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ICL232CBEZT Datasheet(PDF) 5 Page - Intersil Corporation |
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ICL232CBEZT Datasheet(HTML) 5 Page - Intersil Corporation |
5 / 7 page 5 FN3020.7 July 28, 2005 Detailed Description The ICL232 is a dual RS-232 transmitter/receiver powered by a single +5V power supply which meets all ElA RS232C specifications and features low power consumption. The functional diagram illustrates the major elements of the ICL232. The circuit is divided into three sections: a voltage doubler/inverter, dual transmitters, and dual receivers Voltage Converter. An equivalent circuit of the dual charge pump is illustrated in Figure 5. The voltage quadrupler contains two charge pumps which use two phases of an internally generated clock to generate +10V and -10V. The nominal clock frequency is 16kHz. During phase one of the clock, capacitor C1 is charged to VCC. During phase two, the voltage on C1 is added to VCC, producing a signal across C2 equal to twice VCC. At the same time, C3 is also charged to 2VCC, and then during phase one, it is inverted with respect to ground to produce a signal across C4 equal to -2VCC. The voltage converter accepts input voltages up to 5.5V. The output impedance of the doubler (V+) is approximately 200 Ω, and the output impedance of the inverter (V-) is approximately 450 Ω. Typical graphs are presented which show the voltage converters output vs input voltage and output voltages vs load characteristics. The test circuit (Figure 3) uses 1 µF capacitors for C1-C4, however, the value is not critical. Increasing the values of C1 and C2 will lower the output impedance of the voltage doubler and inverter, and increasing the values of the reservoir capacitors, C3 and C4, lowers the ripple on the V+ and V- supplies. Transmitters The transmitters are TTL/CMOS compatible inverters which translate the inputs to RS-232 outputs. The input logic threshold is about 26% of VCC , or 1.3V for VCC = 5V. A logic 1 at the input results in a voltage of between -5V and V- at the output, and a logic 0 results in a voltage between +5V and (V+ - 0.6V). Each transmitter input has an internal 400k Ω pullup resistor so any unused input can be left unconnected and its output remains in its low state. The output voltage swing meets the RS-232C specification of ±5V minimum with the worst case conditions of: both transmitters driving 3k Ω minimum load impedance, VCC = 4.5V, and maximum allowable operating temperature. The transmitters have an internally limited output slew rate which is less than 30V/ µs. The outputs are short circuit protected and can be shorted to ground indefinitely. The powered down output impedance is a 9 9 R2out Receiver 2 TTL/CMOS output. 10 10 T2IN Transmitter 2 TTL/CMOS input, with internal 400K pullup resistor to VCC. 11 11 T1IN Transmitter 1 TTL/CMOS input, with internal 400K pullup resistor to VCC. 12 12 R1OUT Receiver 1 TTL/CMOS output. 13 13 R1IN RS-232 Receiver 1 input, with internal 5K pulldown resistor to GND. 14 14 T1OUT RS-232 Transmitter 1 output ±10V (typical). 15 15 GND Supply Ground. 16 16 VCC Positive Power Supply +5V ±10% Pin Descriptions (Continued) PDIP, CERDIP SOIC PIN NAME DESCRIPTION + - C1 + - C3 + - C2 + - C4 S1 S2 S5 S6 S3 S4 S7 S8 VCC GND RC OSCILLATOR VCC GND V+ = 2VCC GND V- = -(V+) C1+ C1 - C2 - C2+ VOLTAGE INVERTER VOLTAGE DOUBLER FIGURE 5. DUAL CHARGE PUMP T1IN, T2IN T1OUT, T2OUT VOH VOL tr tf 90% 10% Instantaneous Slew Rate (SR) = (0.8) (VOH - VOL) tr or (0.8) (VOL - VOH) tf FIGURE 6. SLEW RATE DEFINITION ICL232 ICL232 |
Similar Part No. - ICL232CBEZT |
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Similar Description - ICL232CBEZT |
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