1. What is an HSD Connector?
The HSD connector was developed by Rosenberger in the early 2000s to serve as a universal digital interface for in-vehicle high-speed data. Unlike FAKRA's single coaxial channel, HSD provides 4 pins in a star quad arrangement — two differential pairs — enabling it to carry both data and power in a single connector.
The connector features a full metal shield with 360° grounding, critical for the noisy EMC environment inside a vehicle. The secondary locking mechanism (similar to FAKRA's snap-on design) prevents accidental disconnection under vibration. HSD connectors are rated for -40°C to +105°C and are available in straight and right-angle PCB mount, inline cable-to-cable, and waterproof (IP67) variants.
The most common HSD application is LVDS camera links: Pair 1 carries the differential video signal (LVDS or FPD-Link), Pair 2 carries DC power (typically 5V or 12V) to the camera module. This eliminates the need for a separate power connector at the camera, simplifying the harness and reducing connector count.
2. HSD Star Quad Pinout Reference
The HSD connector uses a 4-pin layout in a square (star quad) configuration. Opposing pins form each differential pair:
| Pin | Position | Pair | Signal | Typical Function (Camera) | Wire Color (Standard) |
|---|---|---|---|---|---|
| 1 | Top-left | Pair 1 (+) — Pin 1 | LVDS+ (data positive) | Video data + | Green |
| 2 | Top-right | Pair 2 (+) — Pin 2 | Power / AUX+ | VCC (+5V or +12V) | Red |
| 3 | Bottom-left | Pair 2 (−) — Pin 3 | Power / AUX− | GND | Black |
| 4 | Bottom-right | Pair 1 (−) — Pin 4 | LVDS− (data negative) | Video data − | White |
HSD pinout — star quad arrangement with Pair 1 (Pins 1 & 4) for data and Pair 2 (Pins 2 & 3) for power
Key Electrical Parameters
| Parameter | Value |
|---|---|
| Differential impedance | 100 Ω ± 10% |
| Max data rate (per pair) | 1 Gbps (1000BASE-T1) or 3 Gbps (USB 3.0, limited) |
| Max current (power pair) | 3 A per pin (typical camera: < 500 mA) |
| Insertion loss @ 600 MHz | < 1.5 dB (connector only) |
| Crosstalk (pair-to-pair) | < -40 dB @ 600 MHz |
| Mating cycles | ≥ 25 (USCAR-2) |
3. HSD Color Codes: A, B, C, D, Z Variants
Like FAKRA, HSD uses color-coded mechanical keying to prevent mismating. However, HSD has only 5 standard codes compared to FAKRA's 14:
| Code | Color | Application | Notes |
|---|---|---|---|
| A | Black | Universal / LVDS camera | Most common variant. Used in general-purpose LVDS and USB 2.0. |
| B | White | USB 2.0 dedicated | Used when USB must be mechanically separated from camera links. |
| C | Blue | LVDS display / instrument cluster | Dedicated key for display LVDS to prevent mix-up with camera LVDS. |
| D | Bordeaux Violet | Ethernet (100BASE-T1 / 1000BASE-T1) | Legacy automotive Ethernet — being replaced by H-MTD. |
| Z | Water Blue | Universal waterproof (IP67) | Exterior camera applications. Same pinout as Code A, with seal. |
HSD color code variants — A (black) is the universal default for LVDS cameras
4. LVDS Signal Wiring on HSD
The most common HSD application is carrying LVDS (Low-Voltage Differential Signaling) from a camera module to an ECU. Here is the standard wiring scheme:
Pin Assignment for LVDS Camera
- Pins 1 & 4 (Pair 1): LVDS data pair. Pin 1 = LVDS+ (non-inverting), Pin 4 = LVDS− (inverting). This pair carries the video stream at 100 Ω differential.
- Pins 2 & 3 (Pair 2): Power pair. Pin 2 = VCC (+5V or +12V), Pin 3 = GND. In some designs, this pair carries a second data channel (e.g., camera control via I²C back-channel) superimposed on the power rails.
SerDes Compatibility
HSD is protocol-agnostic at the physical layer. It is commonly used with:
- FPD-Link III (TI DS90UB913/933/953): Most common. Carries up to 1.5 Gbps over a single differential pair with bidirectional control channel.
- GMSL (Maxim/Analog Devices MAX9271/96705): Competing SerDes, also compatible with HSD at the connector level.
- APIX3 (Inova Semiconductors): Used in some European OEMs for display links.
The HSD connector does not care which SerDes protocol is running — it only cares about the 100 Ω differential impedance and the frequency content of the signal. However, do not mix SerDes families on the same harness without verifying pin compatibility.
5. HSD Cable Construction: Differential Pairs and Shield
HSD cables use star quad construction — four conductors arranged in a precise square within a cylindrical shield. This is fundamentally different from standard twisted-pair cable:
- Conductor arrangement: Four wires in a square cross-section. Opposing wires (diagonally opposite) form each differential pair. E.g., top-left and bottom-right are Pair 1; top-right and bottom-left are Pair 2.
- Magnetic field cancellation: Because each pair's wires are diagonally opposite, their magnetic fields cancel in all directions simultaneously — superior to standard twisted pair which only cancels in one axis.
- Shielding: A copper braid (≥ 85% coverage) + aluminum foil provides dual-layer shielding. 360° termination at both connector ends is mandatory.
- Jacket: Typically XLPE or PVC for interior applications, ETFE or silicone for high-temperature engine bay applications.
6. HSD vs FAKRA: When to Use Each
| Parameter | HSD | FAKRA |
|---|---|---|
| Pin count | 4-pin (star quad) | 1 coaxial (center pin + shield) |
| Signal type | Differential (2 pairs) | Single-ended / coaxial |
| Power delivery | Some assemblies may support signal and power depending on pin assignment and customer drawing | No — RF signal only (phantom power < 100mA) |
| Max frequency | ~3 GHz (per pair) | 6 GHz |
| Best application | LVDS cameras (video + power in one connector) | RF antennas (GPS, AM/FM, cellular, Wi-Fi) |
| Ethernet use | 100BASE-T1, 1000BASE-T1 (legacy) | 100BASE-T1 only (declining) |
| Waterproof variant | Code Z (IP67) | Code Z (IP67/IP69K) |
Decision rule: If the application needs power + data in one connector (like a camera), use HSD. If it is a pure RF signal (antenna feed), use FAKRA. For new Ethernet designs, use H-MTD instead of either.
7. HSD Crimping and Termination Best Practices
HSD termination is more complex than FAKRA because of the 4-pin star quad arrangement. Each pin must be crimped individually, and the pin insertion order into the housing is critical:
- Strip the cable jacket to expose the shield braid. Do not nick the braid — a single broken strand reduces shield effectiveness by up to 20%.
- Fold back the braid over the jacket, then wrap with copper foil tape for 360° shield termination.
- Strip each conductor to the correct length (typically 2.5-3.0 mm). Use a thermal stripper for PTFE-insulated wires to avoid nicking the conductor.
- Crimp each pin using HSD-specific crimp dies. Verify crimp height with a micrometer — the acceptable range is specified in the connector manufacturer's application specification.
- Insert pins into housing in correct order: Pin 1 (top-left), Pin 2 (top-right), Pin 3 (bottom-left), Pin 4 (bottom-right). The housing is mechanically keyed so that pins can only be inserted in the correct orientation.
- Crimp the outer ferrule over the shield and jacket for strain relief. Verify pull force ≥ 80 N.
After termination, test each assembly for:
- Continuity: Pin 1 to Pin 1, etc. — no opens, no shorts between pins or to shield
- Differential impedance: 100 Ω ± 10% (TDR measurement at 35 ps rise time)
- Pair-to-pair crosstalk: < -40 dB at 600 MHz
- Shield continuity: < 10 mΩ between connector shells
Frequently Asked Questions
Q: What does HSD stand for?
A: HSD stands for High-Speed Data. It is a 4-pin automotive connector system developed by Rosenberger for LVDS camera links, USB 2.0, and automotive Ethernet, using star quad pin arrangement with integrated 360° shielding.
Q: Can HSD carry data and power simultaneously?
A: Yes, in some configurations. HSD's 4-wire star quad carries two differential signal pairs. In LVDS camera applications, one pair often carries the video signal while the other pair can carry power to the camera module (typically 5V or 12V). This is a common configuration for surround-view and ADAS camera systems. The exact pin assignment depends on the ECU and camera module design.
Q: What is Star Quad wiring?
A: Star Quad is a cable construction with four conductors in a square cross-section, opposing conductors forming each differential pair. This geometry provides superior magnetic field cancellation and crosstalk rejection compared to standard twisted pairs.
Q: What cable types work with HSD?
A: HSD requires star quad cable with 100 Ω differential impedance. Common types include Dacar 535 and custom star quad from LEONI, Champlain, and Coficab. Standard Cat5e/Cat6 twisted-pair cables are not compatible with HSD connectors.
Q: Is HSD obsolete with the arrival of H-MTD?
A: HSD is declining but remains active on existing vehicle platforms through 2030+. It is still specified for LVDS camera applications where power-over-signal-cable is needed. For new 1000BASE-T1 Ethernet designs, H-MTD is preferred.
Building an LVDS Camera or Display Link?
We manufacture HSD star quad cable assemblies — Code A/B/C/D/Z, straight and right-angle, with Dacar 535 cable and full TC9 compliance testing. Send your HSD part number and pin assignment.
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