Leads on the two longer edges is what makes a package TSOP Type II. That choice lets a narrow body carry a lot of pins, which is why DRAM, SRAM and MRAM adopted it and parallel flash did not. The family is organized by body width in mils, and the 400-mil branch runs from 44 to 86 leads. Below are the real dimensions, a land pattern computed at 0.80 mm pitch, and what changes when the part goes on both sides of a module.
Key takeaways
- JEDEC’s dictionary places TSOP2 leads on the sides or long edges, against TSOP1 on the ends.
- Type II registrations are indexed by body width: 7.62 mm, 10.16 mm, 12.70 mm and 16 mm, which the industry calls 300, 400, 500 and 630 mil.
- The 400-mil family uses two body lengths, not one. It steps from about 18.5 mm to 22.22 mm at 54 leads, exactly where the lead row outgrows the shorter body.
- At 0.80 mm pitch a 4 mil track fits between adjacent pads once you trim the nominal pad by 0.04 mm. On a 0.50 mm pitch Type I it never fits.
- On double-sided memory modules the back-side placement is mirrored, which drove a generation of reverse-pinout packages.
[IMAGE 1: TSOP Type II 54-lead outline with long-edge lead rows, 11.76 mm lead span and 0.80 mm pitch dimensioned | alt: “TSOP Type II package showing leads on the long edges, 11.76 mm lead span and 0.80 mm pitch”]
What TSOP Type II means
TSOP Type II is a thin small outline package with gull-wing leads on the two longer edges of the body. JEDEC’s dictionary puts TSOP2 leads on the sides or long edges and TSOP1 leads on the ends, and notes that the pitch is often finer than a standard small-outline package. Maximum seated height is 1.20 mm.
Because the lead rows run along the long axis, a Type II body can be narrow and still carry a high pin count. A 54-lead part fits in a 10.16 mm width. That narrowness is the reason the format took over memory modules, where board height is the binding constraint.
Type II is organized by body width, in mils
Type I registrations are indexed by lead count. Type II registrations are indexed by body width, and the industry names them in mils rather than millimetres. Per the JEDEC JEP95 device-type index:
- 7.62 mm, or 300 mil, under MS-025
- 10.16 mm, or 400 mil, under MS-024
- 12.70 mm, or 500 mil, under MO-135
- 16 mm under MO-182
This is why a datasheet says “54-pin TSOP II (400 mil)” rather than giving a pin count alone. The mil figure is the body width and it identifies the family. Two parts with the same lead count can sit in different families: MO-135 registers a 54-lead part on a 12.70 mm body, and MS-024 covers the 54-lead part on 10.16 mm that most SDRAM uses.
Read the mil number first. It tells you more about the footprint than the pin count does.
Inside the 400-mil family
The 400-mil branch is where almost all current Type II memory lives. Renesas publishes drawings for 44, 50, 54, 66 and 86 leads on this body.
| Leads | Body (mm) | Lead span | Pitch | Source |
| 44 | 10.29 × 18.52 | see drawing | 0.80 mm | ISSI IS61C25616AL distributor record |
| 54 | 10.16 × 22.22 | 11.56 / 11.76 / 11.95 mm | 0.80 mm BSC | Everspin TSOP2 guide, per MS-024 |
| 66 | 10.16 ± 0.10 × 22.22 ± 0.05 | 11.76 ± 0.20 mm | 0.65 mm | Renesas PTSB0066JB |
| 86 | 10.16 ± 0.10 × 22.22 ± 0.05 | 11.76 ± 0.20 mm | 0.50 mm | Renesas PTSB0086KB |
Now the part the summary pages miss. The body length is not constant across the family; it takes one step. Work out the lead row, which spans (n/2 − 1) × pitch:
44 leads: 22 per edge, 21 × 0.80 mm = 16.8 mm row in an 18.5 mm body
54 leads: 27 per edge, 26 × 0.80 mm = 20.8 mm row in a 22.22 mm body
66 leads: 33 per edge, 32 × 0.65 mm = 20.8 mm row in a 22.22 mm body
86 leads: 43 per edge, 42 × 0.50 mm = 21.0 mm row in a 22.22 mm body
The step from 18.5 mm to 22.22 mm happens at 54 leads because 20.8 mm of lead row no longer fits the shorter body. Above that point the body stops growing and the pitch does all the work, which is why the 66 and 86-lead parts share a footprint outline with the 54-lead part and differ only in pad pitch.
The full 54-lead outline from the Everspin guide, referenced to MS-024: overall height 1.20 mm max, standoff 0.05 to 0.15 mm, body thickness 0.95 to 1.05 mm, lead width 0.30 to 0.45 mm, foot length 0.40 to 0.60 mm, lead angle 0 to 8 degrees.
The land pattern at 0.80 mm pitch
Type II falls under IPC-7353, gullwing leads on two sides. Using the 54-lead numbers above with Nominal density (Level B) fillet goals of Jt = 0.35 mm, Jh = 0.35 mm and Js = 0.03 mm, and assuming 0.05 mm fabrication allowance and 0.05 mm placement accuracy:
Lead span L runs 11.56 mm to 11.95 mm, so Ltol = 0.39 mm. Inner lead separation S runs from 11.56 − 2(0.60) = 10.36 mm to 11.95 − 2(0.40) = 11.15 mm, so Stol = 0.79 mm. Lead width W runs 0.30 mm to 0.45 mm, so Wtol = 0.15 mm.
Z = Lmin + 2Jt + √(Ltol² + F² + P²) = 11.56 + 0.70 + 0.396 = 12.66 mm
G = Smax − 2Jh − √(Stol² + F² + P²) = 11.15 − 0.70 − 0.793 = 9.66 mm
X = Wmin + 2Js + √(Wtol² + F² + P²) = 0.30 + 0.06 + 0.166 = 0.53 mm
| Land pattern parameter | Value |
| Pad size | 0.53 mm × 1.50 mm |
| Row centreline spacing | 11.16 mm |
| Outer pad extent (Z) | 12.66 mm |
| Inner gap (G) | 9.66 mm |
| Pad pitch | 0.80 mm |
| Pad-to-pad clearance | 0.27 mm |
That 0.27 mm clearance is the payoff of Type II. A 3 mil track needs clearance, track, clearance, or 3 × 0.076 = 0.229 mm, and it fits with 0.04 mm to spare. Trim the pad from 0.53 mm to 0.49 mm and the clearance rises to 0.31 mm, which passes a 4 mil track at standard rules. One track between every pair of pads on the top layer can remove a routing layer from a memory design.
The same calculation on a 0.50 mm pitch Type I comes out the other way, with no track fitting at any sensible pad width. If you have a choice between a 54-lead Type II and a 48-lead Type I for the same function, the pitch is worth more to your layer count than the pin count is.
[IMAGE 2: TSOP Type II land pattern with a track routed between adjacent pads | alt: “TSOP Type II footprint at 0.80 mm pitch with a track routed between pads”]
Mirrored placement and reverse pinouts
Type II is the memory-module package, and modules populate both faces of the board. The Intel PC SDRAM Unbuffered DIMM Specification of February 1998 states the rule directly: for double-sided, non mixed-mode DIMMs the back-side placement should be mirrored from the front side, and for mixed-mode modules the front-side x8 placement is combined with a mirrored back-side x16 placement.
Mirroring the placement reverses the pin order as seen from the front of the board. Flip a package to the underside and its outer address pins end up furthest from the traces that used to serve them. Vendors answered this by building reverse-pinout parts. US patent 5,691,570, describing the prior art, shows a 44-pin memory package in normal and reverse arrangements that are mirror images of each other and otherwise identical, and notes that the reverse construction changed the lead frame position enough to affect heat dissipation.
The practical points for a current design: if you place Type II memory on both sides of a board, decide early whether you are mirroring the placement or mirroring the pinout, because the two produce different net lengths on the outer address lines. And if a supplier offers a part number that differs by one character with the same package drawing, check whether the difference is a reverse pinout before you assume it is a temperature grade.
Stacked Type II
Two JEDEC registrations exist purely for stacked-die Type II parts. MO-201 covers 2-high and 4-high stacks at 32 leads. MO-238 covers 2-high stacks at 54 and 66 leads.
The registrations matter because a stacked part is dimensionally a Type II package but can exceed the height you budgeted from a single-die drawing. If a datasheet mentions die stacking, take the height from that device’s drawing rather than from the family.
Failure modes and sourcing
Two hazards are specific to what ships in Type II.
Magnetic fields. Everspin’s toggle MRAM in the 44-pin TSOP2 has a documented magnetic immunity limit, and the company publishes both a product note on immunity improvements for the 1 Mb and 4 Mb TSOP2 industrial and extended-temperature grades and an application note on approximating the field strength around the part. If you are placing MRAM near a motor, contactor or transformer, this is a real design constraint that has no analogue in flash.
Assembly-site changes. Everspin’s product change notices for the same package record qualifying the 44-pin TSOP2 at ASE Kaohsiung with a new mold compound, G631H, and adding OSE as a second assembly subcontractor. Mold compound and site changes do not alter the drawing, but they can alter reflow behaviour on a marginal profile. Read the PCN list for any long-lived Type II part before you assume this year’s units behave like last year’s.
On availability, Type II is holding up better than its reputation suggests. Renesas lists the 71V016SA10PHGI, a 1 Mbit SRAM in 44-TSOP II, as active at DigiKey with an 18-week factory lead time in tubes. SDRAM in 54-TSOP II is served largely by Alliance Memory and ISSI rather than the original vendors. Older SRAM is thinning: RS has delisted the ISSI IS61C25616AL-10TLI in 44-pin TSOP.
Five mistakes specific to Type II
- Ignoring the mil number. “54-pin TSOP II” without the body width is ambiguous. MO-135 and MS-024 both register 54 leads on different bodies.
- Assuming one body length in the 400-mil family. The 44-lead part is roughly 18.5 mm long; everything from 54 leads up is 22.22 mm.
- Carrying a 54-lead footprint to a 66-lead part. Same outline, different pitch. The pads move.
- Mirroring the placement without checking the pinout. Front and back placements on a module are not the same net-length problem.
- Taking height from the family drawing on a stacked part. MO-201 and MO-238 exist because stacks are dimensionally different.
TSOP Type II FAQ
What is TSOP Type II?
A thin small outline package with gull-wing leads on the two longer edges of the body, at 1.20 mm maximum seated height. JEDEC registers it by body width: 7.62 mm under MS-025, 10.16 mm under MS-024, 12.70 mm under MO-135 and 16 mm under MO-182. Lead counts reach 86 in production parts.
What is the difference between TSOP Type I and Type II?
Lead placement, and what it costs. Type I has leads on the short edges, adds pins by widening the body, and typically runs 0.50 mm pitch. Type II has leads on the long edges, is indexed by body width in mils, and runs 0.50 to 0.80 mm pitch. The footprints are unrelated at any lead count.
What does 400 mil mean on a TSOP II?
It is the body width, 10.16 mm, and it identifies the JEDEC family, MS-024. The 400-mil family covers 44, 50, 54, 66 and 86-lead parts. Body width and lead span stay at 10.16 mm and 11.76 mm across the 54, 66 and 86-lead sizes; only the pitch changes.
Is TSOP-54 Type I or Type II?
Type II. The 54-lead TSOP used for SDRAM, SRAM and MRAM has 27 leads on each long edge, a 10.16 mm body width, a 22.22 mm body length, an 11.76 mm lead span and 0.80 mm pitch. Distributors list it as “54-TSOP II” or “54-TSOP (0.400 in, 10.16 mm Width)”.
Is TSOP Type II still used?
Yes, in specific niches. SRAM and MRAM in 44-TSOP II remain active with long lead times, and SDRAM in 54-TSOP II is supplied mainly by Alliance Memory and ISSI. Newer and faster memory has moved to area-array packages, so treat Type II as a mature format rather than a growing one.
When Type II is the right choice
Choose Type II when the part exists in it, when board height rather than board area is your constraint, and when you want the 0.80 mm pitch to keep the escape routing on the top layer. For SRAM, MRAM and SDRAM in industrial equipment, that combination still beats a BGA on inspectability and rework.
Move to an area-array package when the interface is faster than SDR SDRAM or when the 22 mm body length does not fit.
Before you commit: read the mil figure off the datasheet, confirm the body length against the lead-row arithmetic above, and decide the module-placement question before you route anything. Getting the first two wrong costs a respin. Getting the third wrong costs a timing budget.
[IMAGE 3: 44-lead and 54-lead TSOP II side by side showing the body length step | alt: “TSOP Type II 44-lead and 54-lead packages compared showing the body length step”]
Internal links to add
- [INTERNAL LINK: TSOP package → the full TSOP family, registrations and land patterns]
- [INTERNAL LINK: TSOP Type I → short-side lead layout and escape routing]
- [INTERNAL LINK: IPC-7351 land pattern density levels → choosing Most, Nominal or Least]
- [INTERNAL LINK: SDRAM package selection → TSOP II against FBGA for industrial memory]
- [INTERNAL LINK: moisture sensitivity level → MSL floor life and baking rules]
