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PDF MAX16831 Data sheet ( Hoja de datos )
| Número de pieza | MAX16831 | |
| Descripción | High-Power LED Driver | |
| Fabricantes | Maxim Integrated Products | |
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19-0809; Rev 0; 4/07
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
General Description
The MAX16831 is a current-mode, high-brightness LED
(HBLED) driver designed to control two external
n-channel MOSFETs for the single-string LED current
regulation. The MAX16831 integrates all the building
blocks necessary to implement fixed-frequency HBLED
drivers with wide-range dimming control. The
MAX16831 is configurable to operate as a step-down
(buck), step-up (boost), or step-up/-down (buck-boost)
current regulator.
Current-mode control with leading-edge blanking simpli-
fies control-loop design. Internal slope compensation
stabilizes the current loop when operating at duty cycles
above 50%. The MAX16831 operates over a wide input
voltage range and is capable of withstanding automo-
tive load-dump events. Multiple MAX16831s can be
synchronized to each other or to an external clock. The
MAX16831 includes a floating dimming driver for
brightness control with an external n-channel MOSFET
in series with the LED string.
HBLED drivers using the MAX16831 achieve efficien-
cies of over 90% in automotive applications. The
MAX16831 also includes a 1.4A source and 2.5A sink
www.DataSheet4U.com
gate driver for driving switching MOSFETs in high-power
LED driver applications, such as front light assemblies.
The dimming control allows for wide PWM dimming at
frequencies up to 2kHz. Higher dimming ratios of up to
1000:1 are achievable at lower dimming frequencies.
The MAX16831 is available in a 32-pin thin QFN package
with exposed pad and operates over the -40°C to
+125°C automotive temperature range.
Applications
Automotive Exterior Lighting:
High-Beam/Low-Beam/Signal Lights
Rear Combination Lights (RCL)
Daytime Running Lights (DRL)
Fog Light and Adaptive Front Light Assemblies
Industrial and Architectural Lighting
Emergency Lighting
Projectors with RGB LED Light Sources
Navigation and Marine Indicators
Pin Configuration appears at end of data sheet.
Features
o Wide Input Range: 6V to 76V With Cold-Start
Operation to 5.5V
o Integrated Differential LED Current-Sense
Amplifier
o Floating Dimming Driver Capable of Driving an
n-Channel MOSFET
o 5% LED Current Accuracy
o 200Hz On-Board Ramp Syncs to External PWM
Dimming Signal
o Programmable Switching Frequency (125kHz to
600kHz) and Synchronization
o Output Overvoltage Load Dump, LED Short,
Overtemperature Protection
o Low 107mV LED Current Sense for High
Efficiency
o Enable/Shutdown Input with Shutdown Current
Below 45µA
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
PKG
CODE
MAX16831ATJ+ -40°C to +125°C 32 TQFN-EP* T3255M-4
+Denotes lead-free package.
*EP = Exposed pad.
Typical Operating Circuits
VIN
RUV2
BUCK-BOOST CONFIGURATION
CCLMP
RCS
RUV1
CUVEN
DIM
CREG1
RT
VCC
UVEN
LO CLMP CS- CS+
DIM
REG1
RTSYNC
MAX16831
DGT
DRV
SNS+
SNS-
QGND
HI
RD QS
RSENSE
ROV1
COMP CS FB
AGND SGND REG2
OV
DRI
R1 CREG2
ROV2
C2
R2
C1
LEDs
CF
Typical Operating Circuits continued at end of data sheet.
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1 page  
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
ELECTRICAL CHARACTERISTICS (continued)
(VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 1µF, CCLMP = 0.1µF, RT = 25kΩ, TA = TJ = -40°C to +125°C, unless otherwise noted.
Typical specifications are at TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
THERMAL SHUTDOWN
Thermal Shutdown Temperature
Hysteresis
TSHDN Temperature rising
∆TSHDN
+165
20
°C
°C
Note 1: Dropout voltage is defined as the input to output differential voltage at which the regulator output voltage drops 100mV below
the nominal output voltage.
Note 2: VCLMPTH determines the voltage required to operate the current-sense amplifier. The DIM driver requires 2.5V for (VCLMP - VLO)
to drive the external MOSFET. VHI is typically one diode drop above VCLMP. A large capacitor connected to VCLMP slows the
response of the LED current-sense circuitry, resulting in current overshoot. To ensure proper operation, connect a 0.1µF
capacitor from CLMP to LO.
Typical Operating Characteristics
(VCC = VUVEN = 14V, CREG1 = 1µF, CREG2 = 10µF, CCLMP = 0.1µF, RT = 25kΩ, RCS = 0.1Ω, TA = +25°C, unless otherwise noted.)
www.DataSheet4U.com
SHUTDOWN CURRENT
vs. TEMPERATURE
28
27
26
25
24
23
22
21
20
19
18
-60 -40 -20 0 20 40 60 80 100 120 140
TEMPERATURE (°C)
OPERATING CURRENT
vs. TEMPERATURE
3.0
2.9
2.8
2.7
2.6
2.5
2.4
2.3
2.2
2.1
2.0
-60 -40 -20
DGT AND DRV NOT
SWITCHING
0 20 40 60 80 100 120 140
TEMPERATURE (°C)
VOLTAGE ACROSS LED CURRENT-SENSE
RESISTOR vs. SUPPLY VOLTAGE
120
110
100
90
80
70
60
50
40
30
20
10
0
0 10 20 30 40
SUPPLY VOLTAGE (V)
_______________________________________________________________________________________ 5
5 Page 
High-Voltage, High-Power LED Driver with
Analog and PWM Dimming Control
Reference Voltage Output
The MAX16831 includes a 5% accurate 3V (typ)
buffered reference output, REF. REF is a push-pull out-
put capable of sourcing/sinking 100µA of current and
can drive a maximum load capacitance of 100pF.
Connect REF to DIM through a resistive voltage-divider
to supply an analog signal for dimming. See the
Dimming Input (DIM) section.
Dimming MOSFET Driver (DDR)
The MAX16831 requires an external n-channel
MOSFET for PWM dimming. Connect the MOSFET to
the output of the DDR dimming driver, DGT, for normal
operation. VDGT swings between VLO and VCLMP. The
DDR dimming driver is capable of sinking or sourcing
up to 20mA of current. The average current required to
drive the dimming MOSFET (IDRIVE_DIM) depends on
the MOSFET’s total gate charge (QG_DIM) and the dim-
ming frequency of the converter, fDIM. Use the follow-
ing equation to calculate the average gate drive current
for the n-channel dimming FET.
IDRIVE_DIM = QG_DIM x fDIM
n-Channel MOSFET Switch Driver (DRV)
www.DataSheet4U.com The MAX16831 drives an external n-channel MOSFET.
Use an external supply or connect REG2 to DRI to
power the MOSFET driver. The driver output, VDRV,
swings between ground and VDRI. Ensure that VDRI
remains below the absolute maximum VGS rating of the
external MOSFET. DRV is capable of sinking 2.5A or
sourcing 1.4A of peak current, allowing the MAX16831
to switch MOSFETs in high-power applications. The
average current sourced to drive the external MOSFET
depends on the total gate charge (QG) and operating
frequency of the converter, fSW. The power dissipation
in the MAX16831 is a function of the average output
drive current (IDRIVE). Use the following equations to
calculate the power dissipation in the gate driver sec-
tion of the MAX16831 due to IDRIVE:
IDRIVE = QG x fSW
PD = (IDRIVE + ICC) x VDRI
where VDRI is the supply voltage to the gate driver and
ICC is the operating supply current. IDRIVE should not
exceed 20mA.
Dimming Input (DIM)
The dimming input, DIM, functions with either analog or
PWM control signals. Once the internal pulse detector
detects three successive edges of a PWM signal with a
frequency between 80Hz and 2kHz, the MAX16831 syn-
chronizes to the external signal and pulse-width-modu-
lates the LED current at the external DIM input frequency
with the same duty cycle as the DIM input. If an analog
REF
R3 MAX16831
DIM
AGND
R4
Figure 2. Creating a DIM Input Signal from REF
control signal is applied to DIM, the MAX16831 com-
pares the DC input to an internally generated 200Hz
ramp to pulse-width-modulate the LED current (fDIM =
200Hz). The output current duty cycle is linearly
adjustable from 0 to 100% (0.2V < VDIM < 2.8V).
Use the following formula to calculate the voltage, VDIM,
necessary for a given output-current duty cycle, D:
VDIM = (D x 2.6) + 0.2V
where VDIM is the voltage applied to DIM in volts.
Connect DIM to REF through a resistive voltage-divider
to apply a DC DIM control signal (Figure 2). Use the
required dimming input voltage, VDIM, calculated
above and select appropriate resistor values using the
following equation:
R4 = R3 x VDIM / (VREF - VDIM)
where VREF is the 3V reference output voltage and
30kΩ ≤ R3 + R4 ≤ 150kΩ.
For proper operation at startup or after toggling ENABLE,
the controller needs three clock edges or an analog volt-
age greater than 0.3V on the DIM input.
Oscillator, Clock, and Synchronization
The MAX16831 is capable of stand-alone operation or
synchronizing to an external clock, and driving external
devices in SYNC mode. For stand-alone operation, pro-
gram the switching frequency by connecting a single
external resistor, RT, between RTSYNC and ground.
Select the switching frequency, fSW, from 125kHz to
600kHz and calculate RT using the following formula:
RT
=
500kHz
fSW
×
25kΩ
where the switching frequency is in kHz and RT is in kΩ.
The MAX16831 is also capable of synchronizing to an
external clock signal ranging from 125kHz to 600kHz.
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet MAX16831.PDF ] | |
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