SLLSEY2E March 2017  – November 2017 ISOW7840 , ISOW7841 , ISOW7842 , ISOW7843 , ISOW7844

PRODUCTION DATA. 

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Description (continued)
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Power Ratings
    6. 7.6 Insulation Specifications
    7. 7.7 Safety-Related Certifications
    8. 7.8 Safety Limiting Values
    9. 7.9 Electrical Characteristics—5-V Input, 5-V Output
    10. 7.10Supply Current Characteristics—5-V Input, 5-V Output
    11. 7.11Electrical Characteristics—5-V Input, 3.3-V Output
    12. 7.12Supply Current Characteristics—5-V Input, 3.3-V Output
    13. 7.13Electrical Characteristics—3.3-V Input, 3.3-V Output
    14. 7.14Supply Current Characteristics—3.3-V Input, 3.3-V Output
    15. 7.15Switching Characteristics—5-V Input, 5-V Output
    16. 7.16Switching Characteristics—5-V Input, 3.3-V Output
    17. 7.17Switching Characteristics—3.3-V Input, 3.3-V Output
    18. 7.18Insulation Characteristics Curves
    19. 7.19Typical Characteristics
  8. Parameter Measurement Information
  9. Detailed Description
    1. 9.1Overview
    2. 9.2Functional Block Diagram
    3. 9.3Feature Description
      1. 9.3.1Electromagnetic Compatibility (EMC) Considerations
      2. 9.3.2Power-Up and Power-Down Behavior
      3. 9.3.3Current Limit, Thermal Overload Protection
    4. 9.4Device Functional Modes
      1. 9.4.1Device I/O Schematics
  10. 10Application and Implementation
    1. 10.1Application Information
    2. 10.2Typical Application
      1. 10.2.1Design Requirements
      2. 10.2.2Detailed Design Procedure
      3. 10.2.3Application Curve
  11. 11Power Supply Recommendations
  12. 12Layout
    1. 12.1Layout Guidelines
      1. 12.1.1PCB Material
    2. 12.2Layout Example
  13. 13Device and Documentation Support
    1. 13.1Device Support
      1. 13.1.1Development Support
    2. 13.2Documentation Support
      1. 13.2.1Related Documentation
    3. 13.3Related Links
    4. 13.4Receiving Notification of Documentation Updates
    5. 13.5Community Resources
    6. 13.6Trademarks
    7. 13.7Electrostatic Discharge Caution
    8. 13.8Glossary
  14. 14Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
  • DWE|16
Orderable Information

Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.

Application Information

The ISOW784x devices are high-performance, quad channel digital isolators with integrated DC-DC converter. Typically digital isolators require two power supplies isolated from each other to power up both sides of device. Due to the integrated DC-DC converter in ISOW784x, the isolated supply is generated inside the device that can be used to power isolated side of the device and peripherals on isolated side, thus saving board space. The ISOW784x devices use single-ended CMOS-logic switching technology. When designing with digital isolators, keep in mind that because of the single-ended design structure, digital isolators do not conform to any specific interface standard and are only intended for isolating single-ended CMOS or TTL digital signal lines. The isolator is typically placed between the data controller (that is Microcontroller or UART), and a data converter or a line transceiver, regardless of the interface type or standard.

ISOW784x devices are suitable for applications that have limited board space and desire more integration. These devices are also suitable for very high voltage applications, where power transformers meeting the required isolation specifications are bulky and expensive.

Typical Application

ISOW7840 ISOW7841 ISOW7842 ISOW7843 ISOW7844 TIDesignsLogo.gif

For step-by-step design procedure, circuit schematics, bill of materials, printed circuit board (PCB) files, simulation results, and test results, refer to TI Design TIDA-01333, Eight-Channel, Isolated, High-Voltage Analog Input Module With ISOW7841 Reference Design.

Figure 38 shows the typical schematic for SPI isolation.

ISOW7840 ISOW7841 ISOW7842 ISOW7843 ISOW7844 isow784x-typical-application-schematic.gif Figure 38. Isolated Power and SPI for ADC Sensing Application With ISOW7841

Design Requirements

To design with this device, use the parameters listed in Table 4.

Table 4. Design Parameters

PARAMETERVALUE
Input voltage3 V to 5.5 V
Decoupling capacitor between VCC and GND10.1 µF to 10 µF
Decoupling capacitor between VISO and GND20.1 µF to 10 µF

Because of very-high current flowing through the ISOW7841 VCC and VISO supplies, higher decoupling capacitors typically provide better noise and ripple performance. Although a 10-µF capacitor is adequate, higher decoupling capacitors (such as 47 µF) on both the VCC and VISO pins to the respective grounds are strongly recommended to achieve the best performance.

Detailed Design Procedure

The ISOW784x family of devices only requires external bypass capacitors to operate. These low-ESR ceramic bypass capacitors must be placed as close to the chip pads as possible.

ISOW7840 ISOW7841 ISOW7842 ISOW7843 ISOW7844 isow784x-typical-circuit-hookup.gif Figure 39. Typical ISOW7841 Circuit Hook-Up

The VCC power-supply input provides power to isolated data channels and to the isolated DC-DC converter. Use Equation 1 to calculate the total power budget on the primary side.

Equation 1. ICC = (VISO × IISO) / (η × VCC) + Iinpx

where

  • ICC is the total current required by the primary supply.
  • VISO is the isolated supply voltage.
  • IISO is the external load on the isolated supply voltage.
  • η is the efficiency.
  • VCC is the supply voltage.
  • Iinpx is the total current drawn for the isolated data channels and power converter when data channels are toggling at a specific data rate. This data is shown in the Electrical Characteristics—5-V Input, 5-V Output table.

Application Curve

ISOW7840 ISOW7841 ISOW7842 ISOW7843 ISOW7844 isow784x-soft-start-waveform.gif
VCC = 3.3 V IISO = 70 mA
Input current spike is because of charging the input supply decoupling capacitor
Figure 40. Soft-Start Waveform