JMicron Chip Top Mark and Part Number Format

Sat, 04 Apr 2026 10:00:00 +0800

Each device has a unique top mark used to identify the vendor, device name, part number, manufacturing date code, lot number, and Pin 1 orientation.
The top-mark layout is shown below.

Part Number Format

The part number includes: vendor, product category, device number, package type, material type, product grade (operating temperature), Mask ROM version, and IC revision.
Its format can be written as J M B 5 8 5 - Q H B A 0 A, mapped to fields a b c d e f g h, and divided into Section I and Section II:

Section	Field	Characters	Meaning
Section I	a	`JM`	Brand name
Section I	b	`B`	Product category
Section I	c	`585`	Device number
Section II	d	`Q`	Package type
Section II	e	`H`	Material and grade
Section II	f	`B`	Internal bonding type
Section II	g	`A0`	Mask ROM version
Section II	h	`A`	IC revision

Field	Length	Definition	Code(s)	Notes
a (JM)	2 digits	Brand name	JM	Vendor is JMicron
b (B)	1 digit	Product category	B	`B = Bridge`, `S = SOC`
c (585)	3 digits	Device number	585	Combined with brand and category to form device name `JMB585`
d (Q)	1 digit	Package type	B, L, Q, T	`B = BGA`, `L = LQFP`, `Q = QFN`, `T = TQFP`
e (H)	1 digit	Material and grade	G, H, I, J	`G`: Gold wire, RoHS, halogen-free, Ta: 0 to 70°C; `H`: Copper wire, RoHS, halogen-free, Ta: 0 to 70°C `I`: Gold wire, RoHS, halogen-free, Ta: -40 to 85°C; `J`: Copper wire, RoHS, halogen-free, Ta: -40 to 85°C
f (B)	1 digit	Internal bonding type	A, B, C, …	Internal bonding code
g (A0)	2 digits	Mask ROM version	A0, A1, A2, …; B0, B1, B2, …; Z0	`A` means A-series version; `B` means B-series version; `Z0` means no Mask ROM
h (A)	1 digit	IC revision	A, B, C, …	IC version code

Top Mark on KnightLi Blog

JMicron Chip Top Mark and Part Number Format

Part Number Format