ISO7641FMDWR IC

Technical Specifications of ISO7641FMDWR

Datasheet	ISO7641FMDWR datasheet
Category	Isolators
Family	Digital Isolators
Manufacturer	Texas Instruments
Series	–
Packaging	Tape & Reel (TR)
Part Status	Active
Technology	Capacitive Coupling
Type	General Purpose
Isolated Power	No
Number of Channels	4
Inputs – Side 1/Side 2	3/1
Channel Type	Unidirectional
Voltage – Isolation	4243Vrms
Common Mode Transient Immunity (Min)	25kV/μs
Data Rate	150Mbps
Propagation Delay tpLH / tpHL (Max)	10.5ns, 10.5ns
Pulse Width Distortion (Max)	2ns
Rise / Fall Time (Typ)	1.6ns, 1ns
Voltage – Supply	2.7 V ~ 5.5 V
Operating Temperature	-40°C ~ 125°C
Package / Case	16-SOIC (0.295″, 7.50mm Width)
Supplier Device Package	16-SOIC

ISO7641FMDWR Description

According to UL and VDE, the ISO7640FM and ISO7641FM can provide galvanic isolation of up to 6 KVPK for 1 minute. Moreover, these devices have received certification for up to 5 KVRMS. In accordance with the standards EN/UL/CSA 60950-1 and 61010-1 for end equipment, reinforced isolation is provided at a working voltage of 400 VRMS. The ISO7640F and the ISO7641F are examples of isolators with four channels; however, the ISO7640F has four forward-direction channels, while the ISO7641F has three forward-direction channels and one reverse-direction channel. A fail-safe condition is indicated by the suffix F, which signifies that the output will default to the Low state. High-speed isolators with fast propagation delays are known as M-Grade devices. These devices are capable of data rates of up to 150 Mbps.

Each isolation channel is equipped with a logic input and output buffer partitioned off by an insulation barrier made of silicon dioxide (SiO2). When used in conjunction with an isolated power supply, these devices prevent noise currents on a data bus or other circuits from entering the local ground, which would interfere with or damage sensitive equipment and pose a safety risk. The devices have TTL input thresholds and can function from sources ranging from 2.7 V to 5 V. When fed from 3.3-V or 2.7-V supplies, all inputs can tolerate up to 5-V voltage.

ISO7641FMDWR Features

• 150 Mbps for signaling.
• Low propagation latency: typically, 7 ns.
• Fail-Safe Mode output defaults to Low-State.
• Broad Temperature Range: -40 to 125 degrees Celsius.
• 50-KV/µs Typical Transient Immunity
• SiO2 Isolation Barrier for Extended Life.
• Operates at Supply and Logic Levels of 2.7, 3.3, and 5 Volts.

ISO7641FMDWR Detailed Description

The device’s I/O channel consists of two separate data channels, one with a bandwidth of 100 kbps to 150 Mbps (known as the high-frequency channel, or HF) and the other with a bandwidth of 100 kbps to DC (known as the low-frequency channel, or LF). These are both considered to be input/output channels for the device. Theoretically, an inverter gate at the input will transform a single-ended input signal into a differential signal before sending it across the HF channel. Transients can be isolated and studied by initially applying the capacitor-resistor networks described below to the signal. Two comparators take these spikes and transform them into differential pulses. The outputs of the comparator feed the inputs of the output multiplexer through a NOR-gate flip-flop.

Decision logic (DCL) circuits are placed at the flip-driving flop’s output and measure the intervals between signal transients. When the delay between two subsequent transients exceeds a threshold, the DCL tells the output multiplexer to switch from the high-frequency to the low-frequency channel. This happens whenever a low-frequency signal is being processed. To overcome the capacitive barrier posed by low-frequency input signals without resorting to impractically huge values for the internal capacitors, a pulse-width modulator (PWM) is used in conjunction with the carrier frequency of an internal oscillator. That’s because the internal capacitors must take on unreasonably huge values when fed low-frequency input signals. A low-pass filter (LPF) is used in the modulation process to isolate the information from the high-frequency carrier before it is delivered to the output multiplexer.

Application Information

ISO764x uses TTL (transistor-transistor logic) switching technology, which is single-ended. Its power sources, VCC1 and VCC2, have a voltage range of 3 to 5.5 volts. In this range is where its power comes from. While working with digital isolators, remember that they are only designed to work with single-ended CMOS or TTL digital signal lines and do not adhere to any established interface standards. This is due to the fact that digital isolators can only have one end linked to a signal line due to their design. Whatever the interface type or standard, an isolator is often placed between the data controller (the C or UART) and the data converter or line transceiver. This placement is true for all interface varieties.

Design Requirements

To function, the ISO764x device needs only two external bypass capacitors, in contrast to optocouplers, which need additional components external to the device in order to increase performance, provide bias, or limit current.

Power Supply Recommendations

It is advised that a bypass capacitor of 0.1 microfarads be placed at the device’s input and output supply pins. This will ensure the device operates reliably regardless of the data rate or supply voltage (VCC1 and VCC2). It is important to position the capacitors so that they are in close proximity to the supply pins. If an application only has access to a single power source for the primary side, isolated power can still be created for the secondary side with the assistance of a transformer driver, such as the SN6501 manufactured by Texas Instruments. Recommendations on the power supply design and transformer selection are included in the SN6501 data sheet, which can be consulted for such applications (SLLSEA0).

Layout

● Layout Guidelines

For a PCB design to have a low EMI level, the board must have a minimum of four layers. Stacking layers should be done in the following order (from top to bottom): ground plane, power plane, high-speed signal layer, and low-frequency signal layer.

By routing the high-speed traces on the top layer, it is possible to avoid the usage of vias (and the introduction of their inductances), It, in turn, allows for neat connections between the isolator and the data link’s transmitter and reception circuits.

• Establishing controlled impedance for transmission line interconnects and providing an excellent channel with low inductance for the flow of return current can be accomplished by positioning a solid ground plane immediately adjacent to the high-speed signal layer.
• When the power plane is positioned adjacent to the ground plane, an extra high-frequency bypass capacitance of around 100 pF/in2 is produced.
• It is possible to provide additional flexibility by routing the slower speed control signals on the bottom layer. This is because signal links typically have a margin that allows them to accept discontinuities such as vias.

In the event that an extra supply voltage plane or signal layer is required, a second power and ground plane system should be added to the stack to maintain its symmetrical nature. This ensures that the stack does not distort in any way and makes it mechanically stable. Also, each power system’s power plane and the ground plane can be brought closer to one another, resulting in a large increase in the high-frequency bypass capacitance.

Conclusion

In conclusion, the ISO7641FMDWR is a highly capable isolator device that provides reinforced isolation and has received certification for up to 5 KVRMS. With its SiO2 isolation barrier, the device can prevent noise currents from interfering with or damaging sensitive equipment and pose a safety risk. The device operates at supply and logic levels of 2.7, 3.3, and 5 volts and typically has a low propagation latency of 7 ns.

The ISO7641FMDWR suits various applications, from data converters to line transceivers. With only two external bypass capacitors required, it offers a simpler design and greater reliability than optocouplers. The power supply recommendations include a bypass capacitor of 0.1 microfarads at the input and output supply pins. The device can be used with isolated power supplies created with the help of a transformer driver. The ISO7641FMDWR is an excellent choice for designers looking for a high-performance isolator device.

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