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ISL54206A_1010 Datasheet(PDF) 10 Page - Intersil Corporation |
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ISL54206A_1010 Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 20 page ISL54206A 10 FN6515.3 October 28, 2010 Audio Switches The two audio switches (L, R) are 3Ω switches that can pass signals that swing below ground by as much as 1.5V. They were designed to pass ground reference stereo signals with minimal insertion loss and very low distortion. Crosstalk between the audio switches over the audio band is < -110dB. Over a signal range of ±1V (0.707VRMS) with VDD >2.7V, these switches have an extremely low RON resistance variation. They can pass ground referenced audio signals with very low distortion (<0.06% THD+N) when delivering 15.6mW into a 32Ω headphone speaker load. See Figures 8, Figures 9, Figures 10, and Figures 11 THD+N performance curves. These switches are uni-directional switches. The audio drivers should be connected at the L and R side of the switch (pin 7 and pin 8) and the speaker loads should be connected at the COM side of the switch (pin 3 and pin 4). The audio switches are active (turned ON) whenever the IN voltage is ≤0.5V and the CTRL voltage to ≥1.4V. Note: Whenever the audio switches are ON, the USB transceivers need to be in the high impedance state or static high or low state. USB Switches The two USB switches (D+, D-) are bidirectional switches that can pass rail-to-rail signals. When powered with a 3.6V supply, these switches have a nominal rON of 4.6Ω over the signal range of 0V to 400mV with a rON flatness of 0.4Ω. The rON matching between the D+ and D- switches over this signal range is only 0.06Ω ensuring minimal impact by the switches to USB high speed signal transitions. As the signal level increases, the rON resistance increases. At signal level of 3.3V the switch resistance is nominally 23Ω. The USB switches were specifically designed to pass USB 2.0 high-speed (480Mbps) differential signals typically in the range of 0V to 400mV. They have low capacitance and high bandwidth to pass the USB high-speed signals with minimum edge and phase distortion to meet USB 2.0 high speed signal quality specifications. See high-speed eye diagram Figure 15. The USB switches can also pass USB full-speed signals (12Mbps) with minimal distortion and meet all the USB requirements for USB 2.0 full-speed signaling. See the full-speed eye diagrams, Figures 12 thru 14. The maximum signal range for the USB switches is from -1.5V to VDD. The signal voltage at D- and D+ should not be allowed to exceed the VDD voltage rail or go below ground by more than -1.5V. The USB switches are active (turned ON) whenever the IN voltage is ≥1.4V. Note: Whenever the USB switches are ON, the audio drivers of the CODEC need to be at AC or DC ground or floating to keep from interfering with the data transmission. USB Switch Cell Off-Isolation Due to the unique internal architecture of the ISL54206A part, the USB switch cell has limited off-isolation to a negative signal at the COM side of the part. When driving an audio signal into the L and R inputs a small negative voltage will appear at the D- and D+ lines as the audio signal transitions below ground. With a USB transceiver connected at the D-/D+ pins and with a 32Ω headphone connected at the COM pins Table 1 shows the negative voltage generated at the D-/D+ lines as you increase the audio amplitude across the headphone load. The USB specification (USB Specification Rev 2.0, Chapter 7, Section 7.1.1) states that a USB transceiver must be able to tolerate a -1V signal at its D-/D+ differential inputs. The data in the table shows that the -1V level is never exceeded during audio operation and should have no impact on the long-term reliability of the USB transceiver. ISL54206A Operation The following discussion discusses using the ISL54206A in the typical application shown in the block diagrams on page 9. VDD SUPPLY The DC power supply connected at VDD (pin 1) provides the required bias voltage for proper switch operation. The part can operate with a supply voltage in the range of 2.5V to 5.5V. In a typical USB/Audio application for portable battery powered devices, the VDD voltage will come from a battery or an LDO and be in the range of 2.7V to 3.6V. For best possible USB full-speed operation (12Mbps), it is recommended that the VDD voltage be ≥2.5V in order to get a USB data signal level above 2.5V. LOGIC CONTROL The state of the ISL54206A device is determined by the voltage at the IN pin (pin 2) and the CTRL pin (pin 10). Refer to “Truth Table” on page 2. These logic pins are 1.8V logic compatible when VDD is in the range of 2.7V to 3.6V and can be controlled by a standard µprocessor. The CTRL pin is internally pulled low through a 4MΩ resistor to ground and can be left floating or tri-stated by TABLE 1. AUDIO SIGNAL AMPLITUDE D-/D+ VOLTAGE (V) +25°C +85°C 800mVP-P -0.22 -0.27 880mVP-P -0.24 -0.3 1.08VP-P -0.3 -0.34 2VP-P -0.41 -0.44 2.25VP-P -0.47 -0.5 4VP-P -0.83 -0.85 |
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