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ISL54406IRTZ-T 数据表(PDF) 10 Page - Intersil Corporation |
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ISL54406IRTZ-T 数据表(HTML) 10 Page - Intersil Corporation |
10 / 16 page ISL54406 10 FN6578.1 July 14, 2010 Audio Playback Mode If the SEL1 and SEL2 pins are Logic “1”, the device will be in the Audio Playback mode. In Audio Playback mode the LIN (left) and RIN (right) 2.5Ω audio switches are connected to LOUT and ROUT respectively, and the audio Click and Pop circuitry is inactive (high impedance). When headphones are connected to the LOUT and ROUT outputs of the ISL54406, the audio source drives the headphones with low distortion audio. Audio Mute Mode If SEL1 is Logic “0” and SEL2 is Logic “1”, the device will be in the Audio Mute Mode. In Audio Mute Mode the audio switches are OFF (high impedance), the audio Click and Pop shunt circuitry is OFF (high impedance), and the LOUT and ROUT pins are shorted through 6Ω resistors to ground. Off Isolation performance in Audio Mute Mode gives a 110 dB signal reduction across a 32Ω load when driving with a 0.707VRMS signal at the switch input. Click and Pop Mode Note: Click and Pop Mode should not be used for audio muting applications. In Click and Pop Mode, a low impedance (35Ω) path to ground at the LIN/RIN inputs will degrade Off Isolation performance (see Figure 14). If SEL1 is Logic “1” and SEL2 is Logic “0”, the device will go into Click and Pop Mode. This mode is optimal when powering up or down the audio sources. In Click and Pop Mode the audio in-line 2.5Ω switches are OFF (high impedance). The LOUT and ROUT pins are shorted through 6Ω resistors to ground and the LIN and RIN are shunted through 35Ω resistors to ground (Click and Pop circuitry is active). Before powering down or powering up of the audio source drivers, the ISL54406 should be put in the Click and Pop Mode. In Click and Pop Mode, transients generated at the LIN and RIN pins due to a DC step voltage at the audio drivers will not pass through the ISL54406 audio switches, preventing Click and Pop noise to the load. Shutdown Mode If SEL1 and SEL2 pins are Logic “0”, the device will enter a low powered Shutdown (SHDN) Mode. In SHDN, the audio switches are OFF, the 6Ω path is high impedance, the Click and Pop circuitry is inactive, and the device will draw a typical supply current of 5nA. Note: When the logic inputs are floated, the ISL54406 will automatically be placed in SHDN mode due to the internal 4MΩ pull down resistors on the logic pins. Note: In Shutdown Mode, the Off-Isolation of the audio switch degrades in performance compared to Audio Mute Mode. In SHDN, the negative charge pumps that permit the signal to swing below ground are turned off to reduce power consumption, thus any negative signal swing at the LIN and RIN will appear at the LOUT and ROUT pins. The device should not be placed into SHDN when the source is still active or for high Off-Isolation performance. CLICK AND POP OPERATION Single supply audio sources are biased at a DC offset that generates transients during power on/off of the source. This DC transient is coupled into the load through a blocking capacitor (see “Application Block Diagram” on page 9). When the source is off and suddenly turned on with a DC offset, the capacitor will develop a voltage across it that is equal to the DC offset. If the switch is in Audio mode when this occurs, a transient discharge will occur in the speaker, generating a Click and Pop noise. Proper elimination of Click and Pop transients requires that the ISL54406 be placed in Click and Pop Mode before the audio source is turned on or off. This allows any transients generated by the source to be discharged through the Click and Pop circuitry first. With a typical DC blocking capacitor of 220µF and the Click and Pop circuitry designed to have a resistance of 35Ω, allowing a 100ms dead-time for discharging a transient before placing the switch in Audio mode will eliminate the DC transient generated by the blocking capacitor. Note: The ISL54406 should not be brought into Audio Playback Mode directly from Shutdown Mode and vice versa. A DC transient may occur at the LOUT/ROUT pins when brought from Shutdown directly to Audio Playback mode. The recommended procedure is to place the ISL54406 into Mute mode for at least 100ms when entering or leaving Audio Playback mode. Power supply considerations The power supply connected at VDD and GND provides power to the ISL54406 part. In a typical application VDD will be in the range of +2.7V to +5.0V and will be connected to the battery or LDO of the MP3 player or cellphone. A 0.1µF local decoupling capacitor should be placed near the VDD pin of the IC to eliminate power supply transients. Before power-up and power-down of the ISL54406 part, the SEL1 and SEL2 logic control pins should be driven to Logic “0” or left floating. In a high impedance state, 4MΩ internal pull down resistors on the SEL1 and SEL2 pins will set the ISL54406 logic pins to “0”. This will put the switch in the SHDN state which turns all switches OFF and deactivates the Click and Pop circuitry which will minimize power supply currents and increase battery life. |
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类似说明 - ISL54406IRTZ-T |
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