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PDF A6266 Data sheet ( Hoja de datos )

Número de pieza A6266
Descripción High Current LED Controller
Fabricantes Allegro MicroSystems 
Logotipo Allegro MicroSystems Logotipo



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A6266
Automotive, Boost, High Current LED Controller
Features and Benefits
AEC Q100 Grade 0 Automotive Qualified
Constant current LED drive
5 to 50 V supply
Boost mode
Drives up to 15 LEDs in series
Programmable switching frequency 100 to 700 kHz
Open LED overvoltage indication and protection
Single and multiple LED short indication
LED short to ground and supply protection
PWM dimming control
Applications:
Automotive high power LED lighting systems
Fog lights, reversing lights, daytime running lights
Headlights
Package: 16-pin TSSOP with exposed
thermal pad (suffix LP)
Description
The A6266 is a boost converter controller, providing a
programmable constant current output for driving high power
LEDs in series. Driving the LEDs in series ensures identical
currents and uniform brightness. For automotive applications,
optimum performance is achieved when driving up to 15 LEDs
at currents up to 1 A.
TheA6266 provides a cost-effective solution using an external
logic-level MOSFET and minimum additional external
components. The maximum LED current is set with a single
external sense resistor and can be modified using a current
reference input. Direct PWM control is possible via the Enable
input, which also provides a shutdown mode.
Integrated diagnostics and two fault outputs give indication of
undervoltage, chip overtemperature, output open circuit, LED
short circuit and LED undercurrent, and can be configured to
provide short to supply and short to ground protection for the
LED connections. A unique feature is the ability to detect one
or more shorted LEDs.
The device is provided in a 16-pinTSSOPpackage with exposed
thermal pad (suffix LP). It is lead (Pb) free, with 100% matte
tin leadframe plating.
Not to scale
Typical Application Diagram
12 V or 24 V (50 V max)
Power net
Boost Mode
VBAT(min)
(V)
Maximum
Quantity of
LEDs
6 10
7 12
8 13
9 15
Vf of each LED = 3.5 V,
VBAT measured at VIN pin
D = 85%
Fault
Flags
Enable
VIN
VREG
LN
LP
FF1
FF2
A6266 LF
EN
SG
IREF
CKOUT
SP
OSC
GND
SN
LA
A6266-DS, Rev. 1
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A6266 pdf
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A6266
Automotive, Boost, High Current LED Controller
ELECTRICAL CHARACTERISTICS1 Valid at TJ = –40°C to 150°C, VIN = 6 to 40 V; unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.
Supply and Reference
VIN Functional Operating Range2
VIN Quiescent Current
VREG Output Voltage
Gate Output Drive
IINQ
IINS
VREG
SG open circuit
EN = GND
IREG = 0 to 2 mA
5–
––
–4
4.75 5
Turn-On Time
Turn-Off Time
Maximum Duty Cycle
Pull-Up On Resistance
Pull-Down On Resistance
Output High Voltage
tr
tf
D
RDS(on)UP
RDS(on)DN
CLOAD = 1 nF, 20% to 80%
CLOAD = 1 nF, 80% to 20%
tON × fOSC
TJ = 25°C, IGHx = –100 mA
TJ = 150°C, IGHx = –100 mA
TJ = 25°C, IGLx = 100 mA
TJ = 150°C, IGLx = 100 mA
VSGH ISG = –100 μA
80
VREG
0.1
35
35
85
1.7
1
Output Low Voltage
Logic Inputs and Outputs
VSGL
ISG = 100 μA
––
Fault Output (Open Drain)
Fault Output FF1 Sink Current1
Fault Output FF1 Leakage Current1
Fault Output FF2 Leakage Current1
Input Low Voltage
Input High Voltage
Input Hysteresis
Enable Input Internal Clamp Voltage
Enable Input Current Limit Resistor
Disable Time
Oscillator
VOL
IOH(snk)
IOH1(lkg)
IOH2(lkg)
VIL
VIH
VIhys
VENC
REN
tDIS
IOL = 1 mA, fault not asserted
0.4 V < VO < 50 V, fault not asserted
VO = 12 V, fault asserted
VO = 5 V, fault asserted
Between EN and internal clamp
fOSC = 350 kHz
––
– 1.3
–1 –
–5 –
––
2–
225 330
– 8.4
– 200
– 94
Oscillator Frequency
OSC Pin Voltage
CKOUT Output Delay
OSC Input Low Voltage
OSC Input High Voltage
OSC Input Hysteresis
fOSC
VOSC
tDC
VOIL
VOIH
VOihys
ROSC = 43 kΩ
ROSC = 62 kΩ
ROSC = VREG
ROSC = 62 kΩ
OSC input rise to CKOUT rise
– 500
315 350
– 350
1.15 1.2
– 150
––
3.5 –
300 600
Max.
50
8
10
5.25
3.5
2
VREG
0.1
0.4
1
5
0.8
385
1.25
0.8
Unit
V
mA
μA
V
ns
ns
%
Ω
Ω
Ω
Ω
V
V
V
mA
μA
μA
V
V
mV
V
kΩ
ms
kHz
kHz
kHz
V
ns
V
V
mV
Continued on the next page…
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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A6266 arduino
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A6266
Automotive, Boost, High Current LED Controller
These measurements are used to determine if there is an open
circuit, if one or more LEDs are shorted, if the output is shorted,
or if there is a short across the LED string. Each condition is
described in turn in the following sections.
Open LED–An open circuit is evaluated when:
VSTR > VOCL
(7)
where VOCL is the LED open circuit voltage defined in the Elec-
trical Characteristics table.
Because the output is current-controlled it is possible for an open
circuit on the output to cause extremely high voltages to be pres-
ent. Therefore, to prevent any hazardous voltages or damage to
the circuits, the gate drive output, SG, is immediately driven low
when an open circuit is detected. After an open circuit fault has
been detected, FF2 will become high impedance, and the open
circuit fault state will remain until the open fault time-out period
toto, expires. When the gate drive output is re-enabled at the end
of the open fault time-out period, the output is again monitored
for an open circuit. If the open circuit is still present, then the
fault will again be flagged and the switch drive disabled. This
cycle will continue, as long as the open circuit condition is pres-
ent.
Note that the Fault Blank timer is not used when an open LED
fault occurs. This is to avoid potentially damaging voltages
appearing in the power circuitry.
Shorted LED – A short circuit on one or more LEDs is detected
when:
• for the first (reference) LED:
VSTR > VLED + VSCOR
(8)
• for other than the first (reference) LED:
VLED > VSTR + VSCO
(9)
where VSTR and VLED are as defined above, VSCO is the nonrefer-
ence LED short offset voltage, and VSCOR is the reference LED
short offset voltage. VSCO and VSCOR are defined in the Electrical
Characteristics table.
When a short is present, the fault flag FF2 is high impedance, but
the regulator continues to operate and drives the remaining LEDs
with the correct regulated current. FF2 will remain high imped-
ance while the short circuit condition is present.
A short circuit on one or more LEDs will not cause a hazard
because the output is current-controlled. If one LED fails and
becomes a short circuit, then the remaining LEDs will continue
to be lit with the same current through, and voltage across,
each LED.
Note—Accuracy: The output status monitor relies on all the
LEDs in the load having a similar forward voltage drop. Where
possible all the LEDs forming the load for a single controller
should be taken from the same voltage bin. With only two or
three LEDs a wider variation in forward voltage is acceptable,
but the selection of LEDs from the same bin is more critical when
higher numbers of LEDs are used in a single string.
Shorted LED String or Output Short – A short circuit across
the LED string, is detected when:
VSTR < VSCL
(10)
An output short can consist of the LP, LN, or LF terminals of
the LED string being shorted, either to the battery terminal or
to ground. Either a shorted LED string or output short will be
latched and will only be cleared by pulling EN low for a period
greater than the disable time, or by cycling the power.
If either a shorted LED string, or an output short is detected, the
A6266 will stop the switching action by pulling SG low. The
fault flag FF1 will go high impedance and should be pulled up to
the supply with suitable external pull-up resistors to indicate the
fault. Either a shorted LED string or output short will be latched
and will only be cleared by pulling EN low for a period greater
than the disable time, or by cycling the power.
The FF1 output can also be used with pull-up resistors and a
P-channel MOSFET in the supply, to isolate the switching ele-
ments and the load from the supply. This MOSFET should be
connected, as shown in figure 3, with the source connected to the
supply and the drain connected to the inductor of the converter.
VBAT
To VIN
To FF1
Figure 3. Example of a supply isolation MOSFET
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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