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2MHz, High-Brightness LED Drivers with
Integrated MOSFET and High-Side Current Sense
Undervoltage Lockout (UVLO)
The MAX16822A/MAX16822B include UVLO with
500mV hysteresis. The internal MOSFET turns off when
Applications Information
Selecting R SENSE to Set LED Current
V IN falls below 5.5V to 6.0V.
DIM Input
The LED current is programmed with a current-sense
resistor connected between IN and CS. Use the equa-
tion below to calculate the value of this resistor:
LED dimming is achieved by applying a PWM signal at
I LED ( A )
DIM. A logic level below 0.6V at DIM forces the
MAX16822A/MAX16822B’s output low, thus turning off
the LED current. To turn the LED current on, the logic
R SENSE ( Ω ) =
2
1 ( V SNSHI + V SNSLO )( V )
level at DIM must be greater than 2.8V.
Thermal Shutdown
The MAX16822A/MAX16822B thermal-shutdown fea-
ture turns off the LX driver when the junction tempera-
ture exceeds +165°C. The LX driver turns back on
when the junction temperature drops 10°C below the
shutdown-temperature threshold.
Analog Dimming
The MAX16822A/MAX16822B offer an analog dimming
feature that reduces the output current when the volt-
age at TEMP_I is below the internal 2V threshold volt-
age. The MAX16822A/MAX16822B achieve analog
dimming by either an external DC voltage source con-
nected between TEMP_I and ground or by a voltage on
where V SNSHI is the sense voltage threshold high and
V SNSLO is sense voltage threshold low (see the
Electrical Characteristics table for values).
Current-Regulator Operation
The MAX16822A/MAX16822B regulate the LED current
using a comparator with hysteresis (see Figure 2). As
the current through the inductor ramps up and the volt-
age across the sense resistor reaches the upper
threshold, the internal MOSFET turns off. The internal
MOSFET turns on again when the inductor current
ramps down through the freewheeling diode until the
voltage across the sense resistor equals the lower
threshold. Use the following equation to determine the
operating frequency:
a resistor connected across TEMP_I and ground
induced by an internal current source of 25μA. When
the voltage at TEMP_I is below the internal 2V threshold
limit, the MAX16822A/MAX16822B reduce the LED cur-
f SW =
(V IN ? nV LED ) × nV LED × R SENSE
V IN × Δ V × L
(
)
( A ) = I
( A ) × ? 1 ? FB
? ? × V TFB _ ON A D ( V ) ?
I TF LED SLOPE ?
? V
rent. Use the following formula to set the analog dim-
ming current.
? ? 1 ? ?
? V
? ?
where V TFB_ON = 2V and FB SLOPE = 0.75 are obtained
from the Electrical Characteristics table and V AD is the
voltage at TEMP_I.
where n is the number of LEDs, V LED is the forward
voltage drop of 1 LED, and Δ V = (V SNSHI - V SNSLO ).
Inductor Selection
The MAX16822A/MAX16822B operate up to a switching
frequency of 2MHz. For space-sensitive applications,
the high switching frequency allows the size of the
inductor to be reduced. Use the following formula to
calculate an approximate inductor value and use the
closest standard value:
Thermal Foldback
The MAX16822A/MAX16822B also include a thermal-
foldback feature that reduces the output current when
the temperature of the LED string exceeds a specified
L ( approx .) =
(V IN ? nV LED ) × nV LED × R SENSE
V IN × Δ V × f S W
temperature point. These devices enter thermal-fold-
back mode when the voltage drop on the NTC thermis-
tor, thermally attached to the LEDs and electrically
connected between TEMP_I and ground, drops below
the internal 2V threshold limit.
For component selection, use the MAX16822A/B Design
Tool available at: www.maxim-ic.com/MAX16822-
software .
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相关代理商/技术参数
MAX16823ATE/V+
功能描述:LED照明驱动器 3Ch Linear HB w/Open LED Detection 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
MAX16823ATE/V+T
功能描述:LED照明驱动器 3Ch Linear HB w/Open LED Detection 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
MAX16823ATE+
功能描述:LED照明驱动器 3Ch Linear HB w/Open LED Detection 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
MAX16823ATE+T
功能描述:LED照明驱动器 3Ch Linear HB w/Open LED Detection 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
MAX16823AUE/V+
功能描述:LED照明驱动器 3Ch Linear HB w/Open LED Detection 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
MAX16823AUE/V+T
功能描述:LED照明驱动器 3Ch Linear HB w/Open LED Detection 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
MAX16823AUE+
功能描述:LED照明驱动器 3Ch Linear HB w/Open LED Detection 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
MAX16823AUE+T
功能描述:LED照明驱动器 3Ch Linear HB w/Open LED Detection 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