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HIN208ECA Datasheet(PDF) 10 Page - Intersil Corporation |
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HIN208ECA Datasheet(HTML) 10 Page - Intersil Corporation |
10 / 22 page 10 FN4315.16 November 4, 2005 Detailed Description The HIN2XXE family of high-speed RS-232 transmitters/receivers are powered by a single +5V power supply, feature low power consumption, and meet all ElA RS232C and V.28 specifications. The circuit is divided into three sections: the charge pump, transmitter, and receiver. Charge Pump An equivalent circuit of the charge pump is illustrated in Figure 3. The charge pump contains two sections: the voltage doubler and the voltage inverter. Each section is driven by a two phase, internally generated clock to generate +10V and -10V. The nominal clock frequency is 125kHz. 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 C3 equal to twice VCC. During phase two, C2 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 charge pump accepts input voltages up to 5.5V. The output impedance of the voltage doubler section (V+) is approximately 200 Ω, and the output impedance of the voltage inverter section (V-) is approximately 450 Ω. A typical application uses 0.1 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, increasing the values of the reservoir capacitors, C3 and C4, lowers the ripple on the V+ and V- supplies. During shutdown mode (HIN206E, HIN211E and HIN213E) the charge pump is turned off, V+ is pulled down to VCC, V- is pulled up to GND, and the supply current is reduced to less than 10 µA. The transmitter outputs are disabled and the receiver outputs (except for HIN213E, R4 and R5) are placed in the high impedance state. 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 specifications of ±5V minimum with the worst case conditions of: all 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 minimum of 300 Ω with ±2V applied to the outputs and VCC = 0V. Receivers The receiver inputs accept up to ±30V while presenting the required 3k Ω to 7kΩ input impedance even if the power is off (VCC = 0V). The receivers have a typical input threshold of 1.3V which is within the ±3V limits, known as the transition region, of the RS-232 specifications. The receiver output is 0V to VCC. The output will be low whenever the input is greater than 2.4V and high whenever the input is floating or driven between +0.8V and -30V. The receivers feature 0.5V hysteresis (except during shutdown) to improve noise rejection. The receiver Enable line EN, (EN on HIN213E) when unasserted, disables the receiver outputs, placing them in the high impedance mode. The receiver outputs are also placed in the high impedance state when in shutdown mode (except HIN213E R4 and R5). + - 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 3. CHARGE PUMP TOUT V- < VTOUT < V+ 300 Ω 400k Ω TXIN GND < TXIN < VCC V- V+ VCC FIGURE 4. TRANSMITTER HIN202E, HIN206E, HIN207E, HIN208E, HIN211E, HIN213E, HIN232E |
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