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PDF A8514 Data sheet ( Hoja de datos )
| Número de pieza | A8514 | |
| Descripción | High Efficiency Fault Tolerant LED Driver | |
| Fabricantes | Allegro | |
| Logotipo |  |
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A8514
Wide Input Voltage Range, High Efficiency
Fault Tolerant LED Driver
Features and Benefits
• AEC-Q100 Qualified
• Wide input voltage range of 5 to 40 V for start/stop, cold
crank and load dump requirements
• Fully integrated LED current sinks and boost converter
with 60 V DMOS
• Sync function to synchronize boost converter switching
frequency up to 2.3 MHz, allowing operation above the
AM band
• Excellent input voltage transient response
• Single resistor primary OVP minimizes VOUT leakage
• Internal secondary OVP for redundant protection
• LED current of 80 mA per channel
• Drives up to 12 series LEDs in 4 parallel strings
• 0.7% to 0.8% LED to LED matching accuracy
• PWM and analog dimming inputs
• 5000:1 PWM dimming at 200 Hz
• Provides driver for external PMOS input disconnect switch
• Extensive protection against:
▫ Shorted boost switch or inductor
▫ Shorted FSET or ISET resistor
▫ Shorted output
▫ Open or shorted LED pin
▫ Open boost Schottky
▫ Overtemperature (OTP)
Package: 20-pin TSSOP with exposed
thermal pad (suffix LP)
Not to scale
Description
The A8514 is a multi-output white LED driver for small-size
LCD backlighting. It integrates a current-mode boost converter
with internal power switch and four current sinks. The boost
converter can drive up to 48 LEDs, 12 LEDs per string, at
80 mA. The LED sinks can be paralleled together to achieve
even higher LED currents, up to 320 mA. The A8514 can
operate with a single power supply, from 5 to 40 V, which
allows the part to withstand load dump conditions encountered
in automotive systems.
TheA8514 can drive an external P-FET to disconnect the input
supply from the system in the event of a fault. The A8514
provides protection against output short and overvoltage,
open or shorted diode, open or shorted LED pin, shorted
boost switch or inductor, shorted FSET or ISET resistor, and
IC overtemperature. A dual level cycle-by-cycle current limit
function provides soft start and protects the internal current
switch against high current overloads.
The A8514 has a synchronization pin that allows PWM
switching frequencies to be synchronized in the range of
580 kHz to 2.3 MHz. The high switching frequency allows
the A8514 to operate above the AM radio band.
Continued on the next page…
Applications:
LCD backlighting or LED lighting for:
▫ Automotive infotainment
▫ Automotive cluster
▫ Automotive center stack
8 toVI1N6 V
4.C7INμF
50 V
VC
100 kΩ
Typical Application Circuit
RSC
0.033 Ω
RADJ
249 Ω
2R0CΩ
Optional
22CCnF
Q1
CVDD
0.1 μF
RISET
8.25 kΩ
RFSET
10 kΩ
L1
10 μH
D1
2 A / 60 V
GATE
SW
VSENSE
VIN A8514
VDD
PAD
FAULT
PWM/EN
APWM
ISET
FSET/SYNC
OVP
LED1
LED2
LED3
LED4
COMP
AGND PGND
13R7OkVΩP
CP
120 pF
VOUT
COUT
4.7 μF
50 V
RZ
150 Ω
CZ
0.47 μF
Figure 1. Application with VIN to ground short protection, using optional P-MOSFET for input disconnect protection
A8514-DS, Rev. 5
1 page  
A8514
Wide Input Voltage Range, High Efficiency
Fault Tolerant LED Driver
ELECTRICAL CHARACTERISTICS1,2 Valid at VIN = 16 V, TA = 25°C, indicates specifications guaranteed by design and
characterization over the full operating temperature range with TA = TJ = –40°C to 125°C; unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Unit
Input Voltage Specifications
Operating Input Voltage Range3
VIN
5 – 40 V
UVLO Start Threshold
VUVLOrise VIN rising
− – 4.35 V
UVLO Stop Threshold
UVLO Hysteresis2
Input Currents
VUVLOfall
VUVLOHYS
VIN falling
− – 3.90 V
300 450 600 mV
Input Quiescent Current
IQ PWM/EN = VIH ; SW = 2 MHz, no load
− 5.5 10 mA
Input Sleep Supply Current
IQSLEEP
Input Logic Levels (PWM/EN and APWM)
VIN = 16 V, VPWMEN = VFSETSYNC = 0 V
− 2 10.0 μA
Input Logic Level-Low
VIL VIN throughout operating input voltage range – – 400 mV
Input Logic Level-High
PWM/EN Pin Open Drain
Pull-down Resistor
VIH VIN throughout operating input voltage range
RPWMEN PWM/EN = 5 V
1.5 – – V
60 100 140 kΩ
APWM Pull-down Resistor
APWM
RAPWM PWM/EN = VIH
60 100 140 kΩ
APWM Frequency2
Error Amplifier
fAPWM VIH = 2 V, VIL = 0 V
20
−
1000
kHz
Open Loop Voltage Gain
Transconductance
Source Current
Sink Current
COMP Pin Pull-down Resistance
Overvoltage Protection
AVOL
gm
IEA(SRC)
IEA(SINK)
RCOMP
ΔICOMP = ±10 μA
VCOMP = 1.5 V
VCOMP = 1.5 V
¯F¯¯A¯U¯¯L¯¯T¯ = 0
44 48 52 dB
750
990
1220
μA/V
− –350 −
μA
− 350 −
μA
− 2000 −
Ω
Overvoltage Threshold
VOVP(th) OVP connected to VOUT
7.7 8.1 8.5
V
OVP Sense Current
IOVPH
188 199 210
μA
OVP Leakage Current
IOVPLKG ROVP = 40.2 kΩ, VIN = 16 V, PWM/EN = VIL
− 0.1 1 μA
Secondary Overvoltage Protection
Boost Switch
VOVP(sec)
53 55 58
V
Switch On-Resistance
RSW
ISW = 0.750 A, VIN = 16 V
75 300 600 mΩ
Switch Leakage Current
ISWLKG VSW = 16 V, PWM/EN = VIL
− 0.1 1 μA
Switch Current Limit
Secondary Switch Current Limit2
ISW(LIM)
ISW(LIM2)
Higher than ISW(LIM)(max) for all conditions,
device latches when detected
3.0 3.5 4.2
− 7.00 −
A
A
Soft Start Boost Current Limit
Minimum Switch On-Time
ISWSS(LIM) Initial soft start current for boost switch
tSWONTIME
− 700 − mA
60 85 111 ns
Minimum Switch Off-Time
tSWOFFTIME
30 47 68 ns
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 
A8514
Wide Input Voltage Range, High Efficiency
Fault Tolerant LED Driver
Functional Description
The A8514 incorporates a current-mode boost controller with
internal DMOS switch, and four LED current sinks. It can be
used to drive four LED strings of up to 12 white LEDs in series,
with current up to 80 mA per string. For optimal efficiency,
the output of the boost stage is adaptively adjusted to the mini-
mum voltage required to power all of the LED strings. This is
expressed by the following equation:
Powering up: LED pin short-to-ground check
The VIN pin has a UVLO function that prevents the A8514
from powering-up until the UVLO threshold is reached. After
the VIN pin goes above UVLO, and a high signal is present on
the PWM/EN pin, the IC proceeds to power-up. As shown in
figure 3, at this point the A8514 enables the disconnect switch
and checks if any LEDx pins are shorted to ground and/or are not
used.
where
VOUT = max ( VLED1 ,..., VLED4 ) + VREG
(1)
VLEDx is the voltage drop across LED strings 1 through 4, and
VREG is the regulation voltage of the LED current sinks (typi-
cally 0.7 V at the maximum LED current).
The LED detect phase starts when the GATE voltage of the
disconnect switch is equal to VIN – 4.5 V. After the voltage
threshold on the LEDx pins exceeds 120 mV, a delay of between
3000 and 4000 clock cycles is used to determine the status of the
pins. Thus, the LED detection duration varies with the switching
frequency, as shown in the following table:
Enabling the IC
The IC turns on when a logic high signal is applied on the
PWM/EN pin with a minimum duration of tPWMH for the first
clock cycle, and the input voltage present on the VIN pin is
greater than the 4.35 V necessary to clear the UVLO (VUVLOrise )
threshold. The power-up sequence is shown in figure 2. Before
the LEDs are enabled, the A8514 driver goes through a system
check to determine if there are any possible fault conditions that
might prevent the system from functioning correctly. Also, if the
FSET/SYNC pin is pulled low, the IC will not power-up. More
information on the FSET/SYNC pin can be found in the Sync
section of this datasheet.
Switching Frequency
(MHz)
2
1
0.800
0.600
Detection Time
(ms)
1.5 to 2
3 to 4
3.75 to 5
5 to 6.7
The LED pin detection voltage thresholds are as follows:
LED Pin Voltage
<70 mV
150 mV
325 mV
LED Pin Status
Short-to-ground
Not used
LED pin in use
Action
Power-up is halted
LED removed from operation
None
VDD
C1
FSET/SYNC
C2
ISET
C3
PWM/EN
C4
GATE
GATE = VIN – 4.5 V
C1
LEDx
C2 LED detection period
ISET
C3
C4 PWM/EN
t
Figure 2. Power-up diagram; shows VDD (ch1, 2 V/div.), FSET/SYNC (ch2,
1 V/div.), ISET (ch3, 1 V/div.), and PWM/EN (ch4, 2 V/div.) pins,
time = 200 μs/div.
t
Figure 3. Power-up diagram; shows the relationship of an LEDx pin with
respect to the gate voltage of the disconnect switch (if used) during the
LED detect phase, as well as the duration of the LED detect phase for a
switching frequency of 2 MHz; shows GATE (ch1, 5 V/div.), LED (ch2,
500 mV/div.), ISET (ch3, 1 V/div.), and PWM/EN (ch4, 5 V/div.) pins,
time = 500 μs/div.
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 30 Páginas | |
| PDF Descargar | [ Datasheet A8514.PDF ] | |
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