The PLCC-28 package is a square plastic leaded chip carrier with 28 J-leads at the standard 1.27 mm PLCC pitch, registered under JEDEC MS-018 variation AB (equivalent to the MO-047-AB body size). It’s the package most 22V10-family PLDs shipped in — the GAL22V10 and ATF22V10 are the clearest documented examples. This page gives the verified outline dimensions, the real pin-to-pin mapping from the manufacturer datasheets, and which sockets still fit it today.
Key takeaways
- JEDEC MS-018 variation AB (the PLCC-28 member of the MO-047 body-size family). Lead-tip span 12.319–12.573 mm, body-only span 11.430–11.582 mm, lead pitch 1.27 mm.
- PLCC-28 doesn’t have one fixed pinout — it depends on the IC. The 22V10 PLD family (GAL22V10 / ATF22V10, pin-compatible per Wikipedia) is the clearest documented example and is used below.
- Four PLCC-28 corner positions (pins 1, 8, 15, and 22) are unconnected by default on 22V10-family parts; Atmel’s datasheet notes they can optionally be tied to VCC (pin 1) or GND (pins 8, 15, 22) for better decoupling.
- The classic through-hole PLCC-28 socket (Adam Tech PLCC-28-AT) is discontinued; 3M’s 8428-21A1-RK-TP surface-mount socket is an active equivalent, and a second 3M variant is already on Last Time Buy as of March 2026.
- Standard PLCC-28 sockets are rated 1 A per contact — verify that figure before routing shared current through more than one pin.
PLCC-28 Dimensions
The clearest primary-source drawing comes from Atmel/Microchip’s own ATF22V10C(Q)Z package drawing, labeled “28J” and stated to conform to JEDEC MS-018, variation AB. It gives two separate body measurements that are easy to confuse: the lead-tip-to-lead-tip span (D/E) and the body-only span (D1/E1), which excludes the leads.
| Parameter | Value | Note |
| JEDEC outline | MS-018, variation AB | Equivalent to the MO-047-AB body size family |
| Lead count | 28 | |
| Lead-tip span (D/E) | 12.319–12.573 mm | Matches independently published JEDEC dimension tables for MO-047-AB |
| Body-only span (D1/E1) | 11.430–11.582 mm | Matches distributor-listed body dimensions (“11.51 x 11.51 mm”) |
| Lead pitch (e) | 1.27 mm TYP | |
| Lead width (B1) | 0.330–0.533 mm | |
| Overall height (A) | 4.191–4.572 mm | |
| Standoff (A1) | 2.286–3.048 mm |
The two body figures agree with independent sources: a socket manufacturer’s JEDEC dimension table lists the same 12.32–12.57 mm span for the 28-lead MO-047-AB outline, and a distributor listing for the ATF22V10C-10JU gives an 11.58 mm body dimension consistent with D1/E1. When you’re laying out a footprint, use the lead-tip span (D/E) for lead placement and the body-only span (D1/E1) only for mechanical clearance around the package body.
Worked example: with a 0.533 mm maximum lead width at the fixed 1.27 mm pitch, the minimum gap between adjacent lead edges is 0.737 mm (1.27 mm − 0.533 mm). A 0.6–0.7 mm solder pad keeps a hand-soldered joint inspectable without bridging the next pad.
PLCC-28 Pinout
PLCC-28 has no universal pinout — pin function depends on the IC. The best-documented example is the 22V10 programmable logic device family: Lattice’s GAL22V10 and Microchip/Atmel’s ATF22V10 are pin-compatible replacements for each other, so the same mapping applies to both. The function set below comes straight from the DIP/SOIC pin table (identical function order to the PLCC, just renumbered around four unused corners):
| DIP/SOIC pin | Function | PLCC-28 pin |
| 1 | CLK/IN | 2 |
| 2 | IN | 3 |
| 3 | IN | 4 |
| 4 | IN | 5 |
| 5 | IN | 6 |
| 6 | IN | 7 |
| 7 | IN | 9 |
| 8 | IN | 10 |
| 9 | IN | 11 |
| 10 | IN | 12 |
| 11 | IN | 13 |
| 12 | GND | 14 |
| 13 | VCC | 16 |
| 14 | I/O | 17 |
| 15 | I/O | 18 |
| 16 | I/O | 19 |
| 17 | I/O | 20 |
| 18 | I/O | 21 |
| 19 | I/O | 23 |
| 20 | I/O | 24 |
| 21 | I/O | 25 |
| 22 | I/O | 26 |
| 23 | I/O | 27 |
| 24 | IN | 28 |
PLCC-28 pins 1, 8, 15, and 22 fall between the mapped positions above and carry no dedicated signal on the 22V10. Atmel’s ATF22V10C(Q)Z datasheet notes these four corners can be left unconnected, or — for better decoupling performance — pin 1 can be tied to VCC and pins 8, 15, and 22 tied to GND, since they sit adjacent to the real VCC (pin 16) and GND (pin 14) pins. Confirm this against the specific part’s own datasheet before laying out a board; not every PLCC-28 IC uses the same corner convention.
PLCC-28 Sockets
As with the package itself, socket lifecycle is where most of the risk sits — the through-hole part that’s been the default for decades is discontinued, and even its surface-mount successor already has a sibling on Last Time Buy.
| Parameter | Adam Tech PLCC-28-AT (THT) | 3M 8428-21A1-RK-TP (SMT) |
| Mounting | Through hole, 0.100 in (2.54 mm) post pitch | Surface mount |
| Mating pitch | 0.050 in (1.27 mm) | 0.050 in (1.27 mm) |
| Contact material / plating | Phosphor bronze, tin | Copper alloy, tin, 160 µin thick |
| Current rating | 1 A | 1 A |
| Operating temperature | not stated by this distributor listing | −40 °C to +105 °C |
| Housing material | not stated by this distributor listing | PBT, glass filled, UL94V-0 |
| Lifecycle status | Obsolete / no longer manufactured | Active |
Check further before committing even to the active option: 3M’s related 8428-21B1-RK-TR variant — same 28-position, 1.27 mm SMT socket family, with a slightly different contact finish and a 15 mΩ contact-resistance spec — is already listed with a Last Time Buy date of March 31, 2026. If a BOM calls out any PLCC-28 socket, check the specific manufacturer part number’s lifecycle status individually rather than assuming the family is safe because one variant is Active.
Choosing Between Direct Solder and a Socket
- Production board, part won’t be swapped after assembly → solder the PLCC-28 directly; skip the socket’s added height and contact resistance.
- Bring-up board, or the part is a field-programmable PLD that gets reprogrammed by hand → through-hole or SMT commercial socket, sized to the board’s mounting style and checked for current lithium against your worst-case pin current.
- Repairing or cloning a legacy board that only exists in PLCC-28 → confirm socket lifecycle status before ordering; the classic through-hole part is already gone.
FAQ
What are the dimensions of a PLCC-28 package?
Per JEDEC MS-018 variation AB (the PLCC-28 member of the MO-047-AB body family), the lead-tip span is 12.319–12.573 mm, the body-only span is 11.430–11.582 mm, and lead pitch is 1.27 mm.
Does PLCC-28 have a standard pinout?
No — pin function depends on the specific IC. The 22V10 PLD family (GAL22V10, ATF22V10) is a well-documented example, with pin 2 as clock input, pin 14 as ground, pin 16 as VCC, and four unused corner pins (1, 8, 15, 22).
What socket fits a PLCC-28 package?
Any socket built to JEDEC MO-047-AB/MS-018 AB at 1.27 mm pitch. The Adam Tech PLCC-28-AT through-hole socket is discontinued; 3M’s 8428-21A1-RK-TP surface-mount socket is an active alternative with the same current rating.
What is the lead pitch on a PLCC-28?
1.27 mm (0.05 in), the same fixed pitch used across every JEDEC PLCC size from 20 to 84 leads.
Are the corner pins on a PLCC-28 always unused?
On 22V10-family parts, yes by default — pins 1, 8, 15, and 22 carry no dedicated signal, though the manufacturer allows tying them to VCC or GND for decoupling. Other PLCC-28 ICs may use those positions differently, so check the specific datasheet.
The Decision
Treat the PLCC-28 the same way as any other PLCC size: the JEDEC MS-018/MO-047-AB outline gives you fixed, trustworthy dimensions, but the pin assignment is entirely part-specific — pull it from the exact IC’s datasheet, not from a generic PLCC-28 diagram. For sourcing, check socket lifecycle status individually per manufacturer part number before finalizing a BOM; on this package size, the through-hole option is already gone and even some surface-mount variants are approaching their last order date.
