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| 型号： | MAX5986AETE+ |
| 厂商： | Maxim Integrated |
| 文件页数： | 15/23页 |
| 文件大小： | 843K |
| 描述： | IC POE SWITCH PSE 16TQFN |
| 标准包装： | 60 |
| 类型： | 以太网供电控制器 PD 开关（PoE） |
| 应用： | 供电设备（PSE） |
| 内部开关： | 是 |
| 电流限制： | 201mA |
| 电源电压： | 8.7 V ~ 60 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-WQFN 裸露焊盘 |
| 供应商设备封装： | 16-TQFN-EP（5x5） |
| 包装： | 管件 |
MAX5986AMAX5986C/MAX5987A
IEEE 802.3af-Compliant, High-Efficiency, Class 1/
Class 2, PDs with Integrated DC-DC Converter
15
Maxim Integrated
Frequency Foldback Protection for
High-Efficiency Light-Load Operation
The devices enter frequency foldback mode when eight
consecutive inductor current zero-crossings occur. The
switching frequency is 275kHz, 214kHz, or 430kHz under
loads large enough that the inductor current does not
cross zero. In frequency foldback mode, the switching
frequency is reduced to 137.5kHz, 107kHz, or 215kHz to
increase power conversion efficiency. The device returns
to normal mode when the inductor current does not cross
zero for eight consecutive switching periods. Frequency
foldback mode is forced during startup until 50% of the
soft-start is completed.
Hiccup Mode
The devices include a hiccup protection feature. When
hiccup protection is triggered, the devices turn off the
high-side and turn on the low-side MOSFET until the
inductor current reaches the valley current limit. The
control logic waits 120ms until attempting a new soft-
start sequence. Hiccup mode is triggered if the current
in the high-side MOSFET exceeds the runaway current-
limit threshold, both during soft-start and during normal
operating mode. Hiccup mode can also be triggered in
normal operating mode in the case of an output under-
voltage event. This happens if the regulated feedback
voltage drops below 60% (typ).
RESET Output (MAX5987A)
The MAX5987A features an open-drain RESET output
that indicates if either the LDO or the switching regula-
tor drop out of regulation. The RESET output goes low if
either regulator drops below 92% of its regulated feed-
back value. RESET goes high impedance 100祍 after
both regulators are above 95% of their value.
Maintain Power Signature (MPS)
The MAX5986B/MAX5986C/MAX5987A feature the MPS
to comply to the IEEE 802.3af standard. They are able to
maintain a minimum current (10mA) of the port to avoid
the power disconnection from the PSE. The MAX5986B/
MAX5986C/MAX5987A enter the MPS when the port
current is lower than 14mA and also exit the MPS mode
when the port current is geater than 40mA. The feature
is enabled by connecting the MPS pin to VDRV, or dis-
agbled by connecting the MPS pin to GND.
Applications Information
Operation with Wall Adapter
For applications where an auxiliary power source such
as a wall power adapter is used to power the PD, the
devices feature wall power adapter detection. The device
gives priority to the WAD supply over V
DD
supply, and
smoothly switches the power supply to WAD when it is
detected. The wall power adapter is connected from
WAD to PGND. The devices detect the wall power adapt-
er when the voltage from WAD to PGND is greater than
8.8V. When a wall power adapter is detected, the internal
isolation MOSFET is turned off, classification current is
disabled and the device draws power from the auxiliary
power source through V
CC
. Connect the auxiliary power
source to WAD, connect a diode from WAD to V
CC
. See
the typical application circuit in Figure 2.
Adjusting LDO Output Voltage (MAX5987A)
An uncommitted LDO regulator is available to provide
a supply voltage to external circuits. A preset voltage
of 3.3V is set by connecting LDO_FB directly to VDRV.
For different output voltages connect a resistor divider
from LDO_OUT and LDO_FB to GND. The total feedback
resistance should be in the range of 100k? The maxi-
mum output current is 85mA and thermal considerations
must be taken to prevent triggering thermal shutdown.
The LDO regulator can be powered by VOUT, a differ-
ent power supply, or grounded when not used. The LDO
is enabled once the buck converter has reached the
regulation voltage. The LDO is disabled when the buck
converter is turned off or not regulating.
Adjusting Buck Converter Output Voltage
The buck converter output voltage is set by changing
the feedback resistor-divider ratio. The output voltage
can be set from 3.0V to 5.6V (MAX5986A/MAX5987A) or
5.4V to 14V (MAX5986B/MAX5986C). The FB voltage is
regulated to 1.225V. Keep the trace from the FB pin to
the center of the resistive divider short, and keep the total
feedback resistance around 100k?
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX5986AETE+ | 功能描述:直流/直流开关转换器 IEEE802.3 af PD w/ DC/DC Conv 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 |
| MAX5986AETE+T | 功能描述:直流/直流开关转换器 IEEE802.3 af PD w/ DC/DC Conv 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 |
| MAX5986BETE+ | 功能描述:以太网 IC IEEE802.3 AF HI EFFICIENCY PD RoHS:否 制造商:Micrel 产品:Ethernet Switches 收发器数量:2 数据速率:10 Mb/s, 100 Mb/s 电源电压-最大:1.25 V, 3.45 V 电源电压-最小:1.15 V, 3.15 V 最大工作温度:+ 85 C 封装 / 箱体:QFN-64 封装:Tray |
| MAX5986BETE+T | 功能描述:PMIC 解决方案 IEEE802.3 AF HI EFFICIENCY PD RoHS:否 制造商:Texas Instruments 安装风格:SMD/SMT 封装 / 箱体:QFN-24 封装:Reel |
| MAX5986EVKIT# | 功能描述:电源管理IC开发工具 MAX5986 Eval Kit RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
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