收藏本站
1.5MHz, 30A High-Efficiency, LED Driver
with Rapid LED Current Pulsing
Detailed Description
The MAX16818 is a high-performance average-current-
mode PWM controller for high-power, high-brightness
LEDs (HBLEDs). Average current-mode control is the
ideal method for driving HBLEDs. This technique offers
inherently stable operation, reduces component derat-
ing and size by accurately controlling the inductor cur-
rent. The device achieves high efficiency at high
current (up to 30A) with a minimum number of external
components. The high- and low-side drivers source
and sink up to 4A for lower switching losses while dri-
ving high-gate-charge MOSFETs. The MAX16818 ’s
CLKOUT output is 180° out-of-phase with respect to the
high-side driver. CLKOUT drives a second MAX16818
LED driver out of phase, reducing the input-capacitor
ripple current.
The MAX16818 consists of an inner average current loop
representing inductor current and an outer voltage loop
voltage-error amplifier (VEA) that directly controls LED
current. The combined action of the two loops results in
a tightly regulated LED current. The inductor current is
sensed across a current-sense resistor. The differential
amplifier senses LED current through a sense resistor in
series with the LEDs and the resulting sensed voltage is
compared against an internal 0.6V reference at the error-
amplifier input. The MAX16818 will adjust the LED cur-
rent to within 1% accuracy to maintain emitted spectrum
of the light in HBLEDs.
IN, V CC , and V DD
The MAX16818 accepts either a 4.75V to 5.5V or 7V to
28V input voltage range. All internal control circuitry
operates from an internally regulated nominal voltage of
5V (V CC ). For input voltages of 7V or greater, the inter-
nal V CC regulator steps the voltage down to 5V. The
V CC output voltage is a regulated 5V output capable of
sourcing up to 60mA. Bypass the V CC to SGND with
4.7μF and 0.1μF low-ESR ceramic capacitors for high-
frequency noise rejection and stable operation.
The MAX16818 uses V DD to power the low-side and
high-side drivers. Isolate V DD from V CC with a 1 ? resis-
tor and put a 1μF capacitor in parallel with a 0.1μF
capacitor to ground to prevent high-current noise spikes
created by the driver from disrupting internal circuitry.
P D = V IN x I CC
I CC = I Q + [f SW x (Q G1 + Q G2 )]
where Q G1 and Q G2 are the total gate charge of the
low-side and high-side external MOSFETs at V GATE =
5V, I Q is 3.5mA (typ), and f SW is the switching frequen-
cy of the converter.
Undervoltage Lockout (UVLO)
The MAX16818 includes an undervoltage lockout with
hysteresis and a power-on-reset circuit for converter
turn-on. The UVLO rising threshold is internally set at
4.35V with a 200mV hysteresis. Hysteresis at UVLO
eliminates chattering during startup.
Most of the internal circuitry, including the oscillator,
turns on when the input voltage reaches 4V. The
MAX16818 draws up to 3.5mA of current before the
input voltage reaches the UVLO threshold.
Soft-Start
The MAX16818 has an internal digital soft-start for a
monotonic, glitch-free rise of the output current. Soft-
start is achieved by the controlled rise of the error
amplifier dominant input in steps using a 5-bit counter
and a 5-bit DAC. The soft-start DAC generates a linear
ramp from 0 to 0.7V. This voltage is applied to the error
amplifier at a third (noninverting) input. As long as the
soft-start voltage is lower than the reference voltage,
the system converges to that lower reference value.
Once the soft-start DAC output reaches 0.6V, the refer-
ence takes over and the DAC output continues to climb
to 0.7V, assuring that it does not interfere with the refer-
ence voltage.
Internal Oscillator
The internal oscillator generates a clock with the fre-
quency proportional to the inverse of R T . The oscillator
frequency is adjustable from 125kHz to 1.5MHz with
better than 8% accuracy using a single resistor con-
nected from RT/SYNC to SGND. The frequency accura-
cy avoids the over-design, size, and cost of passive
filter components like inductors and capacitors. Use
the following equation to calculate the oscillator fre-
quency:
For 120k ? ≤ R T ≤ 500k ? :
The TQFN is a thermally enhanced package and can
dissipate up to 2.7W. The high-power packages allow
the high-frequency, high-current converter to operate
from a 12V or 24V bus. Calculate power dissipation in
the MAX16818 as a product of the input voltage and the
R T =
For 40k ? ≤ R T ≤ 120k ? :
6 . 25 x 10 10
f SW
total V CC regulator output current (I CC ). I CC includes qui-
escent current (I Q ) and gate-drive current (I DD ):
R T =
6 . 40 x 10 10
f SW
______________________________________________________________________________________
15
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
MAX16820EVKIT+ EVAL KIT FOR MAX16820
MAX16821BEVKIT+ KIT EVAL FOR MAX16821B
MAX16822BEVKIT+ KIT EVAL FOR MAX16822
MAX16823EVKIT+ EVAL KIT FOR MAX16823
MAX16824EVKIT+ KIT EVAL FOR MAX16824
MAX16825EVKIT+ KIT EVAL FOR MAX16825
MAX16828EVKIT+ EVALUATION KIT FOR MAX16828
MAX16831EVKIT+ KIT EVAL FOR MAX16831
相关代理商/技术参数
MAX16819ATT+ 制造商:Maxim Integrated Products 功能描述:LED DRVR 5V/9V/12V/15V/18V/24V 6TDFN EP - Rail/Tube
MAX16819ATT+T 功能描述:LED照明驱动器 2MHz HB w/HSide Crnt Sense & 5000:1 Dim 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
MAX1681C/D 功能描述:直流/直流开关转换器 125mA High-Speed Switched-Capacitor Voltage Converters RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
MAX1681ESA 功能描述:直流/直流开关转换器 125mA f-Select Swtcd Voltage Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
MAX1681ESA+ 功能描述:直流/直流开关转换器 125mA f-Select Swtcd Voltage Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
MAX1681ESA+ 制造商:Maxim Integrated Products 功能描述:SEMICONDUCTOR ((NW))
MAX1681ESA+T 功能描述:直流/直流开关转换器 125mA f-Select Swtcd Voltage Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT
MAX1681ESA-T 功能描述:直流/直流开关转换器 125mA f-Select Swtcd Voltage Converter RoHS:否 制造商:STMicroelectronics 最大输入电压:4.5 V 开关频率:1.5 MHz 输出电压:4.6 V 输出电流:250 mA 输出端数量:2 最大工作温度:+ 85 C 安装风格:SMD/SMT