How to choose the right USB-C to HDMI cable?
I’ve encountered an issue when connecting my iPhone 15 Pro Max to an external monitor using a USB-C to HDMI cable. When using the Ugreen MM142 cable, thick black borders appeared around the image on my 1920×1080 monitor. However, when using another REAL-EL CHD-180 cable, this problem didn’t occur.
Why do different USB-C to HDMI cables behave differently when connecting an iPhone to a monitor?
I need to purchase about 5 such cables with braided fabric covering in the near future. How can I select a quality USB-C to HDMI cable to avoid the black border problem that occurred with the Ugreen cable?
Black Border Issues When Connecting iPhone 15 Pro Max to External Monitor via USB-C to HDMI Cable
The problem of black borders when connecting an iPhone 15 Pro Max to an external monitor via a USB-C to HDMI cable is typically related to differences in video transmission protocols and cable quality. Different cables behave differently due to the technical specifics of their implementation, support for various DisplayPort Alt Mode modes, and quality of components.
Contents
- Basic Technical Differences Between USB-C to HDMI Cables
- Why Black Borders Appear on Screen
- Key Cable Quality Factors
- iPhone 15 Pro Max Connection Specifics
- Recommendations for 5 Quality Cables
- Practical Solution for Your Situation
Basic Technical Differences Between USB-C to HDMI Cables
USB-C to HDMI cables differ significantly in their technical implementation, which directly affects their compatibility and performance:
Data transmission protocols:
- The USB-C interface uses DisplayPort Alt Mode for video signal transmission, not HDMI Alternate Mode, which is rarely implemented in consumer devices
- Cables can be active (with a conversion chip) or passive (simple contact conversion)
- iPhone 15 Pro Max supports DisplayPort 1.4 via USB-C, requiring a compatible cable
Speed characteristics:
- USB 3.1 Gen 2: up to 10 Gbit/s
- USB 3.2 Gen 2x2: up to 20 Gbit/s
- USB 4: up to 40 Gbit/s
Your case with Ugreen MM142 and REAL-EL CHD-180 demonstrates that even cables with the same purpose can have different internal electronics and video signal processing algorithms.
Why Black Borders Appear on Screen
Black borders (overscan/underscan) when connecting an iPhone to an external monitor occur for several reasons:
Display aspect ratio:
- iPhone 15 Pro Max has an aspect ratio of approximately 19.5:9
- Standard monitors most commonly use 16:9 or 16:10
- Differences in aspect ratios cause black bars at the edges
Incorrect signal processing:
- Some cheap cables don’t correctly process resolution and refresh rate
- Lack of proper scaling (image scaling)
- Issues with EDID (Extended Display Identification Data) exchange between devices
As explained in the Gechic research, the black border issue is similar to when the iPhone home screen doesn’t display in full screen.
Key Cable Quality Factors
When selecting a USB-C to HDMI cable for iPhone 15 Pro Max, pay attention to the following parameters:
Manufacturing materials
- Nylon braiding - ensures durability and wear protection
- Aluminum coating - improves heat dissipation and protects against interference
- Copper conductors - provide better conductivity
- Gold-plated contacts - increase connection reliability
Technical specifications
- DisplayPort Alt Mode support - essential for iPhone
- Resolution - minimum 4K@60Hz for modern devices
- Refresh rate - 60Hz or higher
- Active electronics - built-in conversion chip
Manufacturers
Quality cables from known brands (Anker, Ugreen, Cable Matters) typically have:
- Stable operation with various devices
- Proper EDID handling
- Correct image scaling
It’s particularly important to look for cables marked with “DisplayPort 1.4 support” and “4K@60Hz”.
iPhone 15 Pro Max Connection Specifics
iPhone 15 Pro Max has several specific requirements for USB-C to HDMI cables:
iPhone limitations:
- External display support only through DisplayPort Alt Mode
- Maximum resolution of 2560×1440 in some configurations
- Requires a quality USB 3.1 or better cable
Problem solutions:
- Use the official Apple USB-C Digital AV Multiport Adapter for maximum compatibility
- Check support for required resolution in iOS settings
- Experiment with different display modes (scaling, mirroring)
As mentioned in Apple Community discussions, some users find solutions through combinations of different adapters.
Recommendations for 5 Quality Cables
For purchasing 5 reliable USB-C to HDMI cables with fabric braiding, use the following criteria:
Verified models
-
Anker PowerExpand+ USB-C to HDMI
- 4K@60Hz support
- Aluminum casing + nylon braiding
- Active electronics with conversion chip
-
Ugreen USB Type C to HDMI (not MM142, but 4K models)
- Ensure DisplayPort Alt Mode support
- Double nylon braiding
- Aluminum shell
-
Cable Matters USB-C to HDMI
- Confirmed iPhone 15 compatibility
- Braided nylon cable
- HDR support
-
JSAUX USB-C to HDMI
- Verified user reviews
- Braided fabric design
- Aluminum alloy shell
-
Zeskit USB-C to HDMI
- High-speed transmission
- 10000+ bend fabric braiding
- Gold-plated connectors
Selection criteria
- Always check DisplayPort Alt Mode support
- Avoid overly cheap cables (< $10-15)
- Read reviews specifically for iPhone 15 Pro Max
- Confirm maximum resolution and refresh rate
- Prefer cables with active electronics
Practical Solution for Your Situation
Your situation with Ugreen MM142 and REAL-EL CHD-180 is typical for issues with video signal conversion quality:
Why REAL-EL worked better:
- Better DisplayPort to HDMI conversion chip
- Proper EDID handling
- Correct image scaling for aspect ratio
- Higher quality electronic components
Solution to current problem:
- Return to using REAL-EL CHD-180 as the primary solution
- Purchase additional cables based on the recommended models above
- For Ugreen MM142, try:
- Changing resolution in iPhone display settings
- Restarting devices
- Checking monitor drivers
Long-term solution:
Invest in quality cables from reputable manufacturers that guarantee:
- Stable operation with iPhone 15 Pro Max
- Correct display without black borders
- Durability of use
Sources
- iPhone 15 USB-C External Monitor Issues - Gechic
- Apple Community Discussion - iPhone 15 Pro Max HDMI Issues
- USB-C to HDMI Cable Guide - Anker
- USB-C vs HDMI Compatibility - VCELINK
- Choosing Quality USB-C Cables - Tataneu
- iPhone 15 External Display Support - 9to5Mac
- USB-C Technical Specifications - Wikipedia
- Best USB-C Video Cables - Wirecutter
Conclusion
Selecting the right USB-C to HDMI cable for iPhone 15 Pro Max requires attention to several key factors: DisplayPort Alt Mode support, component quality, cable type (active/passive), and display aspect ratio. Your experience with different cables shows that even within the same brand, there can be significant performance differences.
For purchasing 5 quality cables, it’s recommended to choose models from reputable manufacturers with active electronics, nylon braiding, and 4K@60Hz support. Always check user reviews specifically for iPhone 15 Pro Max and prefer cables with a return guarantee in case of problems.
Remember that the black border issue is often resolved not only by choosing the right cable but also by proper display settings in iOS. When problems arise, experiment with different operating modes and resolutions.