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ISL54212 Arkusz danych(PDF) 9 Page - Intersil Corporation |
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ISL54212 Arkusz danych(HTML) 9 Page - Intersil Corporation |
9 / 15 page 9 FN6556.0 September 18, 2007 signal range of 0V to 400mV with a r(ON) flatness of 0.4Ω. The r(ON) matching between the D+ and D- switches over this signal range is only 0.06 Ω ensuring minimal impact by the switches to USB high speed signal transitions. As the signal level increases the r(ON) resistance increases. At signal level of 3.3V the switch resistance is nominally 23 Ω. 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 the high-speed eye diagram in 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 in Figures 12, 13 and 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 allow 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 ≤0.5V. 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. ISL54212 Operation The sections that follow will discuss using the ISL54212 in the typical application shown in the block diagram on page 8. 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 ISL54212 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 of the data sheet. 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 4M Ω resistor to ground and can be tri-stated by the µprocessor. The CTRL control pin is only active when IN is logic “1”. The IN pin does not have an internal pull-down resistor and must not be allowed to float. It must be driven High or Low. Logic control voltage levels: IN = Logic “0” (Low) when IN ≤0.5V IN = Logic “1” (High) when IN ≥1.4V CTRL = Logic “0” (Low) when ≤0.5V or floating CTRL = Logic “1” (High) when ≥1.4V Audio Mode If the IN pin = Logic “1” and CTRL pin = Logic “1,” the part will be in the Audio mode. In Audio mode the L (left) and R (right) 3 Ω audio switches are ON and the D- and D+ 5Ω USB switches are OFF. When nothing is plugged into the common connector or a headphone is plugged into the common connector, the µprocessor will sense that there is no voltage at the VBUS pin of the connector and will drive and hold the IN control pin of the ISL54212 high. As long as the CTRL = Logic “1,” the ISL54212 part will be in the audio mode and the audio drivers of the media player can drive the headphones and play music. USB Mode If the IN pin = Logic “0” and CTRL pin = Logic “0” or Logic “1” the part will go into USB mode. In USB mode, the D- and D+ 5 Ω switches are ON and the L and R 3Ω audio switches are OFF. When a USB cable from a computer or USB hub is connected at the common connector, the µprocessor will sense the presence of the 5V VBUS and drive the IN pin voltage low. The ISL54212 part will go into the USB mode. In USB mode, the computer or USB hub transceiver and the MP3 player or cell phone USB transceiver are connected and digital data will be able to be transmitted back and forth. When the USB cable is disconnected, the μprocessor will sense that the 5V VBUS voltage is no longer connected and will drive the IN pin high and put the part back into the Audio or Low Power mode. Low Power Mode If the IN pin = Logic “1” and CTRL pin = Logic “0,” the part will be in the Low Power mode. In the Low Power mode, the audio switches and the USB switches are OFF. In this state, the device draws typically 1nA of current. ISL54212 |
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