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PDF A6274-1 Data sheet ( Hoja de datos )
| Número de pieza | A6274-1 | |
| Descripción | Linear Current Regulator and Controller | |
| Fabricantes | Allegro MicroSystems | |
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A6274, A6274-1
A6284, A6284-1
Linear Current Regulator and Controller
for Automotive LED Arrays
FEATURES AND BENEFITS
• Six LED current sinks rated up to 60 mA (A6274) or
120 mA (A6284)
• Total LED drive current—up to 360 mA or 720 mA
• Wide input voltage range of 5 to 42 V for start/stop, cold-
crank, and load-dump requirements
• Low-dropout voltage—drives two series WLEDs from
7 V input
• Gate driver for external ballast P-MOSFET
• LEDs combined in two groups with separate ENx and
ISETx
• LED current level set by external reference resistors
• Internal or external PWM dimming
• Controlled output drivers slew during PWM for lower
EMI
• Fault detection features: LED string open, LED pin
short-to-ground, single LED short, VOUT short-to-
ground, VIN overvoltage, and thermal protection
• Input supply and temperature-based derating
• Automotive K-temperature range (–40°C to 150°C)
PACKAGES:
20-Pin eTSSOP (LP) with Exposed Thermal Pad
AEC-Q100 qualified
DESCRIPTION
The A6274 and A6284 are programmable linear current
regulator ICs for driving automotive LED arrays. The LED
current is programmed by external resistors. These devices
sink up to 60 mA (A6274) or 120 mA (A6284), from each of
six LED pins, to drive strings of high-brightness LEDs. LED
pins can be paralleled to drive even higher current LED strings.
Current settings are typically accurate to 2%, while typical
matching between LED strings is 0.8%.
LED light output can be adjusted by PWM dimming. The ICs
provide an internal PWM dimming circuit that is programmed
by external resistors for PWM frequency and duty cycle. It
can also accept an external PWM signal. Multiple ICs can be
configured in parallel for larger lighting systems. An internal
FULL (VDR > 3.6 V) option is provided to override the PWM-
dimming ratio for full LED current.
LED current derating with temperature and programmable
VIN levels allows operation over a wide range of operating
conditions.
Continued on next page...
APPLICATIONS
• Automotive rear combination light
• DRL/position
• General automotive lighting
Not to scale
Q1
C2
DIM
FULL
D1
D2
D3 C1
R1
C5
EN1
EN2
R2
R3 R4
FFn
R6
R5
R7
R8
R9
C3
GATE COMP OUT
VIN LED1
LED2
EN1 LED3
EN2 LED4
BIAS A6274-84 LED5
VTH
LED6
FFn GND
DR
PWMIN
ISET1
ISET2
C4
A6274-84-DS, Rev. 1
Figure 1: Typical Application Diagram for “-1” Latching Version
1 page  
A6274, A6274-1
A6284, A6284-1
Linear Current Regulator and Controller
for Automotive LED Arrays
ELECTRICAL CHARACTERISTICS: Valid at VIN = 14 V, VENx = 3.3 V; ● indicates specifications across the full operating temperature
range with TJ = –40°C to 150°C; other specifications are at TJ = 25°C, unless noted otherwise. Refer to Figure 1 for typical application circuit.
Characteristics
Symbol
Test Conditions
Min. Typ.
Max.
Unit
INPUT SPECIFICATIONS
Operating Input Voltage Range
Input Quiescent Current 1
Input Sleep Supply Current 1
INTERNAL BIAS CIRCUIT
VIN
IQ
IQSLEEP
VENx = high, FULL mode
VEN1 = VEN2 = 0 V; VDR = VBIAS
●5
–
●–
–
–
–
42 V
6 mA
6 μA
BIAS Pin Voltage
VBIAS
BIAS Pin Dropout
VBIASDROP
VBIAS Undervoltage Release Threshold
VBIASSTART
VBIAS Undervoltage Lockout Stop Threshold
VBIASSTOP
P-CHANNEL MOSFET DRIVER SPECIFICATION
IBIAS = 0 to 7 mA, 5.6 V ≤ VIN ≤ 18 V
Minimum voltage drop across VIN and
BIAS pins. IBIAS < 7 mA, VIN = 5 V
VIN rising
VIN falling
● 4.75
–
●–
●–
5
0.3
–
–
5.25
–
4.6
4.2
V
V
V
V
GATE Sink Current 1
GATE Maximum Voltage (w.r.t. VIN)
GATE Minimum Voltage (w.r.t. VIN)
PMOS Detect Threshold
IGATE(SINK)
VGATE(MAX)
VGATE(MIN)
VGATE(PMOS)
Due to on-chip current limit, 10 V < VIN < 18 V
Due to on-chip current limit, VIN = 5 V
VIN – VGATE, VLEDx = 0.3 V
VIN – VGATE, VLEDx = 1 V
Voltage measured (VIN – VGATE) at end of
startup to detect PMOS connected
4–
– mA
2–
– mA
8 10 12
V
– 130 360 mV
– 600
–
mV
LEDx CURRENT DRIVER SPECIFICATION
LEDx Regulation Voltage 2a
VLEDreg
A6274; not in derating
A6284; not in derating
●–
●–
0.4 0.7
0.55 0.85
V
V
LEDx Accuracy 3
LEDx Matching 4
Maximum LEDx Current
ErrLEDx
Measured at ILED(MAX), LEDx mismatch < 0.5 V,
5 V < VIN < 18 V, TJ = 0°C to 150°C
– 2 3.5
ΔILEDx
ISET2 connected to BIAS; compared to
average ILEDx, measured at ILED(MAX), LEDx ●
mismatch < 1 V, 5 V < VIN < 18 V
–
0.8
3
ILED(MAX)
A6274
A6284
●–
●–
60
120
–
–
%
%
mA
mA
Minimum LEDx Current
ILED(MIN)
A6274
A6284
– 6 – mA
– 12 – mA
Maximum LED Current, ISETx Pin Short-to-
Ground 2
A6274
ILED(ISETshrt) A6284
– 66
– 129
–
–
mA
mA
LED Current Ramp Time
ISETx to ILEDx Gain
tRAMP
gILED
ILEDx 10% to 90% and 90% to 10%
A6274
A6284
–8
– 248
– 492
–
–
–
μs
A/A
A/A
ISETx Voltage Level
VISET
0.015 mA ≤ IISETx ≤ 0.3 mA
– 1.2
–
V
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 
A6274, A6274-1
A6284, A6284-1
Linear Current Regulator and Controller
for Automotive LED Arrays
PWM Dimming in DIM Mode
LED dimming during DIM mode can be controlled internally by
the A6274/84, or externally. For external PWM mode, connect an
external clock pulse on the PWMIN pin, which controls dim-
ming, frequency, and duty cycle. The A6274/84 detects the logic
level on the PWMIN pin. When logic voltage is applied on the
PWMIN pin, the IC switches to external PWM mode where dim-
ming, frequency, and duty cycle are directly controlled by signals
on PWMIN pin.
In internal PWM mode, dimming frequency can be set using a
resistor connected from PWMIN pin to GND as shown in Fig-
ure 1. It is not necessary to select the PWM mode before startup:
the IC will transition from internal to external when PWMIN is
raised above VLOGIC(H); and it will transition from external to
internal when external PWMIN signal is removed for more than
20 ms. LEDx will not blink; they will be off during this period.
The recommended range for PWM frequency is 200 Hz to 2 kHz.
Maximum PWM frequency is limited due to acceptable error
at minimum PWM duty cycle. At higher PWM frequency and
smaller duty cycles, error in LED current increases due to slow
ramp-up and ramp-down in LED current. It is recommended to
use a minimum on-time > 20 µs.
The equation for internal PWM frequency setting with the
PWMIN pin resistor is given by:
fPWM = (14165 ÷ RFPWM) + 19
where fPWM is in Hz and RFPWM is in kΩ. For example, with a
29.4 kΩ resistor, fPWM = 500 Hz.
RFPWM must be greater than 5 kΩ for internal PWM; below this
value, the PWMIN pin is detected at a logic-low level and oper-
ates in external PWM mode.
The voltage on the DR pin determines the operating duty cycle.
For better accuracy, derive this voltage from BIAS using a volt-
age divider. The PWM duty cycle depends on the ratio of the DR
and BIAS pin voltages. The duty cycle can be reduced, down to
5% (see Figure 5), as:
PWM (%) = 139 × VDR ÷ VBIAS
where VDR and VBIAS are in volts (V).
100
80
60
40
20
0
0
0.6 1.2 1.8 2.4 3.0 3.6
VDR (V)
Figure 5: Relationship of Voltage on DR pin (VDR)
and Dimming Duty Cycle
VDR can be varied from 0 to 3.6 V
LED Current Setting
The peak LED current can be set at up to 60 or 120 mA per chan-
nel through the ISETx pin. ISET1 sets current through LED1-3
and ISET2 sets current through LED4-6.
By connecting ISET2 to BIAS, ISET1 current can be mirrored on
all enabled LED channels (LED1-6). This will improve current
matching between LED1-6 when all LED strings are identical.
Connect a resistor, RISETx, between ISETx pin and ground, to set
peak LED current through each channel. The value of peak LED
current through each LEDx sink is given by:
ILED(PEAK) = 298 ÷ RISETx (kΩ) for A6274
ILED(PEAK) = 590 ÷ RISETx (kΩ) for A6284
where ILED is in mA and RISETx in kΩ. This sets the peak current
through each LEDx, referred as the 100% Current. The average
LEDx current can be reduced from the 100% Current value by
dimming PWM duty ratio.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
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| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet A6274-1.PDF ] | |
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