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SP3222ECT Datasheet(PDF) 8 Page - Sipex Corporation |
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SP3222ECT Datasheet(HTML) 8 Page - Sipex Corporation |
8 / 20 page Date: 02/24/05 SP3222E, SP3232E True +3.0 to +5.0V RS-232 Transceivers © Copyright 2005 Sipex Corporation 8 DESCRIPTION The SP3222E/3232E transceivers meet the EIA/ TIA-232 and V.28/V.24 communication proto- cols and can be implemented in battery-pow- ered, portable, or hand-held applications such as notebook or palmtop computers. The SP3222E/ 3232E devices all feature Sipex's proprietary on-board charge pump circuitry that generates 2 x V CC 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 re- quire true RS-232 performance. The SP3222E/ 3232E series have drivers that operate at a typi- cal data rate of 235Kbps fully loaded. The SP3222E and SP3232E are 2-driver/2-re- ceiver devices ideal for portable or hand-held applications. The SP3222E features a 1 µA shutdown mode that reduces power consump- tion 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 1 µA supply current. THEORY OF OPERATION The SP3222E/3232E series are made up of three basic circuit blocks: 1. Drivers, 2. Receivers, and 3. the Sipex proprietary charge pump. Drivers The drivers are inverting level transmitters that convert TTL or CMOS logic levels to ±5.0V EIA/TIA-232 levels inverted relative to the in- put logic levels. Typically, the RS-232 output voltage swing is ±5.5V with no load and at least ±5V minimum fully loaded. The driver outputs are protected against infinite short-circuits to ground without degradation in reliability. Driver outputs will meet EIA/TIA-562 levels of ±3.7V with supply voltages as low as 2.7V. The drivers typically can operate at a data rate of 235Kbps. The drivers can guarantee a data rate of 120Kbps fully loaded with 3K Ω in parallel with 1000pF, ensuring compatibility with PC-to-PC communication software. The slew rate of the driver output is internally limited to a maximum of 30V/ µs in order to meet the EIA standards (EIA RS-232D 2.1.7, Para- graph 5). The transition of the loaded output from HIGH to LOW also meets the monotonic- ity requirements of the standard. The SP3222E/3232E drivers can maintain high data rates up to 235Kbps fully loaded. Figure 8 shows a loopback test circuit used to test the RS-232 drivers. Figure 9 shows the test results of the loopback circuit with all drivers active at 120Kbps with RS-232 loads in parallel with 1000pF capacitors. Figure 10 shows the test results where one driver was active at 235Kbps and all drivers loaded with an RS-232 receiver in parallel with a 1000pF capacitor. A solid RS-232 data transmission rate of 120Kbps provides compatibility with many designs in personal computer peripherals and LAN applications. The SP3222E driver's output stages are turned off (tri-state) when the device is in shutdown mode. When the power is off, the SP3222E 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 V CC or GND. In the shutdown mode, the supply current falls to less than 1 µA, where SHDN = LOW. When the SP3222E 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 V CC and V- pulled to GND. The time required to exit shutdown is typically 100 µs. Connect SHDN to V CC if the shutdown mode is not used. SHDN has no effect on RxOUT or RxOUTB. As they become active, the two driver outputs go to opposite RS-232 levels where one driver input is HIGH and the other LOW. Note that the drivers are enabled only when the magnitude of V- exceeds approximately 3V. |
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