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PDF A6268 Data sheet ( Hoja de datos )
| Número de pieza | A6268 | |
| Descripción | Automotive High Current LED Controller | |
| Fabricantes | Allegro MicroSystems | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de A6268 (archivo pdf) en la parte inferior de esta página. Total 19 Páginas | ||
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A6268
Automotive High Current LED Controller
Features and Benefits
▪ AEC Q100 Grade 0 Automotive Qualified
▪ Constant current LED drive
▪ 5 to 50 V supply
▪ Boost or buck-boost modes
▪ 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
▪ 10 μA shutdown current including LED leakage
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)
Not to scale
Description
The A6268 is a DC-to-DC 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.
TheA6268 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.
This DC-DC converter can be configured as a ground-referenced
boost converter or as a supply-referenced boost converter
providing buck-boost capability.The buck-boost topology used
ensures that there is no leakage path through the LEDs when
in shutdown and no inrush current at power-up.
Integrated diagnostics and two fault outputs give indication of
VIN and VREG 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, LED overcurrent and
shorted LED string protection. 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.
Typical Application Diagrams
VBAT 12VVBAoTr 1224 VV (o5r02V4 Vm(a5x0) V max)
Power nPeot wer net
Buck Boost Mode
VBAT(min)
(V)
Maximum
Quantity of
LEDs
57
68
7 10
8 11
9 13
Vf of each LED = 3.5 V,
D(max) = 85%
VIN VIN
VREG VREG LN
LP
LN
LP
Fault Fault FF1 FF1
Flags Flags FF2 FF2
A6268A62LF68 LF
Enable Enable EN EN SG SG
IREF IREF SP
CKOUTCKOUT
SP
OSC OSC SN SN
GND GLNAD LA
VBAT 12VVBAoTr 1224 VV (o5r02V4 Vm(a5x0) V max)
Power nPeot wer net
VIN VIN
Boost Mode
VBAT(min)
(V)
Maximum
Quantity oFf ault
LEDs Flags
Fault
Flags
VREG VREG LN
LP
FF1 FF1
FF2 FF2
58
A6268A6L2F68
6
7
10
12
Enable Enable EN
EN
SG
8 13
9 15
IREF IREF SP
CKOUTCKOUT
Vf of each LED = 3.5 V,
D(max) = 85%
OSC OSC SN
GND GLNAD
LN
LP
LF
SG
SP
SN
LA
Buck-Boost Mode
(Supply-referenced boost)
A6268-DS, Rev. 3
Boost Mode
1 page  
A6268
Automotive High Current LED Controller
ELECTRICAL CHARACTERISTICS1 Valid at TJ = –40°C to 150°C, VIN = 5 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
VREG Current Limit
Gate Output Drive
IINQ
IINS
VREG
VREGCL
SG open circuit
EN = GND
IREG = 0 to 2 mA, VIN ≥ 5.3 V
IREG = 2 mA, VIN = 5 V
5–
––
–4
4.85 5
4.7 –
25 –
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
30
30
85
1.7
–
0.75
–
–
Output Low Voltage
Logic Inputs and Outputs
VSGL
ISG = 100 μA
––
Fault Output (Open Drain)
Fault Output FF1 Sink Current
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
Boost Mode Select Voltage
Buck-Boost Mode Select Voltage
Disable Time
VOL
IOH(snk)
IOH1(lkg)
IOH2(lkg)
VIL
VIH
VIhys
VENC
REN
VLNB
VLNBB
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
Defined by VLN
Defined by VLN
fOSC = 350 kHz
––
– 1.3
–1 –
–5 –
––
2–
120 180
– 8.4
– 200
––
3.5 –
– 94
Max.
50
8
10
5.15
–
–
–
–
–
–
3.5
–
1.5
VREG
0.1
0.4
–
1
5
0.8
–
–
–
–
0.8
–
–
Unit
V
mA
μA
V
V
mA
ns
ns
%
Ω
Ω
Ω
Ω
V
V
V
mA
μA
μA
V
V
mV
V
kΩ
V
V
ms
Continued on the next page…
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
5 Page 
A6268
Automotive High Current LED Controller
the CKOUT pin of another A6268 as the external clock source.
In this case the switching point of each subsequent A6268 in the
chain will be delayed from that of the previous A6268, and the
current pulses will be spread across the oscillator period.
Diagnostics
The circuit includes several diagnostic and safety functions to
assist in ensuring safe operation of the LEDs, the A6268, and the
external components. When any fault is detected, one or both of
the fault flag outputs, FF1 and FF2, will be inactive (high imped-
ance, open drain) until the fault is removed. The action taken by
the A6268 when a fault occurs is defined in table 1. To be able to
monitor the state of FF1 and FF2, add a suitable external pull-up
resistor.
The A6268 will continue to drive the LEDs under most fault con-
ditions and will only disable the drive to the LEDs when a high
voltage hazard is present or the external components are likely
to be over-stressed. For output short circuits, LED sense resis-
tor overcurrents, LED sense resistor negative overcurrents, or
shorted LED string, the fault status is latched until a power cycle
occurs, or by pulling EN low for a time greater than the disable
time ( > tDIS ). In all other cases the drive will be re-established
when the hazard is removed.
Table 1. Fault Table
Fault
Pin
FF1 FF2
Action
No Fault
LL
No Action
VIN Undervoltage
ZZ
Disable*
VREG Undervoltage Z Z
Disable*
Overtemperature
LZ
No Action
Open LED
LZ
Disable*
Shorted LED
LZ
No Action
LED Undercurrent
LZ
No Action
Output Short
ZL
Disable*
LED Sense Resistor
Overcurrent
Z
L
Disable*
LED Sense Resistor
Negative Overcurrent
Z
L
Disable*
Shorted LED String
ZL
Disable*
*SG low, MOSFET off
L = active pull-down, Z = inactive, open drain
Latched
–
No
No
No
Yes
No
No
Yes
Yes
Yes
Yes
If either FF1 is pulled low (due to an output short or overcur-
rent condition), or FF2 is pulled low when an open LED fault is
indicated, then the output disable will be overridden.
At start-up or during pulse width modulation of the Enable pin, a
fault blank period, tFB , occurs before the fault detection circuitry
becomes active. This period allows steady state conditions to
be established before fault monitoring takes place. Note that the
fault blank period is derived from the oscillator period by a ratio
of 1024:1, so any variation in the oscillator frequency will change
the fault blank period. For the default switching frequency of
350 kHz, this means the fault blank period would be:
tFB = 1024 × (1 / 350 × 103 ) = 3 ms
(6)
Note that no fault blanking is applied to the following faults:
open LED, VIN undervoltage, or VREG undervoltage.
VIN Undervoltage If the voltage at VIN drops below the
specified turn-off voltage, VINUV , the gate drive output, SG, will
be driven low and both fault flags, FF1 and FF2, will be high
impedance. VIN must rise above the turn-on threshold, VINUV +
∆VINUV , before the A6268 can start up.
VREG Undervoltage If the voltage at VREG, VREG , drops
below the specified turnoff voltage, VREGUV , the gate drive
output, SG, will be driven low and both fault flags, FF1 and
FF2, will be high impedance. VREG must rise above the turn-on
threshold, VREGUV + ΔVREGUV , before the output circuits are
activated. This ensures that the external FET is operating in its
fully enhanced state and avoids permanent damage to the FET,
caused by overheating.
The VREG Regulator is designed to operate with a typical maxi-
mum load current of 15 mA. The majority of the VREG load will
be determined by the total gate charge of the external MOSFET.
The VREG pin can be also be used as a pull-up supply for the
fault flag outputs. The current required for this function has to be
considered in the overall load calculation. Note that if FF1 is used
for driving a series protection MOSFET then only FF2 is pulled
up to the VREG supply.
Overtemperature Warning If the chip temperature exceeds
the overtemperature threshold, TJF , fault flag FF2 will be high
impedance. No action will be taken by the A6268 to limit the
chip temperature. An external control circuit must take action
to avoid permanent damage to the A6268 and/or the LEDs. The
temperature will continue to be monitored and the fault flags will
be deactivated when the temperature drops below the recovery
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet A6268.PDF ] | |
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