NCS2302

http://onsemi.com

7

TYPICAL CHARACTERISTICS

Figure 9. High to Low Propagation to SE with

Changing Input Overdrive of SE_DET

PROPAGATION DELAY (ns)

700

400

300

200

100

0

−100

−0.1

0

0.1

0.3

0.4

0.5

0.7

0.8

0.2

0.6

INPUT

OUTPUT

100 mV

50 mV

20 mV

10 mV

−0.5

0

0.5

1.5

2.0

2.5

3.5

4.0

1.0

3.0

500

600

APPLICATIONS INFORMATION

Supply Voltages

The NCS2302 works with a wide range of supply

voltages. The main headset detection circuitry power supply

send/end detection comparator will not be functional unless

voltage. Decoupling capacitors of 0.1

mF should be placed

as close as possible to each power supply pin. Since the

NCS2302 has built in latch−up immunity up to 800 mA,

series resistors are not recommended on VDD or VDD2.

Audio Jack Detection

The NCS2302 is designed to simplify the detection of a

stereo audio connector with a microphone contact. When the

headset is not connected, the internal pull−up resistors on

L_DET and GND_DET pull those pins high. When the

headset is connected to the switched audio jack, the headset

ground and left audio channel trigger L_DET and

GND_DET to logic low.

The NCS2302 can work with either the CTIA or OMTP

standard. In order to support both standards simultaneously,

a cross point switch and additional circuitry is necessary to

detect and swap the ground and microphone pins.

Send/End Button Press Detection

A second integrated comparator allows the send/end

signal to be compared with a reference voltage to detect

whether the send/end button has been pressed.

MIC Pin Biasing

The typical application schematic in Figure 1 shows the

recommended 2.2 k

W pull−up resistor to the MIC bias

as high as 2.95 V. When the headset is not detected, the

internal NMOS transistor is enabled to mute the MIC signal.

In the typical application scenario with a 2.2 k

W pull−up to

a 2.1 V MIC bias voltage, the MIC pin is pulled to 1 mV

when the headset is not present. The internal NMOS

transistor is optimized to sink up to 2 mA of current,

allowing some flexibility in the selection of the pull−up

resistor and MIC bias voltage.