IEEE 802.3af/at-Compliant, Powered Device Interface
Controller with Integrated Power MOSFET
8 ______________________________________________________________________________________
Typical Operating Circuit
Detailed Description
Operating Modes
Depending on the input voltage (V
IN
= V
DD
- V
SS
), the
MAX5972A operates in four different modes: PD detec-
tion, PD classification, mark event, and PD power. The
device enters PD detection mode when the input voltage
is between 1.4V and 10.1V. The device enters PD clas-
sification mode when the input voltage is between 12.6V
and 20V. The device enters PD power mode once the
input voltage exceeds V
ON
.
Detection Mode (1.4V d V
IN
d 10.1V)
In detection mode, the power source equipment (PSE)
applies two voltages on V
IN
in the range of 1.4V to 10.1V
(1V step minimum) and then records the current measure-
ments at the two points. The PSE then computes DV/DI
to ensure the presence of the 24.9k?signature resistor.
Connect the signature resistor (R
DET
) from V
DD
to DET for
proper signature detection. The MAX5972A pulls DET low
in detection mode. DET goes high impedance when the
input voltage exceeds 12.5V. In detection mode, most of
the MAX5972A internal circuitry is off and the offset cur-
rent is less than 10礎.
If the voltage applied to the PD is reversed, install pro-
tection diodes at the input terminal to prevent internal
damage to the MAX5972A (see the Typical Application
Circuit). Since the PSE uses a slope technique (DV/DI) to
calculate the signature resistance, the DC offset due to
the protection diodes is subtracted and does not affect
the detection process.
Classification Mode (12.6V d V
IN
d 20V)
In the classification mode, the PSE classifies the PD
based on the power consumption required by the PD. This
allows the PSE to efficiently manage power distribution.
Class 0 to 5 is defined as shown in Table 1. (The IEEE
802.3af/at standard defines only Class 0 to 4 and Class 5
for any special requirement.) An external resistor (R
CLS
)
connected from CLS to V
SS
sets the classification current.
2-EVENT
CLASSIFICATION
DETECTION
-54V
MAX5972A
V
DD
RTN
WAD
PG
2EC/WAD
2EC
24V/48V
BATTERY
1.5mA
68nF
RJ-45
AND
BRIDGE
RECTIFIER
GND
SMAJ58A
R
DET
24.9kI
R
CLS
V
SS
DET
CLS
ENABLE
DC-DC
CONVERTER
IN+
IN-
GND
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相关代理商/技术参数
MAX5972AEVKIT
制造商:Maxim Integrated Products 功能描述:IEEE 802.3AF/AT-COMPLIANT POWERED DEVICE INTERFACE CONTROLLE - Boxed Product (Development Kits)
MAX5972BETE+
功能描述:热插拔功率分布 IEEE 802.3af/at PDIC Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube
MAX5972BETE+T
功能描述:热插拔功率分布 IEEE 802.3af/at PDIC Controller RoHS:否 制造商:Texas Instruments 产品:Controllers & Switches 电流限制: 电源电压-最大:7 V 电源电压-最小:- 0.3 V 工作温度范围: 功率耗散: 安装风格:SMD/SMT 封装 / 箱体:MSOP-8 封装:Tube
MAX5973BETL+
功能描述:监控电路 Phase Redundancy Power Supervisor RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel
MAX5973BETL+T
功能描述:监控电路 Phase Redundancy Power Supervisor RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel
MAX5973ETL+
功能描述:监控电路 Phase Redundancy Power Supervisor RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel
MAX5973ETL+T
功能描述:监控电路 Phase Redundancy Power Supervisor RoHS:否 制造商:STMicroelectronics 监测电压数: 监测电压: 欠电压阈值: 过电压阈值: 输出类型:Active Low, Open Drain 人工复位:Resettable 监视器:No Watchdog 电池备用开关:No Backup 上电复位延迟（典型值）:10 s 电源电压-最大:5.5 V 最大工作温度:+ 85 C 安装风格:SMD/SMT 封装 / 箱体:UDFN-6 封装:Reel
MAX5974AETE+
功能描述:电流型 PWM 控制器 Current-Mode PWM Controller 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
