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ISL54224IRUEVAL1Z 데이터시트(PDF) 11 Page - Intersil Corporation |
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ISL54224IRUEVAL1Z 데이터시트(HTML) 11 Page - Intersil Corporation |
11 / 18 page 11 FN6969.0 June 7, 2010 For lowest power consumption you should use the lowest VDD supply. A 0.01µF or 0.1µF decoupling capacitor should be connected from the VDD pin to ground to filter out any power supply noise from entering the part. The capacitor should be located as close to the VDD pin as possible. In a typical application, VDD will be in the range of 2.8V to 4.3V and will be connected to the battery or LDO of the portable media device. LOGIC CONTROL The state of the ISL54224 device is determined by the voltage at the SEL pin and the OE/ALM pin. SEL is only active when the OE/ALM pin is logic “1” (High). Refer to “Truth Table” on page 2. The ISL54224 logic pins are designed to minimize current consumption when the logic control voltage is lower than the VDD supply voltage. With VDD = 3.6V and logic pins at 1.4V the part typically draws only 25µA. With VDD = 4.3V and logic pins at 2.6V the part typically draws only 35µA. Driving the logic pins to the VDD supply rail minimizes power consumption. The SEL pin and OE/ALM pin have special circuitry that allows them to be driven with a voltage higher than the VDD supply voltage. These pins can be driven up to 5.25V with a VDD supply in the range of 2.7V to 5.25V. The SEL pin and OE/ALM pin are internally pulled low through 4MΩ resistors to ground and can be tri-stated by a µProcessor. The OE/ALM pin is an open drain connection. It should be pulled high through an external 100kΩ pull-up resistor. The OE/ALM pin can then be driven “Low” by a µProcessor to open all switches or it can be monitored by the µProcessor for a “Low” when the part goes into an over-voltage condition. Logic Control Voltage Levels HSD1 USB Channel If the SEL pin = Logic “0” and the OE/ALM pin = Logic “1”, high-speed Channel 1 will be ON. The HSD1- and HSD1+ switches are ON and the HSD2- and HSD2+ switches are OFF (high impedance). When a computer or USB hub is plugged into the common USB connector and Channel 1 is active, a link will be established between the USB 1 transceiver section of the media player and the computer. The device will be able to transmit and receive data from the computer. HSD2 USB Channel If the SEL pin = Logic “1” and the OE/ALM pin = Logic “1”, high-speed Channel 2 will be ON. The HSD2- and HSD2+ switches are ON and the HSD1- and HSD1+ switches are OFF (high impedance). When a USB cable from a computer or USB hub is connected at the common USB connector and Channel 2 is active, a link will be established between the USB 2 driver section of the media player and the computer. The device will be able to transmit and receive data from the computer. All Switches OFF Mode If the SEL pin = Logic “0” or Logic “1” and the OE/ALM pin = Logic “0”, all of the switches will turn OFF (high impedance). The all OFF state can be used to switch between the two USB sections of the media player. When disconnecting from one USB device to the other USB device, you can momentarily put the ISL54224 switch in the “all off” state in order to get the computer to disconnect from the one device so it can properly connect to the other USB device when that channel is turned ON. Whenever the ISL54224 senses a fault condition on the COM pins, the OE/ALM pin will be internal pulled low by the device and all switches will be turned OFF. USB 2.0 VBUS Short Requirements The USB specification in section 7.1.1 states a USB device must be able to withstand a VBUS short (4.4V to 5.25V) or a -1V short to the D+ or D- signal lines when the device is either powered off or powered on for at least 24 hours. The ISL54224 part has special power-off protection and OVP detection circuitry to meet these short circuit requirements. This circuitry allows the ISL54224 to provide protection to the USB down-stream transceivers connected at its signal pins (HS1D-, HS1D+, HS2D-, HS2D+) to meet the USB specification short circuit requirements. The power-off protection and OVP circuitry allows the COM pins (D-, D+) to be driven up to 5.25V or down to -5V while the VDD supply voltage is in the range of 0V to 5.25V. In these overvoltage conditions with a 500Ω external VDD resistor the part draws < 55µA of current into the COM pins and causes no stress/damage to the IC. In addition, all switches are OFF and the shorted VBUS voltage will be isolated from getting through to the other side of the switch channels, thereby protecting the USB transceivers. TABLE 2. LOGIC CONTROL VOLTAGE LEVELS VDD SUPPLY RANGE LOGIC = “0” (LOW) LOGIC = “1” (HIGH) OE/ALM SEL OE/ALM SEL 2.7V to 3.6V ≤ 0.5V or floating ≤ 0.5V or floating ≥1.4V ≥1.4V 3.7V to 4.2V ≤ 0.7V or floating ≤ 0.7V or floating ≥1.7V ≥1.7V 4.3V to 5.25V ≤ 0.8V or floating ≤ 0.8V or floating ≥2.0V ≥2.0V ISL54224 |
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