ISP1504CBS datasheet(9/84 Pages) PHILIPS

9 / 84 page

ISP1504A_ISP1504C_1

Product data sheet

Rev. 01 — 19 October 2006

9 of 84

NXP Semiconductors

ISP1504A; ISP1504C

ULPI HS USB OTG transceiver

• VBUS comparators to determine the VBUS voltage level. This is required for the VBUS

detection, SRP and HNP.

• Resistors to temporarily charge and discharge VBUS. This is required for SRP.

• Charge pump to provide 5 V power on VBUS. The downstream peripheral can draw its

power from the ISP1504 VBUS.

7.6.1 ID detector

The ID detector detects which end of the mini-USB cable is plugged in. The detector must

ﬁrst be enabled by setting the ID_PULLUP register bit to logic 1. If the ISP1504 senses a

value on ID that is different from the previously reported value, an RXCMD status update

will be sent to the USB link, or an interrupt will be asserted.

• If the mini-B end of the cable is plugged in, the ISP1504 will report that ID_GND is

logic 1. The USB link must change to peripheral mode.

• If the mini-A end of the cable is plugged in, the ISP1504 will report that ID_GND is

logic 0. The USB link must change to host mode.

7.6.2 VBUS comparators

The ISP1504 provides three comparators, VBUS valid comparator, session valid

comparator and session end comparator, to detect the VBUS voltage level.

7.6.2.1

VBUS valid comparator

This comparator is used by hosts and A-devices to determine whether the voltage on

VBUS is at a valid level for operation. The ISP1504 minimum threshold for the VBUS valid

comparator is VA_VBUS_VLD. Any voltage on VBUS below VA_VBUS_VLD is considered a fault.

During power-up, it is expected that the comparator output will be ignored.

7.6.2.2

Session valid comparator

The session valid comparator is a TTL-level input that determines when VBUS is high

enough for a session to start. Peripherals, A-devices and B-devices use this comparator to

detect when a session is started. The A-device also uses this comparator to determine

when a session is completed. The session valid threshold of the ISP1504 is VB_SESS_VLD,

with a hysteresis of Vhys(B_SESS_VLD).

7.6.2.3

Session end comparator

The ISP1504 session end comparator determines when VBUS is below the B-device

session end threshold. The B-device uses this threshold to determine when a session has

ended. The session end threshold of the ISP1504 is VB_SESS_END.

7.6.3 SRP charge and discharge resistors

The ISP1504 provides on-chip resistors for short-term charging and discharging of VBUS.

These are used by the B-device to request a session, prompting the A-device to restore

the VBUS power. First, the B-device makes sure that VBUS is fully discharged from the

previous session by setting the DISCHRG_VBUS register bit to logic 1 and waiting for

SESS_END to be logic 1. Then the B-device charges VBUS by setting the CHRG_VBUS

threshold and starts a session by turning on the VBUS power.

ISP1504CBS Datasheet(PDF) 9 Page - NXP Semiconductors

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