Cirrus Logic CS42L42 Manual page 80

• Tip–Ring–Ring–Sleeve (TRRS)—Like TRS, with an additional ring connector for the HSIN connection. There are
two common pinouts for TRRS plugs:
— One uses the tip for HPOUTA, the first ring for HPOUTB, the second ring for HSGND, and the sleeve for HSIN.
— OMTP, or China, headset, which swaps the third and fourth connections, so that the second ring carries HSIN
and the sleeve carries HSGND.
4.14.2 Tip-Sense/Ring-Sense Methods
The following methods are used to detect the presence or absence of a plug:
• Tip sense (TS)—A sense pin is connected to a terminal on the receptacle such that, if no plug is inserted, the pin is floating.
If a plug is inserted, the pin is shorted to the tip (T) terminal. The tip is sensed by having a small current source in the
device pull up the pin if it is left floating (no plug). If a plug is inserted and the sense pin is shorted to HPOUTA, the sense
pin is assumed to be pulled low via clamps at the HP amp output when it is in power down. If the HP amp is running, the
sense pin is shorted to the output signal and, therefore, is pulled below a certain threshold via the output stage of the HP
amp. Thus, a low level at the sense pin indicates plug inserted, and a high level at the sense pin indicates plug removed.
• Inverted tip sense (ITS)—Like tip sense, but with a connector whose sense pin is shorted to the tip terminal if the
plug is removed and is left floating if it is inserted. Therefore, a low level at the sense pin indicates plug removed
and a high level at the sense pin indicates plug inserted. Inversion is controlled by the following:
— The invert (TIP_SENSE_INV,
— The tip-sense invert (TS_INV,
• Ring sense (RS)—Like tip sense, except that the sense pin is shorted to the second ring terminal (HS3) when a plug
with a metal barrel (TRS or TRSS) is inserted, and floating when a plug with a plastic barrel (OPT) is inserted or the
plug is removed. If a metal plug is inserted and the sense pin is shorted to HS3, it is assumed that the sense pin is
pulled low (to HSGND) or below a certain threshold (to HSBIAS) via switches in the HS type-detect block. As a
result, a low level at the sense pin indicates metal plug inserted and a high level at the sense pin indicates plug
removed (plastic plug inserted or plug removed).
• Inverted ring sense (IRS)—Like ring sense, except that the connector is constructed such that the sense pin is
shorted to the second ring terminal (HS3) when the plug is removed and is left floating when it is inserted. Therefore,
a low level at the sense pin indicates plug removed; a high level indicates metal or plastic plug inserted.
4.14.3 Ring-Sense Configuration
The RING_SENSE pin can be used as a ground sense for the connected plug if the inserted plug is determined to be of
type TRS or TRRS. If the RING_SENSE pin is used as a ground reference, the impedance between the RING_SENSE
plug connector and the plug degrades the common-mode rejection of the output, which in turn affects output offset, step
deviation, and pop/click attenuation. The CS42L42 includes a RING_SENSE impedance-detection circuit to aid in the
decision to use the RING_SENSE input pin as a HP ground reference.
The impedance-detection circuit can be activated to test whether plug-connector-to-plug impedance exceeds ~1 k.
TRIM_T (see p. 132) determines the detection threshold. Pull-up resistance is controlled by the bits shown in
RING_SENSE_PU_HIZ
DS1083F2
p. 150), which goes to the analog and affects a number of other features.
p. 134), which affects only the configuration bits in
Table 4-24. Threshold Detection
(see p. 132) RS_TRIM_R
0
1
1
(See p. 132) Nominal Pull-Up Resistance
x 16.2 k
0 2.25 M
1 1.125 M
CS42L42
4.14 Plug Presence Detect
Section 6.5.
RS_
Table 4-24.
80