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ISL54222IRUZ-T 데이터시트(PDF) 8 Page - Intersil Corporation |
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ISL54222IRUZ-T 데이터시트(HTML) 8 Page - Intersil Corporation |
8 / 15 page 8 FN6835.1 May 27, 2009 range of 1.8V to 3.3V the fault voltage will pass through to the output of an active switch channel. During the fault condition normal operation is not guaranteed until the fault is removed. See the “USB 2.0 VBUS Short Requirements” section below. The HS1 channel switches are active (turned ON) whenever the SEL voltage is Logic ”0” (Low) and the OE voltage is Logic ”0”(Low). The HS2 channel switches are active (turned ON) whenever the SEL voltage is Logic “1” (High) and the OE voltage is Logic “0” (Low). ISL54222 Operation The following will discuss using the ISL54222 shown in the “Application Block Diagram” on page 7. POWER The power supply connected at the VDD pin provides the DC bias voltage required by the ISL54222 part for proper operation. The ISL54222 can be operated with a VDD voltage in the range of 1.8V to 3.3V. 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. LOGIC CONTROL The state of the ISL54222 device is determined by the voltage at the SEL pin and the OE pin. SEL is only active when the OE pin is Logic “0” (Low). Refer to the “Truth Table” on page 2. The ISL54222 logic pins are designed to minimize current consumption when the logic control voltage is lower than the VDD supply voltage. With VDD = 3.3V and logic pins at 1.4V the part typically draws only 35µA of IDD current. With VDD = 1.8V and logic pins at 1.4V the part typically draws only 6µA of IDD current. Driving the logic pins to the VDD supply rail minimizes power consumption. The logic pins must be held High or Low and must not float. Logic Control Voltage Levels With VDD supply voltage in the range of 1.8V to 3.3V the logic levels are: OE = Logic “0” (Low) when VOE ≤ 0.5V OE = Logic “1” (High) when VOE ≥ 1.4V SEL = Logic “0” (Low) when VSEL ≤ 0.5V SEL = Logic “1” (High) when VSEL ≥ 1.4V HSD1 USB Channel If the SEL pin = Logic “0” and the OE pin = Logic “0”, 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 pin = Logic “0”, 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 transceiver 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 pin = Logic “1”, 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 switching from one USB transceiver section to the other USB transceiver section, you can momentarily put the ISL54222 switch in the “ALL OFF” state, in order to get the computer to disconnect from the current USB section, so it can properly connect to the other USB transceiver section when that channel is turned ON. USB 2.0 VBUS Short Requirements The USB 2.0 specification in chapter 7, section 7.1.1 states a USB device must be able to withstand a VBUS short to the D+ or D- signal lines when the device is either powered off or powered on for at least 24 hours. The ISL54222 part has special fault protection circuitry to meet these short circuit requirements. The fault protection circuitry allows the signal pins (D-, D+, HSD1-, HSD1+, HSD2-, HSD2+) to be driven up to 5.5V while the VDD supply voltage is in the range of 0V to 3.3V. In this overvoltage condition the part draws < 300µA of IDD current and causes no stress/damage to the IC. In addition when VDD is at 0V (ground), all switches are OFF and the shorted VBUS voltage is isolated from the other side of the switch. When VDD is in the range of 1.8V to 3.3V, the shorted VBUS voltage will pass through to the output of an active (turned ON) switch channel but not through a turned OFF channel. Any components connected on the active channel must be able to withstand the overvoltage condition. Note: During the fault condition normal operation of the USB channel is not guaranteed until the fault condition is removed. ISL54222 |
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