MAX16814AUP+T ,Integrated, 4-Channel, High-Brightness LED Driver with High-Voltage DC-DC ControllerElectrical Characteristics(V = V = 12V, R = 12.25kI, R = 15kI, C = 1FF, V = V , NDRV = COMP = OUT_ ..
MAX16814BUTP+T ,Integrated, 4-Channel, High-Brightness LED Driver with High-Voltage DC-DC ControllerApplicationssink channels. An integrated current-mode switching • Drives One to Four LED Strings• 4 ..
MAX16814UUP+TCJ3 ,Integrated, 4-Channel, High-Brightness LED Driver with High-Voltage DC-DC Controllerapplications.• Internal MOSFET for Each ChannelAn internal current-mode switching DC-DC control- • ..
MAX16815ASA+ ,High-Voltage, 100mA/200mA Adjustable Linear High-Brightness LED Drivers with PWM DimmingElectrical Characteristics(V = 12V, V = 12V (SO only), C = 0.1µF to GND, I = 0, V = 4V, V - = 0V (S ..
MAX16815ASA+ ,High-Voltage, 100mA/200mA Adjustable Linear High-Brightness LED Drivers with PWM DimmingApplicationsExposed Pad Packages● Emergency Vehicle Warning Lights● -40°C to +125°C Operating Tempe ..
MAX16816ATJ+ ,Programmable Switch-Mode LED Driver with Analog-Controlled PWM DimmingFeatures● EEPROM-Programmable LED Current BinningThe MAX16816 is a current-mode, high-brightness LE ..
MAX4464EXK ,Single/Dual/Quad, +1.8V/750nA, SC70, Rail-to-Rail Op Amps
MAX4465EUK+T ,Low-Cost, Micropower, SC70/SOT23-8, Microphone Preamplifiers with Complete ShutdownELECTRICAL CHARACTERISTICS(V = +5V, V = 0, V = V /2, R = ∞ to V /2, SHDN = GND (MAX4467/MAX4468 onl ..
MAX4465EUK-T ,Low-Cost / Micropower / SC70/SOT23-8 / Microphone Preamplifiers with Complete ShutdownFeaturesThe MAX4465–MAX4469 are micropower op amps opti- +2.4V to +5.5V Supply Voltage Operationmi ..
MAX4466EUK-T ,Low-Cost / Micropower / SC70/SOT23-8 / Microphone Preamplifiers with Complete ShutdownApplicationsMAX4465EUK-T -40°C to +85°C 5 SOT23-5Microphone PreamplifiersMAX4466EXK-T -40°C to +85° ..
MAX4466EXK+T ,Low-Cost, Micropower, SC70/SOT23-8, Microphone Preamplifiers with Complete ShutdownApplicationsMAX4465EUK-T -40°C to +85°C 5 SOT23-5Microphone PreamplifiersMAX4466EXK-T -40°C to +85° ..
MAX4466EXK-T ,Low-Cost / Micropower / SC70/SOT23-8 / Microphone Preamplifiers with Complete ShutdownApplicationsMAX4465EUK-T -40°C to +85°C 5 SOT23-5Microphone PreamplifiersMAX4466EXK-T -40°C to +85° ..
MAX16814AUP+-MAX16814AUP+T-MAX16814BUTP+T-MAX16814UUP+TCJ3
Integrated, 4-Channel, High-Brightness LED Driver with High-Voltage DC-DC Controller
General DescriptionThe MAX16814 high-efficiency, high-brightness LED (HB
LED) driver provides up to four integrated LED current-
sink channels. An integrated current-mode switching
DC-DC controller drives a DC-DC converter that provides
the necessary voltage to multiple strings of HB LEDs.
The MAX16814 accepts a wide 4.75V to 40V input volt-
age 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.
An internal current-mode switching DC-DC control-
ler supports the boost, coupled-inductor boost-buck,
or SEPIC topologies and operates in an adjustable
frequency range between 200kHz and 2MHz. It can
also be used for single-inductor boost-buck topology in
conjunction with the MAX15054 and an additional
MOSFET. The current-mode control with programma-
ble slope compensation provides fast response and
simplifies loop compensation. The MAX16814 also
features an adaptive output-voltage-control scheme that
minimizes the power dissipation in the LED current-sink
paths.
The MAX16814 consists of four identical linear current
source channels to drive four strings of HB LEDs. The
channel current is adjustable from 20mA to 150mA with
an accuracy of ±3% using an external resistor. The
external resistor sets all 4-channel currents to the same
value. The device allows connecting multiple channels
in parallel to achieve higher current per LED string. The
MAX16814 also features pulsed dimming control on all
four channels through a logic input (DIM). In addition,
the MAX16814A_ _ and MAX16814U_ _ include a unique
feature that allows a very short minimum pulse width as
low as 1µs.
The MAX16814 includes output overvoltage, open-
LED detection and protection, programmable shorted-
LED detection and protection, and overtemperature
protection. The device operates over the -40NC to
+125NC automotive temperature range. The MAX16814 is
available in 6.5mm x 4.4mm, 20-pin TSSOP, 4mm x 4mm,
20-pin TQFN and QFND packages.
Beneits and Features●Cost-Effective 4-Channel Linear LED Current Sinks
for Wide Range of LED Lighting ApplicationsDrives One to Four LED Strings4.75V to 40V Input Voltage RangeFull-Scale LED Current Adjustable from 20mA
to 150mA5000:1 PWM Dimming at 200HzLess than 40µA Shutdown Current●Minimal Component Count Saves Cost and SpaceInternal MOSFET for Each ChannelInternal Current-Mode Switching DC-DC Controller
Supporting Boost, Coupled-Inductor Boost-Buck, or
SEPIC Topologies200kHz to 2MHz Programmable Switching Frequency for Optimizing Size vs. EficiencyExternal Switching-Frequency Synchronization●Protection Features and Wide Operating
Temperature Range improves ReliabilityOpen-Drain Fault-Indicator OutputOpen-LED and LED-Short Detection and ProtectionOvertemperature ProtectionAvailable in Thermally Enhanced 20-Pin TQFN,
QFND, and TSSOP PackagesOperation Over -40°C to +125°C Temperature Range
Applications●Automotive Displays LED Backlights●Automotive RCL, DRL, Front Position, and Fog Lights●LCD TV and Desktop Display LED Backlights●Architectural, Industrial, and Ambient Lighting
Typical Operating Circuit and Ordering Information appear
at end of data sheet.
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
EVALUATION KIT AVAILABLE
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional opera-
tion 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.
IN to SGND ............................................................-0.3V to +45V
EN to SGND ...............................................-0.3V to (VIN + 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
VCC to SGND ..........-0.3V to the lower of (VIN + 0.3V) and +6V
DRV, FLT, DIM, RSDT, OVP to SGND .....................-0.3V to +6V
CS, RT, COMP, SETI to SGND .................-0.3V to (VCC + 0.3V)
NDRV to PGND .......................................-0.3V to (VDRV + 0.3V)
NDRV Peak Current (< 100ns) .............................................Q3A
NDRV Continuous Current ............................................Q100mA
OUT_ Continuous Current .............................................Q175mA
VCC Short-Circuit Duration ........................................Continuous
Continuous Power Dissipation (TA = +70NC) (Note 1)
20-Pin TQFN (derate 25.6mW/NC above +70NC) .......2051mW20-Pin Side-Wettable QFND
(derate 26.5mW/NC above +70NC) ............................2050mW
26-Pin TSSOP (derate 26.5mW/NC above +70NC) .....2122mW
Operating Temperature Range
MAX16814A_ _ ..............................................-40NC to +125NC
MAX16814BE_ _ .............................................-40NC to +85NC
MAX16814U_ _and MAX16814BU_ _ ................0NC to +85NC
Junction Temperature .....................................................+150NC
Storage Temperature Range ............................-65NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
Electrical Characteristics(VIN = VEN = 12V, RRT = 12.25kI, RSETI = 15kI, CVCC = 1FF, VCC = VDRV, NDRV = COMP = OUT_ = unconnected, VRSDT = VDIM
= VCC, VOVP = VCS = VLEDGND = VPGND = VSGND = 0V, TA = TJ = -40NC to +125NC for MAX16814A_ _, TA = -40NC to +85NC for
MAX16814BE_ _, and TA = TJ = 0NC to +85NC for MAX16814U_ _ and MAX16814BU_ _, unless otherwise noted. Typical values are at
TA = +25NC.) (Note 2)
Absolute Maximum RatingsNote 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 http://www.maximintegrated.com/thermal-tutorial.
Package Thermal Characteristics (Note 1)20 TQFN/QFND
Junction-to-Ambient Thermal Resistance (BJA) ........+39NC/W
Junction-to-Case Thermal Resistance (BJC) ...............+6NC/W
20 TSSOP
Junction-to-Ambient Thermal Resistance (BJA) .....+37.7NC/W
Junction-to-Case Thermal Resistance (BJC) ............+2.0NC/W
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Operating Voltage RangeVIN4.7540V
Active Supply CurrentIINMAX16814A_ _ and MAX16814U_ _2.55mAMAX16814B_ _ _ only2.755.5
Standby Supply CurrentVEN = 0V1540µA
IN Undervoltage LockoutVIN rising3.9754.34.625V
IN UVLO Hysteresis170mV
VCC REGULATOR
Regulator Output VoltageVCC6.5V < VIN < 10V, 1mA < ILOAD < 50mA4.755.05.25V10V < VIN < 40V, 1mA < ILOAD < 10mA
Dropout VoltageVIN - VCC, VIN = 4.75V, ILOAD = 50mA200500mV
Short-Circuit Current LimitVCC shorted to SGND100mA
VCC Undervoltage Lockout
ThresholdVCC rising4V
VCC UVLO Hysteresis100mV
RT OSCILLATOR
Switching Frequency RangefSW2002000kHz
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Electrical Characteristics (continued)(VIN = VEN = 12V, RRT = 12.25kI, RSETI = 15kI, CVCC = 1FF, VCC = VDRV, NDRV = COMP = OUT_ = unconnected, VRSDT = VDIM
= VCC, VOVP = VCS = VLEDGND = VPGND = VSGND = 0V, TA = TJ = -40NC to +125NC for MAX16814A_ _, TA = -40NC to +85NC for
MAX16814BE_ _, and TA = TJ = 0NC to +85NC for MAX16814U_ _ and MAX16814BU_ _, unless otherwise noted. Typical values are at
TA = +25NC.) (Note 2)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Maximum Duty Cycle
fSW = 200kHz to 600kHz, MAX16814A_ _
and MAX16814U_ _858993fSW = 600kHz to 2000kHz, MAX16814A_ _
and MAX16814U_ _828690
fSW = 200kHz to 600kHz, MAX16814B_ _ 909498
fSW = 600kHz to 2000kHz, MAX16814B _ _ _869094
Oscillator Frequency Accuracy
fSW = 200kHz to 2MHz, MAX16814A_ _
and MAX16814U_ _-7.5+7.5%
fSW = 200kHz to 2MHz, MAX16814B_ _ _-7+7
Sync Rising Threshold4V
Minimum Sync Frequency1.1fSWHz
PWM COMPARATOR
PWM Comparator Leading-Edge
Blanking Time60ns
PWM to NDRV Propagation DelayIncluding leading-edge blanking time90ns
SLOPE COMPENSATION
Peak Slope Compensation
Current Ramp Magnitude
Current ramp added to the CS input,
MAX16814A_ _ only444954
µA x fSWCurrent ramp added to the CS input,
MAX16814U_ _ and MAX16814B_ _ _455055
CS LIMIT COMPARATOR
Current-Limit Threshold(Note 3)396416437mV
CS Limit Comparator to NDRV
Propagation Delay
10mV overdrive, excluding leading-edge
blanking time10ns
ERROR AMPLIFIER
OUT_ Regulation Voltage1V
TransconductancegM340600880µS
No-Load Gain(Note 4)75dB
COMP Sink CurrentVOUT_ = 5V, VCOMP = 2.5V160375800µA
COMP Source CurrentVOUT_ = 0V, VCOMP = 2.5V160375800µA
MOSFET DRIVER
NDRV On-ResistanceISINK = 100mA (nMOS)0.9ωISOURCE = 100mA (pMOS)1.1
Peak Sink CurrentVNDRV = 5V2.0A
Peak Source CurrentVNDRV = 0V2.0A
Rise TimeCLOAD = 1nF6ns
Fall TimeCLOAD = 1nF6ns
LED CURRENT SOURCES
OUT_ Current-Sink RangeVOUT_ = VREF20150mA
Channel-to-Channel MatchingIOUT_ = 100mA±2%
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Note 2: All MAX16814A_ _ are 100% tested at TA = +125NC, while all MAX16814U_ _ and MAX16814B _ _ _ are 100% tested at
TA = +25°C. All limits overtemperature are guaranteed by design, not production tested.
Note 3: CS threshold includes slope-compensation ramp magnitude.
Note 4: Gain = δVCOMP/δVCS, 0.05V < VCS < 0.15V.
Electrical Characteristics (continued)(VIN = VEN = 12V, RRT = 12.25kI, RSETI = 15kI, CVCC = 1FF, VCC = VDRV, NDRV = COMP = OUT_ = unconnected, VRSDT = VDIM
= VCC, VOVP = VCS = VLEDGND = VPGND = VSGND = 0V, TA = TJ = -40NC to +125NC for MAX16814A_ _, TA = -40NC to +85NC for
MAX16814BE_ _, and TA = TJ = 0NC to +85NC for MAX16814U_ _ and MAX16814BU_ _, unless otherwise noted. Typical values are at
TA = +25NC.) (Note 2)
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
Output Current Accuracy
IOUT_ =
100mA
TA = +125°C, MAX16814A_ _
only±3
TA = -40°C to +125°C,
MAX16814A_ _ only±5
IOUT_ =
50mA to
150mA
TA = +25°C, MAX16814U_ _ and
MAX16814B_ _ _±2.75
TA = 0°C to +85°C, MAX16814U_
_ and MAX16814BU _ _±4
TA = -40°C to +85°C for
MAX16814BE _ _±4
OUT_ Leakage CurrentVDIM = 0V, VOUT_ = 40V1µA
LOGIC INPUTS/OUTPUTS
EN Reference Voltage
VEN rising, MAX16814A_ _ only1.1251.231.335VEN rising, MAX16814U_ _ and
MAX16814B_ _ _1.1441.231.316
EN Hysteresis50mV
EN Input CurrentVEN = 40V±600nA
DIM Input High Voltage2.1V
DIM Input Low Voltage0.8V
DIM Hysteresis250mV
DIM Input Current±2µA
DIM to LED Turn-On DelayDIM rising edge to 10% rise in IOUT_100ns
DIM to LED Turn-Off DelayDIM falling edge to 10% fall in IOUT_100ns
IOUT_ Rise and Fall Times200ns
FLT Output Low VoltageVIN = 4.75V and ISINK = 5mA0.4V
FLT Output Leakage CurrentVFLT = 5.5V1.0µA
LED Short Detection ThresholdGain = 3V1.752.02.25V
Short Detection Comparator Delay6.5µs
RSDT Leakage Current±600nA
OVP Trip ThresholdOutput rising1.191.2281.266V
OVP Hysteresis70mV
OVP Leakage CurrentVOVP = 1.25V±200nA
Thermal-Shutdown ThresholdTemperature rising165°C
Thermal-Shutdown Hysteresis15°C
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Typical Operating Characteristics(VIN = VEN = 12V, fSW = 300kHz, RSETI = 15kI, CVCC = 1FF, VCC = VDRV, NDRV = COMP = OUT_ = unconnected, VOVP = VCS =
VLEDGND = VDIM = VPGND = VSGND = 0V, load = 4 strings of 7 white LEDs, TA = +25NC, unless otherwise noted.)
SUPPLY CURRENT
vs. SWITCHING FREQUENCY
MAX16814 toc03
fSW (kHz)
IIN
(mA)
CNDRV = 13pF
VSETI vs. PROGRAMMED CURRENT
MAX16814 toc06
SETI
(V)
SWITCHING WAVEFORM AT 5kHz
(50% DUTY CYCLE) DIMMING
MAX16814 toc01
IOUT1
100mA/div
VOUT
10V/div
VLX
10V/div
40Fs/div
FIGURE 2
SWITCHING FREQUENCY
vs. TEMPERATURE
MAX16814 toc04
TEMPERATURE (NC)
SWITCHING FREQUENCY (kHz)
EN THRESHOLD VOLTAGE
vs. TEMPERATURE
MAX16814 toc07
EN THRESHOLD VOLTAGE (V)
VEN RISING
VEN FALLING
SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX16814 toc02
VIN (V)
IIN
(mA)353025201510
CNDRV = 13pFTA = +125NC
TA = +25NC
TA = -40NC
VSETI vs. TEMPERATURE
MAX16814 toc05
TEMPERATURE (NC)
SETI
(V)
EN LEAKAGE CURRENT
vs. TEMPERATURE
MAX16814 toc08
EN LEAKAGE CURRENT (nA)
VEN = 2.5V
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Typical Operating Characteristics (continued)(VIN = VEN = 12V, fSW = 300kHz, RSETI = 15kI, CVCC = 1FF, VCC = VDRV, NDRV = COMP = OUT_ = unconnected, VOVP = VCS =
VLEDGND = VDIM = VPGND = VSGND = 0V, load =4 strings of 7 white LEDs, TA = +25NC, unless otherwise noted.)
VCC LINE REGULATION
MAX16814 toc09
VIN (V)
(V)3025201510
TA = +125NC
TA = +25NC
TA = -40NC
VCC LOAD REGULATION
MAX16814 toc10
IVCC (mA)
CC
(V)4020
TA = -40NC
TA = +25NC
TA = +125NC
SWITCHING FREQUENCY vs. 1/RT
MAX16814 toc11
1/RT (mS)
SWITCHING FREQUENCY (MHz)
STARTUP WAVEFORM WITH
DIM ON PULSE WIDTH < tSW
MAX16814 toc12
IOUT_
100mA/div
VIN
20V/div
VDIM
5V/div
VLED
20V/div
40ms/div
STARTUP WAVEFORM WITH DIM
ON PULSE WIDTH = 10tSWMAX16814 toc13
IOUT1
100mA/div
VLED
10V/div
VIN
20V/div
VDIM
5V/div
40ms/div
FIGURE 2
STARTUP WAVEFORM WITH DIM
CONTINUOUSLY ONMAX16814 toc14
IOUT1
100mA/div
VLED
10V/div
VIN
20V/div
VDIM
5V/div
40ms/div
FIGURE 2
MOSFET DRIVER ON-RESISTANCE
vs. TEMPERATURE
MAX16814 toc15
ON-RESISTANCE (
pMOS
nMOS
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Typical Operating Characteristics (continued)(VIN = VEN = 12V, fSW = 300kHz, RSETI = 15kI, CVCC = 1FF, VCC = VDRV, NDRV = COMP = OUT_ = unconnected, VOVP = VCS =
VLEDGND = VDIM = VPGND = VSGND = 0V, load = 4 strings of 7 white LEDs, TA = +25NC, unless otherwise noted.)
LED CURRENT SWITCHING WITH DIM
AT 5kHz AND 50% DUTY CYCLEMAX16814 toc16
IOUT3
100mA/div
IOUT4
100mA/div
IOUT1
100mA/div
IOUT2
100mA/div
100Fs/div
FIGURE 2
LED CURRENT RISING AND FALLING
WAVEFORMMAX16814 toc17
VDIM
5V/div
ILED
50mA/div
4Fs/div
FIGURE 2
OUT_ LEAKAGE CURRENT
vs. TEMPERATURE
MAX16814 toc20
OUT_ LEAKAGE CURRENT (nA)
VDIM = 0V
VOUT = 40V
OUT_ CURRENT vs. 1/RSETI
MAX16814 toc18
1/RSETI (mS)
IOUT_
(mA)
OVP LEAKAGE CURRENT
vs. TEMPERATURE
MAX16814 toc21
OVP LEAKAGE CURRENT (nA)
VOVP = 1.25V
COMP LEAKAGE CURRENT
vs. TEMPERATURE
MAX16814 toc19
TEMPERATURE (NC)
COMP LEAKAGE CURRENT (nA)
VDIM = 0V
VCOMP = 4.5V
VCOMP = 0.5V
RSDT LEAKAGE CURRENT
vs. TEMPERATURE
MAX16814 toc22
RSDT LEAKAGE CURRENT (nA)
VRSDT = 0.5V
VRSDT = 2.5V
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Pin Description
Pin ConigurationsPIN
NAMEFUNCTIONTQFN/
QFND TSSOP4INBias Supply Input. Connect a 4.75V to 40V supply to IN. Bypass IN to SGND with a ceramic
capacitor.5ENEnable Input. Connect EN to logic-low to shut down the device. Connect EN to logic-high or IN
for normal operation. The EN logic threshold is internally set to 1.23V.6COMPSwitching Converter Compensation Input. Connect the compensation network from COMP to
SGND for current-mode control (see the Feedback Compensation section). 7RT
Oscillator Timing Resistor Connection. Connect a timing resistor (RT) from RT to SGND to program
the switching frequency according to the formula RT = 7.350 x 109/fsw (for the MAX16814A_ _
and the MAX16814U_ _) or to the formula RT = 7.72 x 109/fsw (for the MAX16814B_ _ _). Apply an
AC-coupled external clock at RT to synchronize the switching frequency with an external clock. 8FLTOpen-Drain Fault Output. FLT asserts low when an open LED, short LED, or thermal shutdown
is detected. Connect a 10kω pullup resistor from FLT to VCC. 9OVPOvervoltage-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. 10SETILED Current-Adjust Input. Connect a resistor (RSETI) from SETI to SGND to set the current
through each LED string (ILED) according to the formula ILED = 1500/RSETI. 11RSDT
LED Short Detection Threshold Adjust Input. Connect a resistive divider from VCC to RSDT and
SGND to program the LED short detection threshold. Connect RSDT directly to VCC to disable
LED short detection. The LED short detection comparator is internally referenced to 2V. 12SGNDSignal Ground. SGND is the current return path connection for the low-noise analog signals.
PGND
OUT4
OUT3IN
VCC
DRV
NDRV
TOP VIEW
MAX16814
LEDGND
OUT2
OUT1RT
COMP8DIMFLT9SGNDOVP10RSDTSETI
EP*
*EXPOSED PAD.
TSSOPFLT
OUT3OUT2OUT1OUT42
NDRV5141211
DRV
VCC
SGND
RSDT
SETI
OVP
MAX16814
COMP
LEDGND
PGND
EP*DIMCS
TQFN/QFND
TOP VIEW
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Pin Description (continued)PIN
NAMEFUNCTIONTQFN/
QFND TSSOP13DIMDigital PWM Dimming Input. Apply a PWM signal to DIM for LED dimming control. Connect DIM
to VCC if dimming control is not used. 14OUT1
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. 15OUT2
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. 16LEDGNDLED Ground. LEDGND is the return path connection for the linear current sinks. Connect
SGND, LEDGND, and PGND at a single point.17OUT3
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. 18OUT4
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. 19CS
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). 20PGNDPower Ground. PGND is the switching current return path connection. Connect SGND,
LEDGND, and PGND at a single point.1NDRVSwitching n-MOSFET Gate-Driver Output. Connect NDRV to the gate of the external switching
power MOSFET.2DRV
MOSFET Gate-Driver Supply Input. Connect a resistor between VCC and DRV to power the
MOSFET driver with the internal 5V regulator. Bypass DRV to PGND with a minimum of 0.1µF
ceramic capacitor. 3VCC5V Regulator Output. Bypass VCC to SGND with a minimum of 1µF ceramic capacitor as close
as possible to the device. —EPExposed Pad. Connect EP to a large-area contiguous copper ground plane for effective power
dissipation. Do not use as the main IC ground connection. EP must be connected to SGND.
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Figure 1. Simplified Functional Diagram
FAULT FLAG
LOGIC
TSHDN
( = 50FA x fsw)
0.425V
OVP
COMP
ILIM
MAX16814
CS BLANKING
TSHDN
TSHDN
PWM
LOGIC
DRV
CLK
2.5V
NDRV
PGND
THERMAL
SHUTDOWN
SOFT-START
100ms
BANDGAP
VREF
SS_REFSS_DONE
UVLO
UVLO
5V LDO
REGULATOR
SLOPE
COMPENSATION
RAMP/RT OSC
LOGIC
(REF/FB
SELECTOR)
SHORT LED
DETECTOR
RSDTFLT
POKDVREF
LEDGND
OUT_
DIM
OPEN-LED
DETECTOR
LOGIC
MIN STRING
VOLTAGE
UNUSED
STRING
DETECTOR
SHDN
SHDN
SHDN
TSHDN
COMP
VCC
POKDPOK
VBG = 1.235V
VBG
VBG
SGND
SETIOVP
SHDN
REF
SGND
dt
1.23V
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Figure 2. Circuit Used for Typical Operating Characteristics
OUT2
OUT1NDRVCSOVP
PGNDLEDGND
OUT3
OUT4
VDRV
VCC
SETI
FLT
RSDT
RTL2
VINC1
SGND
MAX16814
7 HBLEDS
PER STRINGC7
RSETI
RCSRSCOMP
VCC
RCOMP
CCOMP
DIM
COMP
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
Detailed DescriptionThe MAX16814 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 MAX16814 incorporates two major blocks: a DC-DC
controller with peak current-mode control to implement
a boost, coupled-inductor boost-buck, or a SEPIC-type
switched-mode power supply and a 4-channel LED
driver with 20mA to 150mA constant current-sink capa-
bility per channel. Figure 1 is the simplified functional
diagram and Figure 2 shows the circuit used for typical
operating characteristics.
The MAX16814 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-channel MOSFET.
The DC-DC converter implemented using the controller
generates the required supply voltage 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 four LED strings.
The MAX16814 features adaptive voltage control that
adjusts the converter output voltage depending on the
forward voltage of the LED strings. This feature mini-
mizes the voltage drop across the constant current-sink
drivers and reduces power dissipation in the device. A
logic input (EN) shuts down the device when pulled low.
The device includes an internal 5V LDO capable of pow-
ering additional external circuitry.
All the versions of the MAX16814 include PWM dimming.
The MAX16814A_ and the MAX16814U_ versions, in par-
ticular, provide very wide (5000:1) PWM dimming range
where a dimming pulse as narrow as 1µs 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.
Advanced features include detection and string-
disconnect for open-LED strings, partial or fully shorted
strings, and unused strings. Overvoltage protection
clamps the converter output voltage to the programmed
OVP threshold in the event of an open-LED condi-
protection thresholds are programmable using RSDT
and OVP inputs, respectively. An open-drain FLT signal
asserts to indicate open-LED, shorted-LED, and over-
temperature conditions. Disable individual current-sink
channels by connecting the corresponding OUT_ to
LEDGND. In this case, FLT does not assert indicating
an open-LED condition for the disabled channel. The
device also features an overtemperature protection that
shuts down the controller if the die temperature exceeds
+165NC.
Current-Mode DC-DC ControllerThe peak current-mode controller allows boost, coupled-
inductor buck-boost, or SEPIC-type converters to generate
the required bias voltage for the LED strings. The switch-
ing frequency can be programmed over the 200kHz to
2MHz range using a resistor connected from RT to SGND.
Programmable slope compensation is available to com-
pensate for subharmonic oscillations that occur at above
50% duty cycles in continuous-conduction mode.
The external MOSFET is turned on at the beginning of
every switching cycle. The inductor current ramps up
linearly until it is 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 (RCS)
connected from the source of the external MOSFET to
PGND. The MAX16814 features leading-edge blanking to
suppress the external MOSFET switching noise. A PWM
comparator compares the current-sense voltage plus the
slope-compensation signal with the output of the trans-
conductance error amplifier. The controller turns off the
external 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.
Error AmpliierThe internal error amplifier compares an internal feed-
back (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
minimum 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.
The converter stops switching when the LED strings are
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
disconnected from the COMP output to retain the com-
pensation capacitor charge. This allows the converter
to settle to 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.
For the MAX16814A_ _ and the MAX16814U_ _, if the
PWM dimming on-pulse is less than or equal to five
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.
Undervoltage Lockout (UVLO)The MAX16814 features two undervoltage lockouts that
monitor the input voltage at IN and the output of the inter-
nal LDO regulator at VCC. The device turns on after both
VIN and VCC exceed their respective UVLO thresholds.
The UVLO threshold at IN is 4.3V when VIN is rising and
4.15V when VIN is falling. The UVLO threshold at VCC is
4V when VCC is rising and 3.9V when VCC is falling.
EnableEN is a logic input that completely shuts down the
device when connected to logic-low, reducing the
current consumption of the device to less than 40FA.
The logic threshold at EN is 1.23V (typ). The voltage
at EN must exceed 1.23V before any operation can
commence. There is a 50mV hysteresis on EN. The EN
input also allows programming the supply input UVLO
threshold using an external voltage-divider to sense the
input voltage as shown below.
Use the following equation to calculate the value of R1
and R2 in Figure 3:
UVLOVR1-1R21.23V=×
where VUVLO is the desired undervoltage lockout level
and 1.23V is the EN input reference. Connect EN to IN
if not used.
Soft-StartThe MAX16814 provides soft-start with internally set timing. At
power-up, the MAX16814 enters soft-start once unused LED
strings are detected and disconnected (see the Open-LED
Management and Overvoltage Protection section). During
95% of the OVP voltage and uses feedback from the OVP
input. Soft-start terminates when the minimum current-sink
voltage reaches 1V or when the converter output reaches
95% OVP. The typical soft-start period is 100ms. The 1V
minimum OUT_ voltage is detected only when the LED
strings are enabled by PWM dimming. Connect OVP to
the boost converter output through a resistive divider
network (see the Typical Operating Circuit).
When there is an open-LED condition, the converter output
hits the OVP threshold. After the OVP is triggered, open-
LED strings are disconnected and, at the beginning of the
dimming PWM pulse, control is transferred to the adaptive
voltage control. The converter output discharges to a level
where the new minimum OUT_ voltage is 1V.
Oscillator Frequency/External SynchronizationThe internal oscillator frequency is programmable
between 200kHz and 2MHz using a resistor (RT) con-
nected from the RT input to SGND. Use the equation
below to calculate the value of RT for the desired switch-
ing frequency, fSW.SW
7.3510HzRf×=
(for the MAX16814A_ _ and the MAX16814U_ _).SW
7.7210Rf×=
(for the MAX16814B_ _ _).
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:()-3SYNCT
9.862C-0.14410FR≤×µ
where RT is in Ω.
1.23V
VIN
MAX16814
MAX16814Integrated, 4-Channel, High-Brightness LED
Driver with High-Voltage DC-DC Controller
