Maxim MAX22444－6快速低功耗四路数字电流隔离器解决方案

Maxim公司的MAX22444–MAX22446是增强的快速低功耗四路数字电流隔离器，采用Maxim公司的专有工艺技术，能在电路间以不同的功率传输数字信号，1.8V时1Mbps时每路的功率仅为0.74mW，能经受住5kV RMS电压60秒，最大数据速率25Mbps或200Mbps，主要用在隔离SPI接口，工业自动化现场总线通信，隔离RS-485/RS-422和CAN，以及电池管理和医疗系统。本文介绍了MAX22444–MAX22446主要优势和特性，框图和应用电路，以及评估板MAX22444/5FWEVKIT主要特性，电路图，材料清单和PCB设计图。

The MAX22444–MAX22446 are reinforced， fast， low-power 4-channel digital galvanic isolators using Maxim’s proprietary process technology. These devices transfer digital signals between circuits with different power domains， using as little as 0.74mW per channel at 1Mbps （1.8V supply）。 All of the devices in the family feature einforced isolation for a withstand voltage rating of 5kVRMSfor 60 seconds.

The MAX22444–MAX22446 family offers all possible unidirectional channel configurations to accommodate any 4-channel design， including SPI， RS-485， and digital I/O applications. Output enable for the A side of the MAX22445R/S/U/V is active-low， making them ideal for isolating a port on a shared SPI bus since the CS signal can directly enable the MISO signal on the isolator. All other output enables in the MAX22444-MAX22446 family are the traditional active-high.

All channels on the MAX22444–MAX22446M/N are always enabled， however， the default state of the outputs of these devices is selectable.Devices are available with a maximum data rate of either 25Mbps or 200Mbps， and with outputs that are either default-high or default-low. The default is the state the output assumes when the input is either not powered or is open-circuit. See the Ordering Informationand Product Selector Guide for suffixes associated with each option. Independent 1.71V to 5.5V supplies on each side of the isolator also make the devices suitable for use as level translators.

All of the devices in the MAX22444–MAX22446 family are available in a 16-pin wide-body SOIC package with 8mm of creepage and clearance. The package material has a minimum comparative tracking index （CTI） of 600V， which gives it a group 1 rating in creepage tables. All devices are rated for operation at ambient temperatures of -40℃ to +125℃。

MAX22444–MAX22446主要优势和特性：

Reinforced Galvanic Isolation for Fast Digital SignalsUp to 200Mbps Maximum Data Rate

Withstands 5kVRMS for 60s （VISO）

Continuously Withstands 1500VRMS （VIOWM）

Withstands ±10kV Surge Between GNDA and GNDB with 1.2/50μs waveform

High CMTI （50kV/μs， Typical）

Low Power Consumption0.74mW per Channel at 1Mbps with VDD = 1.8V

1.4mW per Channel at 1Mbps with VDD = 3.3V

3.2mW per Channel at 100Mbps with VDD = 1.8V

Options to Support a Broad Range of Applications2 Maximum Data Rates （200Mbps， 25Mbps）

3 Direction Configurations

Active-High or Active-Low Enable Inputs

2 Fixed Output Default States （High/Low） or Pin-Selectable （M/N Versions）

MAX22444–MAX22446应用：

Isolated SPI Interface

Fieldbus Communications for Industrial Automation

Isolated RS-485/RS-422， CAN

Battery Management

Medical Systems

Safety Regulatory Approvals （Pending）

UL According to UL1577

cUL According to CSA Bulletin 5A

VDE 0884-11 Reinforced Isolation

图1.MAX22444–MAX22445功能框图

图2.MAX22446功能框图

图3.MAX22444典型工作电路图

图4.MAX22445典型工作电路图

图5.MAX22446典型工作电路图

评估板MAX22444/5FWEVKIT

The MAX22444–MAX22446 evaluation kits （EV kits） provide a proven design to evaluate the MAX22444– MAX22446， reinforced， four-channel， galvanic digital isolators. Two types of evaluation boards are available to support different channel direction configurations， different ENA polarities and different output default settings of the MAX22444–MAX22446 family. The MAX22445FWEVKIT# is fully assembled and tested， and comes populated with the MAX22445FAWE+. The MAX2244XWEVKIT# is a generic board which has U1 unpopulated allowing the user to select a device from the MAX22444-MAX22446 family （Figure 2）。 Both evaluation boards support the wide-body 16-pin SOIC package type. See Table 1 for EV kit options.

The EV kits should be powered from two independent isolated power supplies with nominal output voltage in range from 1.71V to 5.5V. For evaluating the electrical parameters of the device without any isolation between the two sides， a single power supply can also be used.

评估板MAX22444/5FWEVKIT主要特性：

Broad Range of Data Transfer Rates （from DC to 200Mbps）

Four Unidirectional Channels with 3 Different Channel Direction Configurations

SMA Connectors for Easy Connection to External Equipment

Wide Power Supply Voltage Range from 1.71V to 5.5V

Guaranteed Up to 5kVRMS Isolation for 60s

-40℃ to +125℃ Temperature Range

Proven PCB Layout

图6.评估板MAX22445FWEVKIT外形图图7.评估板MAX2244XWEVKIT外形图

图8.评估板MAX22444/5FWEVKIT电路图

评估板MAX22444/5FWEVKIT材料清单：

图9.评估板MAX2244-6 EVKIT PCB设计图：左：顶层丝印;右：顶层

图10.评估板MAX2244-6 EVKIT PCB设计图：左：L2 GND;右：L3 PWR

图11.评估板MAX2244-6 EVKIT PCB设计图：底部