How Individual Cable Testing Helps Uncover Underlying Cable Issues and Ensures Quality in Production

Creating safe and quality-made cables requires various evaluations and testing before landing in the hands of the consumer. To be certified, cables must go through design validation and compliance testing. But even after cable designs are approved, it is important that cables be tested for quality and safety standards during production. Learn the different ways cables are approved and tested and why individual quality control testing is just as crucial in catching underlying cable issues that might otherwise be overlooked in production.

Cable Standards Organizations

Cable standards organizations, including USB-IF, HDMI.org, VESA, and MFi, each have their own set of standards and oversee the development of cables looking to comply to specifications.

USB – USB-IF

USB-IF, or USB Implementors Forum, is the organization that oversees and administers the set of standards and specifications for all USB cables. The organization also administers the compliance testing procedures, which examines the cable’s design and functionality. Cables that pass compliance tests are able to use the USB certified logo on USB products.

HDMI – HDMI.org

HDMI.org is the organization that oversees and administers the set of standards and specifications for HDMI cables. Over the years, HDMI has released multiple new cable specifications and standards, each encompassing criterion for video quality and speed. HDMI.org administers cable compliance testing, where cables are examined against the cable specification for design, function, and performance. Cables that pass compliance tests are able to use the HDMI certified logo on HDMI products.

DisplayPort – VESA

VESA, or Video Electronics Standards Association, is the organization that established and continues to oversee the development of the DisplayPort interface. VESA has introduced multiple DP specifications over the years, with each new iteration offering higher bandwidth, faster speeds, and new capabilities. VESA administers cable compliance tests that evaluates the cables design and adherence to the cable specifications. Cables that pass compliance testing are able to use the VESA certified logo on DisplayPort products.

Apple Lightning – Apple MFi Program

The Apple MFi program, or Made for iPhone/iPad/iPod, is the official Apple licensing program for developers of hardware and software peripherals that work with Apple's iPod, iPad, and iPhone. This program administers cable design and performance testing for third party Apple Lightning cables to ensure they meet the required standards. If cables adhere to the MFi specifications, cable manufactures are able to use the MFi logo on Apple Lightning products.

Cable Design Validation and Compliance Testing

In order for cable manufacturers to have their cables approved and certified by the cable standard’s organization, they must undergo various evaluations including design validation and compliance testing.

Standards organizations perform design evaluations on cables in order to get an impression of the overall cable design including the connector type, type of wiring, and the cable length. Essentially, cable manufacturers are to submit a “blueprint” of their cable to have their designs validated. Additionally, cable manufacturers are required to submit a sample of the prototyped cable for review. If the design and cable pass, cable manufacturers are approved to move forward in production.

Cable compliance testing is also performed in order for cable manufacturers to acquire certification. Compliance testing consists of performing different tests on multiple facets of the cable including its pin and wiring configurations, power supply and consumption, and cable speed.

While these testing processes for USB, Apple Lightning, HDMI, and DisplayPort verify the cable design and performance, these tests are performed pre-production and do not take into account any variability and errors that occur during production.

Quality Control Testing Methods

Functional Cable Testing Method

Because compliance testing only goes so far in validating cable safety and quality, it is just as important for cable manufacturers to perform quality control testing on their cable during production. The functional testing method is commonly used in lab and production settings as a way to verify the cable is able to perform its function. This generally consists of manufacturers testing the cable with other devices to see if it works as intended, i.e. charging devices or transferring video/audio. While functional testing allows developers to determine utility, it does not verify that cable is up to standard and follows the cable specifications. For instance, if a cable is plugged into a phone and it charges, it appears to function, however, if the power negotiations and power supply and consumption levels are not within specification, this won’t be seen and can be dangerous for the consumer.

Statistical Process Control (SPC) vs Individual Quality Control (IQC)

Other cable testing methods include quality control testing, which can either be performed on a statistical or individual scale.

Statistical Process Control (SPC) is a testing method that allows manufacturers to statistically calculate the failure rate of their product. This is performed by taking a sample lot of the product, testing each lot, and calculating the likelihood that a certain proportion of the product is not up to safety and quality standards.

Individual Quality Control (IQC) is a testing method that allows manufactures to test each product coming off the production line. Rather than estimating the number of failures per lot, this allows manufactures to get a very accurate depiction of which cables meet the standards.

Both SPC and IQC have their pros and cons. While SPC is considered to be less expensive than IQC, the failure rate is only a statistical calculation, which means that there are opportunities for faulty cables to be shipped to customers. IQC, on the other hand, is considered to be a more expensive alternative that requires more resources to execute, but it allows cable manufacturers to be more confident that each cable going to consumers is safe and reliable, minimizing risk.

Why Individual Quality Control is Vital to Lab and Factory Testing

There are multiple ways for cable manufactures to ensure their cables are up to standard, all of which hold equal importance. Manufactures looking to comply with the cable specification and use the cable organization’s “certified” logo need to go through arduous compliance testing to be able to do so. While this approves the cable production process and design, it does not consider the variability that occurs during mass scale production.

Rather than just functional or SPC testing, individual quality control testing is necessary in cable manufacturing and should be performed in addition to design validation and compliance tests. Cable production is an involved process that requires human intervention due to its complexity of soldering pins and wires and assembling the different cable components. With human involvement, the opportunities for product variability rises steeply.

Testing each individual cable is important because cable manufacturers who have neglected to do so have experienced negative consequences that have been damaging to both consumers and the company’s brand.

Common Reasons for Underlying Cable Issues and Failures

Poor Wiring and Pin Alignment

Each cable connector, whether it be USB, HDMI, DisplayPort, or Apple Lightning, has multiple pins that perform specific functions including data signaling and power transfers. It’s important that cable connectors conform to the cable specification so they are interchangeable with other conforming cable connectors and ports with the same functions. If there is poor pin alignment and wiring, including shorts or opens, this can cause failed connections or damage to the devices.

Power Related Issues

Depending on the cable type, certain pins including GND and VBUS carry current across the cable through a resistor, resulting in outputs of DC resistance and voltage drop (IR drop). If the DC resistance and voltage drop measurements are either too high or too low, it can cause power related issues in the cable. The greater the resistance of the circuit, the higher the voltage drop. Low voltages to the powered equipment can cause improper operation to devices, waste power, and cause damage to the device. A high resistance connection may also produce higher levels of heat, which can potentially cause fires in certain environments. Verifying that these power measurements are within specification is important to avoid such dangerous situations.

Invalid E-Marker in USB Type-C Cables

An E-Marker, or electronic marker, is a chip within a USB Type-C cable that provides information about the cable’s parameters, including the data speed, current capacity, power delivery specifications, and other information on the Vendor ID and Product ID. For USB specifications that support higher power levels such as 5A, E-Markers are required so that connected devices can understand the cable’s capabilities. Well-constructed USB Type-C cables with E-Markers are expected to have the same capabilities as its advertised VDO data, so it is important to verify this the E-Marker is valid.

Poor Signal Quality

Poor signal quality prevents cables and devices from effectively communicating with each other. It can cause the cable to operate at slower speeds than supported, causing inefficient transfer of data, and can even attribute to signal drop-outs or no signal lock. Signal degradation can be a result of numerous occurrences, including poor wiring, electrical noise, crosstalk, or insertion loss. Ensuring an effective signal can be difficult since users cannot always see any deviations from the cable specifications with the naked eye. Having the ability to visualize the cable’s signal will help ensure data is being effectively transferred.

Apple Lightning Specific Issues

Apple Lightning cables are made specifically for Apple products and follow their own set of standards and specifications. These cables also have to follow certain lightning plug and power guidelines in order for the cables to meet MFi standards. Apple Lightning cables include additional ways to protect devices, but if not constructed properly, it may cause issues.

Quiescent Current Consumption

Quiescent current is described as the amount of current consumed by a circuit when it is not in use. A high quiescent current can be harmful to a battery within a device, as it can lessen its overall lifespan.

Over-Voltage Protection

Over-voltage protection helps prevent harmful level of voltages from being transferred to devices. Apple Lightning cables that don’t have adequate over-voltage protection may result in an overload of voltage to the device, which can leave the motherboard damaged or dead.

About the Advanced Cable Tester v2 Cable Testing Tool

The Advanced Cable Tester v2 is the next generation cable testing solution offered by Total Phase. Because it supports numerous cable types, it be configured as a USB cable tester, Apple Lightning cable tester, HDMI cable tester, and a DisplayPort cable tester. The Advanced Cable Tester v2 is able to test these cables against the cable specification in a matter of seconds and flag errors for easier debugging. It is an affordable cable testing solution that can test cables during cable development, as well as perform mass quality control testing in factory settings. It tests critical cable components for safety and quality including pin continuity, DC resistance, E-Marker validation, and signal integrity.

Pin Continuity Testing

The Pin Continuity test checks to see if pins from one connector are continuous with pins on the other connector. The report compares both ends of the plug to the expected plug values. If there are any deviations, a flag on the test will occur. This test helps detect shorts, opens, routings, and can help prevent dangerous occurrences like VBUS/GND reversals.

DC Resistance Testing

DC Resistance ("DCR") and IR Drop testing confirms that each power pin (VBUS and GND) is capable of carrying the required current to meet the applicable specification. For USB Type-C cables, each power pin is individually measured, then the cable as a whole is tested. If present, USB Type-C SBU and CC lines are also tested for DCR.

E-Marker Validation

The E-Marker test checks for the presence or absence of E-Marker chip(s) in a USB Type-C connector. The Advanced Cable Tester v2 supports Power Delivery Specification, Revision 2 (PD2) and Power Delivery Specification, Revision 3 (PD3).  If an E-Marker is found to be present, the tester will query the device to read all available Vendor Data Objects (VDOs). Properly constructed USB Type-C cables with E-Markers are expected to have the same VDO data. Any deviations from the expected values are flagged on the report.

Signal Integrity Testing

The Signal Integrity test measures the quality of the differentially paired wires through the cable and is configurable from 1030 MHz up to 12.8 GHz on up to 5 differential pairs. The signal integrity test performs a speed test of the cable and is accompanied by eye diagrams that provide a visualization of the quality of signal, including a mask to provide a reference for the HEO and VEO values. If the test achieves lock on the indicated differential pair, the eye diagram image will be displayed on the test. If no lock was achieved, a no-lock image will be displayed.

Signal integrity test for USB Type-C cable

Passing Signal Integrity test of USB Type-C to USB Type-C cable

 

Apple Lightning Specific Testing*

Apple Lightning testing ensures proper operation of the Lightning plug, including proper Lighting plug power-up, over-voltage, recovery, quiescent current consumption, and current limit testing per the Apple MFi specification. The Advanced Cable Tester v2 is the only tester available that can perform the tests required by the Apple Accessory Interface Specification (R31 and greater).

  • Lightning Plug - indicates what type of Lightning connector was found in the cable under test
  • Over-Voltage Protection - tests the cables over voltage protection
  • Quiescent Current - tests the current draw of the cable under different scenarios
  • Source Measurement Unit - tests the current limit of the cable in different scenarios with a source measurement unit (SMU)

*These test reports are only available to units that have been licensed for MFi members.

Advanced Cable Tester v2

Advanced Cable Tester v2

The Advanced Cable Tester v2 supports the following cable types:

  • USB Type-C to USB Type-C (Type-C 1.3, USB 3.2 and earlier specifications)
  • USB Type-C to USB Standard-A (USB 3.2 and earlier version specifications)
  • USB Type-C to USB Micro-B (USB 3.2 and earlier version specifications)
  • USB Type C to USB Standard-B (USB 3.2 and earlier version specifications)
  • USB Standard-A to USB Micro-B (USB 3.2 and earlier version specifications)
  • USB Standard-A to USB Standard-B (USB 3.2 and earlier version specifications)
  • Lightning (USB 2.0) to USB Standard-A
  • Lightning (USB 2.0) to USB Type-C
  • HDMI Type A to HDMI Type A (up to 12.8 Gbps per channel)
  • DisplayPort to DisplayPort (DisplayPort 2.0 and earlier version specifications)

Watch the Advanced Cable Tester v2 in action:

 

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