MAX20050CATC/V+ [MAXIM]
2A Synchronous-Buck LED Drivers with Integrated MOSFETs;
| 型号： | MAX20050CATC/V+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 2A Synchronous-Buck LED Drivers with Integrated MOSFETs |
| 文件： | 总23页 (文件大小：654K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
General Description
Benefits and Features
● Automotive Ready: AEC-Q100 Qualified
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 mini-
mum number of external components. The MAX20050/
MAX20052 utilize internal loop compensation to mini-
mize component count, while the MAX20051/MAX20053/
MAX20053D use external compensation for full flexibility.
● 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
The wide 4.5V to 65V input supply range supports
extreme automotive cold crank and load-dump condi-
tions. 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 pro-
vides 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 fre-
quency of 2.1MHz. In addition, the MAX20051B has
spread spectrum disabled.
● 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
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 tempera-
ture range of -40°C to +125°C. A 5V, 10mA LDO output is
available for biasing other circuits.
● PWM Dimming Disconnects Both High- and Low-
Side MOSFET Drivers
● 5V, 10mA LDO Output Provides Bias to Other
Circuits
● Ultra-Low Shutdown Current (5µA typ)
● Output Overload, Short-Circuit, and Overtemperature
Protections
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) pack-
ages with an exposed pad.
● 12-Pin (3mm x 3mm) TDFN, 14-Pin (5mm x 4.4mm)
TSSOP, and 24-pin (4mm x 4mm) TQFN Package
Options
Ordering Information appears at end of data sheet.
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)
19-6926; Rev 19; 7/21
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Absolute Maximum Ratings
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
Continuous Current on IN for TQFN ....................................1.8A
Continuous Current on IN for TSSOP..................................2.1A
Short-Circuit Duration on V ...................................Continuous
CC
Continuous Power Dissipation (T = +70°C) (Note 1)
A
12-Pin TDFN-EP (derate 24.4 mW/°C
above +70°C) ........................................................1951.2mW
14-Pin TSSOP-EP (derate 25.6 mW/°C
BST to LX................................................................-0.3V to +6V
PWM, FLT to AGND ................................................-0.3V to +6V
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
V
to AGND ...............................-0.3V to MIN (+6V, IN + 0.3V)
CC
COMP, REFI to AGND.................................-0.3V to V
+ 0.3V
CC
CS+ to CS-..........................................................-0.3V to + 0.3V
Continuous Current on LX....................................................2.1A
Continuous Current on IN for TDFN ....................................1.6A
(Note 1)
Package Thermal Characteristics
TDFN
TQFN
Junction-to-Ambient Thermal Resistance (θ ) ..........41°C/W
Junction-to-Ambient Thermal Resistance (θ ) ..........36°C/W
JA
JA
Junction-to-Case Thermal Resistance (θ )..............8.5°C/W
Junction-to-Case Thermal Resistance (θ ).................3°C/W
JC
JC
TSSOP
Junction-to-Ambient Thermal Resistance (θ ) ..........39°C/W
JA
Junction-to-Case Thermal Resistance (θ ).................3°C/W
JC
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
(V = 12V, V
= 1.2V, V
= V , T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 2)
IN
REFI
PWM CC A J A
PARAMETER
Input Supply Voltage
IN Undervoltage Lockout
SYMBOL
CONDITIONS
MIN
4.5
TYP
MAX
65
UNITS
V
V
IN
MAX20050C/51C/52C/53C/53D only (Note 5)
4.5
36
VIN
V
rising inferred by VCC
UVLOR
4.45
V
UVLO
IN
IN Undervoltage Hysteresis
VINHYSTL
225
mV
V
V
= 12V
5
8
8
PWM = 0
(no switching)
IN
μA
= 65V
20
IN
V
= 12V
IN
(MAX20050/51/
5
10
50C/51C)
Supply Current
IIN
Q
PWM = 100%
V
= 12V
(and during regulation
switching)
mA
IN
(MAX20052/53/
/52C/53C/53D)
20
10
V
= 65V
IN
(MAX20050/51)
V
CC
REGULATOR (V
)
CC
I
I
= 1mA, 5.5V < V < 65V
IN
VCC
= 1mA, 5.5V < V < 36V
VCC
IN
V
Output Voltage
V
4.875
5
5.125
V
CC
CC
(MAX20050C/51C/52C/53C/53D only)
I
= 10mA, 6V < V < 25V
VCC
IN
Maxim Integrated
│ 2
www.maximintegrated.com
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Electrical Characteristics (continued)
(V = 12V, V
= 1.2V, V
= V , T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 2)
IN
REFI
PWM CC A J A
PARAMETER
SYMBOL
CONDITIONS
= 5mA, V = 4.5V
MIN
TYP
50
MAX
100
110
UNITS
V
V
Dropout Voltage
I
mV
CC
VCC
IN
V
= 0V
50
40
4
80
CC
CC
Short-Circuit Current
VCC
mA
CC
IMAX
V
= 0V, MAX20053D
80
110
VCC
Rising
4.2
200
4.35
250
1.20
V
mV
V
UVLOR
V
Undervoltage Lockout
CC
VCC
Hysteresis
150
0.2
UVLHYS
REFI Input Voltage Range
REFI
RNG
REFI Zero-Current
Threshold
REFI
CS
< 5mV
DIFF
0.165
0.18
0.195
V
V
ZC_VTH
REFI Clamp Voltage
REFI
I
sink = 1μA
1.274
1.3
20
20
1.326
200
300
+65
200
70
CLMP
REFI
V
V
= 0 to V
= 0 to V
0
0
REFI
CC
Input Bias Current
REFI
nA
IIN
(MAX200051B only)
REFI
CC
Common-Mode Input Range
CSCM
-0.2
0
V
IN
Differential Signal Range
CS
mV
DIFF
V
V
V
V
- V
- V
- V
- V
= 200mV
= 0V
40
8
CS+
CS+
CS+
CS+
CS-
CS-
CS-
CS-
CS+ Input Bias Current
CS- Input Bias Current
IB
V
= 60V
= 60V
μA
μA
CS+
CS+
15
= 200mV
= 0V
100
66
150
110
IB
V
CS-
CS-
T = 25°C, CSCM 3V to 60V
-0.1
J
IN
Current-Sense Input Offset
CS
3V < CSCM < 60V
-1.8
+1.8
mV
V/V
OS
IN
3V < CSCM < 60V, MAX20053D
IN
-0.1
5
4.95
5.05
(CS+ - CS-) = 200mV,
Current-Sense Voltage Gain
CS
GAIN
3V < CSCM < 60V
IN
B,C,D versions
4.91
215
196
5
5.08
225
204
REFI = 1.4V, 3V < CSCM < 60V
220
200
IN
REFI = 1.2V, 3V < CSCM < 60V
IN
REFI = 1.2V, 3V < CSCM < 60V,
IN
MAX20053D
196
200
205
Regulation Voltage
Accuracy
CS
mV
ACC
REFI = 0.7V, 3V < CSCM < 60V
100
40
IN
REFI = 0.4V, 3V < CSCM < 60V
37.8
37.8
42.2
43.1
IN
REFI = 0.4V, 3V < CSCM < 60V,
IN
MAX20053D
40
V
V
V
= 1.2V 0V < CSCM < 3V
192
35
200
40
208
45
REFI
REFI
REFI
IN
= 0.4V 0V < CSCM < 3V
IN
Regulation Voltage
Accuracy Low Range
= 1.2V 0V < CSCM < 3V,
IN
CS
mV
192
35
200
40
209.1
46.5
ACC
MAX20053D
V
= 0.4V 0V < CSCM < 3V,
REFI
IN
MAX20053D
Maxim Integrated
│ 3
www.maximintegrated.com
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Electrical Characteristics (continued)
(V = 12V, V
= 1.2V, V
= V , T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 2)
IN
REFI
PWM CC A J A
PARAMETER
SYMBOL
CONDITIONS
MIN
2.75
2.5
TYP
2.85
2.6
MAX
2.95
2.7
UNITS
V
V
V
V
V
V
rising
falling
CS+
CS+
CS+
CS+
CS-
CS-
CS Common-Mode Range
Input Selector
RNG
V
SEL
rising, MAX20053D
falling, MAX20053D
2.73
2.47
285
282
2.85
2.6
2.95
2.7
> OUT
300
300
315
315
VTH_LOW
VTH_LOW,
> OUT
MAX20053D
Cycle-by-Cycle Current
Limit
CS
mV
LIM
CS
CS
ACC
+ 5
ACC
V
< OUT
CS
ACC
CS-
VTH_LOW
= 200mV
CS-
- 5
Transconductance
Open-Loop DC Gain
COMP Bias Current
g
V
- V
480
600
75
720
μS
dB
nA
M
CS+
COMP
COMP
PWM = 0
-200
85
+200
115
115
115
115
340
300
IBIAS
V
COMP
V
COMP
V
COMP
V
COMP
= 5V
100
100
100
100
170
140
10
COMP Sink Current
μA
μA
ISINK
= 5V, MAX20053D
= 0V
80
85
COMP Source Current
COMP
ISRC
= 0V, MAX20053D
80
High-Side DMOS RDS
Low-Side DMOS RDS
LX Rise Time
R
I
= 200mA, V = 3V
CS+
mΩ
mΩ
ns
ON
ON,HS
LX
R
V
= 5V, I = 200mA
ON
ON,LS
CC LX
t
RISE,LS
MAX20050/MAX20051, frequency dither
disabled
360
400
440
Switching Frequency
f
kHz
SW
MAX20052/MAX20053, frequency dither
disabled
1890
2100
2310
Minimum On-Time
t
50
50
40
80
80
60
±3
120
120
90
ns
ns
ON_MIN
Minimum Off-Time
t
OFF_MIN
SS
MAX20053D
Spread-Spectrum Range
PWM Input Frequency
Not applicable to B version
%
PWM
10
2000
Hz
FR
Rising (during regulation)
Falling (during regulation)
Rising
2
2
5
5
2
PWM-to-LX Delay
PWM Threshold
PWM
μs
DLY
PWM
PWM
V
VTHR
Falling
800
1
mV
μA
ms
μs
VTHF
PWM Pullup Current
PWM Shutdown Timer
Startup Time
PWM
V
= 12V
2
3
RIN
IN
PWM
PWM low time to enter shutdown mode
IN, PWM rising to LX delay
Rising
140
180
210
250
165
10
300
350
SHDW
t
STUP
°C
°C
Thermal Shutdown
Hysteresis
Maxim Integrated
│ 4
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Electrical Characteristics (continued)
(V = 12V, V
= 1.2V, V
= V , T = T = -40°C to +125°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 2)
IN
REFI
PWM CC A J A
PARAMETER
SYMBOL
LOF
CONDITIONS
MIN
TYP
MAX
UNITS
LED Open-Fault REFI
Range
V
V
V
rising
300
325
350
mV
REFI_RNG
REFI
LED Open-Fault Enable
Rising Threshold
LOF
rising
8
9
10
V
IN_RNG
IN
IN
LED Open-Fault Enable
Falling Threshold
LOF
falling
falling, duty = max
7.3
10
3
8.3
25
6
9.3
40
9
V
%
%
IN_FLNG
LED Open-Fault Threshold
LOF
CS
VTH
DIFF
LED Open-Fault Hysteresis
LOF
VTH_HYS
Output-Voltage Low
Threshold
OUTV
V
falling
1.35
1.5
1.65
0.3
V
V
TH_LOW
CS-
I
= 1mA, V
= 1V, after FAULT
SINK
CS+ DEG
FAULT Output Voltage
FAULT
FAULT
0.05
VOL
elapsed
(Note 3)
(Note 4)
FAULT Deglitch Timer
FAULT Mask Timer
70
105
210
150
300
1
µs
µs
µA
DEG
FAULT
140
MASK
FAULT Leakage Current
FAULT
V
= 5.5V
LGK
FAULT
Note 2: 100% tested at T = +25°C. All limits over temperature are guaranteed by design, not production tested.
A
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.
Maxim Integrated
│ 5
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Typical Operating Characteristics
(V = 12V, V
IN
= 1.2V, V
= V , T = +25°C, unless otherwise noted.)
REFI
PWM CC A
EFFICIENCY vs.
LED CURRENT
EFFICIENCY vs.
LED CURRENT
EFFICIENCY vs.
LED CURRENT
toc01
toc02
toc03
100
90
80
70
60
50
40
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
VIN = 24V (MAX20053)
VIN = 24V (MAX20051)
VIN = 12V (MAX20053)
VIN = 24V (MAX20051)
VIN = 12V (MAX20053)
VIN = 12V (MAX20051)
30
20
10
0
VIN = 12V (MAX20051)
6 SERIES LEDs
VIN = 48V
MAX20051
2 SERIES LEDS
1.5
1 LED
0.0
0.5
1.0
2.0
0.0
0.5
1.0
1.5
2.0
0.0
0.5
1.0
LED CURRENT (A)
1.5
2.0
LED CURRENT (A)
LED CURRENT (A)
VCC VOLTAGE REGULATION vs.
TEMPERATURE
LINE REGULATION
VCC LINE REGULATION
toc04
toc05
toc06
1.05
1.04
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
0.95
5.25
5.20
5.15
5.10
5.05
5.00
4.95
4.90
4.85
4.80
4.75
5.25
5.20
5.15
5.10
5.05
5.00
4.95
4.90
4.85
4.80
4.75
MAX20051
2 SERIES LEDS
ILED = 1A
MAX20051
VREFI = 0V
IVCC = 1mA
0
10
20
30
40
50
0
10
20
30
40
50
60 70
-50
0
50
100
150
VIN (V)
VIN (V)
TEMPERATURE (ºC)
MINIMUM ON-TIME
vs. TEMPERATURE
MINIMUM OFF-TIME
vs. TEMPERATURE
VCC LOAD REGULATION
toc07
toc08
toc09
5.25
5.20
5.15
5.10
5.05
5.00
4.95
4.90
4.85
4.80
4.75
200
200
180
160
140
120
100
80
180
160
140
120
100
80
60
60
40
40
20
20
VREFI = 0V
60
0
0
0
20
40
IVCC (mA)
80
-50
0
50
100
150
-50
0
50
100
150
TEMPERATURE (ºC)
TEMPERATURE (ºC)
Maxim Integrated
│ 6
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Typical Operating Characteristics (continued)
(V = 12V, V
= 1.2V, V
= V , T = +25°C, unless otherwise noted.)
IN
REFI
PWM CC A
VREFI TRANSIENT RESPONSE
(MAX20051)
VIN UVLO THRESHOLDS vs.
TEMPERATURE
SWITCHING FREQUENCY vs.
TEMPERATURE
toc11
toc12
toc10
4.25
4.20
4.15
4.10
4.05
4.00
3.95
2.5
2.0
1.5
1.0
0.5
0.0
UVLO RISING
MAX20053
2V/div
0V
VREFI
1A/div
0A
ILED
UVLO
FALLING
2V/div
VLED
MAX20051
50
0V
-50
0
50
100
150
-50
0
100
150
100µs/div
TEMPERATURE (ºC)
TEMPERATURE (ºC)
VREFI TRANSIENT RESPONSE
(MAX20053)
CURRENT SENSE VOLTAGE
vs. VREFI
toc13
toc14
250
200
150
100
50
2V/div
0V
VREFI
MAX20051
MAX20053
1A/div
0A
ILED
VLED
2V/div
0V
0
3 LEDS
RCS = 100mΩ
-50
100µs/div
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
VREFI (V)
CURRENT SENSE VOLTAGE vs.
TEMPERATURE
SUPPLY CURRENT
vs.TEMPERATURE
toc15
toc16
140
130
120
110
100
90
20
18
16
14
12
10
8
VIN = 12V (MAX20053)
VCS- = 0V
(MAX20053)
VCS- = 0V
(MAX20051)
VIN = 65V (MAX20051)
VIN = 12V (MAX20051)
VCS- = 3V
(MAX20051)
6
80
4
VCS- = 3V
70
(MAX20053)
2
VREFI = 0.7V
100
PWM = 100%
60
0
-50
0
50
TEMPERATURE (ºC)
150
-50
0
50
100
150
TEMPERATURE (ºC)
Maxim Integrated
│ 7
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Pin Configurations
TOP VIEW
CS- NC CS+ CS+ NC
IN
13
LX LX BST
V
REFI AGND
CC
9
18
17
16
15
14
12
11
10
8
7
19
ꢀ
12
PWM
NC
IN
PGND
IN
1
2
3
4
5
6
7
14 LX
13 LX
12 BST
20
21
11
10
PGND
IN
FLT
MAX2005ꢂ
MAX20053
PGND
NC
MAX20053D
MAX20050
MAX20052
11
V
CC
22
23
24
CS+
NC
9
8
7
10 REFI
CS-
COMP
LX
LX
ꢀ
PWM
9
8
AGND
COMP
ꢀ
AGND
FLT
1
2
3
4
5
6
1
2
3
4
5
6
V
PGND IN CS+ CS- PWM FLT
AGND REFI
BST LX
LX
CC
TꢄFꢁ
TSSOꢃ
TDFꢁ
Pin Descriptions
TDFN
TSSOP
NAME
FUNCTION
MAX20050
MAX20052
MAX20051
MAX20053
1
2
1
PGND
IN
Power Ground
Power-Supply Input. Bypass to PGND with a minimum of 1μF ceramic capacitor.
2, 3
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.
3
4
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.
4
5
5
6
CS-
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.
PWM
6
7
8
FLT
Open-Drain Fault Output. Refer to the Fault Pin Behavior section for information on Fault.
Compensation Output (MAX20051/MAX20053). Connect an external RC network for loop
compensation. The MAX20050/MAX20052 are internally compensated.
—
COMP
7
8
9
AGND
REFI
Analog Ground
Analog Dimming-Control Input. Connect an analog voltage from 0 to 1.2V for analog
dimming of LED current.
10
5V Regulator Output. Connect a 1μF ceramic capacitor to AGND from this pin for stable
operation.
9
11
V
CC
High-Side Power Supply for Gate Drive. Connect a 0.1μF ceramic capacitor from BST to
LX.
10
11, 12
—
12
13, 14
—
BST
LX
Switching Node. Connect to one end of output inductor.
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.
EP
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Pin Descriptions (continued)
TQFN
NAME
FUNCTION
MAX20053D
1, 24
2
AGND
REFI
Analog Ground. Pins 1 and 24 should be shorted outside the IC.
Analog Dimming-Control Input. Connect an analog voltage from 0 to 1.2V for analog dimming of
LED current.
3
V
CC
5V Regulator Output. Connect a 1μF ceramic capacitor to AGND from this pin for stable operation.
4
5, 6, 7, 8
9
BST
LX
High-Side Power Supply for Gate Drive. Connect a 0.1μF ceramic capacitor from BST to LX.
Switching Node. Connect to one end of output inductor.
NC
No Connect
10, 11
12, 13
14
PGND
IN
Power Ground
Power-Supply Input. Bypass to PGND with a minimum of 1μF ceramic capacitor.
NC
No Connect
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.
15, 16
17
CS+
NC
No Connect
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.
18
CS-
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.
19
PWM
20
21
22
NC
FLT
NC
No Connect
Open-Drain Fault Output. Refer to the Fault Pin Behavior section for information on Fault.
No Connect
23
—
COMP
EP
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.
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
VCCOK
INUVLO
POK
POKD
80µs
DELAY
V
IN
PWM
OSC
DITHERING
(NON-B VERSIONS)
DUTY MAX
BG
SYNC TO RISING
EDGE OF PWM
V
CC
LDO
INUVLO
VCCOK
BLANKING TIME
RESET
DOMINANT
AGND
REFI
DH
CLOCK
SET
S
Q
Q
PWM COMP
BST
1.3V
CLAMP
PEAK
R
CLR
V
IN
CURRENT
LIMIT
300mV
G
m
DUTY
MAX
CS-
x5
CS+
SOFT-OFF
DH
PWM
COMP
LX
SET
D
Q
Q
POKD
V
CC
RESET
DOMINANT
CLR
4V
SKIP PULSE
DL
PWM
SET
2µA
S
Q
SHUTDOWN
MODE
200ms LOW
STATE TIME
COUNTER
PWM
R
Q
CLR
PGND
FALLING 0.8V
RISING 2.0V
SOFT-OFF
0.5V
REFI ꢁ 325mV
LED
SHORT
1.5V
CS-
ꢀ = 105µs
THERMAL
SHUTDOWN
FLT
MAX20050
MAX20052
REFI
THERMAL
SHUTDOWN
180mV
REFI ꢁ 325mV
ꢁ 9V
V
IN
DUTY = MAX
ꢀ = 105µs
LED
OPEN
25% REFI
Figure 1. Block Diagram of the MAX20050/MAX20052
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
VCCOK
INUVLO
POK
POKD
80µs
DELAY
V
IN
PWM
OSC
DUTY MAX
DITHERING
(NON-B VERSIONS)
BG
SYNC TO RISING
EDGE OF PWM
V
CC
LDO
INUVLO
VCCOK
BLANKING TIME
RESET
DOMINANT
AGND
COMP
DH
CLOCK
SET
S
Q
Q
PWM COMP
BST
PEAK
R
CLR
V
IN
CURRENT
LIMIT
300mV
REFI
1.3V
CLAMP
DUTY
MAX
G
m
CS-
SOFT-OFF
x5
DH
PWM
CS+
LX
COMP
SET
D
Q
Q
POKD
V
CC
RESET
DOMINANT
CLR
4V
SKIP PULSE
DL
PWM
SET
2µA
S
Q
SHUTDOWN
MODE
200ms LOW
STATE TIME
COUNTER
PWM
R
Q
CLR
PGND
REFI ꢁ 325mV
FALLING 0.8V
RISING 2.0V
SOFT-OFF
0.5V
LED
SHORT
1.5V
CS-
ꢀ = 105µs
THERMAL
SHUTDOWN
FLT
REFI
MAX2005ꢀ
MAX20053
THERMAL
SHORT
180mV
REFI = 325mV
ꢁ 9V
V
IN
DUTY = MAX
ꢀ = 105µs
LED
OPEN
25% REFI
Figure 2. Block Diagram of the MAX20051/MAX20053
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MAX20050–MAX20053
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 sig-
nal. 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 ampli-
fied 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.
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 compensa-
tion 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
have an internal switching frequency of 2.1MHz.
High-side current regulation means only a single connec-
tion 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.
The device also includes a PWM dimming input that is
used for PWM dimming of the LED current. When this sig-
nal 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 dim-
ming 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.
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 fre-
quency 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
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.
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Analog Dimming
Switching Node (LX)
The devices have an analog dimming-control input
(REFI). The voltage at REFI sets the LED current level
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
when V
≤ 1.2V. For V
> 1.2V, REFI is clamped
REFI
REFI
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 boost capacitor. The R
of both the high- and
DS(ON)
low-side switching MOSFETs is 0.3Ω maximum at a
junction temperature of +125°C.
Boost Capacitor Node (BST)
The BST pin is used to provide a drive voltage to the
high-side switching MOSFET that is higher than the input
High-Side Current Sense (CS+, CS-)
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 current-
sense resistor (inductor side) and the CS- pin should be
connected to the negative terminal of the current-sense
resistor (LED string anode side).
voltage. An internal diode is connected from BST to V
.
CC
Connect a 0.1µF ceramic capacitor from this pin to the LX
pins. Place the capacitor as close as possible to this pin.
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.
PWM Dimming Control (PWM)
A low signal on this pin turns off both the high- and low-
side 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
Analog Ground (AGND)
This is the analog ground pin for all the control circuitry of
the LED driver. Connect the PGND and the AGND togeth-
er at the negative terminal of the input bypass capacitor.
connect a pull up resistor to V
on this pin. The device
comes out of shutdown mode with the internal current
CC
Compensation (COMP)
(MAX20051/MAX20053)
source pulling the pin high.
The COMP pin is present in the MAX20051/MAX20053.
Connect the external compensation network to this pin for
stable loop compensation.
5V Regulator (V
)
CC
A regulated 5V output is provided for biasing other
circuitries up to 10mA load. Bypass V to AGND with a
CC
Fault Pin Behavior
The FLT pin is an open-drain output. See the LED Open
and LED Short sections.
minimum of 1µF ceramic capacitor as close as possible
to the device.
Input Voltage (IN)
LED Open
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.
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
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
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.
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.
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 anoth-
er 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.
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 dissipa-
tion 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.
LED Short
The LED short is detected when the following two conditions
are true at the same time for a period longer than 105µs:
High-Side Current-Sense Amplifier
● REFI > 325mV
The devices feature a high-bandwidth, high-side current-
sense amplifier that is used to sense the inductor current.
The gain of this current-sense amplifier is 5. The differ-
ential 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 ampli-
fier. The 3dB bandwidth of the high-side current-sense
amplifier is 1.5MHz.
● 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 acti-
vated.
Exposed Pad
Internal Transconductance Amplifier
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.
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 inter-
nally 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.
Inductor Peak Current-Limit Comparator
The peak current comparator provides a path for fast
cycle-by-cycle current limit during extreme fault condi-
tions. The average current-limit threshold, set by the REFI
voltage, limits the output current during short circuit.
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
switching frequency of 2.1MHz. Selecting a higher switch-
ing 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 volt-
age. 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.
Applications Information
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 R
(see Figure 3). When REFI is set to a voltage >1.3V, the
CS
internal reference regulates the voltage across R
220mV. The current is given by:
to
CS
0.220
I
=
For the typical operating circuit of Figure 4 (V = 12V),
IN
LED
R
CS
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
The LED current can also be programmed using the
voltage on REFI when V
The current is given by:
≤ 1.2V (analog dimming).
REFI
Figure 5 (V = 24V), the inductor value has to be in the
IN
range of 33µH to 82µH for the MAX20050. For the typi-
cal application circuit of Figure 6 (V = 40V to 60V), the
(V
− 0.2)
IN
REFI
I
=
LED
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.
(5 x R
)
CS
Inductor Selection
The peak inductor current, selected switching frequency,
and the allowable inductor current ripple determine the
value and size of the output inductor. The MAX20050/
MAX20051 have an internal switching frequency of
400kHz, whereas the MAX20052/MAX20053 have a
INPUT
IN
BST
LX
C1
1µF
C3
MAX20051
MAX20053
L1
0.1µF
R
CS
LX
FAULT FLAG
FLT
CS+
CS-
V
CC
C2
1µF
COMP
AGND
PGND
LED CURRENT CONTROL
REFI
R
COMP
C
C
OUT
P
PWM EP
C
COMP
PWM
Figure 3. Typical Application Circuit Using the MAX20051
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
ceramic capacitors in parallel to achieve the required bulk
capacitance.
Input Capacitor
The discontinuous input-current waveform of the buck
converter causes large ripple currents in the input capaci-
tor. The switching frequency, peak inductor current, and
the allowable peak-to-peak voltage ripple reflected back
to the source dictate the capacitance requirement. The
The output capacitance C
following equation:
is calculated using the
OUT
((V
− V
LED
)× V )
LED
IN_MIN
C
=
OUT
2
input ripple is comprised of ΔV (caused by the capacitor
Q
(∆V × 2×L × V
IN_MAX
× f
)
SW
R
discharge) and ΔV
(caused by the ESR of the capaci-
ESR
where ΔV is the maximum allowable voltage ripple.
tor). Use low-ESR ceramic capacitors with high ripple-
current capability at the input. A 1µF ceramic capacitor is
recommended for most applications.
R
The output capacitance for MAX20050 in Figure 4 has
to be in the range of 0.22µF to 4.7µF for a stable opera-
tion. 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.
Output Capacitor
The function of the output capacitor is to reduce the out-
put 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 ceram-
ic capacitors can dramatically reduce the output ESR and
ESL effects. To reduce the ESL effects, connect multiple
INPUT
IN
BST
LX
INPUT FROM
4.5V TO 16V
C1
1µF
C3
R2
0.1µF
L1
0.133Ω
MAX20050
MAX20052
LX
FAULT FLAG
CS+
CS-
FLT
V
CC
C2
1µF
AGND
PGND
LED VOLTAGE IS FROM 2V TO 10V
LED CURRENT IS 150mA TO 1.5A
LED CURRENT CONTROL
PWM
REFI
C7
PWM EP
Figure 4. Typical Input Voltage (12V)
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
INPUT
IN
BST
LX
INPUT FROM
12V TO 32V
C1
1µF
C3
R2
0.1µF
L1
0.133Ω
MAX20050
LX
FAULT FLAG
FLT
CS+
CS-
V
CC
C2
1µF
AGND
PGND
LED VOLTAGE IS FROM 2V TO 20V
LED CURRENT IS 150mA TO 1.5A
LED CURRENT CONTROL
PWM
C7
REFI
PWM EP
Figure 5. Typical Input Voltage (24V)
INPUT
IN
BST
LX
INPUT FROM
C1
40V TO 60V
1µF
C3
R2
0.1µF
L1
0.133Ω
MAX20050
LX
CS+
CS-
FAULT FLAG
FLT
V
CC
C2
1µF
AGND
PGND
LED VOLTAGE IS FROM 2V TO 50V
LED CURRENT IS 150mA TO 1.5A
LED CURRENT CONTROL
PWM
REFI
C7
PWM EP
Figure 6. Typical Input Voltage (50V)
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MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Table 1. Suggested L–C Network for Internally Compensated Parts
L AND C COMPONENT VALUES (MAX20050, fSW = 400kHz)
V
V
V
V
V
V
= 12V (typ), Figure 4
= 24V (typ), Figure 5
= 55V (typ), Figure 6
= 12V (typ), Figure 4
= 24V (typ), Figure 5
= 55V (typ), Figure 6
0.22
0.47
0.1
22
4.7
4.7
2.2
33
IN
IN
IN
IN
IN
IN
Output Capacitor Range (C7)
Inductor Range (L1)
µF
µH
33
82
47
150
L AND C COMPONENT VALUES (MAX20052, fSW = 2.1MHz)
Output Capacitor Range (C7)
Inductor Range (L1)
V
= 12V (typ), Figure 4
= 12V (typ), Figure 4
0.1
3.3
4.7
10
µF
µH
IN
IN
V
2.25fs and s is the dv/dt of the voltage from the output
Compensation
n
of the G amplifier.
m
The MAX20050/MAX20052 have internal loop com-
pensation 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.
In the MAX20051 the compensation zero formed by
R
C
should be set at 20kHz and for the
COMP COMP
MAX20053 at 100kHz. Initially, the value of the capacitor
can be calculated by the formula:
C
COMP
G
Lf w
s z
m
=
The compensator should be designed as follows. The
high-side current sense amplifier introduces a high-
frequency pole to around 420kHz. This is close to the
switching frequency. The current loop gain is:
1
C
COMP
0.5 + F V Rcs5
m IN
π
where w is the zero at R
C
and f is the
z
COMP COMP s
switching frequency. Initially, F is assumed as 0.555
m
and the initial values of C
is calculated and then
1 + sRC
F V
m IN
R
(
)
COMP
OUT
Ti(s) =
×
R
is calculated based on the zero location at 20kHz
COMP
L
2
1+ s + s LC
OUT
for the MAX20051 and 100kHz for the MAX20053. The
R
R
values of R , C , and C may need to be
COMP
COMP
P
G
sC
+1 5R
(
)
m
COMP COMP
CS
optimized further when testing, so as to get the optimum
loop response.
×
s
sCOMP1+
w
p
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 tem-
perature 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.
where G is the transconductance of the error ampli-
m
fier inside the MAX20051/MAX20053, R
is the current
CS
sense resistor, R is the total dynamic resistance of the LED
string, L is the inductance, R is the compensation
COMP
resistor, C
is the output capacitance, w is the pole
OUT
p
from the high side current sense amplifier at 2πfp and F
m
is the modulator gain that is given by:
1
F
=
m
s
(
+ s T
n s
)
e
where T is 1/f where f is the switching frequency, s
e
s
s
s
is the dv/dt of the ramp in the PWM comparator which is
Maxim Integrated
│ 18
www.maximintegrated.com
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
At this temperature, the voltage on REFI pin is:
2) Place an unbroken ground plane on the layer closest
to the surface layer with the inductor, device, and the
input and output capacitors.
V
× R1 T1
(
)
CC
1.3 =
R1 T1 + R2
(
)
(
)
3) The surface area of the LX and BST nodes should be
as small as possible to minimize emissions.
where V
is 5V and R1(T1) is the resistance of the
CC
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.
resistor from REFI to ground at temperature T1 and R2 is
the resistance from V to REFI.
CC
V
× R1 T1
(
)
)
CC
0.2 =
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 oth-
ers, an additional resistor in series or in parallel or some
other combination may need to be added to provide the
desired resistance.
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 current-sense
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.
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.
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 con-
ducts heat more effectively, thereby reducing thermal
impedance. Thin copper PCBs compromise efficiency
in applications involving high currents.
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 enter-
ing 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.
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.
Maxim Integrated
│ 19
www.maximintegrated.com
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
INPUT
IN
BST
LX
C1
1µF
C3
0.1µF
MAX20050
MAX20052
L1
R
CS
LX
FAULT FLAG
FLT
CS+
CS-
V
CC
C2
1µF
R2
AGND
PGND
REFI
R1
C
OUT
PWM EP
PWM
Figure 7. Application Circuit for LED Current Derating with Temperature
INPUT
IN
BST
LX
C1
1µF
C3
MAX2005ꢀ
MAX20053
0.1µF
L1
R
CS
LX
FAULT FLAG
FLT
CS+
CS-
V
CC
C2
1µF
COMP
AGND
B360A
LED CURRENT CONTROL
REFI
R
COMP
PGND
C
P
C
OUT
PWM EP
C
COMP
PWM
Figure 8. High-Current Application with MAX20051/MAX20053
Maxim Integrated
│ 20
www.maximintegrated.com
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
PGND
LED+
V
IN
C
OUT
5
R
FILTER
R
SENSE
ROUTE ON INNER SIGNAL LAYER
L
6
3
8
C
IN
C
BOOST
1
C
FILTER
4
COMPENSATION
NETWORK
COMPONENT SIDE
SOLDER SIDE
MAX2005x
SIGNAL + POWER
AGND
SIGNAL
PGND
2
4
7
HEAT
Figure 9. Section from MAX20051 EV Kit PCB Layout
Maxim Integrated
│ 21
www.maximintegrated.com
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Ordering Information
SWITCHING
FREQUENCY
PART
TEMP RANGE
COMPENSATION
PIN-PACKAGE
BOND WIRE
MAX20050ATC/V+
MAX20050ATC+
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
-40°C to +125°C
400kHz
400kHz
Internal
Internal
Internal
External
External
External
External
External
Internal
Internal
Internal
Internal
Internal
External
External
External
External
External
12 TDFN-EP*
12 TDFN-EP*
12 TDFN-EP*
14 TSSOP-EP*
14 TSSOP-EP*
14 TSSOP-EP*
14 TSSOP-EP*
14 TSSOP-EP*
12 TDFN-EP*
12 TDFN-EP*
12 TDFN-EP*
12 TDFN-EP*
12 TDFN-EP*
14 TSSOP-EP*
14 TSSOP-EP*
14 TSSOP-EP*
14 TSSOP-EP*
24 TQFN-EP*
Copper
Copper
Copper
Copper
Gold
MAX20050CATC/V+
MAX20051AAUD/V+
MAX20051AUD/V+
MAX20051AAUD+
MAX20051BAUD/V+
MAX20051CAUD/V+**
MAX20052ATC+
400kHz
400kHz
400kHz
400kHz
Copper
Copper
Copper
Copper
Copper
Copper
Copper
Copper
Copper
Copper
Gold
400kHz (No SS)
400kHz
2.1MHz
MAX20052ATC/V+
MAX20052BATC+
MAX20052BATC/V+**
MAX20052CATC/V+
MAX20053AAUD+
MAX20053AAUD/V+
MAX20053AUD/V+
MAX20053CAUD/V+
MAX20053DATG/V+
2.1MHz
2.1MHz (No SS)
2.1MHz (No SS)
2.1MHz
2.1MHz
2.1MHz
2.1MHz
2.1MHz
Copper
Copper
2.1MHz
/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
PROCESS: BiCMOS
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
14 TSSOP-EP U14E+4
21-0664
21-0108
21-0108
21-0139
90-0397
90-0463
90-0463
90-0022
14 TSSOP-EP U14E+4C
24 TQFN-EP T2444+4C
Maxim Integrated
│ 22
www.maximintegrated.com
MAX20050–MAX20053
2A Synchronous-Buck LED Drivers
with Integrated MOSFETs
Revision History
REVISION REVISION
PAGES
CHANGED
DESCRIPTION
NUMBER
DATE
0
3/14
Initial release
—
Updated the LED Open-Fault Enable Threshold min/typ values in Electrical
Characteristics table
1
2
3
11/14
12/15
2/16
4
Updated Current-Sense Input Offset, DMOS RDS , and changed LED Open-Fault
ON
Enable Threshold, LED Open-Fault Enable Hysteresis in Electrical Characteristics table; 3, 4, 9, 10, 12,
changed LED Open and Logic V from 10.5V to 9V in Figures 1 and 2 and in the LED
13, 19
IN
Open section; added new Figure 8 in PCB Layout section
Updated V
Output Voltage in Electrical Characteristics table; removed future product
CC
2, 20
designations in Ordering Information table
4
5
6
7
8
5/16
6/16
6/16
6/16
7/16
Updated Figure 8
19
20
Added MAX20050ATC+ and MAX20051AUD+ to Ordering Information table
Added MAX20050ATC+T and MAX20051AUD+T to Ordering Information table
Changed land pattern number for TSSOP package in Package Information table
Updated PWM pin in Figures 1 and 2
20
20
9, 10
Added MAX20051AAUD/V+ and MAX20053AAUD/V+ to Ordering Information table, as
well as a new column for Bond Wire
9
5/18
20
20
10
10/18
Added U14E+4C package code in Package Information table
Updated Electrical Characteristics table, block diagrams, and Detailed Description
section for B version, added MAX20051BAUD/V+, MAX20052ATC+, and
MAX20053AAUD+ to Ordering Information table
3, 4, 9, 10,
13, 20
11
3/19
12
13
5/19
1/20
Updated Ordering Information table to replace MAX20051AUD+ with MAX20051AAUD+
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
Updated Electrical Characteristics, Typical Operating Characteristics, and Applications
Information
14
15
3/20
4/20
2, 4, 5, 17, 19
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
Updated General Description, Benefits and Features, Package Thermal Characteristics,
Electrical Characteristics, and Ordering Information
16
17
8/20
9/20
1–5, 22
Added MAX20052B information to DS, updated Benefits and Features,
Electrical Characteristics, PWM Dimming Control (PWM), and Ordering Information
1, 3, 13, 22
18
19
11/20
7/21
Updated Applications, Ordering Information
Updated Ordering Information
1, 22
22
For pricing, delivery, and ordering information, please visit Maxim Integrated’s online storefront at https://www.maximintegrated.com/en/storefront/storefront.html.
Maxim Integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim Integrated product. No circuit patent licenses
are implied. Maxim Integrated reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits)
shown in the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
©
Maxim Integrated and the Maxim Integrated logo are trademarks of Maxim Integrated Products, Inc.
2021 Maxim Integrated Products, Inc.
│ 23
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