Switch ‘On’ time
tON 
LI


VIN VLED IAVG x RS  rL  RSW 
VIN = 12V
TA =25ºC
2 LEDs
20ns/div
SW Pin: 2V/div
Off
Switch ‘Off’ time
tOFF 
LI


VLED VD IAVG xRS  rL 
On
Where:
L is the coil inductance (H)
rL is the coil resistance (Ω)
Figure 38 Typical Switching Waveform
RS is the current sense resistance (Ω)
Iavg is the required LED current (A)
∆I is the coil peak-peak ripple current (A)
{Internally set to 0.3 x Iavg}
VIN is the supply voltage (V)
VLED is the total LED forward voltage (V)
RSW is the switch resistance (Ω) {=0.5Ω nominal}
VD is the diode forward voltage at the required load current (V)
Thermal Protection
The AL8807B includes Over-Temperature Protection (OTP) circuitry that will turn off the device if its junction temperature gets too high. This is to
protect the device from excessive heat damage. The OTP circuitry includes thermal hysteresis that will cause the device to restart normal
operation once its junction temperature has cooled down by approximately 55°C.
Thermal Considerations
For continuous conduction mode of operation, the absolute maximum junction temperature must not be exceeded. The maximum power
dissipation depends on several factors: the thermal resistance of the IC package JA, PCB layout, airflow surrounding the IC, and difference
between junction and ambient temperature.
The maximum power dissipation can be calculated using the following formula:
PD(MAX) = (TJ(MAX) − TA) / JA
where
TJ(MAX) is the maximum operating junction temperature  Maximum recommended = 125°C
TA is the ambient temperature, and
JA is the junction to ambient thermal resistance.
JA, is layout dependent and package dependent; the AL8807BMP’s JA on an FR4 51x51mm PCB with 2oz copper standing in still air is
approximately 69°C/W.
So the maximum power dissipation at TA = +25°C is:
PD(MAX) = (125°C − 25°C) / (69°C/W) = 1.41W for the above dimensioned PCB
AL88070B
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AL8807B
Applications Information (cont.)
Figure 39, shows the power derating of the AL8807BMP on an FR4 51x51mm PCB with 2oz copper standing in still air. Changing the PCB
dimensions, material, amount of metal associated with the thermal and other PCB components will change the AL8807BMP’s junction-ambient
thermal impedance.
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Power dissipation (mW)
1600
1400
1200
MSOP-8EP
1000
800
600
400
200
0
-40 -25 -10
5 20 35 50 65 80
Ambient temperature (°C)
95 110 125
Figure 39 Derating Curve for Different PCB
Soft-Start
The AL8807B does not have in-built soft-start action; this can be seen in Figure 40.
Figure 40 LED Current Start-up (VIN = 12V, ILED = 667mA, 2 LEDs)
At power–up VIN rises exponentially, due to the bulk capacitor, the internal reference will reach 2.5V before VIN reaches the Under-Voltage LockOut turn-on threshold at around 5.6V. This causes the CTRL pin voltage to rise and reaches 2.5V – 100% LED current - before the AL8807B
fully turns on. When the AL8807B turns on, its output switch turns on causing the inductor current to increase until it reaches the upper threshold
of the sense current level and the switching process begins.
As the CTRL pin only has PWM functionality, placing a capacitor on the CTRL pin will have no effect on the ramp-up of the LED current; the
capacitor will just delay the ramp-up of the LED current and delay/extend the ramp-down of the LED current.
If some form of extra soft-start is required then the AL8807, AL8807A or PAM2861 should be considered.
AL88070B
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AL8807B
Applications Information (cont.)
EMI and Layout Considerations
The AL8807B is a switching regulator with fast edges and measures small differential voltages; as a result of this care has to be taken with
decoupling and layout of the PCB.To help with these effects the AL8807B has been developed to minimise radiated emissions by controlling the
switching speeds of the internal power MOSFET. The rise and fall times are controlled to get the right compromise between power dissipation
due to switching losses and radiated EMI. The turn-on edge (falling edge) dominates the radiated EMI which is due to an interaction between the
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Schottky diode (D1), Switching MOSFET and PCB tracks. After the Schottky diode reverse recovery time of around 5ns has occurred; the falling
edge of the SW pin sees a resonant loop between the Schottky diode capacitance and the track inductance, LTRACK, See Figure 41.
The tracks from the SW pin to the Anode of the Schottky diode, D1, and then from D1’s cathode to the decoupling capacitors C1 should be as
short as possible. There is an inductance internally in the AL8807B this can be assumed to be around 1nH. For PCB tracks a figure of 0.5nH per
mm can be used to estimate the primary resonant frequency. If the track is capable of handling 1A increasing the thickness will have a minor
effect on the inductance and length will dominate the size of the inductance. The resonant frequency of any oscillation is determined by the
combined inductance in the track and the effective capacitance of the Schottky diode.
An example of good layout is shown in Figure 42 (showing SOT25 package) - the stray track inductance should be less than 5nH.
D1
CD1
LTRACK
~5nH
SW
C1
100nF
AL8807B
GND
Figure 42 Recommended PCB Layout
Figure 41 PCB Loop Resonance
Recommendations for minimising radiated EMI and other transients and thermal considerations are:
1.
The decoupling capacitor (C1) has to be placed as close as possible to the VIN pin and D1 Cathode
2.
The freewheeling diode’s (D1) anode, the SW pin and the inductor have to be placed as close as possible to each other to avoid ringing.
3.
4.
The Ground return path from C1 must be a low impedance path with the ground plane as large as possible
The LED current sense resistor (R1) has to be placed as close as possible to the VIN and SET pins.
5.
The majority of the conducted heat from the AL8807B is through the GND pin 2. A maximum earth plane with thermal vias into a
second earth plane will minimise self-heating
6.
To reduce emissions via long leads on the supply input and LEDs low RF impedance capacitors (C2 and C5) should be used at the
point the wires are joined to the PCB
AL88070B
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AL8807B
Applications Information (cont.)
Fault Condition Operation
Open Circuit LEDs
The AL8807B has by default open LED protection. If the LEDs should become open circuit the AL8807B will stop oscillating; the SET pin will rise
to VIN and the SW pin will then fall to GND. No excessive voltages will be seen by the AL8807B.
LED Chain Shorted Together
If the LED chain should become shorted together (the anode of the top LED becomes shorted to the cathode of the bottom LED) the AL8807B will
NEW PRODUCT
continue to switch and the current through the AL8807B’s internal switch will still be at the expected current - so no excessive heat will be
generated within the AL8807B. However, the duty cycle at which it operates will change dramatically and the switching frequency will most likely
decrease. See Figure 43 for an example of this behavior at 24V input voltage driving 3 LEDs.
The on-time of the internal power MOSFET switch is significantly reduced because almost all of the input voltage is now developed across the
inductor. The off-time is significantly increased because the reverse voltage across the inductor is now just the Schottky diode voltage (See Figure
43) causing a much slower decay in inductor current.
Figure 43 Switching Characteristics (normal operation to LED chain shorted out)
High Temperature Operation and Protection
The AL8807B is a high efficiency switching LED driver capable of operating junction temperatures up to +125°C. This allows it operate with
ambient temperature in excess of +100°C given the correct thermal impedance to free air. If a fault should occur that leads to increased ambient
temperatures and hence junction temperature then the Over-Temperature Protection (OTP) of the AL8807B will cut-in, turning the output of the
AL8807B off. This will allow the junction temperature of the AL8807B to cool down and potentially giving an opportunity for the fault to clear itself.
The OTP shutdown junction temperature of the AL8807B is approximately +155°C with a hysteresis of +55°C. This means that the AL8807B will
never switch-off with a junction temperature below +125°C allowing the designer to design the system thermally to fully utilize the wide operating
junction temperature of the AL8807B.
AL88070B
Document number: DS36191 Rev. 1 - 2
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© Diodes Incorporated
AL8807B
Part Number
Package Code
Packaging
AL8807BMP-13
MP
MSOP-8EP
Quantity
2500
Packing: 13” Tape and Reel
Tape Width
Part Number Suffix
12mm
-13
Marking Information
(1)
MSOP-8EP
(Top View)
8
7
Logo
6
5
YW XE
Part Number
AL8807B
1
2
3
A~Z : Green
MSOP-8EP
Y : Year : 0~9
W : Week: A~Z : 1~26 week;
a~z : 27~52 week;
z represents 52 and 53 week
4
Part Number
Package
AL8807BMP-13
MSOP-8EP
Package Outline Dimensions (All dimensions in mm.)
Please see AP02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version.
(1)
MSOP-8EP
D
4X
10
°
D1
x
E
0.25
E2
Gauge Plane
Seating Plane
y
a
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Ordering Information
1
4X
10
°
8Xb
e
Detail C
E3
A1
A3
c
A2
A
D
L
E1
See Detail C
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Document number: DS36191 Rev. 1 - 2
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MSOP-8EP
Dim Min Max Typ
A
1.10
A1
0.05 0.15 0.10
A2
0.75 0.95 0.86
A3
0.29 0.49 0.39
b
0.22 0.38 0.30
c
0.08 0.23 0.15
D
2.90 3.10 3.00
D1
1.60 2.00 1.80
E
4.70 5.10 4.90
E1
2.90 3.10 3.00
E2
1.30 1.70 1.50
E3
2.85 3.05 2.95
e
0.65
L
0.40 0.80 0.60
a
0°
8°
4°
x
0.750
y
0.750
All Dimensions in mm
March 2014
© Diodes Incorporated
AL8807B
Suggested Pad Layout
Please see AP02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version.
1)
MSOP-8EP
X
C
Y
NEW PRODUCT
G
Y2
Dimensions
C
G
X
X1
Y
Y1
Y2
Y1
X1
Value
(in mm)
0.650
0.450
0.450
2.000
1.350
1.700
5.300
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Copyright © 2014, Diodes Incorporated
www.diodes.com
AL88070B
Document number: DS36191 Rev. 1 - 2
18 of 18
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March 2014
© Diodes Incorporated