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TC232IJE Datasheet(PDF) 3 Page - TelCom Semiconductor, Inc |
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TC232IJE Datasheet(HTML) 3 Page - TelCom Semiconductor, Inc |
3 / 3 page 6-5 TELCOM SEMICONDUCTOR, INC. 7 6 5 4 3 1 2 8 DETAILED DESCRIPTION The TC232 contains a +5V to ±10V dual charge pump voltage converter, a dual transmitter and a dual receiver. +5V to ±10V Dual Charge Pump Voltage Converter The TC232 power supply consists of two charge pumps. One uses external capacitor C1 to double the +5V input to +10V, with output impedance of about 200 Ω. The other uses C2 to invert +10V to – 10V, with overall output impedance of 450 Ω (including effects of +5V to +10V doubler impedance). The clock in the doubler circuit will start at ≈4.2V in the typical part, but external loads may make this point rise to as high as 4.5V with a load of 2 k Ω on each of the two output voltages. Because of this, use of the doubler and inverter to run additional external circuits should be limited. The maximum current should be no more than 2.5 mA from the +10V and - 10V. in order to guarantee start-up of the doubler clock. The test circuit employs 22 µF capacitors for C1 to C4, but the value is not critical. These capacitors usually are low- cost aluminum or tantalum electrolytic capacitors. Increasing C1 and C2 to 47 µF lowers the output impedance of the +10V doubler and the - 10V inverter by the change in the ESR of the capacitors. Increasing C3 and C4 lowers ripple on the ±10V out- puts and 16 kHz ripple on the RS-232 outputs. Where size is critical, the value of C1 to C4 can be lowered to 1 µF. The use of a low ESR capacitor will help lower the output ripple and keep the output impedance of the ±10V as low as possible. Dual Transmitter TC232 transmitters are CMOS inverters driven by ±10V internally-generated voltages. The input is TTL/CMOS com- patible, with a logic threshold of about 26% of VCC (1.3V for 5V VCC). The input of an unused transmitter can be left unconnected, since an internal 400 k Ω pull-up resistor connected between the transmitter input and VCC pulls the input HIGH and forces the unused transmitter output to the LOW state. With VCC at 5V, the outputs will go from (V+ – 0.6V) to V– with no load and will swing ±9V when loaded with 3 kΩ. The minimum output voltage swing, with VCC at 4.5V and at maximum ambient temperature, is ±5V. This conforms to RS-232 specifications for "worst-case" conditions. EIA/TIA RS-232E specs limit the slew rate at output to less than 30V/ µs. The powered-down output impedance (VCC = 0V) is a minimum of 300 Ω with ±2V applied to outputs. V+, V– Output Voltages vs Load Current TEST CIRCUIT TC232 1 2 3 4 16 15 14 13 5 6 7 12 11 8 10 9 C1 22 µF 22 µF + + C2 22 µF 22 µF + + RS-232 INPUT ±30V RS-232 OUTPUT +4.5V TO +5.5V INPUT 3 k Ω RS-232 OUTPUT RS-232 INPUT ±30V TTL/CMOS OUTPUT TTL/CMOS INPUT TTL/CMOS INPUT TTL/CMOS OUTPUT 3 k Ω V+ V – T2OUT R2IN VCC GND T1OUT T1IN R1OUT T2IN R2OUT IN R1 C + 1 C – 1 C + 2 C – 2 C3 C4 10 9 8 7 6 5 4 3 0 1 2 3 45 6 78910 (V = 4.5V) CC (V = 5V) CC (V = 4.5V) CC (V = 5V) CC CONDITIONS: A) T = +25 °C B) TRANSMITTER OUTPUTS OPEN CIRCUIT A | I | (mA) LOAD + V – V – V + V The outputs are protected and can be short-circuited to ground indefinitely. Dual Receiver TC232 receivers meet RS-232 input specifications. Input impedance is between 3 k Ω and 7 kΩ. Switching thresholds are within the ±3V limits, and the receivers withstand up to ±30V inputs. RS-232 and TTL/CMOS input compatible, the receivers have 0.8V VIL and 2.4V VIH with 0.5V hysteresis to reject noise. The TTL/CMOS compatible receiver output is LOW when an RS-232 input is greater than 2.4V. It is HIGH when an input is floating or between +0.8V and – 30V. TC232 DUAL RS-232 TRANSMITTER/ RECEIVER AND POWER SUPPLY |
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