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SP3282EB Datasheet(PDF) 6 Page - Sipex Corporation |
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SP3282EB Datasheet(HTML) 6 Page - Sipex Corporation |
6 / 15 page Date: 02/24/05 SP3282EB Intelligent +2.35V to +5.5V RS-232 Transceivers © Copyright 2005 Sipex Corporation 6 DESCRIPTION The SP3282EB device meets the EIA/TIA-232 and ITU-T V.28/V.24 communication protocols and can be implemented in battery-powered, por- table, or hand-held applications such as notebook or palmtop computers. The SP3282EB device features Sipex's proprietary and patented (U.S. #5,306,954) on-board charge pump circuitry that generates ±5.5V RS-232 voltage levels from a single +3.3V to +5.5V power supply. The SP3282EB will adhere to EIA/TIA-562 voltage levels with V CC as low as 2.35V. The SP3282EB device is an ideal choice for power sensitive designs. The SP3282EB device features AUTO ON-LINE® circuitry which reduces the power supply drain to a 1 µA supply current. In many portable or hand-held applications, an RS- 232 cable can be disconnected or a connected peripheral can be turned off. Under these condi- tions, the internal charge pump and the drivers will be shut down. Otherwise, the system automati- cally comes online. This feature allows design engineers to address power saving concerns with- out major design changes. THEORY OF OPERATION The SP3282EB device is made up of four basic circuit blocks: 1. Drivers, 2. Receivers, 3. The Sipex proprietary charge pump, and 4. AUTO ON-LINE® circuitry. Drivers The drivers are inverting level transmitters that , when V CC is between +3.3V and +5.5V, 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 without degradation in reliability. These drivers comply with the EIA-TIA-232F and all previous RS-232 versions. The driver outputs will adhere to EIA/ TIA-562 when V CC is as low as 2.35V. The SP3282EB drivers can guarantee a data rate of 250 kbps fully loaded with 3k Ω in parallel with 1000pF, ensuring compatibility with PC-to-PC communication software. All unused driver inputs must be connected to V L or GND. Figure 6 shows a loopback test circuit used to test the SP3282EB RS-232 drivers. Figure 7 shows the test results of the loopback circuit with all five drivers active at 120kbps with typical RS-232 loads in parallel with 1000pF capacitors. Figure 8 shows the test results where one driver was active at 250kbps and all five 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 per- sonal computer peripherals and LAN applications. Receivers The receivers convert ±5.0V EIA/TIA-232 levels to TTL or CMOS logic output levels. Receivers are not active when in shutdown. If there is no activity present at the receivers for a period longer than 100 µs during AUTO ON- LINE® mode or when SHUTDOWN is enabled, the device goes into a standby mode where the circuit draws 1 µA. The truth table logic of the driver and receiver outputs can be found in Table 3. Figure 5. Interface Circuitry Being Controlled by Microprocessor Supervisory Circuit SP3282EB 28 25 3 1 27 4 26 GND C1+ C1- C2+ C2- V+ V- VCC 0.1µF 0.1µF 0.1µF + C2 C5 C1 + + C3 C4 + + 0.1µF 0.1µF 13 14 15 VCC 2 ONLINE SHUTDOWN STATUS µP Supervisor IC VCC VIN RESET 5kΩ 5kΩ 5kΩ 24 23 22 21 20 18 5 6 7 8 9 11 RS-232 OUTPUTS RS-232 INPUTS T 1IN R 1OUT R 1IN T 2OUT T 2IN T 3IN T 3OUT T 1OUT R 2IN R 3IN R 2OUT R 3OUT UART or Serial µC TxD RTS DTR RxD CTS DSR DCD RI 19 17 10 12 T 4OUT T 4IN T 5IN T 5OUT 16 VL |
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