The PLCC-44 package is a square plastic leaded chip carrier with 44 J-leads at the standard 1.27 mm PLCC pitch, registered under JEDEC MS-018, variation AC. It’s the package most 8051-family microcontrollers shipped in through the 1990s and 2000s — the Atmel/Microchip AT89C51 and AT89S51 are the clearest documented examples, used throughout this page for pinout. PLCC-44 is also the largest PLCC size still commonly specified in new designs.
Key takeaways
- JEDEC MS-018, variation AC. Body span 16.51–16.66 mm (0.650–0.656 in) square, lead pitch 1.27 mm, overall height up to 4.57 mm.
- PLCC-44 doesn’t have one fixed pinout — it depends on the IC. The 8051 microcontroller family (AT89C51/AT89S51) is a well-documented example, used below.
- Four corner positions are unconnected on the 8051 PLCC-44 pinout, evenly spaced 11 pins apart — the same corner-skip pattern seen on PLCC-28, just scaled up.
- Both the through-hole and surface-mount Adam Tech PLCC-44-AT sockets are discontinued; Preci-Dip’s 540-88-044-17-400 SMD socket is a current, in-stock alternative.
- Standard PLCC-44 sockets are rated 1 A per contact — check that figure before routing shared current through more than one pin.
PLCC-44 Dimensions
Microchip’s own 44-Lead PLCC Package Outline drawing (package code PJ), registered under JEDEC MS-018 variation AC, gives a 0.653 in x 0.653 in nominal body with a 0.050 in (1.27 mm) pitch and a maximum height of 0.180 in (4.57 mm).
| Parameter | Value | Note |
| JEDEC outline | MS-018, variation AC | Equivalent to MO-047-AC |
| Lead count | 44 | |
| Body-only span (D1/E1) | 16.51–16.66 mm (0.650–0.656 in), square | |
| Lead-tip span (D/E) | 17.40–17.65 mm (0.685–0.695 in), square | |
| Lead pitch (e) | 1.27 mm (0.050 in) BSC | |
| Lead width (b) | 0.33–0.53 mm (0.013–0.021 in) | |
| Overall height (A) | 4.19–4.57 mm (0.165–0.180 in) | |
| Standoff (A1) | 2.29–3.05 mm (0.090–0.120 in) |
A distributor listing for the Microchip AT89S51-24JU gives its body as 16.66 x 16.66 x 4.06 mm — consistent with the D1/E1 body span above, with the height figure sitting just under the datasheet’s stated maximum, which is normal part-to-part variation within tolerance.
Worked example: at the 1.27 mm pitch, a 0.53 mm maximum lead width leaves a 0.74 mm minimum gap between adjacent lead edges (1.27 mm − 0.53 mm) — identical to every other PLCC size, since lead width and pitch are fixed across the family regardless of lead count. A 0.6–0.7 mm solder pad keeps a hand-soldered joint inspectable without bridging.
PLCC-44 Pinout
PLCC-44 has no universal pinout — function depends on the IC — but the 8051 microcontroller family gives a clearly documented, verifiable example. The base AT89C51/AT89S51 uses the standard 40-pin DIP signal order; PLCC-44 carries the same 40 signals plus 4 unconnected corner positions.
| PLCC-44 pin | Function | PLCC-44 pin | Function |
| 1 | NC (corner) | 23 | NC (corner) |
| 2 | P1.0 | 24 | P2.0/A8 |
| 3 | P1.1 | 25 | P2.1/A9 |
| 4 | P1.2 | 26 | P2.2/A10 |
| 5 | P1.3 | 27 | P2.3/A11 |
| 6 | P1.4 | 28 | P2.4/A12 |
| 7 | P1.5 | 29 | P2.5/A13 |
| 8 | P1.6 | 30 | P2.6/A14 |
| 9 | P1.7 | 31 | P2.7/A15 |
| 10 | RST | 32 | PSEN |
| 11 | P3.0/RXD | 33 | ALE/PROG |
| 12 | NC (corner) | 34 | NC (corner) |
| 13 | P3.1/TXD | 35 | EA/VPP |
| 14 | P3.2/INT0 | 36 | P0.7/AD7 |
| 15 | P3.3/INT1 | 37 | P0.6/AD6 |
| 16 | P3.4/T0 | 38 | P0.5/AD5 |
| 17 | P3.5/T1 | 39 | P0.4/AD4 |
| 18 | P3.6/WR | 40 | P0.3/AD3 |
| 19 | P3.7/RD | 41 | P0.2/AD2 |
| 20 | XTAL2 | 42 | P0.1/AD1 |
| 21 | XTAL1 | 43 | P0.0/AD0 |
| 22 | VSS (GND) | 44 | VCC |
This mapping is anchored to values published directly in Atmel/Microchip’s own AT89C51RB2/RC2 datasheet, which gives an explicit DIL-to-LCC pin correlation table: VSS at DIP pin 20 maps to PLCC pin 22, VCC at DIP pin 40 maps to PLCC pin 44, and Port 0 (P0.0–P0.7) at DIP pins 39–32 maps to PLCC pins 43–36. The remaining pins follow the standard 8051 DIP signal order around the same evenly spaced, 4-corner PLCC layout. Confirm pin function against the exact part’s own datasheet before laying out a board — enhanced 8051 variants with extra peripherals (SPI, ADC, additional ports) reassign some of these positions.
PLCC-44 Sockets
As with PLCC-32, the classic board-mount socket for this size is gone in both mounting styles, while alternatives from other manufacturers remain available.
| Parameter | Adam Tech PLCC-44-AT / -AT-SMT | Preci-Dip 540-88-044-17-400 |
| Mounting | Through hole or SMT (both discontinued) | Surface mount |
| Mating pitch | 0.050 in (1.27 mm) | 1.27 mm |
| Contact material / plating | not stated by this distributor listing | Phosphor bronze, tin |
| Current rating | not stated by this distributor listing | 1.0 A |
| Voltage rating | not stated by this distributor listing | 100 V / 150 V |
| Contact pressure | not stated by this distributor listing | 1.5 N min per contact |
| Mechanical life | not specified | 50 cycles min |
| Housing material | not stated by this distributor listing | Glass-fiber-reinforced PPS |
| Lifecycle status | Obsolete / no longer manufactured (both variants) | In stock, currently available |
Note the mechanical-life figure: Preci-Dip’s 540 series is rated for a minimum of 50 insertion cycles, which is adequate for occasional chip swaps on a bring-up board but far below a dedicated test socket’s 10,000-cycle rating. If a design needs frequent reprogramming cycles rather than occasional service swaps, a test/burn-in-grade socket is the better fit, not a board-mount part like this one.
Choosing Between Direct Solder and a Socket
- Production board, part won’t be swapped after assembly → solder the PLCC-44 directly; skip the socket’s added height and contact resistance.
- Bring-up board, or the part is a field-programmable microcontroller or CPLD reprogrammed occasionally by hand → a board-mount socket rated for the mounting style and current needed, sourced and lifecycle-checked first.
- Frequent reprogramming, test, or burn-in use → a dedicated test socket rated for a stated high mating-cycle count, not a board-mount part rated for only tens of cycles.
FAQ
What are the dimensions of a PLCC-44 package?
Per JEDEC MS-018 variation AC, the PLCC-44 body span is 16.51–16.66 mm (0.650–0.656 in) square, with a 1.27 mm lead pitch and an overall height up to 4.57 mm.
Does PLCC-44 have a standard pinout?
No — pin function depends on the IC. The 8051 microcontroller family (AT89C51/AT89S51) is a documented example, with pin 22 as ground, pin 44 as VCC, and four unused corner pins spaced 11 positions apart.
What socket fits a PLCC-44 package?
Any socket built to JEDEC MS-018 variation AC at 1.27 mm pitch. Adam Tech’s through-hole and SMT PLCC-44-AT sockets are both discontinued; Preci-Dip’s 540-88-044-17-400 SMD socket is a current in-stock alternative.
What is the lead pitch on a PLCC-44?
1.27 mm (0.05 in), the same fixed pitch used across every JEDEC PLCC size from 20 to 84 leads.
How many corner pins are unused on a PLCC-44?
Four, on 8051-family parts — evenly spaced 11 positions apart around the package. Other PLCC-44 ICs may use those positions differently, so check the specific datasheet.
The Decision
Treat the PLCC-44 the way you would any other PLCC size: JEDEC MS-018 variation AC gives fixed, trustworthy dimensions, but pin assignment is entirely part-specific — verify it against the exact IC’s datasheet rather than assuming every 8051-family part matches the mapping shown here. For sourcing, check socket lifecycle and mechanical-life rating together: the familiar Adam Tech board-mount part is gone in both mounting styles, and its replacement’s 50-cycle rating is fine for occasional service but not for a design that gets reprogrammed often.
