MAX16813BAUP/V+ [MAXIM]
Integrated, 4-Channel, High-Brightness LED Driver with High-Voltage DC-DC Controller and Battery Disconnect;
| 型号： | MAX16813BAUP/V+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Integrated, 4-Channel, High-Brightness LED Driver with High-Voltage DC-DC Controller and Battery Disconnect 电池 |
| 文件： | 总27页 (文件大小：1804K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
EVALUATION KIT AVAILABLE
MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
General Description
Benefits and Features
The MAX16813B high-efficiency, high-brightness LED
(HB LED) driver provides four integrated LED current-
sink channels. An integrated current-mode switching
controller drives a DC-DC converter that provides the
necessary voltage to multiple strings of HB LEDs. The
device accepts a wide 4.75V to 40V input voltage range
and withstands direct automotive load-dump events. The
wide input range allows powering HB LEDs for small- to
medium-sized LCD displays in automotive and general
lighting applications.
● 4-Channel Linear LED Current Sinks with Internal
MOSFETs Independently Drive Multiple LED Strings
• Full-Scale LED Current, Adjustable from 20mA
to 150mA
• Drives 1 to 4 LED Strings
• 10000:1 PWM Dimming at 200Hz
● Flexible Current-Mode Architecture Supports a Wide
Range of Applications While Minimizing Interference
• Boost or SEPIC Current-Mode DC-DC Controller
• 200kHz to 2MHz Programmable Switching
Frequency
An internal current-mode switching DC-DC controller
supports boost or SEPIC topologies and operates in an
adjustable frequency range between 200kHz and 2MHz.
An integrated spread-spectrum mode helps reduce EMI.
Current-mode control with programmable slope compen-
sation provides fast response and simplifies loop compen-
sation. An adaptive output-voltage control scheme mini-
mizes power dissipation in the LED current-sink paths.
The device has a separate p-channel drive (PGATE) pin
that is used for output undervoltage protection. Whenever
the output falls below the threshold, the external
p-MOSFET is latched off, disconnecting the input source.
Cycling the EN or the input supply is required to restart
the converter. The external p-MOSFET is off when the EN
pin is below 0.3V (typ). The shutdown current is 1µA (typ)
at an input voltage of 12V.
• External Switching-Frequency Synchronization
• Spread-Spectrum Mode
● Protection Features Enhance Fault Detection and
System Reliability
• Output-to-Ground Undervoltage Protection
• Open-Drain Fault-Indicator Output
• Open-LED and LED-Short Detection and
Protection
• Overtemperature Protection
● Adaptive Output-Voltage Optimization to Minimize
Power Dissipation
• Less than 2µA Shutdown Current
Applications
● Automotive Displays LED Backlights
The device consists of four identical linear current-sink
channels, adjustable from 20mA to 150mA with an
accuracy of ±3% using a single external resistor. Multiple
channels can be connected in parallel to achieve higher
current per LED string. The device also features a unique
pulsed dimming control through a logic input (DIM),
with minimum pulse width as low as 500ns. Protection
features include output overvoltage, open-LED detection
and protection, programmable shorted-LED detection and
protection, output undervoltage detection and protection,
and overtemperature protection. The device operates
over the -40°C to +125°C automotive temperature range.
The MAX16813B is available in 20-pin (6.5mm x 4.4mm)
TSSOP and 20-pin (4mm x 4mm) TQFN packages.
● Automotive RCL, DRL, Front Position, and Fog Lights
● LCD TV and Desktop Display LED Backlights
● Architectural, Industrial, and Ambient Lighting
Ordering Information appears at end of data sheet.
19-100144; Rev 1; 1/18
MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Absolute Maximum Ratings
IN to SGND ...........................................................-0.3V to +45V
EN, PGATE to SGND...................................-0.3V to (IN + 0.3V)
PGND to SGND....................................................-0.3V to +0.3V
LEDGND to SGND...............................................-0.3V to +0.3V
OUT_ to LEDGND.................................................-0.3V to +45V
OUT_ Continuous Current..............................................±175mA
Short-Circuit Duration........................................Continuous
V
CC
Continuous Power Dissipation (T = +70°C) (Note 1)
A
20-Pin TQFN (derate 25.6mW/°C above +70°C)......2051mW
20-Pin TSSOP (derate 26.5mW/°C above +70°C)....2122mW
Operating Temperature Range......................... -40°C to +125°C
Junction Temperature......................................................+150°C
Storage Temperature Range............................ -65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow).......................................+260°C
V
to SGND............-0.3V to the lower of (IN + 0.3V) and +6V
CC
FLT, DIM, RSDT, OVP to SGND.............................-0.3V to +6V
CS, NDRV, RT, COMP, SETI to SGND.... -0.3V to (V + 0.3V)
NDRV Peak Current (< 100ns) .............................................±3A
NDRV Continuous Current.............................................±100mA
CC
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these
or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect
device reliability.
(Note 1)
Package Thermal Characteristics
TQFN
TSSOP
Junction-to-Ambient Thermal Resistance (θ ) .....+37.7°C/W
Junction-to-Ambient Thermal Resistance (θ ) ........+39°C/W
JA
JA
Junction-to-Case Thermal Resistance (θ )...............+6°C/W
Junction-to-Case Thermal Resistance (θ )............+2.0°C/W
JC
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.
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.
20 TSSOP-EP
20 TQFN-EP
U20E+6
T2044+3
21-0108
21-0139
90-0114
90-0037
Electrical Characteristics
(V = V
= 12V, R = 12.25kΩ, R
= 15kΩ, C
= 1µF, NDRV = COMP = OUT_ = PGATE = unconnected, V
= V
=
IN
EN
RT
SETI
VCC
RSDT
DIM
V
, V
= 0.7V, V
= V
= V
= V
= 0V, T = T = -40°C to +125°C, unless otherwise noted. Typical values are
CC OVP
CS
LEDGND
PGND
SGND A J
at T = +25°C.) (Note 2)
A
PARAMETER
SUPPLIES
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Operating Voltage Range
V
4.75
40
V
IN
V
= 1.266V, all channels on,
= 0.5V
OVP
Supply Current
I
3.4
5.7
mA
IN
V
OUT_
Standby Supply Current
IN Undervoltage Lockout
IN UVLO Hysteresis
I
V
= 0V
1
2
µA
V
IN_Shdn
EN
IN
V
rising
3.975
4.3
170
4.625
mV
Maxim Integrated
│ 2
www.maximintegrated.com
MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Electrical Characteristics (continued)
(V = V
= 12V, R = 12.25kΩ, R
= 15kΩ, C
= 1µF, NDRV = COMP = OUT_ = PGATE = unconnected, V
= V
=
IN
EN
RT
SETI
VCC
RSDT
DIM
V
, V
= 0.7V, V
= V
= V
= V
= 0V, T = T = -40°C to +125°C, unless otherwise noted. Typical values are
CC OVP
CS
LEDGND
PGND
SGND A J
at T = +25°C.) (Note 2)
A
PARAMETER
REGULATOR
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
6.5V < V < 10V, 1mA < I
< 50mA
< 10mA
4.75
4.75
5
5.25
5.25
500
IN
LOAD
Regulator Output Voltage
V
V
CC
10V < V < 40V, 1mA < I
5
IN
LOAD
Dropout Voltage
V
V
- V , V = 4.75V, I = 50mA
LOAD
200
100
mV
mA
IN
CC IN
Short-Circuit Current Limit
V
shorted to SGND
CC_ILIM
CC
V
Undervoltage-Lockout
CC
V
rising
4
V
CC
Threshold
V
UVLO Hysteresis
125
mV
CC
RT OSCILLATOR
Switching Frequency Range
f
Frequency dithering disabled
200
90
2000
98.5
95
kHz
%
SW
f
f
f
= 200kHz to 600kHz
= 600kHz to 2000kHz
94.5
90.5
SW
SW
SW
Maximum Duty Cycle
86
= 200kHz to 2000kHz, frequency dither
Oscillator Frequency Accuracy
Frequency Dither
-7.5
+7.5
-9
%
%
disabled
Dither enabled, f
2000kHz
= from 200kHz to
SW
f
-5
4
-7
DITH
Sync Rising Threshold
Minimum Sync Frequency
PWM COMPARATOR
V
1.1f
kHz
SW
PWM Comparator Leading-Edge
Blanking
60
90
ns
ns
PWM-to-NDRV Propagation
Delay
Including leading-edge blanking time
SLOPE COMPENSATION
Peak Slope Compensation
Current Ramp Magnitude
Current ramp added to the CS input
(Note 3)
45
50
55
µA
CURRENT-SENSE COMPARATOR
Current-Limit Threshold
396
416
10
437
mV
ns
CS Limit Comparator to NDRV
Propagation Delay
10mV overdrive, excluding leading edge
blanking time
ERROR AMPLIFIER
OUT_ Regulation Voltage
Transconductance
No-Load Gain
1
V
g
V
= 2V
340
600
75
880
µS
dB
µA
M
COMP
(Note 4)
COMP Sink Current
V
V
= 2.25V, V
= 2V
160
160
375
800
800
OUT_
OUT_
COMP
COMP Source Current
= 0V, V
= 1.0V
375
µA
COMP
Maxim Integrated
│ 3
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Electrical Characteristics (continued)
(V = V
= 12V, R = 12.25kΩ, R
= 15kΩ, C
= 1µF, NDRV = COMP = OUT_ = PGATE = unconnected, V
= V
=
IN
EN
RT
SETI
VCC
RSDT
DIM
V
, V
= 0.7V, V
= V
= V
= V
= 0V, T = T = -40°C to +125°C, unless otherwise noted. Typical values are
CC OVP
CS
LEDGND
PGND
SGND A J
at T = +25°C.) (Note 2)
A
PARAMETER
MOSFET DRIVER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
I
I
= 100mA (nMOS)
0.9
1.1
2
Ω
Ω
SINK
NDRV On-Resistance
= 50mA (pMOS)
SOURCE
Peak Sink Current
Peak Source Current
Rise Time
V
= 5V
A
NDRV
NDRV
V
= 0V
2
A
C
= 1nF
= 1nF
6
ns
ns
LOAD
LOAD
Fall Time
C
6
LED CURRENT SOURCE
OUT_ Current Sink Range
20
-2
150
+2
mA
%
Channel-to-Channel Matching
I
= 100mA
OUT_
R
R
R
R
R
R
= 30kΩ, T = +25°C
48.25
47.50
97
50
50
51.75
52.50
103
SETI
SETI
SETI
SETI
SETI
SETI
DIM
A
= 30kΩ, T = -40°C to +125°C
A
= 15kΩ, T = +25°C
100
100
150
150
A
OUT_ Current
mA
µA
= 15kΩ, T = -40°C to +125°C
96
104
A
= 10kΩ, T = +25°C
145.50
144
-2
154.50
156
A
= 10kΩ, T = -40°C to +125°C
A
OUT_ Leakage Current
LOGIC INPUTS and OUTPUTS
EN Input Logic-High
EN Input Logic-Low
V
= 0V, V
= 40V
+2
OUT_
2.1
V
V
0.4
EN Hysteresis
260
7.5
mV
µA
nA
V
V
V
= 12V
15
EN
EN Input Current
= 0.3V
100
200
EN
DIM Input Logic-High
DIM Input Logic-Low
DIM Hysteresis
2.1
-2
0.8
+2
V
250
mV
µA
ns
ns
ns
DIM Input Current
V
= 5V
DIM
DIM to LED Turn-On Delay
DIM to LED Turn-Off Delay
DIM rising edge to 10% rise in I
150
50
OUT_
OUT_
DIM falling edge to 10% fall in I
I
I
Rise Time
Fall Time
10% to 90% I
90% to 10% I
200
OUT_
OUT_
OUT_
50
ns
V
OUT_
V
V
V
= 4.75V and I
= 5mA
SINK
0.4
+1
FLT Output Low Voltage
IN
-1
µA
V
= 5.5V
FLT Output Leakage Current
LED Short-Detection Threshold
FLT
= 2V
6.1
7
7.9
RSDT
Short-Detection Comparator
Delay
6.5
µs
Maxim Integrated
│ 4
www.maximintegrated.com
MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Electrical Characteristics (continued)
(V = V
= 12V, R = 12.25kΩ, R
= 15kΩ, C
= 1µF, NDRV = COMP = OUT_ = PGATE = unconnected, V
= V
=
IN
EN
RT
SETI
VCC
RSDT
DIM
V
, V
= 0.7V, V
= V
= V
= V
= 0V, T = T = -40°C to +125°C, unless otherwise noted. Typical values are
CC OVP
CS
LEDGND
PGND
SGND A J
at T = +25°C.) (Note 2)
A
PARAMETER
RSDT Leakage Current
OVP Trip Threshold
OVP Hysteresis
SYMBOL
CONDITIONS
MIN
-600
TYP
MAX
+600
1.266
UNITS
nA
V
= 2.5V
RSDT
OVP rising
1.190
1.228
70
V
mV
nA
OVP Leakage Current
V
= 1.25V
-200
+200
OVP
OVP Undervoltage-Detection
Threshold
OVP falling, PGATE latched off
0.485
0.585
10
0.685
V
OVP Undervoltage-Detection
Delay
OVP falling
5
20
µs
Thermal-Shutdown Threshold
Thermal-Shutdown Hysteresis
PGATE DRIVER
Temperature rising
165
15
°C
°C
PGATE On-Resistance
PGATE Soft-Start Current
PGATE Soft-Start Time
PGATE Leakage Current
R
I
= 10mA
PGATE
100
350
10
250
490
13.25
1
Ω
PGATE
Active during PGATE soft-start time
210
µA
ms
µA
6.35
V
= 12V, V
= 0V
0.01
PGATE
EN
Note 2: 100% tested at T = +25°C. All limits over temperature are guaranteed by design, not production tested.
A
Note 3: CS threshold includes slope compensation ramp magnitude.
Note 4: Gain = dV
/dV , 0.05V < V
< 0.15V.
COMP
CS
CS
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Typical Operating Characteristics
(V = V
= 12V, R
= 21kΩ, R
= 15kΩ, C
= 1µF, NDRV = COMP = OUT_ = PGATE = unconnected, V
= 0.7V,
IN
EN
RT
SETI
VCC
OVP
V
= V
= V
= V
= V
= 0V, load = 4 strings of 7 white LEDs, T = +25°C, unless otherwise noted.)
CS
LEDGND
DIM
PGND
SGND
A
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SUPPLY CURRENT
vs. SWITCHING FREQUENCY
V
LINE REGULATION
CC
5.03
5.02
5.01
5.00
4.99
4.98
4.97
5.0
4.8
4.6
4.4
4.2
4.0
3.8
3.6
3.4
5.0
4.8
4.6
4.4
4.2
4.0
3.8
3.6
C
= 13pF
C
= 13pF
NDRV
NDRV
T
= +125°C
A
T
T
= +125°C
= +25°C
A
T
T
= +25°C
= -40°C
A
A
A
T
A
= -40°C
30
5
10
15
20
V
25
(V)
35
40
5
10
15
20
V
25
(V)
30
35
40
200 400 600 800 1000 1200 1400 1600 1800 2000
(kHz)
f
IN
IN
SW
EN THRESHOLD VOLTAGE
vs. TEMPERATURE
EN INPUT CURRENT
vs. TEMPERATURE
V
CC
LOAD REGULATION
5.02
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
10.0
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
T
A
= +125°C
V
RISING
EN
5.00
4.98
4.96
4.94
4.92
T
= +25°C
A
V
EN
FALLING
T
A
= -40°C
0
20
40
I
60
(mA)
80
100
-50 -25
0
25
50
75 100 125
-50 -25
0
25
50
75 100 125
TEMPERATURE (°C)
TEMPERATURE (°C)
VCC
OUT_ LEAKAGE CURRENT
vs. TEMPERATURE
I
vs. 1/R
V
SETI
ERROR vs. TEMPERATURE
OUT(AVG)
SETI
160
140
120
100
80
0.1
0
100
10
I
= (I
I
+ I
OUT1 OUT2
+
V
V
= 0V
OUT(AVG)
DIM
+ I
)/4
= 40V
OUT3 OUT4
OUT_
-0.1
-0.2
-0.3
-0.4
-0.5
1
60
0.1
0.01
40
20
10
25
40
55
70
85
100
-50 -25
0
25
50
75 100 125
-50 -25
0
25
50
75 100 125
1/R
(mS)
TEMPERATURE (°C)
TEMPERATURE (°C)
SETI
Maxim Integrated
│ 6
www.maximintegrated.com
MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Typical Operating Characteristics (continued)
(V = V
= 12V, R
= 21kΩ, R
= 15kΩ, C
= 1µF, NDRV = COMP = OUT_ = PGATE = unconnected, V
= 0.7V,
IN
EN
RT
SETI
VCC
OVP
V
= V
= V
= V
= V = 0V, load = 4 strings of 7 white LEDs, T = +25°C, unless otherwise noted.)
CS
LEDGND
DIM
PGND
SGND A
RSDT LEAKAGE CURRENT
OVP LEAKAGE CURRENT
vs. TEMPERATURE
SWITCHING WAVEFORM AT 5kHz
(50% DUTY CYCLE) DIMMING
vs. TEMPERATURE
toc12
2.0
300
250
200
150
100
50
V
OVP
= 0.7V
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
LX
10V/div
0V
0A
V
RSDT
= 2.5V
I
OUT_
100mA/div
V
BOOST
10V/div
0V
-50 -25
0
25
50
75 100 125
-50 -25
0
25
50
75 100 125
40µs/div
TEMPERATURE (°C)
TEMPERATURE (°C)
LED CURRENT WAVEFORM WITH
DIM ON PULSE WIDTH OF 25µs
LED CURRENT WAVEFORM WITH
DIM ON PULSE WIDTH OF 1µs
toc13
toc14
V
V
DIM
5V/div
DIM
5V/div
0V
0V
0A
I
I
OUT_
50mA/div
OUT_
50mA/div
0A
4µs/div
200ns/div
STARTUP WAVEFORM WITH
STARTUP WAVEFORM WITH
DIM ON PULSE WIDTH < 24t
DIM ON PULSE WIDTH ≥ 24t
SW
SW
toc15
toc16
V
V
IN
20V/div
IN
20V/div
0V
0V
0V
0V
V
DIM
5V/div
V
DIM
5V/div
I
I
OUT_
100mA/div
OUT_
100mA/div
0A
0V
0A
0V
V
V
BOOST
20V/div
BOOST
10V/div
20ms/div
20ms/div
Maxim Integrated
│ 7
www.maximintegrated.com
MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Typical Operating Characteristics (continued)
(V = V
= 12V, R
= 21kΩ, R
= 15kΩ, C
= 1µF, NDRV = COMP = OUT_ = PGATE = unconnected, V
= 0.7V,
IN
EN
RT
SETI
VCC
OVP
V
= V
= V
= V
= V = 0V, load = 4 strings of 7 white LEDs, T = +25°C, unless otherwise noted.)
CS
LEDGND
DIM
PGND
SGND A
STARTUP WAVEFORM OF PGATE
AND INDUCTOR CURRENT WITH
DIM CONTINUOUSLY ON
STARTUP WAVEFORM WITH
DIM CONTINUOUSLY ON
toc17
toc18
V
V
EN
2V/div
IN
20V/div
0V
0V
0A
0V
0V
0V
V
DIM
5V/div
V
BOOST
10V/div
I
OUT_
100mA/div
V
PGATE
10V/div
V
BOOST
10V/div
I
LX
1A/div
0V
0A
20ms/div
20ms/div
STARTUP WAVEFORMS WITH
DELAYED DIM INPUT
OUTPUT UNDERVOLTAGE FAULT
toc20
toc19
V
V
IN
PGATE
0V
0V
10V/div
10V/div
0V
0V
0V
V
FLT
V
DIM
5V/div
5V/div
V
V
BOOST
BOOST
0V
0V
20V/div
10V/div
V
OVP
I
BOOST
200mV/div
500mA/div
0A
1s/div
1ms/div
FUNCTIONALITY WITH DIM = 0
FOR DURATION > 38ms (TYP)
DIM LOW DETECTION PERIOD
toc21
toc22
V
IN
V
DIM
10V/div
5V/div
0V
0V
0V
V
V
DIM
BOOST
5V/div
10V/div
38ms
V
BOOST
20V/div
0V
0A
0V
0A
I
I
BOOST
BOOST
500mA/div
500mA/div
100ms/div
10ms/div
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Pin Configuration
TOP VIEW
ꢄ
15
14
13
12
11
NDRV
1
2
3
4
5
6
7
8
9
20 PGND
19 CS
PGATE
DIM
10
9
CS 16
V
18 OUT4
17 OUT3
16 LEDGND
15 OUT2
14 OUT1
13 DIM
CC
IN
SGND
PGND 17
NDRV 18
MAX16813B
MAX16813B
EN
COMP
RT
8
RSDT
SETI
OVP
PGATE
7
19
20
6
V
EP*
5
CC
FLT
ꢄ
OVP
12 SGND
11 RSDT
1
2
3
4
EP*
SETI 10
ꢀꢅꢅꢆꢇ
ꢀꢁꢂꢃ
*EXPOSED PAD.
Pin Description
PIN
NAME
FUNCTION
TQFN TSSOP
Bias Supply Input. Connect a 4.75V to 40V supply to IN. Bypass IN to SGND with a ceramic
capacitor.
1
2
3
4
5
6
IN
EN
Enable Input. Connect EN to logic-low to shut down the device. Connect EN to logic-high or IN
for normal operation. The EN input should not be left open.
Switching Converter Compensation Input. Connect the compensation network from COMP
to SGND for current-mode control (see the Feedback Compensation section).
COMP
Oscillator Timing Resistor Connection. Connect a timing resistor (R ) from RT to SGND to
T
9
program the switching frequency according to the formula R = 7.72 x 10 /f . Apply an
T
SW
4
7
RT
AC-coupled external clock at RT to synchronize the switching frequency with an external clock.
When the oscillator is synchronized with the external clock, the spread spectrum is disabled.
Open-Drain Fault Output. FLT asserts low when an open LED, short LED, output undervoltage,
5
6
7
8
9
FLT
OVP
SETI
or thermal shutdown is detected. Connect a pullup resistor from FLT to V
.
CC
Overvoltage/Undervoltage-Threshold Adjust Input. Connect a resistor-divider from the switching
converter output to OVP and SGND. The OVP comparator reference is internally set to 1.23V.
LED Current-Adjust Input. Connect a resistor (R
) from SETI to SGND to set the current
SETI
10
through each LED string (I
), according to the formula I
= 1500/R
.
LED
LED
SETI
LED Short Detection Threshold-Adjust Input. Connect a resistive divider from V
to RSDT and
CC
8
11
RSDT
SGND to program the LED short detection threshold. Connect RSDT directly to V
to disable
CC
LED short detection.
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Pin Description (continued)
PIN
NAME
FUNCTION
TQFN TSSOP
Signal Ground. SGND is the current return path connection for the low-noise analog signals.
Connect SGND, LEDGND, and PGND at a single point.
9
12
13
SGND
DIM
Digital PWM Dimming Input. Apply a PWM signal to DIM for LED dimming control. Connect DIM
10
to V
if dimming control is not used.
CC
LED String Cathode Connection 1. OUT1 is the open-drain output of the linear current sink that
controls the current through the LED string connected to OUT1. OUT1 sinks up to 150mA. If
unused, connect OUT1 to LEDGND.
11
14
OUT1
LED String Cathode Connection 2. OUT2 is the open-drain output of the linear current sink that
controls the current through the LED string connected to OUT2. OUT2 sinks up to 150mA. If
unused, connect OUT2 to LEDGND.
12
13
14
15
16
17
OUT2
LEDGND
OUT3
LED Ground. LEDGND is the return path connection for the linear current sinks. Connect
SGND, LEDGND, and PGND at a single point.
LED String Cathode Connection 3. OUT3 is the open-drain output of the linear current sink that
controls the current through the LED string connected to OUT3. OUT3 sinks up to 150mA. If
unused, connect OUT3 to LEDGND.
LED String Cathode Connection 4. OUT4 is the open-drain output of the linear current sink that
controls the current through the LED string connected to OUT4. OUT4 sinks up to 150mA. If
unused, connect OUT4 to LEDGND.
15
16
18
19
OUT4
CS
Current-Sense Input. CS is the current-sense input for the switching regulator. A sense resistor
connected from the source of the external power MOSFET to PGND sets the switching current
limit. A resistor connected between the source of the power MOSFET and CS sets the slope
compensation ramp rate (see the Slope Compensation section).
Power Ground. PGND is the switching current return path connection. Connect SGND,
LEDGND, and PGND at a single point.
17
18
19
20
—
20
1
PGND
NDRV
PGATE
Switching n-MOSFET Gate-Driver Output. Connect NDRV to the gate of the external switching
power MOSFET.
External p-MOSFET Gate connection. Connect a resistor from this pin to the external
p-MOSFET gate. Connect PGATE to PGND through a resistor (0 to 10kΩ) if not used.
2
5V Regulator Output. Bypass V
as possible to the device.
to SGND with a minimum of 1µF ceramic capacitor as close
CC
3
V
CC
Exposed Pad. Connect EP to a large-area contiguous copper ground plane for effective power
dissipation. Do not use EP as the main IC ground connection. EP must be connected to SGND.
—
EP
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
RSDT
(SHORTED-LED THRESHOLD)
FLT
PWROND
UNUSED–
STRING
DETECTOR
MAX16813B
FAULT FLAG
LOGIC
SHORT-LED
DETECTOR
OPEN-LED
DETECTOR
UV
V
CC
SHDN
TSHDN
DRIVER
NDRV
PGND
PWM
LOGIC
CLK
OUT1–
OUT4
MINIMUM
STRING
VOLTAGE
PWM
COMP
RT OSCILLATOR/RAMP
FOR SLOPE
RT
COMPENSATION
COMP
$ARRAY = 4
DRIVER
PGATE
PGATE
SOFT–START
POK
g
M
0
ILIM
PWRON
R
LOGIC
IN
0.425V
0
1
UVLO
SHDN
V
CC
LEDGND
1
CLK
5V LDO
BANDGAP
MINSTR
LODIMB
MINIMUM CYCLES
BLOCK
MINSTR
_REF
THERMAL
SHUTDOWN
OVP
COMPARATOR
POK
TSHDN
UVLO
IN
0
1
DIM
INTERNAL
DPWM
EN
CS
UV
0.585V
0.185V
SS
SHDN
DETECTION
BLOCK
INPUT
BUFFER
SHDN
V
CC
V
BG
PWROND TSHDN
CS BLANKING
SSDONE
SS_REF
POK
PWRON
SS
SOFT-START
100ms
SLOPE
COMPENSATION
0.95*VBG
PWROND
SD_MIN
RAMP FROM
TSHDN
RT OSCILLATOR
SGND
OVP
SETI
Figure 1. Simplified Functional Diagram
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Q2
L1
D1
22µH
V
IN
C1
1µF
C2
22µF
8 LEDs
PER
STRING
D2
R10
15kΩ
C7
0.047µF
D3
R1
261kΩ
Q1
R
CS
0.15Ω
R2
10kΩ
R
SCOMP
3.32kΩ
R7
1.4kΩ
NDRV
CS
OVP
PGATE
OUT1
OUT2
ENABLE INPUT
EN
IN
OUT3
OUT4
MAX16813B
V
CC
R
SETI
C3
18.2kΩ
1µF
SETI
FLT
R6
10kΩ
V
CC
DIM
COMP
R3
30.1kΩ
R
COMP
825Ω
RSDT
RT
C
COMP
2.2µF
SGND
PGND
LEDGND
RT
18.7Ω
R4
20kΩ
Figure 2. Typical Operating Circuit
The device features a constant-frequency peak current-
mode control with programmable slope compensation to
control the duty cycle of the PWM controller. The high-
current FET driver can provide up to 2A of current to the
external n-MOSFET. The DC-DC converter implemented
using the controller generates the required supply volt-
age for the LED strings from a wide input supply range.
Connect LED strings from the DC-DC converter output to
the 4-channel constant-current sink drivers that control
the current through the LED strings. A single resistor
connected from the SETI input to ground adjusts the
forward current through all 4 LED strings.
Detailed Description
The MAX16813B high-efficiency HB LED driver
integrates all the necessary features to implement a
high-performance backlight driver to power LEDs in
small- to medium-sized displays for automotive as well as
general applications. The device provides load-dump
voltage protection up to 40V in automotive applications.
The device incorporates two major blocks: a DC-DC
controller with peak-current-mode control to implement a
boost or a SEPIC-type switched-mode power supply and
a 4-channel LED driver with 20mA to 150mA constant-
current sink capability per channel. Figure 1 is the
simplified functional diagram and Figure 2 shows a
typical operating circuit.
The device features adaptive voltage control that adjusts
the converter output voltage depending on the forward
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
voltage of the LED strings. This feature minimizes the
voltage drop across the constant-current sink drivers
and reduces power dissipation in the device. The device
includes an internal 5V LDO capable of powering addi-
tional external circuitry. A logic input (EN) shuts down the
device when pulled low. When the EN pin is pulled below
0.3V (typ), the quiescent input current to the device is less
than 1µA (typ).
Current-Mode DC-DC Controller
The peak current-mode controller allows boost or SEPIC-
type converters to generate the required bias voltage
for the LED strings. The switching frequency can be
programmed over the 200kHz to 2MHz range using a
resistor connected from RT to SGND. Programmable
slope compensation is available to compensate for sub-
harmonic oscillations that occur at above 50% duty cycles
in continuous-conduction mode.
The device provides a very wide (10000:1) PWM
dimming range where a dimming pulse as narrow as
500ns is possible at a 200Hz dimming frequency. This
is made possible by a unique feature that detects short
PWM dimming input pulses and adjusts the converter
feedback accordingly.
The external n-MOSFET is turned on at the beginning
of every switching cycle. The inductor current ramps up
linearly until turned off at the peak current level set by
the feedback loop. The peak inductor current is sensed
from the voltage across the current-sense resistor (R
)
CS
connected from the source of the external n-MOSFET
to PGND. The device features leading-edge blanking
to suppress the external n-MOSFET switching noise.
A PWM comparator compares the current-sense volt-
age plus the slope-compensation signal with the output
of the transconductance error amplifier. The controller
turns off the external n-MOSFET when the voltage at
CS exceeds the error amplifier’s output voltage. This
process repeats every switching cycle to achieve peak-
current-mode control.
Advanced features include detection and string
disconnect for open-LED strings, partial or fully short-
ed strings, and unused strings. Overvoltage protection
clamps the converter output voltage to the programmed
OVP threshold in the event of an open-LED condition.
Shorted-LED string-detection and overvoltage-protection
thresholds are programmable using the RSDT and OVP
inputs, respectively. An open-drain FLT signal asserts
to indicate open-LED, shorted-LED, output undervolt-
age and overtemperature conditions. Disable individual
current sink channels by connecting the correspond-
ing OUT_ to LEDGND. In this case, FLT does not
assert indicating an open-LED condition for the disabled
channel. The device also features an overtempera-
ture protection that shuts down the controller if the die
temperature exceeds +165°C.
Error Amplifier
The internal error amplifier compares an internal feedback
(FB) with an internal reference (REF) and regulates its
output to adjust the inductor current. An internal mini-
mum string detector measures the minimum-current sink
voltage with respect to SGND out of the four constant-
current sink channels. During normal operation, this mini-
mum OUT_ voltage is regulated to 1V through feedback.
The error amplifier takes 1V as the REF and the minimum
OUT_ voltage as the FB input. The amplified error at
the COMP output controls the inductor peak current to
regulate the minimum OUT_ voltage at 1V. The resulting
DC-DC converter output voltage is the highest LED string
voltage plus 1V.
There are two levels of output undervoltage protection in
the device. The first output undervoltage protection is set
at 180mV and this is enabled 43ms after power-up. If the
OVP pin is lower than 180mV after 43ms, it turns off the
converter and disconnects the p-MOSFET from the input.
The second undervoltage threshold is activated after the
soft-start period of the DC-DC converter. This is set at
585mV. If the OVP pin is below 585mV after the soft-start
period of the DC-DC converter, the converter is turned off
and the p-MOSFET disconnects the input voltage from
the LED driver. See the Startup Sequence section for
more details.
The converter stops switching when the LED strings are
turned off during PWM dimming. The error amplifier is
disconnected from the COMP output to retain the
compensation capacitor charge. This allows the converter
to settle to a steady-state level almost immediately when
the LED strings are turned on again. This unique feature
provides fast dimming response without having to use
large output capacitors.
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
If the PWM dimming on-pulse is less than or equal to 24
switching cycles, the feedback controls the voltage on
OVP so that the converter output voltage is regulated at
95% of the OVP threshold. This mode ensures that narrow
PWM dimming pulses are not affected by the response
time of the converter. During this mode, the error amplifier
remains connected to the COMP output continuously and
the DC-DC converter continues switching.
recycled. If there is no undervoltage, soft-start terminates
when the minimum current sink voltage reaches 1V (typ)
or when an internal 100ms timeout expires.
After soft-start, the device detects open LED and discon-
nects any strings with an open LED from the internal
minimum OUT_ voltage detector. The converter output
discharges to a level where the new minimum OUT_
voltage is 1V and then control is handed over to the
internal minimum OUT_ voltage detector.
Input and V
Undervoltage Lockout (UVLO)
CC
A second output undervoltage protection is enabled
100ms after the converter is enabled. A fault is detected
whenever the OVP pin falls below an internal threshold
of 585mV (typ) and the power converter is latched off
and PGATE goes high. Cycling the EN pin or the supply
is required to start up again, once the fault condition has
been removed.
The device features two undervoltage lockouts that monitor
the input voltage at IN and the output of the internal LDO
regulator at V . The device turns on after both IN and
CC
V
CC
exceed their respective UVLO thresholds. The UVLO
threshold at IN is 4.3V when IN is rising and 4.13V when
IN is falling. The UVLO threshold at V is 4V when V
CC
CC
is rising and 3.875V when V
is falling.
CC
Oscillator Frequency/External
Synchronization
The internal oscillator frequency is programmable between
200kHz and 2MHz using a timing resistor (R ) connected
from the RT input to SGND. Use the equation below
Enable
The device is enabled using the EN logic input pin. The
EN input can handle voltages up to IN, providing flexibil-
ity in terms of control signals/supplies. To shut down the
device, drive the EN pin with a logic-low, which reduces
current consumption to 1µA (typ). Connect the EN pin to
IN if not used. EN should not be left open.
T
to calculate the value of R for the desired switching
T
frequency (f ):
SW
9
Startup Sequence
Once EN is driven high, the controller remains off until
7.72×10
R
=
T
f
SW
both IN and V
trip their rising thresholds.
CC
where f
is in Hz.
SW
Once UVLO conditions are satisfied, the driver of the
external p-MOSFET is turned on. A constant current
of 350µA (typ) flows into the PGATE pin of the device
for approximately 10ms (typ). The current flowing into
resistor R7 and capacitor C7 (see Figure 2) pulls down
the gate of the external p-MOSFET. This capacitor
controls the turn-on time of the external p-MOSFET.
Synchronize the oscillator with an external clock by
AC-coupling the external clock to the RT input. The
capacitor used for the AC-coupling should satisfy the
following relation:
9.862
-3
C
≤
− 0.144×10
µF
(
)
SYNC
R
T
After the external p-MOSFET Q2 (Figure 2) is turned
on and the 10ms timeout expires, the device detects
and then disconnects any unused current sink
channels before enabling the converter. Disable the
unused current sink channels by connecting the
corresponding OUT_ to LEDGND. This avoids asserting
the FLT output for the unused channels. The detection of
unused channels takes approximately 0.7ms (typ).
where R is in ohms.
T
The pulse width for the synchronization pulse should sat-
isfy the following relations:
t
PW
V
< 0.5
S
t
CLK
t
t
PW
CLK
t
0.8 −
V
+ V > 3.4
S
t
S
Once the above phase is completed, the DC-DC converter
is enabled and the soft-start is initiated. During soft-start,
the DC-DC converter output ramps up as the loop regu-
lates the voltage at the OVP pin to follow an internal ramp-
ing voltage. 33ms (typ) after the converter is enabled, the
OVP pin is monitored, and if the voltage at the OVP pin
is less than 180mV (typ), FLT is asserted low, the power
converter is turned off, the external p-MOSFET is turned
off, and they all stay off until the EN pin or the supply is
CLK
t
<
− 1.05 × t
CLK
(
)
PW
CI
t
CI
where t
is the synchronization source pulse width,
PW
t
is the synchronization clock time period, t is the
CLK
CI
programmed clock period, and V is the synchronization
pulse voltage level.
S
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
LED string, use two or more of the current source outputs
(OUT_) connected together to drive the string, as shown
in Figure 3.
Spread-Spectrum Mode
The device includes a unique spread-spectrum mode
(SSM) that reduces emission (EMI) at the switching
frequency and its harmonics.
LED Dimming Control
The spread spectrum uses a pseudorandom dithering
technique where the switching frequency is varied in the
range of 93% of the programmed switching frequency, to
100% of the programmed switching frequency set through
the external resistor from RT to SGND.
The device features LED brightness control using an
external PWM signal applied to DIM. A logic-high signal
on the DIM input enables all four LED current sources and
a logic-low signal disables them.
The duty cycle of the PWM signal applied to DIM also
controls the DC-DC converter’s output voltage. If the
turn-on duration of the PWM signal is less than 24 oscil-
lator clock cycles (DIM pulse width increasing), the boost
converter regulates its output based on feedback from
the OVP input. While in this mode, the converter output
voltage is regulated to 95% of the overvoltage threshold
at the OVP pin. If the turn-on duration of the PWM signal
is greater than or equal to 24 oscillator clock cycles (DIM
pulse width increasing), the converter regulates its output
so that the minimum voltage at OUT_ is 1V.
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 is only disabled if external synchroniza-
tion is used.
5V LDO Regulator (V
)
CC
The internal LDO regulator converts the input voltage
at IN to a 5V output voltage at V . The LDO regulator
CC
supplies up to 50mA current to provide power to internal
At power-up, if the converter has completed the soft-start
period of 100ms (typ) and the PWM signal at the DIM pin
is still low, the device regulates the output voltage based
on the feedback signal coming from the OVP pin. Once a
PWM pulse width greater than 24 oscillator clock cycles
is applied, the converter regulates its output so that the
minimum voltage at OUT_ is 1V.
control circuitry and the gate driver. Bypass V
with a minimum of 1µF ceramic capacitor as close as
possible to the device.
to SGND
CC
PWM MOSFET Driver
The NDRV output is a push-pull output with the
on-resistance of the p-MOSFET (typically 1.1Ω) and
the on-resistance of the n-MOSFET (typically 0.9Ω).
The converter output voltage is regulated to 95% of the
overvoltage threshold at the OVP pin whenever the PWM
signal at the DIM pin is forced low for a duration longer
than 38ms (typ).
NDRV swings from PGND to V
to drive an external
CC
n-MOSFET. The driver typically sources 2.0A and sinks
2.0A allowing for fast turn-on and turn-off of high gate-
charge MOSFETs.
The power dissipation in the device is mainly a function
of the average current sourced to drive the external
BOOST CONVERTER
OUTPUT
MOSFET (I
) if there are no additional loads on
VCC
V
. I
depends on the total gate charge (QG) and
CC VCC
operating frequency of the converter.
40mA TO 300mA
PER STRING
LED Current Control
The device features four identical constant-current sources
used to drive multiple HB LED strings. The current through
each one of the four channels is adjustable between
OUT1
20mA and 150mA using an external resistor (R
)
SETI
OUT2
MAX16813B
connected between SETI and SGND. Select R
the following formula:
using
SETI
OUT3
OUT4
R
= 1500/I
OUT_
SETI
where I
is the desired output current for each of
OUT_
the four channels. If more than 150mA is required in an
Figure 3. Configuration for Higher LED String Current
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Connect the OUT_ of all channels without LED con-
nections to LEDGND before power-up to avoid OVP
triggering at startup. When an open-LED overvoltage
condition occurs, FLT is latched low. Open-LED detection
is disabled when PWM dimming pulse width is less than
24 switching clock cycles.
Fault Protections
Fault protections in the device include cycle-by-cycle
current limiting using the PWM controller, DC-DC
converter output overvoltage protection, open-LED detec-
tion, short-LED detection and protection, output under-
voltage protection, and overtemperature shutdown. An
open-drain fault flag output (FLT) goes low when an open-
LED string is detected, a shorted-LED string is detected,
an output undervoltage, or during thermal shutdown. FLT
is cleared when the fault condition is removed during
thermal shutdown and shorted LEDs. FLT is latched low
for an open-LED or output undervoltage condition, and
can be reset by cycling power or toggling the EN pin. The
thermal-shutdown threshold is +165°C and has +15°C
hysteresis.
Short-LED Detection
The device checks for shorted LEDs at each rising edge
of DIM. An LED short is detected at OUT_ if the following
condition is met:
V
OUT_
> V + 3 x V
MINSTR RSDT
where V
is the voltage at OUT_, V
is
MINSTR
OUT_
the minimum current sink voltage, and V
is the
RSDT
programmable-LED short-detection threshold set at the
RSDT input (with V less than or equal to 2.5V).
RSDT
Open-LED Management and
Overvoltage Protection
Adjust V
to a voltage less than or equal to 2.5V
RSDT
using a voltage-divider resistive network connected at
the V output, RSDT input, and SGND. Once a short is
On power-up, the device detects and disconnects any
unused current sink channels before entering the DC-DC
converter soft-start. Disable the unused current sink
channels by connecting the corresponding OUT_ to
LEDGND. This avoids asserting the FLT output for the
unused channels. After soft-start, the device detects
open LED and disconnects any strings with an open
LED from the internal minimum OUT_ voltage detector.
This keeps the DC-DC converter output voltage within
safe limits and maintains high efficiency. During normal
operation, the DC-DC converter output regulation loop
uses the minimum OUT_ voltage as the feedback input.
If any LED string is open, the voltage at the opened
CC
detected on any of the strings, the LED strings with the
short are disconnected and the FLT output flag asserts
until the device detects that the shorts are removed on
any of the following rising edges of DIM. Connect RSDT
directly to V
to always disable LED short detection.
CC
Short-LED detection is disabled when PWM dimming
pulse width is less than 24 switching clock cycles.
Applications Information
DC-DC Converter
Three different converter topologies are possible
with the DC-DC controller in the device, which has
the ground-referenced outputs necessary to use
the constant-current sink drivers. If the LED string
forward voltage is always more than the input
supply voltage range, use the boost converter
topology. If the LED string forward voltage falls within
the supply voltage range, use the buck-boost converter
topology. Buck-boost topology is implemented using
OUT_ goes to V
. The DC-DC converter output
LEDGND
voltage then increases to the overvoltage-protection
threshold set by the voltage-divider network connected
between the converter output, OVP input, and SGND. The
overvoltage-protection threshold at the DC-DC converter
output (V ) is determined using the following formula:
OVP
R1
R2
V
= 1.23 × 1+
(see Figure 2)
OVP
either
a conventional SEPIC configuration or a
coupled-inductor buck-boost configuration. The latter is
basically a flyback converter with 1:1 turns ratio. 1:1-
coupled inductors are available with tight coupling
suitable for this application. Figure 4 shows the cou-
pled-inductor buck-boost configuration. It is also pos-
sible to implement a single inductor converter using the
MAX15054 high-side FET driver.
where 1.23V (typ) is the OVP threshold. Select R1 and
R2 such that the voltage at OUT_ does not exceed
the absolute maximum rating. As soon as the DC-DC
converter output reaches the overvoltage-protection
threshold, the PWM controller is switched off setting
NDRV low. Any current sink output with V
< 300mV
OUT_
(typ) is disconnected from the minimum voltage detector.
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MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
The boost converter topology provides the highest effi-
ciency among the above-mentioned topologies. The
coupled-inductor topology has the advantage of not using
a coupling capacitor over the SEPIC configuration. Also,
the feedback loop compensation for SEPIC becomes
complex if the coupling capacitor is not large enough.
range, the maximum voltage needed to drive the LED
strings including the minimum 1V across the constant
LED current sink (V
), and the total output current
LED
needed to drive the LED strings (I
) as follows:
LED
I
= I
x N
LED
SRTING SRTING
where I
is the LED current per string in amperes
SRTING
Power-Circuit Design
and N
is the number of strings used.
SRTING
First select a converter topology based on the above
factors. Determine the required input supply voltage
V
IN
4.75V TO 40V
T1
(1:1)
D1
C1
UP TO 40V
C2
R1
R2
N
R
R
CS
SCOMP
IN NDRV
CS
OVP
EN
V
OUT1
OUT2
OUT3
OUT4
CC
C3
MAX16813B
PGATE
R
SETI
SETI
FLT
DIM
V
CC
COMP
R3
RSDT
RT
R
C
COMP
R4
SGND
PGND
LEDGND
COMP
R
T
Figure 4. Coupled-Inductor Buck-Boost Configuration
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Integrated, 4-Channel, High-Brightness
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Calculate the maximum duty cycle (D
following equations:
) using the
IL . The recommended saturation current limit of the
P
MAX
selected inductor is 10% higher than the inductor peak
current for boost configuration. For the coupled inductor,
the saturation limit of the inductor with only one winding
For boost configuration:
(V
+ V − V
)
LED
D1
IN_MIN
conducting should be 10% higher than IL .
D
=
P
MAX
(V
+ V − V
− 0.3V)
LED
D1
DS
SEPIC Configuration
For SEPIC and coupled-inductor buck-boost configurations:
(V + V
Power-circuit design for the SEPIC configuration is very
similar to a conventional design with the output voltage
referenced to the input supply voltage. For SEPIC, the
output is referenced to ground and the inductor is split into
two parts (see Figure 5 for the SEPIC configuration). One of
the inductors (L2) takes LED current as the average current
and the other (L1) takes input current as the average current.
)
D1
− 0.3V + V
LED
D
=
MAX
(V
− V
+ V
)
IN_MIN
DS
LED
D1
where V
is the forward drop of the rectifier diode in
D1
volts (approximately 0.6V), V
supply voltage in volts, and V
is the minimum input
is the drain-to-source
IN_MIN
DS
voltage of the external MOSFET in volts when it is on,
and 0.3V is the peak current-sense voltage. Initially, use
Use the following equations to calculate the average
inductor currents (IL1
, IL2 ) and peak inductor
AVG AVG
an approximate value of 0.2V for V
to calculate D
.
DS
MAX
currents (IL1 , IL2 ) in amperes:
P
P
Calculate a more accurate value of D
after the power
MAX
MOSFET is selected based on the maximum inductor
I
×D
1− D
×1.1
MAX
LED
IL1
=
AVG
current. Select the switching frequency (f ) depending
SW
MAX
on the space, noise, and efficiency constraints.
The factor 1.1 provides a 10% margin to account for the
converter losses:
Boost and Coupled-Inductor Configurations
In all three converter configurations, the average
inductor current varies with the input line voltage and the
maximum average current occurs at the lowest input line
voltage. For the boost converter, the average inductor
current is equal to the input current. Select the maximum
peak-to-peak ripple on the inductor current (ΔIL). The
recommended peak-to-peak ripple is 60% of the average
inductor current.
IL2
= I
AVG
LED
Assuming the peak-to-peak inductor ripple ∆IL is ±30% of
the average inductor current:
∆IL1 = IL1
x 0.3 x 2
AVG
and:
and:
∆IL1
2
IL1 = IL1
+
P
AVG
∆IL2 = IL2
x 0.3 x 2
Use the following equations to calculate the maximum
AVG
average inductor current (IL
) and peak inductor
AVG
∆IL2
2
current (IL ) in amperes:
IL2 = IL2
+
P
P
AVG
I
LED
IL
=
AVG
Calculate the minimum inductance values L1
and
MIN
1− D
MAX
L2
in henries with the inductor current ripples set to
MIN
Allowing the peak-to-peak inductor ripple ∆IL to be ±30%
the maximum value as follows:
of the average inductor current:
(V − V
− 0.3V)×D
MAX
IN_MIN
DS
L1
=
∆IL = IL
x 0.3 x 2
MIN
AVG
f
× ∆IL1
SW
and
∆IL
2
(V
− V
− 0.3V)×D
IL = IL
+
IN_MIN
DS MAX
P
AVG
L2
=
MIN
f
× ∆IL2
SW
Calculate the minimum inductance value (L
) in henries
MIN
with the inductor current ripple set to the maximum value:
where 0.3V is the peak current-sense voltage. Choose
inductors that have a minimum inductance greater than
(V
− V
− 0.3V)×D
IN_MIN
DS
MAX
L
=
MIN
the calculated L1
and L2
and current rating greater
MIN
MIN
f
× ∆IL
SW
than IL1 and IL2 , respectively. The recommended
P
P
where 0.3V is the peak current-sense voltage. Choose
an inductor that has a minimum inductance greater
saturation current limit of the selected inductor is 10%
higher than the inductor peak current.
than the calculated L
and current rating greater than
MIN
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Integrated, 4-Channel, High-Brightness
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For simplifying further calculations, consider L1 and L2
as a single inductor with L1 and L2 connected in parallel.
The combined inductance value and current is calculated
as follows:
Select coupling capacitor C so that the peak-to-peak
S
ripple on it is less than 2% of the minimum input supply
voltage. This ensures that the second-order effects created
by the series resonant circuit comprising L1, C , and L2 do
S
not affect the normal operation of the converter. Use the
L1
×L2
+ L2
MIN
MIN
MIN
L
=
following equation to calculate the minimum value of C :
S
MIN
L1
MIN
I
×D
MAX
× 0.02× f
SW
LED
C
≥
S
and:
V
IN_MIN
IL
AVG
= IL1
+ IL2
AVG AVG
where C is the minimum value of the coupling capacitor
S
where IL
represents the total average current through
AVG
in farads, I
is the LED current in amperes, and the
LED
both the inductors together for SEPIC configuration. Use
these values in the calculations for SEPIC configuration
in the following sections.
factor 0.02 accounts for 2% ripple.
C4
L1
D1
V
IN
C1
C2
R1
L2
Q1
R
CS
R2
R
SCOMP
NDRV
PGATE
CS
OVP
OUT1
OUT2
ENABLE
INPUT
EN
IN
OUT3
OUT4
MAX16813B
R
SETI
SETI
V
CC
V
CC
C3
R6
FLT
DIM
R3
RSDT
RT
COMP
R
COMP
RT
R4
SGND
PGND
LEDGND
C
COMP
Figure 5. SEPIC LED Driver
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The ESR, ESL, and the bulk capacitance of the out-
put capacitor contribute to the output ripple. In most of
Slope Compensation
The device generates a current ramp for slope
compensation. This ramp current is in sync with the
switching frequency and starts from zero at the beginning
of every clock cycle and rises linearly to reach 50µA
at the end of the clock cycle. The slope-compensating
the applications, using low-ESR ceramic capacitors can
dramatically reduce the output ESR and ESL effects. To
reduce the ESL and ESR effects, connect multiple ceramic
capacitors in parallel to achieve the required bulk capaci-
tance. To minimize audible noise during PWM dimming,
the amount of ceramic capacitors on the output is usually
minimized. In this case, an additional electrolytic or tanta-
lum capacitor provides most of the bulk capacitance.
resistor, (R ), is connected between the CS input
SCOMP
and the source of the external MOSFET. This adds a
programmable ramp voltage to the CS input voltage to
provide slope compensation.
Use the following equation to calculate the value of slope
External Switching-MOSFET Selection
compensation resistance (R
):
SCOMP
The external switching MOSFET should have a voltage
rating sufficient to withstand the maximum output voltage
together with the rectifier diode drop and any possible
overshoot due to ringing caused by parasitic inductances
For boost configuration:
V
−2V
×R ×3
(
)
LED
L
IN_MIN
CS
R
=
SCOMP
× 50µA× f
× 4
and capacitances. The recommended MOSFET V
DS
MIN
SW
voltage rating is 30% higher than the sum of the maximum
output voltage and the rectifier diode drop.
For SEPIC and coupled inductor:
V
×R × 3
LED− VIN_MIN
CS
(
)
The recommended continuous-drain current rating of the
MOSFET (ID), when the case temperature is at +70°C, is
greater than that calculated below:
R
=
SCOMP
L
× 50µA× f
× 4
SW
MIN
where V
and V
are in volts, R
and R
LED
are in ohms, L
IN_MIN
is in henries, and f
value of the switch current-sense resistor, (R ) can be
SCOMP CS
2
is in hertz. The
MIN
SW
ID
=
IL
×D
×1.3
RMS
AVG
MAX
CS
calculated as follows:
For boost:
The MOSFET dissipates power due to both switching
losses and conduction losses. Use the following equation
to calculate the conduction losses in the MOSFET:
D
(
× V
(
− 2V
×R ×3
CS
)
)
MAX
LED
4 ×L
IN_MIN
0.396 × 0.9 = I ×R
+
CS
LP
2
P
COND
= IL
x D
x R
× f
AVG
MAX DS(ON)
MN SW
where R
is the on-state drain-to-source resistance
DS(ON)
For SEPIC:
of the MOSFET. Use the following equation to calculate
the switching losses in the MOSFET:
D
(
× V
(
− V
×R
×3
)
)
MAX
LED
4 ×L
IN_MIN
CS
0.396 × 0.9 = I ×R
+
CS
LP
× f
2
MN SW
IL
× V
× C × f
GD SW
1
1
AVG
LED
P
=
×
+
SW
2
I
I
GOFF
where 0.396 is the minimum value of the peak current-
sense threshold. The current-sense threshold also
includes the slope-compensation component. The
minimum current-sense threshold of 0.396 is multiplied
by 0.9 to take tolerances into account.
GON
where I
and I
are the gate currents of the
GOFF
GON
MOSFET in amperes when it is turned on and turned
off, respectively. C is the gate-to-drain MOSFET
capacitance in farads.
GD
Output Capacitor Selection
Rectifier Diode Selection
For all three converter topologies, the output capaci-
tor supplies the load current when the main switch is
on. The function of the output capacitor is to reduce the
converter output ripple to acceptable levels. The entire
output-voltage ripple appears across constant-current sink
outputs because the LED string voltages are stable due to
the constant current. For the device, limit the peak-to-peak
output-voltage ripple to 200mV to get stable output current.
Using a Schottky rectifier diode produces less forward drop
and puts the least burden on the MOSFET during reverse
recovery. A diode with considerable reverse-recovery time
increases the MOSFET switching loss. Select a Schottky
diode with a voltage rating 20% higher than the maximum
boost-converter output voltage and current rating greater
than that calculated in the following equation:
I
= IL
(1− D )×1.2
MAX
D
AVG
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Integrated, 4-Channel, High-Brightness
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relationship between the RSDT voltage and the recom-
mended maximum OUT_ voltage, assuming all the active
channels are at the same voltage level.
Setting RSDT Pin Voltage
As described in the Short-LED Detection section, the
actual LED short detection threshold depends on the
RSDT pin voltage and the minimum current sink (OUT_)
voltage.
With higher OUT_ voltages, an erroneous LED short
condition can sometimes be detected when the converter
output voltage is transitioning from regulation based on
the OVP input to regulation based on the OUT_ voltages.
An optimum choice of RSDT voltage should take into
account the maximum voltage at the OUT_ pins when
the converter is regulating its output voltage based on the
OVP pin.
The plot shown here can be used when selecting the OVP
resistor divider and the RSDT voltage. It is recommended
that the RSDT voltage be chosen to be below the curve.
In general, performance is improved when the OVP resis-
tor divider is selected to set a maximum output voltage
close to the maximum LED string voltage needed in the
application.
In particular, it is recommended that the OVP resistor
divider be selected to set the output voltage of the con-
verter (when using the OVP input) so that the voltage on
the OUT_ pins does not exceed a threshold that depends
on the RSDT setting. The plot in Figure 6 shows the
MAXIMUM OUT_VOLTAGE vs. RSDT VOLTAGE
WITH V = 5V
CC
ACTIVE OUT_ PINS AT THE SAME VOLTAGE LEVEL
45
40
35
30
25
NOT
RECOMMENDED
20
15
10
5
RECOMMENDED
0
0.3
0.9
1.1
1.3
1.5
1.7
2.3
0.5
1.9
0.7
2.1
2.5
V
RSDT
(V)
Figure 6. Maximum Output Voltage vs. RSDT Voltage
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Integrated, 4-Channel, High-Brightness
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33ms, the p-MOSFET has to sustain the highest input
voltage and the programmed current limit.
External Disconnect MOSFET Selection
An external p-MOSFET can be used to disconnect the
boost output from the battery in the event of an output
overload or short condition. In the case of the SEPIC or
buck-boost, this protection is not necessary and in those
cases there is no need for the p-MOSFET. Connect the
PGATE pin to ground in the case of the SEPIC and buck-
boost. If it is necessary to have an output short protection
for the boost even at power-up, then the current through
the p-MOSFET (Figure 7) has to be sensed. Once the
current-sense voltage exceeds a certain threshold, it
should limit the input current to the programmed threshold.
This threshold should be set at a sufficiently high level so
that it never trips at startup or under normal operating con-
ditions. Check the safe operating area of the p-MOSFET
so that the current-limit trip threshold and the voltage on
the MOSFET do not exceed the limits of the SOA curve of
the p-MOSFET at the highest operating temperature. The
current-limit protection circuit is active for 33ms before
the short trip threshold is triggered in the device, discon-
necting the p-MOSFET from the input source. During the
Overvoltage Protection
The minimum overvoltage-protection threshold at the
DC-DC converter output (V
following formula:
) is determined using the
OVP
V
= (1.19 - OVP Hysteresis) x (1 + R1/R2)
OVPmin
volts (see Figure 2) where 1.19V is the minimum over-
voltage threshold and OVP hysteresis is 70mV. Set this
minimum overvoltage threshold so that at 92% of this
threshold the circuit can still regulate the current in the
LED string when the forward-voltage drop on all the LEDs
in the LED string are at the maximum. Use the following
formula to calculate the minimum overvoltage-threshold
set point:
V
+ 1 = 0.92 x V
OVPmin
LEDmax
where V
is the maximum voltage drop that can
LEDmax
occur on LED string.
Q2
R11
L1
D1
V
IN
TO LED STRINGS
C1
D2
R12
D3
C7
Q1
C8
R10
R
CS
Q3
R7
R
SCOMP
PGATE NDRV
CS
IN
MAX16813B
Figure 7. External Disconnect MOSFET
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Integrated, 4-Channel, High-Brightness
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where f is in hertz, V
is in volts, I
is in amperes,
LED
Feedback Compensation
P1
LED
and C
is in farads. Compensation components
OUT
During normal operation, the feedback control loop
regulates the minimum OUT_ voltage to 1V when LED
string currents are enabled during PWM dimming. When
LED currents are off during PWM dimming, the control
loop turns off the converter and stores the steady-state
condition in the form of capacitor voltages, mainly the
output filter capacitor voltage and compensation capacitor
voltage. When the PWM dimming pulses are less than 24
switching clock cycles, the feedback loop regulates the
converter output voltage to 95% of the OVP threshold.
(R
and C ) perform two functions. C
COMP COMP
COMP
introduces a low-frequency pole that presents a -20dB/
decade slope to the loop gain. R flattens the gain
COMP
of the error amplifier for frequencies above the zero
formed by R and C . For compensation, this
COMP
COMP
zero is placed at the output pole frequency (f ) so that it
provides a -20dB/decade slope for frequencies above f
to the combined modulator and compensator response.
P1
P1
The value of R needed to fix the total loop gain at
COMP
f
so that the total loop gain crosses 0dB with -20dB/
P1,
The worst-case condition for the feedback loop is when
the LED driver is in normal mode regulating the minimum
OUT_ voltage to 1V. The switching converter small-signal
transfer function has a right-half plane (RHP) zero for
boost configuration if the inductor current is in continuous-
conduction mode. The RHP zero adds a 20dB/decade
gain together with a 90° phase lag, which is difficult to
compensate.
decade slope at 1/5 the R
as follows:
zero frequency, is calculated
HP
For boost configuration:
f
×R
×I
CS LED
ZRHP
R
=
COMP
5 × f × GM
× V
×(1− D
)
MAX
P1
COMP
LED
For SEPIC and coupled-inductor buck-boost configurations:
The worst-case RHP zero frequency (f
as follows:
) is calculated
f
×R
×I
× V
×D
ZRHP
ZRHP
CS LED MAX
R
=
COMP
5 × f × GM
×(1− D
)
MAX
P1
COMP
LED
For boost configuration:
where R
is the compensation resistor in ohms,
COMP
2
)
V
(1− D
MAX
f
and f are in hertz, R is the switch current-sense
LED
ZRHP
P1 CS
f
=
ZRHP
2π ×L ×I
resistor in ohms, and GM
of the error amplifier (600μS).
is the transconductance
COMP
LED
For SEPIC and coupled-inductor buck-boost configurations:
2
The value of C is calculated as follows:
COMP
V
(1− D
)
MAX
×D
LED
f
=
ZRHP
1
2π ×L ×I
C
=
LED
MAX
COMP
2π ×R
× f
Z1
COMP
where f
is in hertz, V
is in volts, L is the
ZRHP
LED
where f
is the compensation zero placed at 1/5 of
the crossover frequency that is, in turn, set at 1/5 of the
. If the output capacitors do not have low ESR, the
ESR zero frequency may fall within the 0dB crossover
frequency. An additional pole may be required to cancel
out this pole placed at the same frequency. This is
usually implemented by connecting a capacitor in parallel
Z1
inductance value of L1 in henries, and I
is in amperes.
LED
A simple way to avoid this zero is to roll off the loop gain
to 0dB at a frequency less than 1/5 of the RHP zero
frequency with a -20dB/decade slope.
f
ZRHP
The switching converter small-signal transfer function
also has an output pole. The effective output impedance,
together with the output filter capacitance, determines the
with C
and R
. Figure 5 shows the SEPIC
COMP
COMP
output pole frequency (f ) that is calculated as follows:
P1
configuration and Figure 4 shows the coupled-inductor
buck-boost configuration.
For boost configuration:
I
LED
f
=
Design Verification
The following criteria must be satisfied before the design
can go into production:
P1
2× π × V
× C
OUT
LED
For SEPIC and coupled-inductor buck-boost configurations:
1) The chosen inductor must not saturate at the lowest
input line voltage and the maximum output current
condition. The inductor must not saturate at the high-
est operating case temperature. Adequate margin
should be provided.
I
×D
LED
MAX
× C
OUT
f
=
P1
2× π × V
LED
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Integrated, 4-Channel, High-Brightness
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2) Verify that the slope compensation is adequate.
Inadequate slope compensation can cause subhar-
monic oscillation. For more information on select-
ing the proper slope-compensation resistor, see the
SSlope Compensation section.
on the boost will change. The boost output voltage drops
when there is a transition from low dim to normal dim
made. If the closed-loop phase margin is less than 45°,
the output voltage might ring when the transition from LO
dim to normal dim occurs. This can cause flicker of the
LEDs and this flicker needs to be prevented by increasing
the phase margin. If the flicker is still present even when
the phase margin exceeds 60°, it may be necessary to
increase the output capacitor.
3) At the lowest input line voltage and the maximum
power condition, the signal on the CS pin should be
close to the current-limit voltage on the CS pin.
4) Select Schottky diodes, MOSFETs, and resistors that
meet the power and voltage ratings.
TEST
5) Select input and output capacitors that meet ripple-
voltage and ripple-current requirements.
RINJ
REF
6) Set the overvoltage at the appropriate point.
7) After the compensation values are designed, verify the
design by measuring the loop stability.
1N4148W
OUTPUT
Loop-Stability Verification
C2
To verify the loop stability, it is a good idea to use a loop
analyzer to study the closed-loop gain and phase with
frequency. To check the closed-loop gain, connect the
test and reference probes of the analyzer, as shown in
Figure 8.
R1
R2
LED
STRINGS
Check the voltages on the OUT_ pins with dimming at
100% duty cycle. Then insert a diode and the injection
resistor in the string where the OUT_ voltage is closest
to 1V. The added diode in series with the LED string
keeps the string where the injection resistor is added as
the string that controls the output voltage. Use an injec-
tion transformer to insert the injection voltage from test to
ref. The loop analyzer can plot the gain and phase of the
TO OVP
TO OUT1
TO OUT2
TO OUT3
TO OUT4
closed loop where the loop gain is T /R . The cross-
JW JW
Figure 8. Loop Analyzer Connection to MAX16813B Circuit
over frequency occurs at the frequency where the gain is
0db. The phase margin at that frequency should exceed
45° for guaranteed stable operation. The optimum phase
margin should exceed 60°. An example of the closed-loop
gain and phase margin on a MAX16813B boost is shown
in Figure 9. This measurement was done on the typical
application shown in Figure 2 at an input voltage of 12V.
100
80
60
40
20
0
200
150
100
50
TR1: MAG (GAIN)
TR2: PHASE (GAIN)
The crossover frequency (f ) in the design is 12kHz and
C
0
the phase margin is 74°. It is important to verify the loop
stability and phase margin before the design goes into
production. The typical crossover frequency should be in
-20
-40
-50
-100
-150
-200
the range of f
/10 > f > f
/20 where f is the cross-
SW C
-60
SW
C
over frequency. The phase margin should exceed 60° if
possible. It is also important to check the performance of
the design at the transition point from low dim to high dim
and vice versa. When the device is switching over from
low DIM mode to normal DIM mode, the output voltage
-80
-100
2
10
3
4
5
10
10
10
f/Hz
Figure 9. Closed-Loop Gain and Phase Margin
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Integrated, 4-Channel, High-Brightness
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rectifier diode, and current-sense resistor). Connect
PGND to the power ground plane as close as possible
to PGND. Connect all other ground connections to the
Analog Dimming Using External
Control Voltage
Connect a resistor (R ) to the SETI input as shown in
SETI2
power ground plane using vias close to the terminals.
Figure 10 for controlling the LED string current using an
external control voltage. The device applies a fixed 1.23V
bandgap reference voltage at SETI and measures the
current through SETI. This measured current multiplied by
a factor of 1220 is the current through each one of the four
constant-current sink channels. Adjust the current through
SETI to get analog dimming functionality by connecting
the external control voltage to SETI through the resistor
3) There are two loops in the power circuit that carry
high-frequency switching currents. One loop is when
the MOSFET is on (from the input filter capacitor
positive terminal, through the inductor, the internal
MOSFET, and the current-sense resistor, to the input
capacitor negative terminal). The other loop is when
the MOSFET is off (from the input capacitor positive
terminal, through the inductor, the rectifier diode,
output filter capacitor, to the input capacitor nega-
tive terminal). Analyze these two loops and make the
loop areas as small as possible. Wherever possible,
have a return path on the power ground plane for the
switching currents on the top-layer copper traces, or
through power components. This reduces the loop
area considerably and provides a low-inductance path
for the switching currents. Reducing the loop area also
reduces radiation during switching.
(R
). The resulting change in the LED current with
SETI2
the control voltage is linear and inversely proportional.
The LED current control range remains between 20mA
to 150mA.
Use the following equation to calculate the LED current
set by the control voltage applied:
1.23 − V
(
)
×1220
1500
C
I
=
+
OUT
R
R
SETI2
SETI
PCB Layout Considerations
4) Connect the power ground plane for the constant-
current LED driver portion of the circuit to LEDGND
as close as possible to the device. Connect SGND to
PGND at the same point.
LED driver circuits based on the MAX16813B device use
a high-frequency switching converter to generate the
voltage for LED strings. Take proper care while laying
out the circuit to ensure proper operation. The switching-
converter part of the circuit has nodes with very fast
voltage changes that could lead to undesirable effects
on the sensitive parts of the circuit. Follow the guidelines
below to reduce noise as much as possible:
MAX16813B
1) Connect the bypass capacitor on V
as close as
CC
R
SETI2
SETI
possible to the device and connect the capacitor
ground to the analog ground plane using vias close to
the capacitor terminal. Connect SGND of the device to
the analog ground plane using a via close to SGND.
Lay the analog ground plane on the inner layer, prefer-
ably next to the top layer. Use the analog ground plane
to cover the entire area under critical signal compo-
nents for the power converter.
1.23V
R
V
C
SETI
2) Have a power ground plane for the switching-converter
power circuit under the power components (input filter
capacitor, output filter capacitor, inductor, MOSFET,
Figure 10. Analog Dimming with External Control Voltage
Maxim Integrated
│ 25
www.maximintegrated.com
MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Ordering Information
Chip Information
PROCESS: CMOS
PART
TEMP RANGE
PIN-PACKAGE
MAX16813BATP/V+
MAX16813BAUP/V+
-40°C to +125°C 20 TQFN-EP*
-40°C to +125°C 20 TSSOP-EP*
/V denotes an automotive qualified part.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Maxim Integrated
│ 26
www.maximintegrated.com
MAX16813B
Integrated, 4-Channel, High-Brightness
LED Driver with High-Voltage DC-DC Controller
and Battery Disconnect
Revision History
REVISION REVISION
PAGES
DESCRIPTION
CHANGED
NUMBER
DATE
0
1
8/17
Initial release
Removed future product status from MAX16813BAUP/V+ in Ordering Information
—
1/18
26
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
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.
2018 Maxim Integrated Products, Inc.
│ 27
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