ISP1109 Просмотр технического описания (PDF) - Philips Electronics

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ISP1109

Universal Serial Bus transceiver with carkit support

Philips Electronics 

Philips Semiconductors

ISP1109

USB transceiver with carkit support

7.7 Audio switches

The audio switches provide low impedance path for analog audio signals to be multiplexed

on the DP and DM lines, or loopback between the MIC and SPKR lines.

There are five analog switches that are controlled by register bits. The impedance of the

switches will be between 50 Ω and 150 Ω. Table 5 shows the relation between the control

bits and the switches. Figure 5 shows the audio switches.

Table 5: Audio switch control

AUDIO_EN

AUDIO_MONO S1

S2

S3

0

X

off

off

off

1

0

on

off

on

1

1

off

on

off

S1

SPKR_R

DP

SW_MIC_

S2

SPKR_R

MIC

SW_MIC_

SPKR_L

S3

DM

SPKR_L

Fig 5. Audio switches.

004aaa518

7.8 ISET detector

The ISET detector will set the ISET pin HIGH when either of the following conditions is

met:

• ID > Vth(ID_FM), VCC > Vth(ISET) and VBUS > Vth(svc)

• DP and DM SE1 detected, VCC > Vth(ISET) and VBUS > Vth(svc).

The DP and DM SE1 detector will time the length of the SE1 condition. The timer value is

programmable using register bit TMR_SE1. The timer ranges from 0 ms to 15 ms, with

1 ms interval.

The ID > Vth(ID_FM) detector, and the SE1 detector (with timer) requires bias current.

In Power-down mode, the bias current is turned off to minimize current ICC. The bias

current needs to be enabled so that the ISET detector can function as described earlier.

• If the Power-down is because VCC(I/O) is disconnected, the bias will be enabled if the

VBUS voltage goes above the SESS_VLD threshold.

9397 750 13355

Product data sheet

Rev. 01 — 14 July 2005

© Koninklijke Philips Electronics N.V. 2005. All rights reserved.

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