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SP3222EBCY-LTR Datasheet(PDF) 9 Page - Exar Corporation |
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SP3222EBCY-LTR Datasheet(HTML) 9 Page - Exar Corporation |
9 / 21 page Exar Corporation 48720 Kato Road, Fremont CA, 94538 • 510-668-7017 • www.exar.com SP3220E_EB_EU_101_060311 9 The SP3220E/EB/EU devices meet the EIA/TIA-232 and ITU-T V.28/V.24 commu- nication protocols and can be implemented in battery-powered, portable, or hand-held applications such as notebook or palmtop computers. The SP3220E/EB/EU devices feature Exar's proprietary 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 SP3220EB device has a driver that can operate at a data rate of 250kbps fully loaded.The SP3220EU can operate at 1000kbps; the SP3220E device can operate at a typical data rate of 235kbps when fully loaded. The SP3220E/EB/EUisa1-driver/1-receiver device ideal for portable or hand-held ap- plications. The SP3220E/EB/EU features a 1µA shutdown mode that reduces power consumption and extends battery life in por- table 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 SP3220E/EB/EU series is made up of three basic circuit blocks: 1. Driver 2. Receiver 3. The Exar proprietary charge pump Driver Thedriverisaninvertingleveltransmitterthat converts 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 +5.5V with no load and at least +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 SP3220EB driver can guarantee a data rate of 250kbps fully loaded with 3kΩ in parallel with 1000pF, ensuring compatability withPC-to-PCcommunicationsoftware.The SP3220EU driver can guarantee a data rate of 1000kbps fully loaded with 3kΩ in parallel with 250pF. The slew rate of the SP3220E and SP3220EB outputs are 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 meet the monotonicity requirements of the standard. The slew rate of the SP3220EU is not limited. This allows it to transmit at much faster data rates. Figure 12 shows a loopback test circuit used to test the RS-232 Driver. Figure 13 shows the test results of the loopback circuit with the SP3220EB driver active at 250kbps with RS-232 load in parallel with a 1000pF capacitor. Figure 14 shows the test results where the SP3220EU driver was active at 1000kbps and loaded with an RS-232 receiver in parallel with 250pF ca- pacitors. A solid RS-232 data transmission rate of 250kbps provides compatibility with many designs in personal computer periph- erals and LAN applications. The SP3220E/EB/EU driver's output stage is turned off (tri-state) when the device is in shutdown mode. When the power is off, the SP3220E/EB/EU 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 SP3220E/EB/EU device is shut down, the device's driver output is disabled DESCRIPTION |
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