Philips ISP1520 사용자 설명서

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Philips Semiconductors
ISP1520
Hi-Speed USB hub controller
Product data
Rev. 03 — 24 November 2004
42 of 51
9397 750 13701
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
17. Application information
17.1 Descriptor configuration selection
17.2 Overcurrent detection limit adjustment
For an overcurrent limit of 500 mA per port, a PMOS with R
DSON
 of approximately
100 m
Ω
 is required. If a PMOS with a lower R
DSON
 is used, analog overcurrent
detection can be adjusted by using a series resistor; see
.
V
PMOS
=
V
trip
=
V
trip(intrinsic)
(I
OC(nom)
×
R
td
), where:
V
PMOS
= voltage drop on PMOS
I
OC(nom)
= 0.6
µ
A.
The I
2
C-bus cannot be shared between the EEPROM and the external microcontroller; see
.
(1) The function on port 4, which is a non-removable port, is optional.
Fig 17. Descriptors configuration selection application diagram.
004aaa303
ISP1520
ROM
external microcontroller
acting as I
2
C-bus master
USB function
EEPROM
I
2
C-bus
4 USB downstream facing ports
green and
amber LEDs,
port 1
green and
amber LEDs,
port 2
green and
amber LEDs,
port 3
green and
amber LEDs,
port 4(1)
upstream
 facing port GoodLink
(1) R
td
 is optional.
Fig 18. Adjusting analog overcurrent detection limit (optional).
004aaa259
VREF(5V0)
Rtd(1)
5 V
ISP1520
OCn_N
PSWn_N
IOC