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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
General Description
The MAX20050–MAX20053 are high-brightness LED (HB
LED) drivers for automotive exterior lighting applications.
Consisting of a fully synchronous step-down converter
with integrated MOSFETs, the devices are capable of
driving a series string of LEDs at up to 2A, with a minimum number of external components. The MAX20050/
MAX20052 utilize internal loop compensation to minimize component count, while the MAX20051/MAX20053/
MAX20053D use external compensation for full flexibility.
The wide 4.5V to 65V input supply range supports
extreme automotive cold crank and load-dump conditions. A low- and high-switching frequency option (400kHz
or 2.1MHz) provides the designer with the flexibility to
optimize for solution size or efficiency, while avoiding
interference within the AM band. Spread spectrum provides further options for the designer to reduce EMI at the
system level. The MAX20050/MAX20051 have an internal
switching frequency of 400kHz, while the MAX20052/
MAX20053/MAX20053D have an internal switching frequency of 2.1MHz. In addition, the MAX20051B has
spread spectrum disabled.
High-side current regulation means only a single
connection to the LED string is required; grounding of the
string can be done locally. In addition to PWM dimming,
the ICs provide analog dimming using the REFI pin. Fullscale current regulation accuracy is ±2.5%, while the
accuracy is ±8% at 10% of full-scale over the full temperature range of -40°C to +125°C. A 5V, 10mA LDO output is
available for biasing other circuits.
Fault-protection mechanisms include output overload,
short-circuit, and device overtemperature protection. The
devices are specified for operation over the full -40°C to
+125°C temperature range and are available in thermally
enhanced 12-pin (3mm x 3mm) TDFN and 14-pin (5mm
x 4.4mm) TSSOP and 24-pin TQFN (4mm x 4mm) packages with an exposed pad.
Benefits and Features
● Automotive Ready: AEC-Q100 Qualified
● Fully Synchronous 2A Step-Down Converter with
Integrated 0.14Ω (typ) MOSFETs
● Wide 4.5V to 65V Input Supply Range
● Two Switching Frequency Options: 400kHz and
2.1MHz
● Internal Loop Compensation (MAX20050/MAX20052)
and External Loop Compensation
(MAX20051/MAX20053/MAX20053D) Options
● Switching Frequency Synchronized to PWM Dimming
Signal
● Active-Low Fault (FLT) Indicator
● Output Short-Circuit Protection
● High-Side Current Regulation Eliminates One
Connection to LED String
● Spread-Spectrum Mode Alleviates EMI Problems
● Low 200mV Full-Scale High-Side Current-Sense
Voltage
● REFI Pin Adjusts LED Current Down to Zero
● PWM Dimming Disconnects Both High- and LowSide MOSFET Drivers
● 5V, 10mA LDO Output Provides Bias to Other
Circuits
● Ultra-Low Shutdown Current (5µA typ)
● Output Overload, Short-Circuit, and Overtemperature
Protections
● 12-Pin (3mm x 3mm) TDFN, 14-Pin (5mm x 4.4mm)
TSSOP, and 24-pin (4mm x 4mm) TQFN Package
Options
Applications
●
●
●
●
●
●
●
●
Daytime Running Lamps (DRLs)
Fog Lamps
Clearance Lamps (CLLs)
Corner Lamps (CLs)
Rear Lamps
Head Lamps
Commercial, Industrial, and Architectural Lighting
Driver Monitoring Systems (DMS)
Ordering Information appears at end of data sheet.
19-6926; Rev 20; 7/21
© 2021 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners.
One Analog Way, Wilmington, MA 01887 U.S.A.
|
Tel: 781.329.4700
|
© 2021 Analog Devices, Inc. All rights reserved.
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Absolute Maximum Ratings
Continuous Current on IN for TQFN.....................................1.8A
Continuous Current on IN for TSSOP...................................2.1A
Short-Circuit Duration on VCC....................................Continuous
Continuous Power Dissipation (TA = +70°C) (Note 1)
12-Pin TDFN-EP (derate 24.4 mW/°C
above +70°C) .........................................................1951.2mW
14-Pin TSSOP-EP (derate 25.6 mW/°C
above +70°C) .........................................................2051.3mW
Operating Temperature Range...........................-40ºC to +125ºC
Junction Temperature....................................................... +150ºC
Storage Temperature Range..............................-65ºC to +150ºC
Lead Temperature (soldering, 10s).................................. +300ºC
Soldering Temperature (reflow)........................................ +260ºC
IN to AGND............................................................-0.3V to +70V
IN to AGND (MAX20050C/51C/52C/53C/53D only).-0.3V to 40V
PGND to AGND.....................................................-0.3V to +0.3V
CS+, CS-, LX to AGND.................................-0.3V to (IN + 0.3V)
BST to AGND.........................................................-0.3V to +75V
BST to AGND (MAX20050C/51C/52C/53C/53D only).... -0.3V to
45V
BST to LX.................................................................-0.3V to +6V
PWM, FLT to AGND.................................................-0.3V to +6V
VCC to AGND................................-0.3V to MIN (+6V, IN + 0.3V)
COMP, REFI to AGND.................................-0.3V to VCC + 0.3V
CS+ to CS-...........................................................-0.3V to + 0.3V
Continuous Current on LX.....................................................2.1A
Continuous Current on IN for TDFN.....................................1.6A
Package Thermal Characteristics (Note 1)
TDFN
Junction-to-Ambient Thermal Resistance (θJA)...........41°C/W
Junction-to-Case Thermal Resistance (θJC)...............8.5°C/W
TSSOP
Junction-to-Ambient Thermal Resistance (θJA)...........39°C/W
Junction-to-Case Thermal Resistance (θJC)..................3°C/W
TQFN
Junction-to-Ambient Thermal Resistance (θJA)...........36°C/W
Junction-to-Case Thermal Resistance (θJC)..................3°C/W
Note 1: Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/thermal-tutorial.
Electrical Characteristics
(VIN = 12V, VREFI = 1.2V, VPWM = VCC, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
Input Supply Voltage
IN Undervoltage Lockout
IN Undervoltage Hysteresis
SYMBOL
VIN
VINUVLO
CONDITIONS
MAX20050C/51C/52C/53C/53D only (Note 5)
MAX
4.5
65
4.5
36
4.45
VINHYSTL
IINQ
TYP
VIN rising inferred by VCCUVLOR
225
PWM = 0
(no switching)
Supply Current
MIN
PWM = 100%
(and during regulation
switching)
V
V
mV
VIN = 12V
5
8
VIN = 65V
8
20
VIN = 12V
(MAX20050/51/
50C/51C)
5
10
VIN = 12V
(MAX20052/53/
/52C/53C/53D)
VIN = 65V
(MAX20050/51)
UNITS
μA
mA
20
10
VCC REGULATOR (VCC)
IVCC = 1mA, 5.5V < VIN < 65V
VCC Output Voltage
VCC
IVCC = 1mA, 5.5V < VIN < 36V
(MAX20050C/51C/52C/53C/53D only)
4.875
5
5.125
V
IVCC = 10mA, 6V < VIN < 25V
www.analog.com
Analog Devices │ 2
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Electrical Characteristics (continued)
(VIN = 12V, VREFI = 1.2V, VPWM = VCC, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
SYMBOL
MIN
TYP
MAX
UNITS
50
100
mV
VCC = 0V
50
80
110
VCC = 0V, MAX20053D
40
80
110
VCCUVLOR
Rising
4
4.2
4.35
V
VCCUVLHYS
Hysteresis
150
200
250
mV
1.20
V
VCC Dropout Voltage
VCC Short-Circuit Current
VCC Undervoltage Lockout
REFI Input Voltage Range
REFI Zero-Current
Threshold
REFI Clamp Voltage
CONDITIONS
IVCC = 5mA, VIN = 4.5V
VCCIMAX
REFIRNG
REFIZC_VTH
REFICLMP
0.2
mA
CSDIFF < 5mV
0.165
0.18
0.195
V
IREFI sink = 1μA
1.274
1.3
1.326
V
VREFI = 0 to VCC
0
20
200
VREFI = 0 to VCC (MAX200051B only)
0
20
300
Input Bias Current
REFIIIN
Common-Mode Input Range
CSCMIN
-0.2
+65
V
Differential Signal Range
CSDIFF
0
200
mV
CS+ Input Bias Current
IBCS+
VCS+ = 60V
CS- Input Bias Current
IBCS-
VCS- = 60V
VCS+ - VCS- = 200mV
40
70
VCS+ - VCS- = 0V
8
15
VCS+ - VCS- = 200mV
100
150
VCS+ - VCS- = 0V
66
110
TJ = 25°C, CSCMIN 3V to 60V
Current-Sense Input Offset
CSOS
3V < CSCMIN < 60V
Regulation Voltage
Accuracy
Regulation Voltage
Accuracy Low Range
www.analog.com
CSGAIN
-1.8
CSACC
CSACC
+1.8
5
5.05
4.91
5
5.08
REFI = 1.4V, 3V < CSCMIN < 60V
215
220
225
REFI = 1.2V, 3V < CSCMIN < 60V
196
200
204
REFI = 1.2V, 3V < CSCMIN < 60V,
MAX20053D
196
200
205
B,C,D versions
μA
mV
-0.1
4.95
(CS+ - CS-) = 200mV,
3V < CSCMIN < 60V
μA
-0.1
3V < CSCMIN < 60V, MAX20053D
Current-Sense Voltage Gain
nA
REFI = 0.7V, 3V < CSCMIN < 60V
V/V
mV
100
REFI = 0.4V, 3V < CSCMIN < 60V
37.8
40
42.2
REFI = 0.4V, 3V < CSCMIN < 60V,
MAX20053D
37.8
40
43.1
VREFI = 1.2V 0V < CSCMIN < 3V
192
200
208
VREFI = 0.4V 0V < CSCMIN < 3V
35
40
45
VREFI = 1.2V 0V < CSCMIN < 3V,
MAX20053D
192
200
209.1
VREFI = 0.4V 0V < CSCMIN < 3V,
MAX20053D
35
40
46.5
mV
Analog Devices │ 3
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Electrical Characteristics (continued)
(VIN = 12V, VREFI = 1.2V, VPWM = VCC, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
CS Common-Mode Range
Input Selector
Cycle-by-Cycle Current
Limit
Transconductance
SYMBOL
RNGSEL
CSLIM
CONDITIONS
TYP
VCS+ rising
2.7
2.85
3.0
2.45
2.6
2.75
VCS- > OUTVTH_LOW
285
300
315
VCS- > OUTVTH_LOW, MAX20053D
282
300
315
VCS+ - VCS- = 200mV
CSACC
CSACC
CSACC
-5
+5
480
Open-Loop DC Gain
COMP Bias Current
MAX
VCS+ falling
VCS- < OUTVTH_LOW
gM
MIN
600
720
75
COMPIBIAS
COMP Sink Current
COMPISINK
COMP Source Current
COMPISRC
PWM = 0
-200
UNITS
V
mV
μS
dB
+200
VCOMP = 5V
85
100
115
VCOMP = 5V, MAX20053D
80
100
115
VCOMP = 0V
85
100
115
VCOMP = 0V, MAX20053D
80
100
115
nA
μA
μA
High-Side DMOS RDSON
RON,HS
ILX = 200mA, VCS+ = 3V
170
340
mΩ
Low-Side DMOS RDSON
RON,LS
VCC = 5V, ILX = 200mA
140
300
mΩ
LX Rise Time
tRISE,LS
Switching Frequency
fSW
Minimum On-Time
tON_MIN
Minimum Off-Time
tOFF_MIN
Spread-Spectrum Range
PWM Input Frequency
PWM-to-LX Delay
PWM Threshold
PWM Pullup Current
PWM Shutdown Timer
Startup Time
Thermal Shutdown
www.analog.com
SS
10
MAX20050/MAX20051, frequency dither
disabled
360
MAX20052/MAX20053, frequency dither
disabled
1890
2100
2310
50
80
120
50
80
120
40
60
90
MAX20053D
2000
5
Falling (during regulation)
2
5
Falling
VIN = 12V
ns
ns
%
2
Rising
tSTUP
±3
10
PWMVTHF
PWMRIN
440
Rising (during regulation)
PWMVTHR
PWMSHDW
400
kHz
Not applicable to B version
PWMFR
PWMDLY
ns
2
800
Hz
μs
V
mV
1
2
3
μA
PWM low time to enter shutdown mode
140
210
300
ms
IN, PWM rising to LX delay
180
250
350
μs
Rising
165
°C
Hysteresis
10
°C
Analog Devices │ 4
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Electrical Characteristics (continued)
(VIN = 12V, VREFI = 1.2V, VPWM = VCC, TA = TJ = -40°C to +125°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 2)
PARAMETER
LED Open-Fault REFI
Range
SYMBOL
CONDITIONS
LOFREFI_RNG VREFI rising
MIN
TYP
MAX
UNITS
300
325
350
mV
LED Open-Fault Enable
Rising Threshold
LOFIN_RNG
VIN rising
8
9
10
V
LED Open-Fault Enable
Falling Threshold
LOFIN_FLNG
VIN falling
7.3
8.3
9.3
V
CSDIFF falling, duty = max
10
25
40
%
3
6
9
%
1.35
1.5
1.65
V
0.05
0.3
V
µs
LED Open-Fault Threshold
LOFVTH
LED Open-Fault Hysteresis
LOFVTH_HYS
Output-Voltage Low
Threshold
OUTVTH_LOW VCS- falling
FAULT Output Voltage
FAULTVOL
ISINK = 1mA, VCS+ = 1V, after FAULTDEG
elapsed
FAULT Deglitch Timer
FAULTDEG
(Note 3)
70
105
150
FAULT Mask Timer
FAULTMASK
(Note 4)
140
210
300
µs
1
µA
FAULT Leakage Current
FAULTLGK
VFAULT = 5.5V
Note 2: 100% tested at TA = +25°C. All limits over temperature are guaranteed by design, not production tested.
Note 3: The time duration for which the fault condition has to remain active before asserting FLT pin.
Note 4: The mask timer occurs each time PWM goes from low to high. Open LED condition cannot be detected during the
mask time period.
Note 5: Device is designed for use in applications with continuous 18V operation, and meets Electrical Characteristics table up to
the maximum supply voltage.
www.analog.com
Analog Devices │ 5
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Typical Operating Characteristics
(VIN = 12V, VREFI = 1.2V, VPWM = VCC, TA = +25°C, unless otherwise noted.)
EFFICIENCY vs.
LED CURRENT
toc01
EFFICIENCY vs.
LED CURRENT
100
80
80
80
70
70
70
VIN = 24V (MAX20053)
VIN = 24V (MAX20051)
50
VIN = 12V (MAX20053)
40
VIN = 12V (MAX20051)
30
60
30
10
10
0.5
1.0
1.5
0
2.0
VIN = 24V (MAX20051)
40
20
0.0
VIN = 12V (MAX20053)
50
20
2 SERIES LEDS
VIN = 12V (MAX20051)
40
30
0.0
0.5
1.0
1.5
LINE REGULATION
0
2.0
toc04
VCC VOLTAGE REGULATION vs.
TEMPERATURE
toc05
5.25
5.20
5.15
5.15
1.02
5.10
5.10
1.01
1.00
VCC (V)
5.20
5.05
5.00
4.95
0.98
4.90
4.90
4.85
4.85
0
10
20
30
40
4.80
4.75
50
VIN (V)
toc07
-50
0
50
100
4.75
150
MINIMUM ON-TIME
vs. TEMPERATURE
200
toc08
160
140
140
4.95
4.90
4.85
4.80
40
IVCC (mA)
www.analog.com
60
120
100
80
60
40
20
VREFI = 0V
20
MINIMUM OFF-TIME (ns)
160
5.10
MINIMUM ON-TIME (ns)
5.15
0
0
10
20
80
0
30
40
50
MINIMUM OFF-TIME
vs. TEMPERATURE
200
180
4.75
VREFI = 0V
60
70
VIN (V)
180
5.00
toc06
MAX20051
4.80
IVCC = 1mA
5.20
5.05
2.0
VCC LINE REGULATION
TEMPERATURE (ºC)
VCC LOAD REGULATION
5.25
1.5
5.00
4.95
MAX20051
2 SERIES LEDS
ILED = 1A
1.0
5.05
0.99
0.95
0.5
5.25
1.03
0.96
0.0
LED CURRENT (A)
1.04
0.97
6 SERIES LEDs
VIN = 48V
MAX20051
LED CURRENT (A)
VCC (V)
ILED (A)
50
10
1 LED
toc03
60
20
LED CURRENT (A)
1.05
EFFICIENCY (%)
90
60
EFFICIENCY vs.
LED CURRENT
100
90
0
VCC (V)
toc02
90
EFFICIENCY (%)
EFFICIENCY (%)
100
toc09
120
100
80
60
40
20
-50
0
50
100
TEMPERATURE (ºC)
150
0
-50
0
50
100
150
TEMPERATURE (ºC)
Analog Devices │ 6
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Typical Operating Characteristics (continued)
(VIN = 12V, VREFI = 1.2V, VPWM = VCC, TA = +25°C, unless otherwise noted.)
SWITCHING FREQUENCY vs.
TEMPERATURE
toc10
2.5
4.25
UVLO RISING
MAX20053
VIN UVLO (V)
SWITCHING FREQUENCY (MHz)
1.5
1.0
0.0
4.15
1A/div
ILED
4.10
-50
0
2V/div
VLED
4.00
50
100
3.95
150
0A
UVLO
FALLING
4.05
MAX20051
2V/div
0V
VREFI
4.20
2.0
0.5
VREFI TRANSIENT RESPONSE
(MAX20051)
toc12
VIN UVLO THRESHOLDS vs.
TEMPERATURE
toc11
0V
-50
0
50
100
150
100µs/div
TEMPERATURE (ºC)
TEMPERATURE (ºC)
VREFI TRANSIENT RESPONSE
(MAX20053)
toc13
250
2V/div
0V
200
1A/div
150
ILED
0A
VLED
VCS+ - VCS- (mV)
VREFI
MAX20051
MAX20053
100
50
2V/div
0
0V
100µs/div
CURRENT SENSE VOLTAGE
vs. VREFI
toc14
-50
3 LEDS
RCS = 100mΩ
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
VREFI (V)
CURRENT SENSE VOLTAGE vs.
TEMPERATURE
toc15
VCS+ - VCS- (mV)
120
16
VCS- = 0V
(MAX20051)
110
100
90
60
-50
0
VIN = 65V (MAX20051)
10
VIN = 12V (MAX20051)
6
2
VREFI = 0.7V
50
100
TEMPERATURE (ºC)
www.analog.com
12
4
VCS- = 3V
(MAX20053)
70
14
8
VCS- = 3V
(MAX20051)
80
toc16
VIN = 12V (MAX20053)
18
VCS- = 0V
(MAX20053)
130
SUPPLY CURRENT
vs.TEMPERATURE
20
IIN (mA)
140
150
0
PWM = 100%
-50
0
50
100
150
TEMPERATURE (ºC)
Analog Devices │ 7
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Pin Configurations
TOP VIEW
LX
LX
12
11
BST VCC REFI AGND
10
9
8
7
MAX20050
MAX20052
+
1
2
3
PGND IN
4
5
6
+
PWM
19
LX
NC
20
12
BST
FLT
21
11
VCC
NC
22
5
10
REFI
COMP
23
PWM
6
9
AGND
FLT
7
8
COMP
AGND
24
PGND
1
IN
2
IN
3
CS+
4
CS-
MAX20051
MAX20053
14
LX
13
CS-
NC CS+ CS+ NC
18
17
16
15
12 IN
10 PGND
MAX20053D
9 NC
8 LX
+
2
3
4
AGND REFI VCC BST
5
6
LX
LX
7 LX
TQFN
TSSOP
TDFN
13
11 PGND
1
CS+ CS- PWM FLT
14
IN
Pin Descriptions
TDFN
TSSOP
MAX20050
MAX20052
MAX20051
MAX20053
NAME
1
1
PGND
2
2, 3
IN
3
4
FUNCTION
Power Ground
Power-Supply Input. Bypass to PGND with a minimum of 1μF ceramic capacitor.
CS+
Current-Sense Positive Pin. This is the positive input of the high-side average currentmode control amplifier. See the Programming the LED Current section for information on
setting the resistor value. The output inductor and current-sense resistor are connected at
this node.
4
5
CS-
Current-Sense Negative Pin. This is the negative input of the high-side average currentmode control amplifier. See the Programming the LED Current section for information on
setting the resistor value. This node goes to the anode of the LED string. One end of the
current-sense resistor connects to this pin.
5
6
PWM
Logic-Level Dimming Input. Drive PWM low to turn off the current regulator. Drive PWM
high to enable the current regulator. If PWM is driven low for greater than 210ms, the
device turns off.
6
7
FLT
Open-Drain Fault Output. Refer to the Fault Pin Behavior section for information on Fault.
—
8
COMP
Compensation Output (MAX20051/MAX20053). Connect an external RC network for loop
compensation. The MAX20050/MAX20052 are internally compensated.
7
9
AGND
Analog Ground
8
10
REFI
9
11
VCC
10
12
BST
11, 12
13, 14
LX
Switching Node. Connect to one end of output inductor.
—
—
EP
Exposed Pad. Connect EP to a large-area ground plane for effective power dissipation.
Connect EP to AGND. Do not use as the only ground connection.
www.analog.com
Analog Dimming-Control Input. Connect an analog voltage from 0 to 1.2V for analog
dimming of LED current.
5V Regulator Output. Connect a 1μF ceramic capacitor to AGND from this pin for stable
operation.
High-Side Power Supply for Gate Drive. Connect a 0.1μF ceramic capacitor from BST to
LX.
Analog Devices │ 8
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Pin Descriptions (continued)
TQFN
MAX20053D
NAME
FUNCTION
1, 24
AGND
2
REFI
Analog Dimming-Control Input. Connect an analog voltage from 0 to 1.2V for analog dimming of
LED current.
3
VCC
5V Regulator Output. Connect a 1μF ceramic capacitor to AGND from this pin for stable operation.
4
BST
High-Side Power Supply for Gate Drive. Connect a 0.1μF ceramic capacitor from BST to LX.
5, 6, 7, 8
LX
Switching Node. Connect to one end of output inductor.
9
NC
No Connect
10, 11
PGND
12, 13
IN
Power-Supply Input. Bypass to PGND with a minimum of 1μF ceramic capacitor.
14
NC
No Connect
15, 16
CS+
Current-Sense Positive Pin. This is the positive input of the high-side average current-mode
control amplifier. See the Programming the LED Current section for information on setting the
resistor value. The output inductor and current-sense resistor are connected at this node.
17
NC
No Connect
18
CS-
Current-Sense Negative Pin. This is the negative input of the high-side average current-mode
control amplifier. See the Programming the LED Current section for information on setting the
resistor value. This node goes to the anode of the LED string. One end of the current-sense
resistor connects to this pin.
19
PWM
Logic-Level Dimming Input. Drive PWM low to turn off the current regulator. Drive PWM high to
enable the current regulator. If PWM is driven low for greater than 210ms, the device turns off.
20
NC
No Connect
21
FLT
Open-Drain Fault Output. Refer to the Fault Pin Behavior section for information on Fault.
22
NC
No Connect
23
COMP
—
EP
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Analog Ground. Pins 1 and 24 should be shorted outside the IC.
Power Ground
Compensation Output. Connect an external RC network for loop compensation.
Exposed Pad. Connect EP to a large-area ground plane for effective power dissipation. Connect
EP to AGND. Do not use as the only ground connection.
Analog Devices │ 9
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
VCCOK
POK
INUVLO
VIN
PWM
VCC
LDO
BG
INUVLO
OSC
SYNC TO RISING
EDGE OF PWM
VCCOK
DITHERING
(NON-B VERSIONS)
DUTY MAX
BLANKING TIME
AGND
POKD
80µs
DELAY
CLOCK
RESET
DOMINANT
S
DH
SET Q
PWM COMP
1.3V
CLAMP
REFI
300mV
Gm
CS-
PEAK
CURRENT
LIMIT
x5
CS+
BST
R CLR Q
VIN
DUTY
MAX
SOFT-OFF
PWM
COMP
D
DH
LX
SET Q
POKD
RESET
DOMINANT
CLR Q SKIP PULSE
4V
PWM
2µA
PWM
FALLING 0.8V
RISING 2.0V
200ms LOW
STATE TIME
COUNTER
MAX20050
MAX20052
S
SHUTDOWN
MODE
0.5V
REFI
SET Q DL
R CLR Q
SOFT-OFF
THERMAL
SHUTDOWN
REFI > 325mV
1.5V
VCC
PGND
LED
SHORT
t = 105µs
FLT
CSTHERMAL
SHUTDOWN
180mV
REFI > 325mV
VIN > 9V
DUTY = MAX
25% REFI
LED
OPEN
t = 105µs
Figure 1. Block Diagram of the MAX20050/MAX20052
www.analog.com
Analog Devices │ 10
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
VCCOK
POK
INUVLO
VIN
PWM
VCC
LDO
BG
INUVLO
OSC
SYNC TO RISING
EDGE OF PWM
VCCOK
DUTY MAX
DITHERING
(NON-B VERSIONS)
BLANKING TIME
AGND
CLOCK
COMP
POKD
80µs
DELAY
RESET
DOMINANT
S
DH
SET Q
PWM COMP
300mV
1.3V
CLAMP
REFI
PEAK
CURRENT
LIMIT
BST
R CLR Q
VIN
DUTY
MAX
Gm
CS-
SOFT-OFF
x5
CS+
PWM
COMP
D
DH
LX
SET Q
POKD
RESET
DOMINANT
CLR Q SKIP PULSE
4V
PWM
2µA
PWM
FALLING 0.8V
RISING 2.0V
200ms LOW
STATE TIME
COUNTER
MAX20051
MAX20053
S
SHUTDOWN
MODE
0.5V
REFI
SET Q DL
R CLR Q
REFI > 325mV
SOFT-OFF
1.5V
PGND
LED
SHORT
t = 105µs
CS-
THERMAL
SHUTDOWN
VCC
FLT
THERMAL
SHORT
180mV
REFI = 325mV
VIN > 9V
DUTY = MAX
25% REFI
LED
OPEN
t = 105µs
Figure 2. Block Diagram of the MAX20051/MAX20053
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Analog Devices │ 11
MAX20050–MAX20053
Detailed Description
The MAX20050–MAX20053 are HB LED drivers for
automotive exterior lighting applications. Consisting of
a fully synchronous step-down converter with integrated
MOSFETs, the devices are capable of driving a series
string of LEDs at up to 2A, with a minimum number of
external components. The MAX20050/MAX20052 utilize
internal loop compensation to minimize component count,
while the MAX20051/MAX20053 use external compensation for full flexibility.
The wide 4.5V to 65V input supply range supports extreme
automotive cold-crank and load-dump conditions. A lowand high-switching frequency option (400kHz or 2.1MHz)
provides the designer with the flexibility to optimize for
solution size or efficiency, while avoiding interference
within the AM band. Spread spectrum provides further
options for the designer to reduce EMI at the system level.
The MAX20050/MAX20051 have an internal switching
frequency of 400kHz, while the MAX20052/MAX20053
have an internal switching frequency of 2.1MHz.
High-side current regulation means only a single connection to the LED string is required; grounding of the string
can be done locally. In addition to PWM dimming, the ICs
provide analog dimming using the REFI pin. Full-scale
current regulation accuracy is ±2.5%, while the accuracy
is ±8% at 10% of full scale, over the full temperature
range of -40°C to +125°C. A 5V, 10mA LDO output is
available for biasing other circuits.
Fault-protection mechanisms include output overload,
short-circuit, and device overtemperature protections.
Functional Operation of MAX20050–MAX20053
The MAX20050–MAX20051 are monolithic, constant
frequency average current mode step-down DC-DC
LED drivers. A fixed frequency internal oscillator sets the
switching frequency of the devices. For the MAX20050/
MAX20051, the switching frequency is set at 400kHz,
and for the MAX20052/MAX20053, the switching frequency is set at 2.1MHz. Spread spectrum is added to
the internal oscillator to improve the EMI performance
of the LED driver at higher frequencies. The oscillator
turns on the internal top power switch at the beginning of
each clock cycle. Current in the inductor then increases
until the internal PWM comparator trips and turns off the
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2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
top power switch. The duty cycle at which the top switch
turns off is controlled by an internal PWM comparator that
has the output of an error amplifier going to the negative
input of the comparator and a saw tooth ramp going to
the positive input of the comparator. The error amplifier
is a transconductance amplifier that compares the analog
control voltage REFI with an amplified current sense signal. The output of the error amplifier is then fed to a PWM
comparator. The other input of the PWM comparator is
a saw tooth ramp with a peak to peak voltage of 2.25V.
The REFI voltage programs the LED current. When the
top power switch turns off, the synchronous power switch
at the bottom turns on until the next clock cycle begins.
The current sense signal is derived by a current sense
resistor in series with the output inductor. This current
sense signal is amplified by a factor of 5 and is then fed
to the input of the error amplifier. This amplified signal is
also fed to a comparator input which compares the amplified current sense signal with a 300mV reference. If the
amplified current sense signal exceeds 300mV, then the
top switch is immediately turned off independent of the
PWM comparator and the bottom synchronous switch is
turned on until the start of the next oscillator cycle. In the
MAX20050/MAX20052, the output of the error amplifier
is not available and the loop compensation is fixed inside
the device. In the MAX20051/MAX20053, the output of
the error amplifier appears on a pin and the loop can be
compensated externally.
The device also includes a PWM dimming input that is
used for PWM dimming of the LED current. When this signal is low both, the top and bottom switches are turned off
and when the PWM signal goes high the inductor current
is controlled by the device. The rising edge of the PWM
signal also restarts the internal oscillator allowing the top
switch to be turned on at the same instant as the rising
edge of the PWM signal. This provides consistent dimming performance at low dimming duty cycles. The PWM
signal can also be used as an enable input where if the
PWM signal stays low for a period exceeding 200ms the
device goes into a shutdown mode. In shutdown mode,
the quiescent current drawn by the device goes to 5µA at
an input of 12V.
The devices also feature a fault flag that indicates open or
shorts on the output. Thermal shutdown shuts down the
devices to protect them from damage at high temperatures.
Analog Devices │ 12
MAX20050–MAX20053
Analog Dimming
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Switching Node (LX)
The devices have an analog dimming-control input
(REFI). The voltage at REFI sets the LED current level
when VREFI ≤ 1.2V. For VREFI > 1.2V, REFI is clamped
to 220mV (typ). The maximum withstand voltage of this
input is 5.5V. The LED current is guaranteed to be at zero
when the REFI voltage is at or below 0.18V. The LED
current can be linearly adjusted from zero to full scale for
the REFI voltage in the range of 0.2V to 1.2V.
The source of the internal high-side switching MOSFET
and the drain of the low-side synchronous switching
MOSFET is connected to these pins. Connect these pins
together externally and connect them to the inductor and
the boost capacitor. The RDS(ON) of both the high- and
low-side switching MOSFETs is 0.3Ω maximum at a
junction temperature of +125°C.
High-Side Current Sense (CS+, CS-)
The BST pin is used to provide a drive voltage to the
high-side switching MOSFET that is higher than the input
voltage. An internal diode is connected from BST to VCC.
Connect a 0.1µF ceramic capacitor from this pin to the LX
pins. Place the capacitor as close as possible to this pin.
A resistor is connected between the inductor and the
anode of the LED string to program the maximum LED
current. The full-scale signal is 200mV. The CS+ pin
should be connected to the positive terminal of the currentsense resistor (inductor side) and the CS- pin should be
connected to the negative terminal of the current-sense
resistor (LED string anode side).
PWM Dimming Control (PWM)
A low signal on this pin turns off both the high- and lowside MOSFETs. The device goes into shutdown mode if
there is no positive-going dimming pulse for 210ms. In
shutdown mode, the input current is less than 5µA (typ).
In applications where the PWM pin is pulled low with an
open drain transistor to get into shutdown mode, do not
connect a pull up resistor to VCC on this pin. The device
comes out of shutdown mode with the internal current
source pulling the pin high.
5V Regulator (VCC)
A regulated 5V output is provided for biasing other
circuitries up to 10mA load. Bypass VCC to AGND with a
minimum of 1µF ceramic capacitor as close as possible
to the device.
Input Voltage (IN)
The input supply pin (IN) must be locally bypassed with a
minimum of 1µF capacitance close to the pin. All the input
current that is drawn by the LED driver goes through this
pin. The positive terminal of the bypass capacitor must be
placed as close as possible to this pin and the negative
terminal of the bypass capacitor must be placed as close
as possible to the PGND pin.
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Boost Capacitor Node (BST)
Power Ground (PGND)
The source of the internal low-side power MOSFET is
connected to this pin. Place the negative terminal of
the input bypass capacitor as close as possible to the
PGND pin.
Analog Ground (AGND)
This is the analog ground pin for all the control circuitry of
the LED driver. Connect the PGND and the AGND together at the negative terminal of the input bypass capacitor.
Compensation (COMP)
(MAX20051/MAX20053)
The COMP pin is present in the MAX20051/MAX20053.
Connect the external compensation network to this pin for
stable loop compensation.
Fault Pin Behavior
The FLT pin is an open-drain output. See the LED Open
and LED Short sections.
LED Open
The LED open is detected when the following conditions
are true at the same time for a period longer than 105µs:
● Input voltage > 9V
● REFI > 325mV
● Current sense < 25% expected REFI value
● Max duty cycle
Analog Devices │ 13
MAX20050–MAX20053
If an LED open is detected and the input voltage goes
below 9V or REFI goes below 325mV, the FLT flag
remains asserted until the input voltage goes above 9V
and REFI goes above 325mV. If PWM is high and a LED
open occurs, the FLT pin asserts after a deglitch period
of 105µs. When the PWM goes low, the FLT status is
latched. LED open condition cannot be detected if PWM
pulse width is shorter than the maximum mask timer
period of 300µs.
The LED open condition cannot be detected if the PWM
pulse width is shorter than the mask timer period. The
mask timer counter uses an internal clock (15µs typical
period) to perform the mask timing measurement. If the
PWM dimming pulse is in the range of 140µs to 300µs,
there is a timing window of 1-clock cycle width (210µs
-225µs typical), where the FLT pin can toggle between
high and low state from one PWM dimming pulse to another in case of an LED open fault. If the PWM pulse width is
longer than the mask timer period and an LED open fault
is detected, the FLT flag goes low. Once the open LED
fault condition disappears, the FLT flag goes high.
LED Short
The LED short is detected when the following two conditions
are true at the same time for a period longer than 105µs:
● REFI > 325mV
● Output voltage < 1.5V
After LED short is recovered, the fault flag is deasserted,
irrelevant to the input voltage.
Thermal Shutdown
The FLT pin goes low when thermal shutdown is activated.
Exposed Pad
The device package features an exposed thermal pad
on its underside that should be used as a heat sink. This
pad lowers the package’s thermal resistance by providing
a direct heat-conduction path from the die to the PCB.
Connect the exposed pad and AGND together using a
large pad or ground plane, or multiple vias to the AGND
plane layer.
Inductor Peak Current-Limit Comparator
The peak current comparator provides a path for fast
cycle-by-cycle current limit during extreme fault conditions. The average current-limit threshold, set by the REFI
voltage, limits the output current during short circuit.
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2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Spread-Spectrum Modulation
The devices include a unique spread-spectrum mode that
reduces emission (EMI) at the switching frequency and
its harmonics.
The spread spectrum uses a pseudorandom dithering
technique, where the switching frequency is varied in the
range of 400kHz ±3% for the MAX20050/MAX20051 and
2.1MHz ±3% for the MAX20052/MAX20053.
Instead of a large amount of spectral energy present at
multiples of the switching frequency, the total energy at
the fundamental and each harmonic is spread over a
wider bandwidth, reducing the energy peak.
Spread-spectrum modulation is disabled in B versions of
the device.
Thermal Protection
The devices feature thermal protection. When the junction
temperature exceeds +165°C, the LX pin starts operating
at the minimum pulse width to reduce the power dissipation in the internal power MOSFETs. The part returns
to regulation mode once the junction temperature goes
below +155°C. This results in a cycled output during
continuous thermal-overload conditions.
High-Side Current-Sense Amplifier
The devices feature a high-bandwidth, high-side currentsense amplifier that is used to sense the inductor current.
The gain of this current-sense amplifier is 5. The differential voltage between CS+ and CS- is fed to the internal
high-side current-sense amplifier. This amplified signal is
then transferred to the low side and is then connected to
the negative input of an internal transconductance amplifier. The 3dB bandwidth of the high-side current-sense
amplifier is 1.5MHz.
Internal Transconductance Amplifier
The devices have a built-in transconductance amplifier
used to amplify the error signal inside the feedback loop.
The output of the high-side current-sense amplifier, plus
an offset voltage of 0.2V, is fed to the negative input of
this internal transconductance amplifier. The positive
input is the voltage on the REFI pin. In the case of the
MAX20050/MAX20052, the loop of this amplifier is internally compensated and is not available as an output pin.
In the case of the MAX20051/MAX20053, the output of
this amplifier is available on the COMP pin and can be
compensated with an external compensation network.
The transconductance of this amplifier is 600µS.
Analog Devices │ 14
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Applications Information
switching frequency of 2.1MHz. Selecting a higher switching frequency reduces the inductance requirements, but
at the cost of efficiency. The charge/discharge cycle of
the gate capacitance of the internal switching MOSFET’s
gate and drain capacitance create switching losses,
which worsen at higher input voltages since the switching
losses are proportional to the square of the input voltage. Choose inductors from the standard high-current,
surface-mount inductor series available from various
manufacturers. High inductor ripple current causes large
peak-to peak flux excursion, increasing the core losses at
higher frequencies.
Programming the LED Current
Normal sensing of the LED current should be done on
the high side where the LED current-sense resistor is
connected to the inductor. The other side of the LED
current-sense resistor goes to the anode of the external
LED string. The LED current is programmed using RCS
(see Figure 3). When REFI is set to a voltage >1.3V, the
internal reference regulates the voltage across RCS to
220mV. The current is given by:
ILED =
0.220
R CS
The LED current can also be programmed using the
voltage on REFI when VREFI ≤ 1.2V (analog dimming).
The current is given by:
ILED =
(VREFI − 0.2)
(5 x R CS )
Inductor Selection
The peak inductor
and the allowable
value and size of
MAX20051 have
400kHz, whereas
current, selected switching frequency,
inductor current ripple determine the
the output inductor. The MAX20050/
an internal switching frequency of
the MAX20052/MAX20053 have a
INPUT
C1
1µF
FAULT FLAG
IN
BST
MAX20051
MAX20053
FLT
C2
1µF
LED CURRENT CONTROL
LX
For the typical operating circuit of Figure 4 (VIN = 12V),
the inductor value has to be in the range of 22µH to 33µH
for the MAX20050 and in the range of 10µH to 68µH
for the MAX20052. For the typical application circuit of
Figure 5 (VIN = 24V), the inductor value has to be in the
range of 33µH to 82µH for the MAX20050. For the typical application circuit of Figure 6 (VIN = 40V to 60V), the
inductor value has to be in the range of 47µH to 150µH
for the MAX20050. For the MAX20051/MAX20053, the
inductor value can be optimized further and can be higher
or lower than the values suggested for the MAX20050/
MAX20052. The MAX20051/MAX20053 have an external
compensation pin for loop stability and this gives more
flexibility for output inductor values.
C3
0.1µF
L1
RCS
LX
CS+
VCC
CSCOMP
AGND
REFI
PGND
PWM
RCOMP
CP
EP
PWM
COUT
CCOMP
Figure 3. Typical Application Circuit Using the MAX20051
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Analog Devices │ 15
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Input Capacitor
The discontinuous input-current waveform of the buck
converter causes large ripple currents in the input capacitor. The switching frequency, peak inductor current, and
the allowable peak-to-peak voltage ripple reflected back
to the source dictate the capacitance requirement. The
input ripple is comprised of ΔVQ (caused by the capacitor
discharge) and ΔVESR (caused by the ESR of the capacitor). Use low-ESR ceramic capacitors with high ripplecurrent capability at the input. A 1µF ceramic capacitor is
recommended for most applications.
Output Capacitor
The function of the output capacitor is to reduce the output ripple to acceptable levels. The ESR, ESL, and the
bulk capacitance of the output capacitor contribute to the
output ripple. In most applications, using low-ESR ceramic capacitors can dramatically reduce the output ESR and
ESL effects. To reduce the ESL effects, connect multiple
INPUT
INPUT FROM
4.5V TO 16V
C1
1µF
FAULT FLAG
C2
1µF
LED CURRENT CONTROL
IN
BST
MAX20050
MAX20052
LX
C3
0.1µF
ceramic capacitors in parallel to achieve the required bulk
capacitance.
The output capacitance COUT is calculated using the
following equation:
C OUT =
((VIN_MIN − VLED ) × VLED )
( ∆VR × 2 × L × VIN_MAX × f SW 2 )
where ΔVR is the maximum allowable voltage ripple.
The output capacitance for MAX20050 in Figure 4 has
to be in the range of 0.22µF to 4.7µF for a stable operation. The output capacitance for MAX20052 has to be in
the range of 0.1uF to 4.7µF. For the application circuit of
Figure 5, the output capacitance has to be in the range
of 0.47µF to 4.7µF for the MAX20050. For the application
circuit of Figure 6, the output capacitance has to be in the
range of 0.1µF to 2.2µF for the MAX20050.
L1
R2
0.133Ω
LX
FLT
CS+
VCC
CSAGND
REFI
PGND
PWM
LED VOLTAGE IS FROM 2V TO 10V
LED CURRENT IS 150mA TO 1.5A
C7
EP
PWM
Figure 4. Typical Input Voltage (12V)
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Analog Devices │ 16
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
INPUT
INPUT FROM
12V TO 32V
C1
1µF
FAULT FLAG
C2
1µF
LED CURRENT CONTROL
IN
BST
MAX20050
LX
C3
0.1µF
L1
R2
0.133Ω
LX
FLT
CS+
VCC
CSAGND
REFI
LED VOLTAGE IS FROM 2V TO 20V
LED CURRENT IS 150mA TO 1.5A
C7
PGND
PWM
EP
PWM
Figure 5. Typical Input Voltage (24V)
INPUT
INPUT FROM
40V TO 60V
C1
1µF
FAULT FLAG
C2
1µF
LED CURRENT CONTROL
IN
BST
LX
MAX20050
C3
0.1µF
L1
R2
0.133Ω
LX
FLT
CS+
VCC
CSAGND
REFI
PGND
PWM
LED VOLTAGE IS FROM 2V TO 50V
LED CURRENT IS 150mA TO 1.5A
C7
EP
PWM
Figure 6. Typical Input Voltage (50V)
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Analog Devices │ 17
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Table 1. Suggested L–C Network for Internally Compensated Parts
L AND C COMPONENT VALUES (MAX20050, fSW = 400kHz)
Output Capacitor Range (C7)
Inductor Range (L1)
VIN = 12V (typ), Figure 4
0.22
4.7
VIN = 24V (typ), Figure 5
0.47
4.7
VIN = 55V (typ), Figure 6
0.1
2.2
VIN = 12V (typ), Figure 4
22
33
VIN = 24V (typ), Figure 5
33
82
VIN = 55V (typ), Figure 6
47
150
µF
µH
L AND C COMPONENT VALUES (MAX20052, fSW = 2.1MHz)
Output Capacitor Range (C7)
VIN = 12V (typ), Figure 4
0.1
4.7
µF
Inductor Range (L1)
VIN = 12V (typ), Figure 4
3.3
10
µH
Compensation
The MAX20050/MAX20052 have internal loop compensation and there is no user-available adjustability of
the loop compensation components. In the case of the
MAX20051/MAX20053, an external COMP pin is present
and an external compensation network is required for
stable operation. See Figure 3 for the typical application
circuit using the MAX20051.
The compensator should be designed as follows. The
high-side current sense amplifier introduces a highfrequency pole to around 420kHz. This is close to the
switching frequency. The current loop gain is:
Ti(s)
=
×
(1 + sRC OUT )
Fm VIN
×
L
R
2
1 + s R + s LC OUT
G m ( sC COMPR COMP + 1) 5R CS
s
sCOMP 1 +
wp
where Gm is the transconductance of the error amplifier inside the MAX20051/MAX20053, RCS is the current
sense resistor, R is the total dynamic resistance of the LED
string, L is the inductance, RCOMP is the compensation
resistor, COUT is the output capacitance, wp is the pole
from the high side current sense amplifier at 2πfp and Fm
is the modulator gain that is given by:
Fm =
1
(s e + s n )Ts
where Ts is 1/fs where fs is the switching frequency, se
is the dv/dt of the ramp in the PWM comparator which is
www.analog.com
2.25fs and sn is the dv/dt of the voltage from the output
of the Gm amplifier.
In the MAX20051 the compensation zero formed by
RCOMPCCOMP should be set at 20kHz and for the
MAX20053 at 100kHz. Initially, the value of the capacitor
CCOMP can be calculated by the formula:
Gm
=
C COMP
0.5 +
Lf s w z
1
F V Rcs5
π m IN
where wz is the zero at RCOMPCCOMP and fs is the
switching frequency. Initially, Fm is assumed as 0.555
and the initial values of CCOMP is calculated and then
RCOMP is calculated based on the zero location at 20kHz
for the MAX20051 and 100kHz for the MAX20053. The
values of RCOMP, CCOMP, and CP may need to be
optimized further when testing, so as to get the optimum
loop response.
LED Current Derating Using REFI
The MAX20050–MAX20053 are designed specifically
for driving high current LEDs. High current LEDs require
derating the maximum current based on operating temperature to prevent damage of the LEDs. Some LEDs
come with an accompanying thermistor in the same
package. The thermistor may be an NTC. Under normal
operating conditions the voltage on the REFI pin is above
the clamp voltage of the MAX20050–MAX20053 .See
Figure 7. As the temperature of the LEDs increase, the
resistance R1 decreases until the voltage on the REFI
pin reaches 1.3V. The resistors R2 and R1 should be
selected so that the voltage on REFI is 1.3V at the desired
temperature T1. It may also be necessary that at a certain
temperature T2, the current in the LEDs are close to zero.
Analog Devices │ 18
MAX20050–MAX20053
At this temperature, the voltage on REFI pin is:
1.3 =
VCC × R1(T1)
(R1(T1) + R2)
where VCC is 5V and R1(T1) is the resistance of the
resistor from REFI to ground at temperature T1 and R2 is
the resistance from VCC to REFI.
0.2 =
VCC × R1(T1)
(R1(T2) + R2)
where R1(T2) is the resistance of the resistor of the
resistor from REFI to ground at temperature T2. In some
cases, the NTC in the LED can be used as is and in others, an additional resistor in series or in parallel or some
other combination may need to be added to provide the
desired resistance.
High Peak-Current, Low Duty-Cycle
Applications
The MAX20050–MAX20053 family of parts can be used for
applications that require peak currents up to 5A with low
duty cycle. The RMS current should not exceed 1.5A. A 3A
Schottky diode must be added between LX and PGND pins
when used in these applications. See Figure 8.
Low Dimming-Frequency Applications
For applications with low PWM dimming frequencies, it
may be undesirable for the IC to go into shutdown mode
between every PWM pulse. To prevent the IC from entering shutdown mode, a very narrow PWM pulse, typically
20ns to 100ns, can be sent by the microcontroller once
every 100ms. This pulse will be short enough that it does
not turn on the LEDs, but long enough that it keeps the
IC awake.
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
2) Place an unbroken ground plane on the layer closest
to the surface layer with the inductor, device, and the
input and output capacitors.
3) The surface area of the LX and BST nodes should
be as small as possible to minimize emissions.
4) The exposed pad on the bottom of the package must
be soldered to ground so that the pad is connected
to ground electrically and also acts as a heat sink
thermally. To keep thermal resistance low, extend the
ground plane as much as possible, and add thermal
vias under and near the device to additional ground
planes within the circuit board.
5) Run the current-sense lines (CS+ and CS-) very
close to each other to minimize the loop area. Do not
cross these critical signal lines with power circuitry.
Sense the current right at the pads of the currentsense resistors. The current-sense signal has a
full-scale amplitude of 200mV. To prevent contamination of this signal from high dv/dt and high di/dt
components and traces, use a ground plane layer to
separate the power traces from this signal trace.
6) Use separate ground planes on different layers of
the PCB for AGND and PGND. Connect both of
these planes together at a single point close to the
input bypass capacitor.
7) Use 2oz or thicker copper to keep trace inductances
and resistances to a minimum. Thicker copper conducts heat more effectively, thereby reducing thermal
impedance. Thin copper PCBs compromise efficiency in applications involving high currents.
8) Place capacitor C3 as close as possible to the BST
and LX pins.
PCB Layout
For proper operation and minimum EMI, PCB layout
should follow the guidelines below (also see Figure 9):
1) Large switched currents flow in the IN and PGND
pins and the input capacitor C1 of Figure 3. The loop
formed by the input capacitor should be as small as
possible by placing this capacitor as close as
possible to the IN and PGND pins. The input capacitor, device, output inductor, and output capacitor
should be placed on the same side of the PCB and
the connections should be made on the same layer.
www.analog.com
Analog Devices │ 19
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
INPUT
IN
C1
1µF
MAX20050
MAX20052
FAULT FLAG
C2
1µF
BST
FLT
VCC
LX
C3
0.1µF
L1
RCS
LX
CS+
CS-
R2
AGND
REFI
PGND
R1
PWM
COUT
EP
PWM
Figure 7. Application Circuit for LED Current Derating with Temperature
INPUT
C1
1µF
FAULT FLAG
C2
1µF
IN
BST
MAX20051
MAX20053
FLT
VCC
LX
C3
0.1µF
L1
RCS
LX
CS+
CS-
COMP
LED CURRENT CONTROL
AGND
REFI
PGND
PWM
EP
PWM
B360A
RCOMP
CP
CCOMP
COUT
Figure 8. High-Current Application with MAX20051/MAX20053
www.analog.com
Analog Devices │ 20
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
PGND
VIN
LED+
COUT
5
RFILTER
RSENSE
ROUTE ON INNER SIGNAL LAYER
L
6
3
8
CIN
CBOOST
1
CFILTER
4
COMPENSATION
NETWORK
COMPONENT SIDE
MAX2005x
4
7
SOLDER SIDE
2
SIGNAL + POWER
AGND
SIGNAL
PGND
HEAT
Figure 9. Section from MAX20051 EV Kit PCB Layout
www.analog.com
Analog Devices │ 21
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Ordering Information
TEMP RANGE
SWITCHING
FREQUENCY
COMPENSATION
PIN-PACKAGE
MAX20050ATC/V+
-40°C to +125°C
400kHz
Internal
12 TDFN-EP*
MAX20050ATC+
-40°C to +125°C
400kHz
Internal
12 TDFN-EP*
MAX20050CATC/V+
-40°C to +125°C
400kHz
Internal
12 TDFN-EP*
MAX20051AAUD/V+
-40°C to +125°C
400kHz
External
14 TSSOP-EP*
MAX20051AUD/V+
-40°C to +125°C
400kHz
External
14 TSSOP-EP*
MAX20051AAUD+
-40°C to +125°C
400kHz
External
14 TSSOP-EP*
MAX20051BAUD/V+
-40°C to +125°C
400kHz (No SS)
External
14 TSSOP-EP*
PART
MAX20051CAUD/V+**
-40°C to +125°C
400kHz
External
14 TSSOP-EP*
MAX20052ATC+
-40°C to +125°C
2.1MHz
Internal
12 TDFN-EP*
MAX20052ATC/V+
-40°C to +125°C
2.1MHz
Internal
12 TDFN-EP*
MAX20052BATC+
-40°C to +125°C
2.1MHz (No SS)
Internal
12 TDFN-EP*
MAX20052BATC/V+**
-40°C to +125°C
2.1MHz (No SS)
Internal
12 TDFN-EP*
MAX20052CATC/V+
-40°C to +125°C
2.1MHz
Internal
12 TDFN-EP*
MAX20053AAUD+
-40°C to +125°C
2.1MHz
External
14 TSSOP-EP*
MAX20053AAUD/V+
-40°C to +125°C
2.1MHz
External
14 TSSOP-EP*
MAX20053AUD/V+
-40°C to +125°C
2.1MHz
External
14 TSSOP-EP*
MAX20053CAUD/V+
-40°C to +125°C
2.1MHz
External
14 TSSOP-EP*
MAX20053DATG/V+
-40°C to +125°C
2.1MHz
External
24 TQFN-EP*
/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
**Future product—contact factory for availability.
Chip Information
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maximintegrated.com/packages. Note
that a “+”, “#”, or “-” in the package code indicates RoHS status
only. Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
12 TDFN-EP
TD1233+1C
21-0664
90-0397
14 TSSOP-EP
U14E+4
21-0108
90-0463
14 TSSOP-EP
U14E+4C
21-0108
90-0463
24 TQFN-EP
T2444+4C
21-0139
90-0022
www.analog.com
PROCESS: BiCMOS
Analog Devices │ 22
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
MAX20050–MAX20053
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
0
3/14
Initial release
—
1
11/14
Updated the LED Open-Fault Enable Threshold min/typ values in Electrical
Characteristics table
4
2
12/15
Updated Current-Sense Input Offset, DMOS RDSON, and changed LED Open-Fault
Enable Threshold, LED Open-Fault Enable Hysteresis in Electrical Characteristics table;
changed LED Open and Logic VIN from 10.5V to 9V in Figures 1 and 2 and in the LED
Open section; added new Figure 8 in PCB Layout section
3, 4, 9, 10, 12,
13, 19
3
2/16
Updated VCC Output Voltage in Electrical Characteristics table; removed future product
designations in Ordering Information table
2, 20
DESCRIPTION
4
5/16
Updated Figure 8
19
5
6/16
Added MAX20050ATC+ and MAX20051AUD+ to Ordering Information table
20
6
6/16
Added MAX20050ATC+T and MAX20051AUD+T to Ordering Information table
20
7
6/16
Changed land pattern number for TSSOP package in Package Information table
20
8
7/16
Updated PWM pin in Figures 1 and 2
9
5/18
Added MAX20051AAUD/V+ and MAX20053AAUD/V+ to Ordering Information table, as
well as a new column for Bond Wire
20
10
10/18
Added U14E+4C package code in Package Information table
20
11
3/19
Updated Electrical Characteristics table, block diagrams, and Detailed Description
section for B version, added MAX20051BAUD/V+, MAX20052ATC+, and
MAX20053AAUD+ to Ordering Information table
12
5/19
Updated Ordering Information table to replace MAX20051AUD+ with MAX20051AAUD+
13
1/20
Updated General Description, Absolute Maximum Ratings, Electrical Characteristics,
Applications Information, and Ordering Information to add MAX2005xC parts
1, 2, 3, 14, 17,
18, 20
14
3/20
Updated Electrical Characteristics, Typical Operating Characteristics, and Applications
Information
2, 4, 5, 17, 19
15
4/20
Updated General Description, Benefits and Features, Package Thermal Characteristics,
Electrical Characteristics, Pin Configurations, Pin Descriptions, Typical Operating
Characteristics, and Ordering Information
1, 2, 4, 7, 8,
21
16
8/20
Updated General Description, Benefits and Features, Package Thermal Characteristics,
Electrical Characteristics, and Ordering Information
1–5, 22
17
9/20
Added MAX20052B information to DS, updated Benefits and Features,
Electrical Characteristics, PWM Dimming Control (PWM), and Ordering Information
18
11/20
Updated Applications, Ordering Information
19
7/21
Updated Ordering Information
20
7/21
Updated Electrical Characteristics and Ordering Information
9, 10
3, 4, 9, 10,
13, 20
20
1, 3, 13, 22
1, 22
22
4, 22
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is
assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that
may result from its use.Specifications subject to change without notice. No license is granted by implicationor
otherwise under any patent or patent rights of Analog Devices. Trademarks andregistered trademarks are the
property of their respective owners.
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