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ISL54230IRTZ Datasheet(PDF) 10 Page - Intersil Corporation |
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ISL54230IRTZ Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 18 page 10 FN6825.2 May 28, 2009 unexpectedly shut down if transient voltages trigger the POR. Overvoltage and Short Circuit Considerations The ISL54230 should be protected from overvoltage conditions. The IC contains ESD protection diodes that are back biased from the switch terminals to ground. Negative voltages on the switch terminals that are large enough to forward-bias these ESD protection diodes will result in a large current flowing from ground that may destroy these diodes. Thus, signals on the switch terminals should not swing below ground and cannot exceed the specified “Absolute Maximum Ratings” on page 5 for safe operation. The ISL54230 can have signals that go above the positive supply rail with no adverse effects up to +5.5V. The ESD protection circuitry permits the signal from going beyond the VDD supply (even with VDD = 0V) without inducing large leakage currents on the switch pins when the supply voltage is less than +5.5V. This feature complies with the USB 2.0 Specifications for short circuit protection in the event that the 5.25V VBUS line shorts to the USB signal lines. Note: When the supply voltage is above the POR threshold and a VBUS fault conditions occurs, the VBUS signal will be passed to the other side of the switch if the logic control pins are biased such that the switch is turned ON. USB Switches (COM2x and COM3x) The four USB FS and HS capable switches are bi-directional analog switches that can pass rail-to-rail signals with minimal distortion. With a 3.0V power supply, these switches have a nominal ON-resistance of 6 Ω in the 0V to 400mV signal range. The low capacitance and high bandwidth of the switches makes them ideal for USB applications. They are specifically designed to pass both USB FS (12Mbps) and USB HS (480Mbps) differential signals while meeting the USB 2.0 signal quality eye diagrams (Figures 25 and 26). The USB switches are designed with integrated protection circuitry for fault conditions as defined in the USB 2.0 Specifications-Section 7.1.1. If a condition where VBUS (5.25V) is shorted to the D+ or D- pin this will not damage the device, even without power to the IC. 1 Ω Switches (COM1A and COM4A) and 6Ω Switches (COM1B and COM4B) The two 1 Ω switches are bi-directional analog switches that can pass rail-to-rail signals, making them well suited for analog or digital signal routing. The low ON-resistance of the switches makes them ideal for switching ON/OFF power supply lines for applications that interface with devices that require power (ie: SIM cards or flash memory devices). With a ON-resistance of 1 Ω the power dissipation through the switch is minimal. The two 6 Ω switches are bi-directional analog switches that can pass rail-to-rail signals, making them well suited for analog or digital signal routing such as audio, UART or Full-Speed USB. The low ON-resistance of these switches are well suited for passing audio signals with good THD performance, even with low impedance loads such as 32 Ω headphones (see Figure 24 for THD performance curves). Logic Control Pins The ISL54230 contains six logic control pins, IN1 through IN4 for independently controlling each DPDT switch and two OE enable pins. The logic control pins determine the state of the switches. Refer to the “Input Select” and “OE Control” Truth Tables on page 3. When the OEx control pins are logic LOW, only the switches on COM2x and COM3x are active and the switch state determined by IN2 and IN3 respectively. When the OEx control pins are logic HIGH, all switches are active and the switch state determined by the INx control pins. When the OEx control pins are in opposing logic states either COM1x and COM2x are active or COM3x and COM4x are active depending on what states OE1 and OE2 are at. The active switches are controlled by the respective INx control pin. This feature is useful for applications that interface the ISL54230 to Master/Slave devices or controlling two SIM cards in Dual SIM Card cellphones. The OEx control pins permit total deactivation of each half of the switch blocks to disable devices connected to those switches. LOGIC CONTROL VOLTAGE LEVELS OEx = Logic “0” (Low) when VOEx ≤ 0.5V OEx = Logic “1” (High) when VOEx ≥ 1.4V INx = Logic “0” (Low) when VINx ≤ 0.5V INx = Logic “1” (High) when VINx ≥ 1.4V The logic control pins are +1.8V CMOS logic compatible (0.45V VOLMAX and 1.35V VOHMIN) for supply voltages from +1.8V to +3.6V. over a supply range of 1.8V to 3.3V (see Figure 23). At 3.6V the VIL level is 0.5V maximum. This is still below the 1.8V CMOS guaranteed low output maximum level of 0.45V, but noise margin is reduced. At 3.6V the VIH level is 1.4V minimum. While this is above the 1.8V CMOS guaranteed high output minimum of 1.35V under most operating conditions the switch will recognize this as a valid logic high. The digital input stages draws a larger supply current whenever the digital input voltage is not at one of the supply rails. Driving the digital input signals from GND to V+ with a fast transition time minimizes power dissipation. The ISL54230 has been designed to minimize the supply current whenever the digital input voltage is not driven to the supply rails (0V to V+). For example driving the device with 1.8V logic high while operating with a 3.6V supply the device draws only 1µA of current. ISL54230 |
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