Can a Tab-Up RJ45 Jack Replace a Tab-Down One? Latch Orientation, Mirrored Pinouts and LED Position Checks | VOOHU
Can a Tab-Up RJ45 Jack Replace a Tab-Down One? Latch Orientation, Mirrored Pinouts and LED Position Checks | VOOHU
It happens during board revisions and shortages all the time: the tab-up RJ45 jack on the BOM is out of stock, and a tab-down part is available. Same data rate, same integrated magnetics, same LED colors, and the body looks about the same size. So someone solders it onto the existing footprint to see what happens. The LEDs stay dark, the link never comes up, or the plug will not even go through the panel cutout.
Many engineers treat latch orientation as a purely mechanical detail, something that only changes which way you press the plug clip. In practice, flipping the tab also changes the contact order, the PCB pin pattern, the LED left/right position and the panel opening. This article uses the 774 part numbers in the VOOHU RJ45 selection table to show how many tab-up and tab-down options exist, which combinations have almost no tab-down parts, and what to check before you change orientation.
1. Short answer: tab-up and tab-down jacks are not interchangeable
The tab is the slot in the jack that receives the plug latch. On a 90° right-angle jack, a slot on the side away from the PCB is Tab Up, and a slot next to the PCB is Tab Down. The difference is equivalent to rotating the whole jack 180° around the insertion axis. Viewed from the front, contact 1 moves to the opposite side, and the PCB pin pattern changes with it.
So even when two parts share the same data rate, magnetics circuit, LED colors and mounting style, a different tab orientation means a different footprint. Draw a new PCB footprint and re-check the panel cutout. Never reuse the old pads.
180° vertical jacks are a separate case. The plug enters from above the board, so up or down relative to the PCB has no real meaning. Of the 118 vertical parts in the selection table, 115 are marked Up, 2 are blank and only SYT52F11880011101 is marked Down. For vertical jacks, read the latch direction from the drawing instead of filtering by this field.
2. Why it fails: the contact order is mirrored
Try a thought experiment with a plain jack without magnetics. Keep the PCB pads, but swap a tab-up jack for a tab-down one. The pad that used to reach contact 1 now reaches contact 8, pad 2 reaches contact 7, and so on. The whole row is reversed:
| Original pins | Land on | Pair effect | Result |
|---|---|---|---|
| 1, 2 | 8, 7 | Pair A → pair D | The 100BASE-TX transmit pair lands on 7-8, which Fast Ethernet does not use; no link |
| 3, 6 | 6, 3 | Pair B, polarity reversed | Most PHYs correct polarity automatically |
| 4, 5 | 5, 4 | Pair C, polarity reversed | Also correctable |
| 7, 8 | 2, 1 | Pair D → pair A | Gigabit Auto-MDIX swaps A↔B and C↔D only; it cannot fix A↔D |
Here is the counterintuitive part. Many engineers assume that modern PHYs with Auto-MDIX will sort out any pair mix-up. Auto-MDIX only handles crossover-style swaps (A↔B, C↔D). A mirrored jack produces an A↔D swap, which the PHY cannot recover. A Fast Ethernet port will not link at all, and a Gigabit port usually fails to negotiate.
Jacks with integrated magnetics (MagJacks) are more complicated. The pins on the board are the PHY-side pins of the internal transformer, and their layout depends on internal routing rather than a simple mirror. For example, SYT111Q066AA2A1D (Tab Down) and SYT211Q066CD2A4D (Tab Up) both carry the Q066 code, both are Gigabit, through-hole, G/Y LEDs and shield tabs. The selection fields match except for the tab. You still have to compare the two drawings pin by pin for TD±, center taps, LEDs and shield pins before assuming a shared footprint.
3. LED positions and pins move too
The LED field in the selection table (G/Y, Y/G and so on) gives the left and right LED colors as seen from the front of the jack. Flip the tab and the LEDs move relative to the latch. A panel legend that reads green on the left and yellow on the right can end up wrong, and the LED height may change too, so field staff misread port status.
The LED pins move as well. If the old footprint is kept, the LED anode and cathode end up reversed. The LED is fine but reverse-biased, so it stays dark and the jack gets blamed. Among the 85 single-port, integrated-magnetics, tab-down parts, 46 are G/Y, 9 are Y/G and 18 have no LEDs. Matching the color code is not enough; confirm each LED's anode and cathode pins on the drawing.
4. What the selection table shows: far fewer tab-down parts
Counts from the VOOHU RJ45 selection table (774 parts, retrieved 7 October 2026): 431 Tab Up, 204 Tab Down, 136 Up/Down (stacked) and 3 unmarked. Broken down further, tab-down parts are clearly scarce in several common combinations:
| Combination | Tab Up | Tab Down | Note |
|---|---|---|---|
| Single port, integrated magnetics (all) | 193 | 85 | Tab-down is about 44% of tab-up |
| Single port, magnetics, SMT | 29 | 2 | Both tab-down parts are 10/100M without LEDs |
| Single port, magnetics, PoE | 27 | 10 | Tab-down PoE tops out at 720 mA |
| Single port, magnetics, 10G | 13 | 6 | All tab-down 10G parts are through-hole |
| RJ45 + USB combo jacks | 32 | 0 | Every combo jack is tab-up |
Two points stand out:
First, the table has only two SMT, integrated-magnetics, tab-down jacks: SYT111B002IWA7S and SYT111B002GWA7S. Both are 10/100M with no LEDs; the first has no shield tabs, the second does. For Gigabit SMT you are essentially limited to tab-up parts such as SYT211Q106AB2A7CBS057. If integrated magnetics are not required, a discrete transformer plus an SMT tab-down offset jack such as SYTCB681188GWA6SB1075 is another route.
Second, high-current PoE parts are almost all tab-up. Single-port tab-down PoE parts stop at 720 mA; SYT111Q334AB2A2DP057, for example, is rated 600 mA. For 1000 mA and above, look at tab-up parts such as SYT411F570DF5A2DP359 (2.5G, 1000 mA) and SYT4A11Q855HWA10DPB1359 (10G, 1.5 A). If the mechanical design has already fixed a tab-down jack and the product needs PoE++, review the plan with the hardware team early.
5. Stacked jacks give you no choice: top port up, bottom port down
Stacked jacks from 2×1 to 2×8 account for 136 parts in the table, and all but one blank entry are marked Up/Down. The top row latches up and the bottom row latches down, back to back. This is set by the stacked construction; there is no all-up version.
That creates an easy-to-miss issue: inside one part, the top and bottom ports already have mirrored contact orders. When drawing the schematic and routing, do not copy and paste the TX/RX pairs and LED pins from one port to the other; connect each port from its own drawing. Typical parts include the Gigabit 2×1 SYT21Q085DA1A2D057, the 10/100M 2×1 SYT21B002DB2A5D068 and the 10G, 1000 mA PoE 2×6 SYT26Q766HWA3DPA1359.
6. Can the part number tell you the orientation?
It works for a first screen, but not as a substitute for the datasheet. The selection table shows these patterns in the VOOHU SYT family:
| Prefix | Tab field in the table | Exceptions |
|---|---|---|
| SYT1 | 125 of 130 are Tab Down | 5 SYT1511 low-profile/offset parts are Up, e.g. SYT1511Q184CB2W4CBD057 |
| SYT2 | Single-row parts all Up; stacked parts Up/Down | None |
| SYT3, SYT4 | Mostly Up | 2 SYT3 parts are Down |
| SYT5 | 76 Up and 55 Down among 90° parts, plus 106 vertical parts | Prefix alone is not enough |
So SYT111, SYT112 and SYT114 prefixes very likely mean tab-down single, dual and quad ports. SYT5 parts come in both orientations, so always check the Tab field and confirm on the drawing.
7. Re-check the panel cutout and mechanical clearance
With a tab-down jack, the finger that presses the latch has to reach between the plug and the PCB. If the lower edge of the panel opening is close to the board, or the jack is a sink-mount type, or the chassis floor has a flange, the user cannot reach the latch and the cable will not come out. With a tab-up jack, leave room above the opening; watch 1U chassis and designs with a heat sink right above the port.
Changing orientation also changes the cutout shape: the latch slot, LED light openings and shield springs all swap top and bottom. The sheet-metal panel, front overlay and legends need to be redone from the new drawing. For parts with EMI fingers, confirm the fingers still press on a conductive panel surface after the change.
8. If you must change orientation: a four-step check
Step 1: Decide the mechanics first. Agree on the panel opening, latch clearance and LED viewing direction with the mechanical engineer, then choose tab-up or tab-down. Do not change it after the PCB is finished.
Step 2: Filter on all the conditions together. In the selection table, lock Tab, port count, data rate, PoE current, SMT or through-hole and LED colors at the same time. If a tab-down SMT Gigabit or a tab-down high-current PoE part does not come up, adjust the mechanics or switch to discrete magnetics early.
Step 3: Redraw the footprint. Build the footprint from the new part's drawing and check TD±, center taps, LED anodes/cathodes and shield pins one by one. For stacked jacks, check the top and bottom ports separately.
Step 4: Validate the prototype. Assemble samples into the real panel, plug and unplug cables, and confirm link speed, LED status and latch feel before releasing to production.
9. Prototype checklist (10 items)
| No. | Check | How |
|---|---|---|
| 1 | Tab field matches the intended orientation | Check both the selection table and the datasheet |
| 2 | Location of pin 1 on the footprint | Redraw from the new drawing; do not reuse old pads |
| 3 | Connections of the four TD± pairs | Compare pin by pin with the PHY; no A↔D swap |
| 4 | Center taps and Bob Smith termination | For PoE parts, also check the power pins |
| 5 | LED anode, cathode and color | Power up and confirm each LED's color and behavior |
| 6 | Shield tabs and alignment post holes | Hole size and position per drawing; tabs reach chassis ground |
| 7 | Panel cutout and latch clearance | Plug in a real cable and press the latch by hand |
| 8 | EMI fingers contact the panel | Inspect the contact surface after assembly |
| 9 | Top and bottom ports of stacked jacks | Check pairs and LEDs separately; no copy-paste |
| 10 | Link speed and stability | Repeated mating plus long traffic runs; no downshift or drops |
10. FAQ
Q1: The tab-up and tab-down parts have the same outline. Can they share one footprint?
Not recommended. A similar outline does not mean the same pin pattern. Flipping the tab changes the contact order and the LED pins, so each part needs a footprint built from its own drawing.
Q2: The PHY supports Auto-MDIX. Won't it fix swapped pairs?
Auto-MDIX only handles crossover-style swaps (A↔B, C↔D). A mirrored jack gives an A↔D swap that the PHY cannot correct, so both Fast Ethernet and Gigabit links may fail.
Q3: Do tab-up and tab-down parts with the same circuit code (such as Q066) use the same magnetics?
A shared middle code suggests a similar circuit, but the housing and pin layout differ, so you still need to check the drawings. Electrical ratings follow each part's own datasheet.
Q4: Is there a Gigabit, SMT, integrated-magnetics, tab-down jack?
Not in the current selection table. The only SMT, integrated-magnetics, tab-down parts are two 10/100M jacks. Options are a tab-up SMT part, or a discrete transformer with a tab-down SMT jack. You can also contact us about custom options.
Q5: Does the Tab field matter for 180° vertical jacks?
For vertical jacks the latch direction is not tied to the board surface, and almost all are marked Up in the table. Use the drawing to see which side of the enclosure the latch faces and whether there is room to press it.
Q6: Can a stacked jack have both rows latching up?
Standard stacked jacks have the top port up and the bottom port down, and all 136 stacked parts in the table follow that layout. If the enclosure requires the same direction for both rows, use two single-row jacks or ask our FAE team to evaluate.
Need samples or selection support?
If you are moving a port from tab-up to tab-down, or deciding between a stacked jack and single-row jacks, send us the panel drawing, PHY part number, data rate and PoE requirement. VOOHU FAEs will shortlist suitable parts from the selection table and support drawing and footprint checks.
——— VOOHU Engineering Team
Technical support: fae.thorne@voohu.cn | Tel: 400-1048-018
Suzhou VOOHU Electronic Technology Co., Ltd. | www.voohuele.com
