Allegro A6216 2 a maximum output over operating temperature range Datasheet

A6214 and A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
FEATURES AND BENEFITS
DESCRIPTION
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The A6214 is a single-IC switching regulator that provides
constant-current output to drive high-power LEDs. It integrates
a high-side N-channel DMOS switch for DC-to-DC step- down
(buck) conversion. A true average current is output using a
cycle-by-cycle, controlled on-time method.
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AEC-Q100 qualified
Supply voltage 4.5 to 55 V
2 A maximum output over operating temperature range
Integrated MOSFET switch
Able to use either Schottky or silicon low-side diode
True average output current control
Internal control loop compensation
Integrated 5 V, 10 mA regulator for driving external load
PWM dimming via direct logic input down to 0.1% at 200 Hz
Standalone internal PWM dimming (A6216)
Analog dimming for brightness calibration and thermal
foldback
Low-power shutdown (1 µA typical)
Fault flag output (A6216)
LED string open and short protection
Cycle-by-cycle current limit
Undervoltage lockout (UVLO) and thermal shutdown (TSD)
Robust protection against:
□□ Adjacent pin-to-pin short
□□ Pin-to-GND short
□□ Component open/short faults
PACKAGES:
Output current is user-selectable by an external current sense
resistor. Output voltage is automatically adjusted to drive
various numbers of LEDs in a single string. This ensures the
optimal system efficiency.
LED dimming is accomplished by a direct logic input
pulse-width-modulation (PWM) signal at the Enable pin.
Alternatively, an Analog Dimming input can be used to calibrate
the LED current, or implement thermal foldback in conjunction
with external NTC thermistor.
The A6216 has the added capability to generate its own PWM
dimming frequency and duty cycle in stand-alone mode.
The A6214 is provided in a compact 10-pin narrow SOIC
package (suffix LK). The A6216 is in 16-pin TSSOP (suffix
LP), both with exposed pad for enhanced thermal dissipation.
It is lead (Pb) free, with 100% matte-tin leadframe plating.
APPLICATIONS:
A6214: 10-Pin SOICN (suffix LK)
Automotive lighting
• Daytime running lights
• Front and rear fog lights
• Turn/stop lights
• Map light
• Dimmable interior lights
Not to scale
A6216: 16-Pin eTSSOP (suffix LP)
Not to scale
VIN (4.5 to 55 V)
CIN
1
GND
RON
External PWM
dimming signal
External analog
dimming signal
2
EN/PWM
3
4
ADIM
5
C2
VIN
TON
A6214
SW
BOOT
EN
CSH
ADIM
CSL
VCC
GND
10
9
8
L1
CBOOT
RSENSE
D1
LED+
7
6
CLED
GND
Figure 1: A6214 (LK Package) Typical Application Circuit
A6214-16-DS, Rev. 4
January 21, 2013
November 1, 2016
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
VIN (4.5 to 55 V)
CIN
External PWM
dimming signal
External analog
dimming signal
1
RON
GND
EN/PWM
2
3
4
ADIM
VCC
CBIAS
FULL = “HIGH” = 100% Duty Cycle
FULL = “LOW” = DR controls Duty Cycle
5
R1*
R2*
FULL
6
7
8
VIN
A6216
TON
SW
BOOT
CBOOT
CSH
ADIM
CSL
VCC
GND
L1
15
RSENSE
D1
14
EN/PWM
LED+
13
CLED
12
DR
FAULT
GND
FPWM
FULL
16
RANGE
VCC
11
10
FAULT
GND
R3*
9
RANGE = “HIGH” = 0 to 100% Duty Cycle
RANGE = “LOW” = 0 to 30% Duty Cycle
RANGE
* R1, R2, R3 used in stand-alone
mode for internal PWM dimming
Figure 2: A6216 (LP Package) Typical Application Circuit
SELECTION GUIDE
Part Number
Internal PWM and
FAULT Flag
Package
Packing
A6214KLKTR-T
No
10-pin SOICN with exposed thermal pad
3000 pieces per 13-in reel
A6216KLPTR-T
Yes
16-pin TSSOP with exposed thermal pad
4000 pieces per 13-in reel
Table of Contents
Features and Benefits
Description
Applications
Packages
Typical Application Circuit (A6214)
Typical Application Circuit (A6216)
Selection Guide
Specifications
Absolute Maximum Ratings
Thermal Characteristics
1
1
1
1
1
2
2
3
3
3
Pinout Diagrams and Terminal List Tables
Functional Block Diagrams
Electrical Characteristics
Characteristic Performance
Functional Description
Application Circuit Diagrams
System Failure Detection and Protection
Package Outline Drawings
4
5
7
9
11
18
21
23
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
Characteristic
Supply Voltage
Bootstrap Drive Voltage
Switching Voltage
Symbol
Notes
Rating
Unit
VIN
–0.3 to 60
V
VBOOT
–0.3 to VIN + 8
V
VSW
Continuous
Pulsed, t < 20 ns
–1.5 to VIN + 0.3
V
–0.3 to VIN + 3
V
Enable and TON Voltage
VEN , VTON
–0.3 to VIN + 0.3
V
Linear Regulator Terminal
VCC
–0.3 to 7
V
VADIM
–0.3 to 7
V
VCSH, VCSL
–0.3 to VIN + 0.3
V
–0.3 to 7
V
–0.3 to VCC + 0.3
V
–40 to 125
°C
ADIM Pin Voltage
Current Sense Voltages
FAULT, FULL, RANGE, and
FPWM Voltages
DR Pin Voltage
VFAULT, VFULL,
VRANGE, VFPWM
VDR
A6216 only
A6216 only; DR pin voltage must not be higher
than VCC even when device is off (VCC = 0 V)
Operating Ambient Temperature
TA
Maximum Junction Temperature
TJ(max)
150
°C
Tstg
–55 to 150
°C
Storage Temperature
K temperature range for automotive
THERMAL CHARACTERISTICS*: May require derating at maximum conditions; see application section for optimization
Characteristic
Symbol
Test Conditions*
A6214 Package LK
Package Thermal Resistance
(Junction to Ambient)
Package Thermal Resistance
(Junction to Pad)
RθJA
A6216 Package LP
RθJP
Value
Unit
On 4-layer PCB based on JEDEC standard
35
°C/W
On 4-layer PCB based on JEDEC standard
34
°C/W
On 2-layer PCB with 3.8 in.2 of copper area each side
43
°C/W
2
°C/W
*Additional thermal information available on the Allegro™ website.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
Pinout Diagram for A6214
(LK Package)
10 SW
VIN 1
TON 2
EN 3
9 BOOT
PAD
8 CSH
ADIM 4
7 CSL
VCC 5
6 GND
Pinout Diagram for A6216
(LP Package)
ADIM 4
VCC 5
Function
1
VIN
Supply voltage input voltage for IC and buck regulator
2
TON
Regulator on-time setting resistor terminal. Connect a resistor
between VIN and TON to set the switching frequency.
3
EN/PWM
4
ADIM
Analog dimming control voltage input
5
VCC
Internal IC bias regulator output. Connect 1uF MLCC to GND.
Can be used to supply up to 10mA for external load.
6
GND
Ground terminal
7
CSL
Current Sense (Lower end) feedback input for LED current
8
CSH
Current Sense (Higher end) feedback input for LED current
9
BOOT
10
SW
Switched output terminal
-
PAD
Exposed pad for enhanced thermal dissipation; connect to GND
Logic input for Enable and PWM dimming
DMOS gate driver bootstrap terminal
Terminal List Table for A6216 (LP Package)
1
VIN
Supply voltage input voltage for IC and buck regulator
2
TON
Regulator on-time setting resistor terminal. Connect a resistor
between VIN and TON to set the switching frequency
13 CSL
3
EN/PWM
12 GND
4
ADIM
Analog dimming control voltage input
5
VCC
Internal IC bias regulator output. Connect 1uF MLCC to GND.
Can be used to supply up to 10mA for external load
6
DR
7
GND
Ground terminal
8
FULL
Selects 100% dimming duty cycle or DR control of duty cycle
9
RANGE
Selects DR control range, high range gives DR control from 5%
to 100%, low range gives DR control from 5% to 33%.
10
FPWM
Dimming PWM frequency control. In stand-alone mode, connect
a resistor to GND to set the dimming PWM frequency
11
FAULT
Open-drain output which is pulled low in case of fault. Connect
through an external pull-up resistor to the desired logic level.
12
GND
Ground terminal
13
CSL
Current Sense (Lower end) feedback input for LED current
14
CSH
Current Sense (Higher end) feedback input for LED current
15
BOOT
16
SW
Switched output terminal
-
PAD
Exposed pad for enhanced thermal dissipation; connect to GND
14 CSH
PAD
Name
Name
15 BOOT
EN/PWM 3
Number
Number
16 SW
VIN 1
TON 2
Terminal List Table for A6214 (LK Package)
DR 6
11 FAULT
GND 7
10 FPWM
FULL 8
9 RANGE
Function
Logic input for Enable and PWM dimming
Dimming Ratio control. In stand-alone mode: connect to resistor
divider network from VCC to set the dimming PWM duty cycle
DMOS gate driver bootstrap terminal
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
FUNCTIONAL BLOCK DIAGRAMS
VIN (4.5 to 55 V)
CIN
VIN
RON
TON
GND
EN/PWM
VOUT
EN/PWM
VIN
CBIAS
ADIM
VIN
CBOOT
On-Time
Select
On-Time
VCC
BOOT
VCC
SW
Duty
Cycle
Control
RSENSE
D1
GND
VOUT
LED+
CSH
Enable
LDO
L1
CSL
VREF
Radj
CLED
GND
Internal 5 V
ADIM
iLED
Reference
A6214
Radj is optional. It can be used to fine-adjust the LED current
in case the desired value of R SENSE is not available.
Figure 3: Simplified Functional Block Diagram for A6214
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
VIN (4.5 to 55 V)
VIN
VOUT
RON
CIN
TON
On-Time
Select
VIN
VCC
EN/PWM
CBOOT
Buck
Converter
Duty Cycle
Control
On-Time
LDO
Internal
5 V bias
LED
Current
EN/PWM
VOUT
LED+
CSH
CSL
CLED
Radj
Enable
GND
DR
R2
FPWM
RFPWM
ADIM
RSENSE
D1
GND
VCC
R1
L1
SW
Differential
Amp
Up to 10 mA
external load
CBIAS
VIN
Gate
Driver
GND
BOOT
VCC
ADIM
RANGE
Internal PWM
Duty Cycle
Generator
OSC
FULL
VCC
FAULT
(200 Hz to 1 kHz)
VREF
(0 to 200 mV)
iLED
Reference
FAULT
FAULT
Mode
A6216
Figure 4: Simplified Functional Block Diagram for A6216
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
ELECTRICAL CHARACTERISTICS: Valid at VIN = 12 V, VOUT = 6 V, TA = –40°C to 125°C, typical values at TA = 25°C, unless
otherwise noted
Characteristics
Symbol
Input Supply Voltage
VIN Undervoltage Lockout Threshold
VIN Undervoltage Lockout Hysteresis
VUVLO
IIN
IINSD
Buck Switch Current Limit Threshold
ISWLIM
Buck Switch On-Resistance
R
BOOT Undervoltage Lockout
Threshold
BOOT Undervoltage Lockout
Hysteresis
VIN increasing
DS(on)
VBOOTUV
Max.
Unit
–
55
V
–
4.3
V
150
300
mV
VCSH – VCSL = 0.5 V, EN = VIH, RON = 402 kΩ
–
5
–
mA
EN = VIL
–
1
10
µA
2.5
3.25
4
A
–
0.25
0.4
Ω
3.1
3.4
3.7
V
–
750
–
mV
–
75
100
ns
VBOOT = VIN + 4.3 V, TA = 25°C, ISW = 0.5 A
VBOOT to VSW increasing
Switching Minimum Off-Time
tOFFmin
VCSH – VCSL = 0 V
Switching Minimum On-Time
tONmin
VCSH – VCSL = 0.3 V
tON
Typ.
4.5
–
VBOTUVHYS VBOOT to VSW decreasing
Selected On-Time
Min.
–
VUVLO_HYS VIN decreasing
VIN Pin Supply Current
VIN Pin Shutdown Current
Test Conditions
VIN
–
75
100
ns
800
1000
1200
ns
VCSH – VCSL decreasing, SW turns on, ADIM
tied to VCC
194
200
206
mV
2.65
–
50
V
RON = 402 kΩ
REGULATION COMPARATOR AND ERROR AMPLIFIER
Load Current Sense Regulation
Threshold at 100% 1
VCSREG
Output Current Sense Common
Mode Voltage (measured at CSL pin)
VOUT
VIN = 55 V, fSW = 500 kHz, iLED = 0.5 A
CSH Input Sense Current
ICSH
VCSH – VCSL = 0.2 V
–
–190
–
µA
CSL Input Sense Current
ICSL
VCSH – VCSL = 0.2 V
50
75
100
µA
VCC
0 mA < ICC < 5 mA, VIN > 6 V
INTERNAL LINEAR REGULATOR
VCC Regulated Output
VCC Current Limit 2
VCC Dropout Voltage
iVCCLIM
VLDO
4.85
5
5.15
V
VCC ≥ 4.75 V
10
20
–
mA
Measure VIN – VCC. VIN = 5 V, iVCC = 9 mA
–
0.15
0.35
V
ENABLE/PWM INPUT
Logic High Voltage
VIH
VEN increasing
1.8
–
–
V
Logic Low Voltage
VIL
VEN decreasing
–
–
0.4
V
RENPD
VEN = 5 V
–
100
–
kΩ
tPWML
Measured while EN = low, during dimming
control, and internal references are powered-on
(exceeding tPWML results in shutdown)
10
17
–
ms
External RFPWM = 30 kΩ from FPWM pin to GND
180
200
220
Hz
–
–
0.8
V
EN Pin Pull-down Resistance
Maximum PWM Dimming Off-Time
INTERNAL PWM DIMMING (A6216 ONLY)
Internal PWM Dimming Frequency
fPWM
FULL, RANGE Pins Input Low Voltage
VIL
FULL, RANGE Pins Input High Voltage
VIH
Internal PWM Duty Cycle
2
–
–
V
DPWM5(L)
VDR driven by resistor divider from VCC,
VCC / VDR = 9.72, fPWM = 200 Hz, RANGE = low
4.75
5
5.25
%
DPWM5(H)
VDR driven by resistor divider from VCC,
VCC / VDR = 29.2, fPWM = 200 Hz, RANGE = high
4.5
5
5.5
%
DPWM90(H)
VDR driven by resistor divider from VCC,
VCC / VDR = 1.62, fPWM = 200 Hz, RANGE = high
87
90
93
%
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
7
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
ELECTRICAL CHARACTERISTICS (continued): Valid at VIN = 12 V, VOUT = 6 V, TA = –40°C to 125°C, typical values at
TA = 25°C, unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Unit
2.1
–
–
V
–
100
–
mV
38.4
40
41.4
mV
ANALOG DIMMING INPUT
Input Voltage for 100% LED Current
VADIMH
Regulation Threshold at 50% Analog
Dimming
VCSREG50
VADIM = 1 V
Regulaton Threshold at 20% Analog
Dimming
VCSREG20
VADIM = 0.4 V
FAULT Pull-Down Voltage
VFAULT(PD)
Fault condition asserted, pull-up current = 1 mA
–
–
0.4
V
FAULT Pin Leakage Current
VFAULT(LKG)
Fault condition cleared, pull-up to 5 V
–
–
1
µA
VCSH – VCSL = VCSREG
FAULT PIN (A6216 ONLY)
TIMERS
Cool Down Timer for Fault Retry
tRETRY
–
1
–
ms
Delay Timer for Reporting LED Open
Fault
tOPEN
–
50
–
µs
Thermal Shutdown Threshold 3
TSD
150
165
180
°C
Thermal Shutdown Hysteresis
TSDHYS
–
25
–
°C
THERMAL SHUTDOWN
In test mode, a ramp signal is applied across CSH and CSL pins to determine the CS regulation threshold voltage. In actual application, the average
CS voltage is regulated at VCSREG regardless of ripple voltage.
2 The internal linear regulator is capable of supplying up to 10 mA to external devices.
3 Determined by design and characterization. Not production tested.
1
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
CHARACTERISTIC PERFORMANCE
Average LED Current vs. PWM Duty Cycle
Normalized LED Current vs ADIM Voltage
1
(VIN = 12 V, VOUT = 6 V, iLED = 1 A, TA = 25°C)
100%
Normalize LED Current
Normalized LED Current (%)
80%
60%
Measured Current
40%
(RTON = 442 kΩ, load = 2× LED at 1.5 A, fPWM = 200 Hz)
0.1
0.01
VIN = 24 V, L = 47 µH
Target
VIN = 12 V, L = 22 µH
20%
VIN = 12 V, L = 47 µH
Ideal
0.001
0%
0
0.4
0.8
1.2
ADIM Voltage (V)
1.6
2
0.1
2.4
Internal PWM Duty Cycle vs DR Pin Voltage
Frequency of Internal PWM vs. FPWM Resistance
(VIN = 12 V, VOUT = 6 V, VDR = 1.7 V, TA = 25°C)
100
90
1600
80
1400
Measured for RANGE=H
60
Target for RANGE=H
1200
fPWM (Hz)
70
Measured for RANGE=L
1000
800
Calculated
600
Measured
Target for RANGE=L
40
100
Figure 6: PWM Dimming Performance –
Duty cycle down to ~0.1% (1000:1) can be achieved
with higher VIN or lower inductance.
(VIN = 12 V, VOUT = 6 V, RTON = 300 kΩ, fPWM = 300 Hz, TA = 25ºC)
Duty Cycle (%)
10
PWM Duty Cycle (%)
Figure 5: Analog Dimming Performance –
LED current can be reduced linearly down to 10%
using the ADIM pin voltage.
50
1
30
400
20
200
10
0
0
0
0
0.4
0.8
1.2
1.6
2
VDR (V)
2.4
2.8
3.2
3.6
4
Figure 7: Internal PWM Dimming Operation (A6216 only) –
Duty cycle is controlled by the voltage at DR pin.
10
RFPWM (kΩ)
20
30
Figure 8: Internal PWM Dimming Frequency
(A6216 only) as a function of FPWM Resistance
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
CHARACTERISTIC PERFORMANCE (continued)
CH1 = VPWM (5 V/div)
CH2 = VSW (5 V/div)
CH3 = VOUT (5 V/div)
CH4 = iLED (500 mA/div)
Time Scale= 500 µs/div
Figure 9: Startup for PWM Dimming operation –
RTON = 442 kΩ, L = 22 µH, VIN = 12 V, Output = 2× LED at
1.5 A, PWM = 1 kHz 50%. Note that there is a ~150 µs delay
for the first PWM = H pulse, but none for subsequent pulses.
CH1 = VPWM (5 V/div)
CH2 = VSW (5 V/div)
CH3 = VOUT (5 V/div)
CH4 = iLED (500 mA/div)
Time Scale= 5 µs/div
Figure 10: PWM Dimming with on-time of just 10 µs –
RTON = 442 kΩ, L = 22 µH, VIN = 12 V, Output = 2× LED at
1 A. Note that the LED current takes ~5µs to ramp up to
its steady-state value.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
FUNCTIONAL DESCRIPTION
The A6214 is a buck regulator designed for driving a high-current
LED string. It utilizes average current mode control to maintain
constant LED current and consistent brightness. The LED current
level is easily programmable by selection of an external sense
resistor, with a value determined as follows:
RSENSE = VCSREG / iLED
fSW = 1 / [ k × (RTON + RINT )]
where k = 0.00434, with fSW in MHz, tON in µs, and RON and
RINT (internal resistance, 20 kΩ) in kΩ.
2200
2000
If necessary, a resistor can be inserted in series with the CSL pin
to fine-tune the LED current, as shown below:
1800
1600
1400
fSW (kHz)
where VCSREG = VCSH – VCSL = 0.2 V typical.
1200
iCSH
iLED
CSH
VCSREG
tON = k × (RTON + RINT ) × ( VOUT / VIN )
CSL
iCSL
Radj
RSENSE
+
VSENSE
–
–
+
iCSL × Radj
VCSREG = iLED × RSENSE + iCSL × Radj
Therefore
iLED = (VCSREG – iCSL × Radj) / RSENSE
Figure 11: How To Fine-Tune LED Current Using Radj
For example, with a desired LED current of 1.4 A, the required
RSENSE = 0.2 V / 1.4 A = 0.143 Ω. But the closest power resistor
available is 0.13 Ω. Therefore, the difference is
Radj × iCSL = 0.2 V – 1.4 A × 0.13 Ω = 0.018 V
where iCSL = 75 µA typical
Radj = 0.018 V / 75 µA = 240 Ω
The LED current is further modulated by the ADIM (Analog
Dimming) pin voltage. This feature can be used for LED brightness calibration, or for thermal foldback protection. See Analog
Dimming section for details.
Switching Frequency
The A6214 operates in fixed on-time mode during switching. The
on-time (and hence switching frequency) is programmed using
an external resistor connected between the VIN and TON pins, as
given by the following equation:
1000
800
600
400
200
0
0
100
200
300
400
500
600
700
800
900
1000
RTON (kΩ)
Figure 12: Switching Frequency vs. TON resistance
ENABLE AND DIMMING
The IC is activated when a logic high signal is applied to the EN
(enable) pin. The buck converter ramps up the LED current to a
target level set by RSENSE.
When the EN pin is forced from high to low, the buck converter
is turned off, but the IC remains in standby mode for up to 10 ms.
If EN goes high again within this period, the LED current is
turned on immediately. Active dimming of the LED is achieved
by sending a PWM (pulse-width modulation) signal to the EN
pin. The resulting LED brightness is proportional to the duty cycle
(tON / Period) of the PWM signal. A practical range for PWM dimming frequency is between 100 Hz (Period = 10 ms) and 2 kHz.
If EN is low for more than 17 ms, the IC enters shutdown mode
to reduce power consumption. The next high signal on EN will
initialize a full startup sequence, which includes a startup delay
of approximately 150 µs. This startup delay is not present during
PWM operation.
The EN pin is high-voltage tolerant and can be directly connected
to a power supply. However, if EN is higher than the VIN voltage
at any time, a series resistor (1-10 kΩ) is required to limit the current flowing into the EN pin. This series resistor is not necessary
if EN is driven from a logic input.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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11
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
PWM DIMMING RATIO
The brightness of the LED string can be reduced by adjusting the
PWM duty cycle at the EN pin as follows:
Dimming ratio = PWM on-time / PWM period
For example, by selecting a PWM period of 5 ms (200 Hz PWM
frequency) and a PWM on-time of 5 µs, a dimming ratio of 0.1%
can be achieved. This is sometimes referred to as “1000:1 dimming.”
In an actual application, the minimum dimming ratio is determined by various system parameters, including: VIN , VOUT ,
inductance, LED current, switching frequency, and PWM
frequency. As a general guideline, the minimum PWM on-time
should be kept at 5 µs or longer. A shorter PWM on-time is
acceptable under more favorable operating conditions, such as
higher VIN and lower inductance.
INTERNAL PWM DIMMING (A6216 ONLY)
In addition to external PWM dimming through EN pin, the
A6216 is able to generate an internal PWM dimming signal in
stand-alone mode. Frequency of the internal PWM signal can be
set by connecting a resistor between FPWM pin and GND, as
given by the following equation:
fPWM = c / (RFPWM + RINT)
where c = 6400, with fPWM in Hz, and RFPWM and RINT (internal
resistance, 0.5 kΩ) in kΩ.
This frequency can be between 200 Hz and 1 kHz when RANGE
is High, or 200 Hz and 500 Hz when RANGE is Low. Duty cycle
of PWM signal is linearly proportion to the voltage at DR (Dimming Ratio) pin. This is illustrated by the following chart:
Internal PWM
Duty Cycle
To disable internal PWM generation, tie DR pin to VCC pin. (Do
NOT leave DR pin floating or connected to GND.) The FPWM
pin can be either left open, or tied to VCC. Note that at any time
during stand-alone PWM dimming mode, if EN pin goes low, the
LED is turned off immediately. This is illustrated in figure below.
Internal PWM
External PWM
(EN pin)
LED Current
Figure 14: LED Current when Both Internal and External PWM Dimming Signals are Applied
ANALOG DIMMING
In addition to PWM dimming, the A6214/16 also provides an
analog dimming feature. When VADIM is over 2 V, the LED current is at 100% level (as defined by the SENSE resistor). When
VADIM is below 2 V, the LED current decreases linearly down to
20% at VADIM = 0.4 V. This is shown in the following figure:
200 mV
±6 mV
(100%)
VCSREG
RANGE = High
100%
100 mV
90%
ADIM pin
voltage
40 mV
0
RANGE = Low
33%
30%
0.4 V
DR pin
voltage (V)
5%
0%
0V
are with VCC = 5 V. For better accuracy, derive the DR pin voltage using a resistor divider connected between VCC and GND.
A practical range of internal PWM duty cycle when RANGE =
High is between 5% (VDR = 0.17 V) and 90% (VDR = 3.08 V).
To improve accuracy at low duty cycles between 5% and 30%,
set RANGE to Low. If DR pin is above 3.4 V, duty cycle stays at
around 99% if RANGE = High, 33% if Low.
0.17
0.514
3.08 3.43
~4
5
Figure 13: Variation of PWM Duty Cycle
with respect to DR Pin Voltage
It should be noted that the internal PWM duty cycle depends on
the ratio between VCC and VDR. The voltages shown in the chart
1V
2V
Figure 15: ADIM Pin Voltage Controls SENSE Reference
Voltage (hence LED current)
It is possible to pull ADIM pin below 0.4 V to achieve lower
than 20% analog dimming. However, the linearity may suffer if
the LED ripple current become too large compared to the average current. For example, if the LED ripple current is ±100 mA,
then the average current can only be dimmed down to 100 mA
linearly.
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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12
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
ADIM pin can be used in conjunction with PWM dimming to
provide wider LED dimming range over 1000:1. In addition, the
IC can provide thermal foldback protection by using an external
NTC (negative temperature coefficient) thermistor, as shown
below:
VIN
MOS
CIN
VCC
RS
NTC
R1
ADIM
RP
VSW
VIN
t
0
–VD
iL
iRIPPLE
where D is the duty cycle, and VD is the forward drop of the
diode D1 (typically under 0.5 V for Schottky diode).
t
During SW on-time:
iRIPPLE = (VIN – VOUT) / L × tON = (VIN – VOUT) / L × t × D
where D = tON / t.
During SW off-time:
iRIPPLE = (VOUT + VD) / L × tOFF = (VOUT + VD) / L × t × (1 – D)
RSC
VOUT
GND
If analog dimming is not required, the ADIM pin must be connected to VCC pin. (Do NOT leave ADIM pin floating or connected to GND.)
D = tON / (tON + tOFF )
iL
D
Figure 16: Using an External NTC Thermistor
to Implement Thermal Foldback
OUTPUT VOLTAGE AND DUTY CYCLE
The figure below provides simplified equations for approximating output voltage. The output voltage of a buck converter is
approximately given as:
VOUT = VIN × D – VD × (1 – D ) ≈ VIN × D, if VD << VIN
L
SW
tON
tOFF
Period, t
Figure 17: Simplified Waveforms for a Buck Converter
Simplified equation for output voltage:
VOUT = VIN × D – VD × (1 – D)
If VD << VIN, then VOUT = VIN × D approximately.
More precisely:
VOUT = (VIN – iAVG × RDS(on)) × D – VD × (1 – D) – iAVG × (DCR + RSC)
where DCR is ther internal resistance of inductor and RSC is the
sense resistance.
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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13
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
MINIMUM AND MAXIMUM OUTPUT VOLTAGES
For a given input voltage, the maximum output voltage depends
on the switching frequency and minimum tOFF . For example, if
tOFF(min) = 150 ns and fSW = 2 MHz, then the maximum duty
cycle is 80%. So for a 12.5 V input, the maximum output is
approximately 10 V (based on the simplified equation of VOUT
= VIN × D). This means up to 3 LEDs can be operated in series,
assuming Vf = 3.2 V or less for each LED.
The minimum output voltage depends on minimum tON and
switching frequency. For example, if the minimum tON = 100 ns
and fSW = 1 MHz, then the minimum duty cycle is 10%. That
means with VIN = 24 V, the theoretical minimum VOUT is just
2.4 V. However, the internal current sense amplifier is designed
to operate down to VOUT = 2.65 V. Therefore the output voltage
should not go lower than 2.65 V, or else the current accuracy will
suffer.
To a lesser degree, the output voltage is also affected by other
factors such as LED current, on-resistance of the high-side
switch, DCR of the inductor, and forward drop of the low-side
diode.
As a general rule, switching at lower frequencies allows a wider
range of VOUT , and hence more flexible LED configurations.
24
22
20
18
VOUT (V)
16
14
VOUT(max) (V)
12
VOUT(min) (V)
If the LED string is completely shorted (VOUT = 0 V), LED
current regulation will become impossible. The output current
will increase until it trips SW overcurrent protection. The IC
then shuts down and retries after approximately 1 ms cooldown
period.
THERMAL BUDGETING
The A6214 is capable of supplying a 2 A current through its
high-side switch. However, depending on the duty cycle, the
conduction loss in the high-side switch may cause the package to
overheat. Therefore care must be taken to ensure the total power
loss of package is within budget. For example, if the maximum
temperature rise allowed is ∆T = 50°C at the device case surface,
then the maximum power dissipation of the IC is 1.4 W. Assuming the maximum RDS(on) = 0.4 Ω and a duty cycle of 85%, then
the maximum LED current is limited to 2 A approximately. At a
lower duty cycle, the LED current can be higher.
FAULT HANDLING
The A6214 is designed to handle the following faults:
• Pin-to-ground short
• Pin-to-neighboring pin short
• Pin open
• External component open or short
• Output short to GND
The waveform in the figure below illustrates how the A6214
responds in the case in which the current sense resistor or the
CSH and CSL pins are shorted together. Note that the SW pin
overcurrent protection is tripped at around 3.5 A, and the part
shuts down immediately. The part then goes through startup retry
after approximately 1 ms of cooldown period.
10
8
6
4
2
0
0
0.2
0.4
0.6
0.8
1
1.2
Frequency (MHz)
1.4
1.6
1.8
2
Figure 18: Minimum and Maximum Output Voltage vs.
Switching Freqency
(VIN = 24 V, minimum tON and tOFF of 100 ns)
If the required output voltage is lower than that permitted by the
minimum tON , the controller will automatically extend the tOFF ,
in order to maintain the correct duty cycle. This means that the
switching frequency will drop lower when necessary, in order to
keep the LED current in regulation.
CH1 = VPWM (5 V/div)
CH2 = VSW (5 V/div)
CH3 = VOUT (5 V/div)
CH4 = iLED (1 A/div)
Time Scale = 200 µs/div
Figure 19: In case of sense resistor short fault –
Output current rises until it trips SW OCP at ~3.5 A. The
IC shuts off and retries after ~1 ms cooldown period.
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115 Northeast Cutoff
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14
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
As another example, the waveform in figure below shows the
fault case where external diode D1 is missing or open. As LED
current builds up, a larger-than-normal negative voltage is
developed at the SW node during off-time. This voltage trips the
missing detection function of the IC. The IC then shuts down
immediately, and waits for a cooldown period before retry.
CH1 = VFAULT (5 V/div)
CH2 = VSW (5 V/div)
CH3 = VOUT (5 V/div)
CH4 = iLED (1 A/div)
Time Scale = 1 µs/div
Figure 20: In case of missing low-side diode –
SW voltage fall below –2 V and trips Missing-Diode
fault. FAULT pin (A6216 only) is pulled Low immediately. The IC shuts off and retries after cooldown period.
COMPONENT SELECTIONS
The inductor is often the most critical component in a buck converter. Follow the procedure below to derive the correct parameters for the inductor:
1. Determine the saturation current of the inductor. This can be
done by simply adding 20% to the average LED current:
iSAT ≥ iLED × 1.2.
2. Determine the ripple current amplitude (peak-to-peak value). As
a general rule, ripple current should be kept between 10% and
30% of the average LED current:
0.1 < iRIPPLE(pk-pk) / iLED < 0.3.
3. Calculate the inductance based on the following equations:
L = (VIN – VOUT ) × D × t / iRIPPLE , and
D = (VOUT + VD ) / ( VIN + VD ) ,
where
D is the duty cycle,
t is the period 1/ fSW , and
VD is the forward voltage drop of the Schottky diode D1.
OUTPUT FILTER CAPACITOR
The A6214 is designed to operate in current regulation mode.
Therefore it does not require a large output capacitor to stabilize
the output voltage. This results in lower cost and smaller PCB
area. In fact, having a large output capacitor is not recommended.
In most applications, however, it is beneficial to add a small filter
capacitor (around 0.1 μF) across the LED string. This cap serves
as a filter to eliminate switching spikes seen by the LED string.
This is very important in reducing EMI noises, and may also help
in ESD testing.
ADDITIONAL NOTES ON RIPPLE CURRENT
• For consistent switching frequency, it is recommended to
choose the inductor and switching frequency to ensure the inductor ripple current percentage is at least 10% over normal operating voltage range (ripple current is lowest at lowest VIN).
If ripple current is less than 10%, the switching frequency may
jitter due to insufficient ripple voltage across CSH and CSL pins.
However, the average LED current is still regulated.
• For best accuracy in LED current regulation, a low current
ripple of less than 20% is required.
• There is no hard limit on the highest ripple current percentage
allowed. A 40% ripple current is still acceptable, as long as both
the inductor and LEDs can handle the peak current (average current × 1.2 in this case). However, higher ripple current % affects
the accuracy of LED current, and limits the minimum current that
can be regulated when using ADIM.
• In general, allowing a higher ripple current percentage enables
lower-inductance inductors to be used, which results in smaller
size and lower cost.
• If lower ripple current is required for the LED string, one solution is to add a small capacitor (such as 1 to 2.2 μF) across the
LED string from LED+ to GND. In this case, the inductor ripple
current remains high while the LED ripple current is greatly
reduced.
• The effectiveness of this filter capacitor depends on many factors, such as: switching frequency, inductors used, PCB layout,
LED voltage and current, and so forth.
• The addition of this capacitor introduces a longer delay in LED
current during PWM dimming operation. Therefore the accuracy
of average LED current is reduced at short PWM on-time.
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
15
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
INDUCTOR SELECTION CHART
The chart in figure below summarizes the relationship between
LED current, switching frequency, and inductor value. Based on
this chart: assuming LED current = 1 A and L = 22 μH, then minimum fSW = 0.7 MHz in order to keep the ripple current at 20% or
lower. (Note: VOUT = VIN / 2 is the worst case for ripple current).
If the switching frequency is lower, then a larger inductance must
be used to meet the same ripple current requirement.
2.0
Switching Frequency (MHz)
1.8
1.6
1.4
1.2
L = 10 µH
1.0
L = 15 µH
0.8
L = 22 µH
0.6
L = 33 µH
0.4
L = 47 µH
0.2
0.0
0
0.5
1
LED Current (A)
1.5
2
Figure 21: Relation between minimum switching frequency and LED current, given different inductance used
(VIN = 12 V, VOUT = 6 V, ripple current = 20%)
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115 Northeast Cutoff
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16
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
Effects of Output Capacitor on LED Ripple Current
VIN
VIN
L1
RSENSE
D1
L1
iRIPPLE
LED+
iRIPPLE
RSENSE
D1
LED+
iRIPPLE
GND
Without output capacitor:
The same inductor ripple current flows through
sense resistor and LED string.
GND
With a small capacitor across LED string:
Ripple current through LED string is reducted, while
ripple voltage across RSENSE remains high.
Figure 22: Using an Output Filter Capacitor to Reduce
Ripple Current in LED String
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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17
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
APPLICATION CIRCUIT DIAGRAMS
VIN (20 to 55 V)
C1
33 µF
63 V
C2
4.7 µF
100 V
GND
L1
47 µH 2 A
1
R1
2
442 kΩ
EN/PWM
A6214
VIN
BOOT
TON
3
SW
CSH
EN
4
CSL
ADIM
5
GND
VCC
C5
1 µF
10
C4
9
0.1 µF
RSENSE
0.15 Ω
D1
60 V
2A
8
LED+
Radj
7
71.5 Ω
6
LED
String
(~15 V)
C3
0.1 µF
100 V
GND
iLED = (VCSREG – iCSL × Radj) / RSENSE
= (0.2 – 0.000007 × 71.5) / 0.15 = 1.3 A
Suggested Components
Symbol
Part Number
Manufacturer
C1
HHXA630ARA330MHA0G
United Chemi-Con
C2
C3225X7S2A475M200AB
TDK
C3
CGA4J2X7R2A104M125AA
TDK
L1
CDRH105RNP-470NC
Sumida
D1
10MQ060NTRPBF
Vishay
RSENSE
RL1632R-R150-F
Susumu
Figure 23: Application Circuit Example for A6214
(for driving 15 V LED at 1.3 A, fSW = 500 kHz)
VIN (4.5 to 55 V)
CIN
External PWM
dimming signal
1
RON
GND
442 kΩ
EN/PWM
2
3
4
VCC
R1
RS
RP
CBIAS
1 µF
5
6
7
NTC
8
VIN
A6216
TON
SW
BOOT
CBOOT
0.1 µF
15
14
EN/PWM
CSH
ADIM
CSL
VCC
GND
FAULT
GND
FPWM
RANGE
iLED = 1 A
before foldback
RSENSE
0.2 Ω
D1
60 V
2A
LED+
13
12
DR
FULL
L1
47 µH 2 A
16
VCC
11
10 kΩ
10
9
CLED
0.1 µF
GND
FAULT
VCC
Thermal Foldback using NTC
Figure 24: Application Circuit Example for A6216
(with External PWM and Thermal Foldback)
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115 Northeast Cutoff
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18
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
APPLICATION CIRCUIT DIAGRAMS (continued)
VIN
VIN
A6214/6
A6214/6
L1
SW
LED+
RCS1
iLED1
GND
RCS2
SW
iLED2
D1
D2
CLED
GND
CLED
CSH
CSL
L2
CSH
LED–
CSL
Figure 25: Using two (or more) A6214/16 in parallel to drive the same LED string. Total
LED current is the sum of currents from each driver.
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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19
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
APPLICATION CIRCUIT DIAGRAMS (continued)
PROTECTION FROM OUTPUT LC-RESONANCE
During normal operation, if the LED load becomes disconnected
(due to a bad connector, for example), the output capacitor CLED
will be charged up to VOUT = VIN. Later, when the LED load is
reconnected, higher voltage stored in CLED will create a huge
current spike through the load. Normally this does not create
any problems, since the current spike will decay within a few
microseconds. However, if the LED load is connected through
long cables, the parasitic inductance LK in the cable will form an
LC-resonant circuit with CLED. If the resonant circuit is underdamped, VOUT may oscillate and becomes negative. This could
subject CSH and CSL pins to negative spike voltage exceeding
their Absolute Maximum Ratings. Therefore the following precautions are recommended to avoid output oscillation:
• Use shortest possible LED cables to reduce LK.
• Use lower capacitance for CLED to reduce stored energy
(EC = 0.5 × CLED × VIN2).
• Critically damp the output LC-resonant circuit, as shown
in Figure 26. The drawback is additional power loss during
PWM dimming operation (since C1 is charged and discharged
through R1 during each PWM cycle).
In case the output LC resonance cannot be eliminated (due to
long LED cables, for example), consider adding a Schottky barrier diode (SBD) in parallel with CLED, as shown in Figure 28.
The SBD clamps the negative spike of the LC resonance, so CSH
and CSL pins are protected. This is the most effective protection
with minimal side effects.
CLED initially charged to
VOUT = 50 V when load is open
In critically-damped circuit,
VOUT stays positive
In underdamped circuit,
VOUT goes negative
Time/µs
Figure 27: Simulation Results Showing Difference in VOUT
Between Underdamped and Critically-Damped Circuits
L1
L1
CSH
RSENSE
CSL
VOUT
Total parasitic
inductance of cable
S1
LK 0.4 µH
VLED
CSH
RSENSE
CSL
VOUT
S1
Total parasitic
inductance of cable
LK
ic = 0 A
R1
1Ω
C1
0.22 µF
Add R1 and C1 to
critically damp the
LC-resonant circuit
ESR
10 mΩ
CLED
0.1 µF
ic = 50 V
Large current spike
when S1 is closed
ROUT
1Ω
Total resistance
of output path
GND
Figure 26: Countermeasure to Prevent VOUT Oscillation
During Output Intermittent Open/Short Fault
CLED
VLED
Add D2 to clamp the
negative voltage of
LC-resonant circuit
D2
(60 V 1 A)
GND
Figure 28: Using Schottky Diode to Clamp the Negative
spike from Output LC-Resonance
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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20
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
SYSTEM FAILURE DETECTION AND PROTECTION
VIN C1, C2 = open or short
1
GND
R1 = open
or short
2
EN/PWM
3
4
C5 = open
or short
5
VIN
A6214
SW
BOOT
TON
EN
CSH
ADIM
CSL
GND
VCC
10
9
C4 open
or short
L1 = open
or short
RSENSE
open or short
D1 = open
or short
8
LED+
7
6
LED string open
or short to GND
C3 open
or short
GND
SYSTEM-LEVEL FAILURE MODES
Protected against open/short fault for all external
components, including:
• LED string
• Sense resistor
• Inductor
• Diode
• Input/output caps, etc.
IC-LEVEL FAILURE MODES
Protected against:
• Any pin open
• Any pin shorted to GND
• Adjacent pin-to-pin short
Figure 29: Showing Various Possible Fault Cases in an
Application Circuit
System Failure Mode Table (partial)
Symptom Observed
FAULT flag
(A6216)
asserted?
A6214/16 Response
Inductor shorted
Dim light from LED
Yes
Current spike trips SW secondary OCP and turns off switching. Retries after 1 ms.
Sense resistor open
No light from LED
Yes
High differential sense voltage causes IC to shut off switching. Retries after 1 ms.
Failure Mode
Sense resistor shorted
Dim light from LED
Yes
Increases SW current, which eventually trips SW secondary OCP fault. Retries
after 1 ms.
Diode open
Dim light from LED
Yes
Detects missing diode fault and shuts off switching. Retries after 1 ms.
Diode shorted
No light from LED
Yes
Trips SW secondary OCP and turns off switching. Retries after 1 ms.
LED string open
No light from LED
Yes*
Continue to switch at maximum tON (Since this fault cannot be distinguished from
VIN too low for LED forward drop)
LED string shorted to GND,
or Output cap shorted
No light from LED
Yes*
IC unable to regulate LED current at VOUT = 0 V. SW current increases and trips
OCP. IC shuts down and retries after 1 ms.
LED string partially shorted
Some LEDs are not on
NO
Normal operation (since IC has no way to know how many LED is supposed to
be in series).
Continued on the next page…
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
21
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
System Failure Mode Table (partial) (continued)
Symptom Observed
FAULT flag
(A6216)
asserted?
Normal light from LED
NO
Normal operation (since IC only monitors inductor current).
Boot cap open
Dim light from LED
Yes*
IC attempts to switch but can’t fully turn on SW. Short current spikes through
LED string.
Boot cap shorted
No light from LED
Yes*
IC detects undervoltage fault across Boot cap and will not start switching.
TON resistor open
Dim light from LED
Yes
SW turns on and hits secondary current limit, then shuts down. Retries after 1 ms.
NO
Operates at maximum switching frequency (minimum tON and tOFF). May hit
thermal limit.
Failure Mode
Output cap open
TON resistor shorted
Dim light from LED
A6214/16 Response
Note (*)
• In case of LED current not in regulation, FAULT flag is asserted after approximately 50 µs timeout delay.
• For PWM dimming operation with on-time < 50 µs, FAULT flag is asserted if LED current fails to reach regulation after 16 PWM = H pulses.
• For PWM dimming operation with on-time > 50 µs, FAULT flag is only asserted when PWM = H. However, if the fault persists for 16 consecutive
PWM cycles, FAULT flag will be pulled Low and then it stays Low until the fault is cleared.
CH1 = VPWM (5 V/div)
CH2 = VFAULT (5 V/div)
CH3 = VOUT (5 V/div)
CH4 = iLED (500 mA/div)
Time Scale = 5 ms/div
Figure 30: VIN too low for LED regulation. PWM = 500 Hz
2% (40 µs). FAULT = L after 16 PWM pulses.
CH1 = VPWM (5 V/div)
CH2 = VFAULT (5 V/div)
CH3 = VOUT (5 V/div)
CH4 = iLED (500 mA/div)
Time Scale = 5 ms/div
Figure 31: VIN too low for LED regulation. PWM = 500 Hz
20% (400 µs). FAULT toggles each time PWM = H, but
stays Low after 16 PWM pulses.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
22
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
PACKAGE OUTLINE DRAWINGS
For Reference Only – Not for Tooling Use
NOT TO SCALE
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
4.90
+0.08
–0.10
0.55
3.30 ±0.25
8º
0º
10
1.75
0.25
0.19
B
2.41 ±0.25
3.91
+0.08
–0.10
1.00
10
2.41
6.00 ±0.20
5.60
A
0.685 ±0.20
1
2
Branded Face
1
0.25 BSC
3.30
SEATING PLANE
10X
0.10
C
1.55 ±0.10
C
0.40
0.30
SEATING
PLANE
1.00 BSC
0.10 ±0.05
2
GAUGE PLANE
C
PCB Layout Reference View
A
Terminal #1 mark area
B
Exposed thermal pad (bottom surface)
C
Reference land pattern layout; all pads a minimum of 0.20 mm from all adjacent pads;
adjust as necessary to meet application process requirements and PCB layout tolerances;
when mounting on a multilayer PCB, thermal vias at the exposed thermal pad land can
improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5)
Package LK, 10-Pin SOICN with Exposed Thermal Pad
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
23
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
For Reference Only – Not for Tooling Use
(Reference MO-153 ABT)
Dimensions in millimeters. NOT TO SCALE
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
0.65
0.45
8º
0º
5.00 ±0.10
16
16
0.20
0.09
1.70
B
3 NOM 4.40 ±0.10
3.00
6.40 ±0.20
A
6.10
0.60 ±0.15
1.00 REF
1
2
3 NOM
1
0.25 BSC
2
Branded Face
3.00
SEATING PLANE
C
16X
0.10
SEATING
PLANE
C
0.30
0.19
GAUGE PLANE
C
PCB Layout Reference View
1.20 MAX
0.65 BSC
NNNNNNN
YYWW
LLLL
0.15
0.00
A
Terminal #1 mark area
B
Exposed thermal pad (bottom surface); dimensions may vary with device
C
Reference land pattern layout (reference IPC7351 SOP65P640X110-17M);
All pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances; when
mounting on a multilayer PCB, thermal vias at the exposed thermal pad land
can improve thermal dissipation (reference EIA/JEDEC Standard JESD51-5)
D
1
D Standard Branding Reference View
N = Device part number
= Supplier emblem
Y = Last two digits of year of manufacture
W = Week of manufacture
L = Characters 5-8 of lot number
Branding scale and appearance at supplier discretion
Package LP, 16-Pin TSSOP with Exposed Thermal Pad
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
24
A6214 and
A6216
Automotive-Grade, Constant-Current 2 A
PWM Dimmable Buck Regulator LED Driver
Revision History
Number
Date
Description
–
September 23, 2015
Initial release
1
March 17, 2016
Added Load Current Sense Regulation Threshold footnote (page 7-8); updated Additional Notes on
Ripple Current (page 15).
2
April 6, 2016
Added Parallel Operation figure (page 19) and SBD Protection figure (page 20); updated Protection
from Output LC-Resonance (page 19); corrected LK package drawing dimension (page 23).
3
June 17, 2016
4
November 1, 2016
Updated k value (page 11).
Updated Functional Description (page 11); added Table of Contents.
Copyright ©2016, Allegro MicroSystems, LLC
Allegro MicroSystems, LLC reserves the right to make, from time to time, such departures from the detail specifications as may be required to
permit improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that
the information being relied upon is current.
Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of
Allegro’s product can reasonably be expected to cause bodily harm.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no responsibility for its
use; nor for any infringement of patents or other rights of third parties which may result from its use.
For the latest version of this document, visit our website:
www.allegromicro.com
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
25