Power supply – Philips ISP1520 User Manual

Page 8

Philips Semiconductors

UM10014_4

ISP1520 Hi-Speed USB Hub Demo Board

User manual

Rev. 04.00 — 11 May 2004

8 of 18

The hub demo board also contains an option to disable the overcurrent detection. This can be
done in two stages. First place the NOOC jumper in the appropriate position to set the hub’s

descriptor (see Table 5-2).

Table 5-2: Overcurrent Detection Selection Using NOOC

Then, desolder R28, R29, R30 and R31, and solder R32, R33, R34 and R36 on the PCB (see
schematics).

As a lower cost alternative, there are provisions on the board to use polyswitches to handle
overcurrent conditions. In this case the port switching transistors are bypassed. If this solution is

preferred, then the overcurrent detection circuit inside the chip must be switched to the digital
mode

Table 5-3: Mode Selection Using ADOC

*—

Default

settings.

5.5. Power

Supply

This hub demo board can be used as a self-powered USB hub. When used as a self-powered hub,
use the provided power supply.

The SW1 switch sets the powering mode in the hub’s descriptors; see Table 5-4.

NOOC

Overcurrent Detection

Logic State

ON YES 0

(LOW)

OFF NO 1

(HIGH)

ADOC

Mode

Logic State

ON Digital 0

(LOW)

OFF Analog* 1

(HIGH)