ISP1521 datasheet(16/53 Pages) PHILIPS

16 / 53 page

Philips Semiconductors

ISP1521

Hi-Speed USB hub controller

Product data

Rev. 03 — 24 November 2004

16 of 53

9397 750 13702

Both analog and digital overcurrent modes are supported; see Table 7.

For digital overcurrent detection, the normal digital TTL level is accepted on the

overcurrent input pins. For analog overcurrent detection, the threshold is given in the

DC characteristics. In this mode, to ﬁlter out false overcurrent conditions because of

in rush and spikes, a dead time of 15 ms is built into the IC, that is, overcurrent must

persist for 15 ms before it is reported to the host.

9.1.4

Non-removable port

A non-removable port, by deﬁnition, is a port that is embedded inside the hub

application box and is not externally accessible. The LED port indicators

(pins AMBn_N) of such a port are not used. Therefore, the corresponding amber LED

port indicators are disabled to signify that the port is non-removable; see Table 8.

More than one non-removable port can be speciﬁed by appropriately connecting the

corresponding amber LED indicators. At least one port should, however, be left as a

removable port.

The detection of any non-removable port sets the hub descriptor into a compound

hub.

9.1.5

Port indicator support

The port indicator support can be disabled by grounding all green port indicators (all

pins GRNn_N); see Table 9. This is a global feature. It is not possible to disable port

indicators for only one port.

Table 6:

Overcurrent protection mode pin conﬁguration

Power switching mode

NOOC

PSW1_N PSW2_N PSW3_N PSW4_N PSW5_N PSW6_N PSW7_N

None

HIGH

ground

Global

LOW

internal

pull-up

ground

Individual

LOW

internal

pull-up

internal

pull-up

internal

pull-up

internal

pull-up

internal

pull-up

internal

pull-up

internal

pull-up

Table 7:

Overcurrent detection mode selection pin conﬁguration

Pin ADOC

Mode selection

Description

3.3 V or 5.0 V

analog

threshold

∆Vtrip

Ground

digital

normal digital TTL level

Table 8:

Non-removable port pin conﬁguration

AMBn_N (n=1to7)

Non-removable port

Ground

non-removable

Pull-up with amber LED

removable

Table 9:

Port indicator support: pin conﬁguration

GRN1_N to GRN7_N

Port indicator support

Ground

not supported

LED pull-up green LED for at least one port

supported

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