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| 型号： | MAX17149ETE+T |
| 厂商： | Maxim Integrated |
| 文件页数： | 13/21页 |
| 文件大小： | 0K |
| 描述： | IC LED DRVR 6CH STEP UP 16QFN |
| 标准包装： | 2,500 |
| 系列： | Quick-PWM™ |
| 拓扑： | 开路漏极，PWM，升压（升压） |
| 输出数： | 6 |
| 内部驱动器： | 是 |
| 类型 - 主要： | 车载，背光 |
| 类型 - 次要： | 白色 LED |
| 频率： | 可调节/可选择 |
| 电源电压： | 3 V ~ 26 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-WFQFN 裸露焊盘 |
| 供应商设备封装： | 16-TQFN（3x3） |
| 包装： | 带卷 (TR) |
| 工作温度： | -40°C ~ 85°C |
Low-Cost, 6-String WLED Drivers with
Quick-PWM Step-Up Converter
T OFF =
Detailed Description
The MAX17129/MAX17149 are high-efficiency drivers for
arrays of white LEDs. They contain a Quick-PWM step-up
controller, a 3.8V linear regulator, PWM dimming control
circuit, internal power MOSFET, and six regulated current
sources. Figure 2 shows the devices' functional diagram.
When enabled, the step-up controller boosts the output
voltage to provide sufficient headroom for the current
sources to regulate their respective string currents. The
devices feature adjustable pseudo-fixed frequency,
which allows trade-offs between external component
size and operating efficiency.
Both devices have a wide input voltage range, from 6V
to 26V; when IN and V CC are tied together, the range is
extended to the 3V to 5.5V range.
Both devices can implement two different brightness-
control methods: PWM dimming and hybid dimming.
When in direct PWM mode, the LED brightness is con-
trolled by the frequency and duty cycle of the square-
wave signal applied on the BRT pin. When in hybrid
dimming mode, the amplitude of LED current is adjusted
to 25% of the full-scale value, which is set by the resistor
from the ISET pin to GND.
The devices have multiple features to protect the control-
ler from faulty conditions. A separate feedback loop lim-
its the output voltage in all circumstances. The devices
monitor each FB_ voltage during the operation. If one or
more strings are open, the corresponding FB_ voltages
are pulled below 700mV (max) and the OVP output is
forced to increase over the overvoltage threshold; once
the open fault is detected, the respective current sources
are so disabled. When one or more LEDs are shorted
and the related FB_ voltage exceeds 8V, short fault is
detected and the respective current source is disabled.
When in LED open or short conditions, only the faulty
string is disabled while other strings can still operate
normally.
The devices also feature other kinds of fault protec-
tions, which are overcurrent, output overvoltage, and
thermal shutdown. The cycle-by-cycle current limit is to
provide consistent operation and soft-start protection;
when in overcurrent condition, the devices latch off after
a 0.8ms typical (at full brighteness) overcurrent fault
timer expires. An output overvoltage protection prevents
the devices from switching when the output exceeds a
threshold voltage; A thermal-shutdown circuit prevents
the devices from excessive power dissipation.
Quick-PWM Step-Up Controller
The step-up converter is a Quick-PWM type for good
performance. The Quick-PWM control architecture is
a pseudo-fixed-frequency, constant-off-time, current-
mode regulator. The control algorithm is simple: the
internal switch off-time is determined solely by a one-
shot whose period is inversely proportional to output volt-
age, and directly proportional to input voltage. Figure 4
shows the functional diagram with Quick-PWM control
architecture. The off-time one-shot triggers when the
error comparator goes low, the inductor current is below
the current-limit threshold, and the minimum on-time
one-shot times out.
Once the step-up starts up, the output voltage is regu-
lated by selecting the minimum FB voltage between the
detected active current-balancer outputs and compar-
ing it to the OVP divider. The soft-start mechanism is
inserted to provide a controlled current profile during
step-up startup phases.
Off-Time One-Shot
The Quick-PWM core contains a fast, low-jitter, adjust-
able one-shot that sets the internal MOSFETs off-time.
The one-shot varies the off-time in response to the input
and feedback voltages. The internal switch off-time is
inversely proportional to the output voltage (V OVP ), and
proportional to the input voltage (V IN ):
V IN
V OVP × K
where the switching period (K) is set by the FSEL pin.
This algorithm results in a nearly constant switching
frequency and balanced inductor currents despite the
lack of a fixed-frequency clock generator. The benefits
of a near-constant switching frequency are two-fold: first,
the frequency can be selected to avoid noise-sensitive
regions; second, the inductor ripple-current operating
point remains relatively constant, resulting in easy design
methodology and predictable output-voltage ripple. The
off-time one-shots have good accuracy at the operating
points specified in the Electrical Characteristics table.
Off-times translate only roughly to switching frequencies.
The off-times guaranteed in the Electrical Characteristics
table are influenced by internal switching delays. Resistive
losses, including the inductor, internal MOSFET, the for-
ward voltage of the output diode, output capacitor ESR,
and PCB copper losses in the output and ground tend to
raise the switching frequency at higher output currents.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX1714AEEP | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1714AEEP+ | 功能描述:电流型 PWM 控制器 Step-Down Controller for Notebook RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1714AEEP+T | 功能描述:电流型 PWM 控制器 Step-Down Controller for Notebook RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1714AEEP-T | 功能描述:电流型 PWM 控制器 RoHS:否 制造商:Texas Instruments 开关频率:27 KHz 上升时间: 下降时间: 工作电源电压:6 V to 15 V 工作电源电流:1.5 mA 输出端数量:1 最大工作温度:+ 105 C 安装风格:SMD/SMT 封装 / 箱体:TSSOP-14 |
| MAX1714AEEP-TG068 | 制造商:Rochester Electronics LLC 功能描述: 制造商:Maxim Integrated Products 功能描述: |
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