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SP3232EUCA-L Datasheet(PDF) 8 Page - Exar Corporation |
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SP3232EUCA-L Datasheet(HTML) 8 Page - Exar Corporation |
8 / 20 page 8 Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3222EU/SP3232EU_102_031413 The SP3222EU/SP3232EU transceivers meet the EIA/TIA-232 and ITU-T V.28/V.24 communication protocols and can be imple- mented in battery-powered, portable, or hand-held applications such as notebook or palmtop computers. The SP3222EU/ SP3232EU devices feature Exar's propri- etary on-board charge pump circuitry that generates ±5.5V for RS-232 voltage levels from a single +3.0V to +5.5V power supply. This series is ideal for +3.3V-only systems, mixed +3.3V to +5.5V systems, or +5.0V- only systems that require true RS-232 performance. The SP3222EU/SP3232EU devices can operate at a minimum data rate of 1000kbps. The SP3222EU and SP3232EU are 2- driver/2- receiver devices ideal for portable or hand-held applications. The SP3222EU features a 1µA shutdown mode that reduces power consumption and extends battery life in portable systems. Its receivers remain active in shutdown mode, allowing external devices such as modems to be monitored using only 1µA supply current. THEORY OF OPERATION The SP3222EU/SP3232EU series is made up of three basic circuit blocks: 1. Drivers 2. Receivers 3. The Exar proprietary charge pump Drivers The drivers are inverting level transmitters that convert TTL or CMOS logic levels to +5.0V EIA/TIA-232 levels with an inverted sense relative to the input logic levels. Typically, the RS-232 output voltage swing is +5.4V with no load and +5V minimum fully loaded. The driver outputs are protected against infinite short-circuits to ground with- out degradation in reliability. Driver outputs will meet EIA/TIA-562 levels of +/-3.7V with supply voltages as low as 2.7V. The drivers have a minimum data rate of 1000kbps fully loaded with 3kΩ in parallel with 250pF, ensuring compatability with PC- to-PC communication software. Figure 11 shows a loopback test circuit used to test the RS-232 Drivers. Figure 12 shows the test results of the loopback circuit with all drivers active at 250kbps with RS-232 loads in parallel with a 1000pF capacitor. Figure 13 shows the test results where one driver was active at 1000kbps and all drivers loaded with an RS-232 receiver in parallel with 250pF capacitors. The SP3222EU driver's output stages are turned off (tri-state) when the device is in shutdown mode. When the power is off, the SP3222EU device permits the outputs to be driven up to +/-12V. The driver's inputs do not have pull-up resistors. Designers should connect unused inputs to Vcc or GND. In the shutdown mode, the supply current falls to less than 1µA, where SHDN = LOW. When the SP3222EU device is shut down, the device's driver outputs are disabled (tri- stated) and the charge pumps are turned off with V+ pulled down to Vcc and V- pulled to GND. The time required to exit shutdown is typically 100µs. Connect SHDN to Vcc if the shutdown mode is not used. Receivers The Receivers convert EIA/TIA-232 levels to TTL or CMOS logic output levels. The SP3222EU receivers have an inverting tri-state output. These receiver outputs (RxOUT) are tri-stated when the enable control EN = HIGH. In the shutdown mode, the receivers can be active or inactive. EN has no effect on TxOUT. The truth table logic ofthe SP3222EUdriverandreceiveroutputs can be found in Table 2. DESCRIPTION |
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