Hi-Speed Universal Serial Bus hub controller
Rev. 03 — 24 November 2004
1. General description
The ISP1521 is a stand-alone Universal Serial Bus (USB) hub controller IC that
Universal Serial Bus Speciﬁcation Rev. 2.0.
It supports data transfer at
high-speed (480 Mbit/s), full-speed (12 Mbit/s) and low-speed (1.5 Mbit/s).
The upstream facing port can be connected to a Hi-Speed USB host or hub or to an
Original USB host or hub. If the upstream facing port is connected to a Hi-Speed USB
host or hub, then the ISP1521 will operate as a Hi-Speed USB hub. That is, it will
support high-speed, full-speed and low-speed devices connected to its downstream
facing ports. If the upstream facing port is connected to an Original USB host or hub,
then the ISP1521 will operate as an Original USB hub. That is, high-speed devices
that are connected to its downstream facing ports will operate in full-speed mode
The ISP1521 is a full hardware USB hub controller. All Original USB devices
connected to the downstream facing ports are handled using a single Transaction
Translator (TT), when operating in a cross-version environment. This allows the
whole 480 Mbit/s upstream bandwidth to be shared by all the Original USB devices
on its downstream facing ports.
The ISP1521 has seven downstream facing ports. If not used, ports 3 to 7 can be
disabled. The vendor ID, product ID and string descriptors on the hub are supplied by
the internal ROM; they can also be supplied by an external I
C-bus™ EEPROM or a
The ISP1521 is suitable for self-powered hub designs.
An analog overcurrent detection circuitry is built into the ISP1521, which can also
accept digital overcurrent signals from external circuits; for example, Micrel MOSFET
switch MIC2026. The circuitry can be conﬁgured to trip on a global or an individual
Each port comes with two status indicator LEDs.
Target applications of the ISP1521 are monitor hubs, docking stations for notebooks,
internal USB hub for motherboards, hub for extending Intel
Easy PCs, hub boxes,
and so on.