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전자부품 데이터시트 검색엔진 |
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전자부품 데이터시트 검색엔진 |
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SP3243 데이터시트(PDF) 8 Page - Sipex Corporation |
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SP3243 데이터시트(HTML) 8 Page - Sipex Corporation |
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8 / 19 page  Rev. 6/30/03 SP3238 Intelligent +3.0V to +5.5V RS-232 Transceiver © Copyright 2003 Sipex Corporation 8 DESCRIPTION The SP3238 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 SP3238 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 +3.0V to +5.5V power supply. The SP3238 device can guarantee a data rate of 250kbps fully loaded. The SP3238 is a 5-driver/3-receiver device, ideal for portable or hand-held applications. The SP3238 includes one complementary always-active receiver that can monitor an external device (such as a modem) in shutdown. This aids in protecting the UART or serial controller IC by preventing forward biasing of the protection diodes where VCC may be disconnected. The SP3238 device is an ideal choice for power sensitive designs. The SP3238 device features AUTO ON-LINE® circuitry which re- duces the power supply drain to a 1 µA supply current. In many portable or hand-held applica- tions, an RS-232 cable can be disconnected or a connected peripheral can be turned off. Under these conditions, the internal charge pump and the drivers will be shut down. Otherwise, the system automatically comes online. This feature allows design engineers to address power saving concerns without major design changes. THEORY OF OPERATION The SP3238 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 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 drivers can guarantee a data rate of 250kbps fully loaded with 3k Ω in parallel with 1000pF, ensuring compatibility with PC-to-PC commu- nication software. All unused driver inputs must be connected to VCC or GND. 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, Paragraph 5). The transition of the loaded output from HIGH to LOW also meets the monotonicity requirements of the standard. Figure 6. Interface Circuitry Controlled by Microprocessor Supervisory Circuit SP3238 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 16 21 20 18 5 6 7 8 9 11 RS-232 OUTPUTS RS-232 INPUTS T 1IN R 1OUT R 1IN T 2OUT R 1OUT 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 |
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