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MAX16838
Integrated, 2-Channel, High-Brightness LED Driver
with High-Voltage Boost and SEPIC Controller
=
( ? )
R ISET
Connect a 4.7 I resistor from V CC to DRV to power the
rest of the chip from the V CC pin with the 5V internal
regulator. Bypass DRV to PGND with a minimum of 1 F F
ceramic capacitor as close as possible to the device. For
input voltage range of 4.5V to 5.5V, connect IN to V CC .
LED Current Control (ISET)
The MAX16838 features two identical constant-current
sources used to drive multiple HB LED strings. The
current through each of the channels is adjustable
between 20mA and 150mA using an external resistor
(R ISET ) connected between ISET and SGND. Select
R ISET using the following formula:
1512
I OUT _
where I OUT_ is the desired output current for both
channels in amps.
For single-channel operation, connect channel 1 and
channel 2 together. See Figure 2.
LED Dimming Control
The MAX16838 features LED brightness control using an
external PWM signal applied at DIM. The device accepts
a minimum pulse width of 1 F s. Therefore, a 5000:1 dim-
ming ratio is achieved when using a PWM frequency of
200Hz. Drive DIM high to enable both LED current sinks
and drive DIM low to disable both LED current sinks.
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 five
oscillator clock cycles, then the boost converter regu-
lates its output based on feedback from the OV input.
During this mode, the converter output voltage is regu-
lated to 95% of the OV threshold voltage. If the turn-on
duration of the PWM signal is greater than or equal to
six oscillator clock cycles, then the converter regulates
its output such that the minimum voltage at OUT_ is 1V.
Fault Protections
The MAX16838 fault protections include cycle-by-cycle
current limiting, DC-DC converter output overvoltage
protection, open-LED detection, short-LED detection,
and overtemperature detection. An open-drain LED fault
flag output ( FLT ) goes low when an open-LED/short-LED
or overtemperature condition is detected.
Open-LED Management and Overvoltage Protection
The MAX16838 monitors the drains of the current sinks
(OUT_) to detect any open string. If the voltage at
any output falls below 300mV and the OV threshold is
triggered (i.e., even with OUT_ at the OV voltage the
string is not able to regulate above 300mV), then the
MAX16838 interprets that string to be open, asserts FLT,
and disconnects that string from the operation loop. The
MAX16838 features an adjustable overvoltage threshold
input (OV). Connect a resistor-divider from the switching
converter output to OV and SGND to set the overvoltage
threshold level. Use the following formula to program the
= 1.23V × ? 1 +
R2 OV ?
R1 OV ?
BOOST
CONVERTER
OUTPUT
overvoltage threshold:
V OV
?
?
?
40mA TO 300mA
Open-LED detection is disabled when PWM pulse width
is less than five switching clock cycles.
Short-LED Detection
The MAX16838 features a two-level short-LED detection
MAX16838
OUT1
OUT2
circuitry. If a level 1 short is detected on any one of the
strings, FLT is asserted. A level 1 short is detected if
the difference between the total forward LED voltages
of the two strings exceeds 4.2V (typ). If a level 2 short
is detected on any one of the strings, the particular LED
string with the short is turned off after 6 F s and FLT is
asserted. A level 2 short is detected if the difference
between the total forward LED voltages of the two strings
exceeds 7.8V (typ). The strings are reevaluated on each
Figure 2. Configuration for Higher LED String Current
14
DIM rising edge and FLT is deasserted if the short is
removed. Short-LED detection is disabled when PWM
pulse width is less than five switching clock cycles.
Maxim Integrated
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MAX16838EVKIT+ 功能描述:LED 照明开发工具 MAX16838 evaluation kit RoHS:否 制造商:Fairchild Semiconductor 产品:Evaluation Kits 用于:FL7732 核心: 电源电压:120V 系列: 封装:
MAX16839ASA+ 功能描述:LED照明驱动器 High-Voltage Linear w/LED Open Detect RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N
MAX16839ASA+T 功能描述:LED照明驱动器 High-Voltage Linear w/LED Open Detect RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N
MAX16839ATT/V+ 制造商:Maxim Integrated Products 功能描述:
MAX16839ATT/V+T 功能描述:LED照明驱动器 High-Voltage Linear High-Brightness LED Driver with LED Fault Open Detect RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N
MAX16839ATT+ 制造商:Maxim Integrated Products 功能描述:HIGH-VOLTAGE LINEAR HIGH-BRIGHTNES - Bulk
MAX16839ATT+T 功能描述:LED照明驱动器 High-Voltage Linear w/LED Open Detect RoHS:否 制造商:STMicroelectronics 输入电压:11.5 V to 23 V 工作频率: 最大电源电流:1.7 mA 输出电流: 最大工作温度: 安装风格:SMD/SMT 封装 / 箱体:SO-16N