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ADM211AR датащи(PDF) 9 Page - Analog Devices |
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ADM211AR датащи(HTML) 9 Page - Analog Devices |
9 / 12 page ADM205–ADM211/ADM213 REV. 0 –9– 10 90 100 0% 5V 0.8 V A3 5V 5 B Lw 1Ms H O Figure 20. Charge Pump, V+, V– Exiting Shutdown 10 90 100 0% 5V 0.8 V A3 5 B Lw 5 µs H O Figure 21. Transmitter Output Loaded Slew Rate 10 90 100 0% 5V 0.8 V A3 5 B Lw 1 µs H O Figure 22. Transmitter Output Unloaded Slew Rate GENERAL INFORMATION The ADM205-ADM211 and ADM213 family of RS-232 driv- ers/receivers are designed to solve interface problems by meeting the EIA-232-E specifications while using a single digital +5 V supply. The EIA-232-E standard requires transmitters which will deliver ±5 V minimum on the transmission channel and re- ceivers which can accept signal levels down to ±3 V. The ADM205-ADM211 and ADM213 meet these requirements by integrating step up voltage converters and level shifting trans- mitters and receivers onto the same chip. CMOS technology is used to keep the power dissipation to an absolute minimum. A comprehensive range of transmitter/receiver combinations is available to cover most communications needs. The ADM205– ADM211 and ADM213 are modifications, enhancements and improvements to the AD230–AD241 family and derivatives thereof. They are essentially plug-in compatible and do not have materially different applications. The ADM205, ADM206, ADM211, and ADM213 are particu- larly useful in battery powered systems as they feature a low power shutdown mode which reduces power dissipation to less than 5 µW. The ADM205 is designed for applications where space saving is important as the charge pump capacitors are molded into the package. The ADM209 includes only a negative charge pump converter and are intended for applications where a positive 12 V is available. To facilitate sharing a common line or for connection to a mi- croprocessor data bus the ADM205, ADM206, ADM209, ADM211 and ADM213 feature an enable (EN) function. When disabled, the receiver outputs are placed in a high impedance state. CIRCUIT DESCRIPTION The internal circuitry in the ADM205-ADM211 and ADM213 consists of three main sections. These are: (a) A charge pump voltage converter (b) RS-232 to TTL/CMOS receivers (c) TTL/CMOS to RS-232 transmitters Charge Pump DC-DC Voltage Converter The charge pump voltage converter consists of an oscillator and a switching matrix. The converter generates a ±10 V supply from the input 5 V level. This is done in two stages using a switched capacitor technique as illustrated in Figures 23 and 24. First, the 5 V input supply is doubled to 10 V using capacitor C1 as the charge storage element. The 10 V level is then in- verted to generate –10 V using C2 as the storage element. S1 S3 V+ = 2V CC S2 S4 INTERNAL OSCILLATOR C1 C3 V CC GND V CC Figure 23. Charge-Pump Voltage Doubler S1 S3 S2 S4 INTERNAL OSCILLATOR C2 C4 V– = – (V+) GND V+ GND FROM VOLTAGE DOUBLER Figure 24. Charge-Pump Voltage Inverter Capacitors C3 and C4 are used to reduce the output ripple. Their values are not critical and can be reduced if higher levels of ripple are acceptable. The charge pump capacitors C1 and C2 may also be reduced at the expense of higher output imped- ance on the V+ and V– supplies. The V+ and V– supplies may also be used to power external cir- cuitry if the current requirements are small. |
Аналогичный номер детали - ADM211AR |
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Аналогичное описание - ADM211AR |
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