THVD4431 has an integrated high-efficiency and low-noise charge pump to generate large output voltages for RS-232 signaling. Charge pump consists of a voltage doubler and an inverter to regulate the voltage. Voltage is regulated to nominal ± 5.5V for a 3.3V V_CC or to ±9.5V for a 5V V_CC operation. The internal charge pump is controlled in a way that the output voltage stays regulated for varying load capacitance or varying data rate. Load capacitance emulates the capacitance offered by the cable between the driver and receiver RS-232 nodes. Also different applications can have different data rates, as such having regulated output voltage at any data rate is beneficial.

The Maxlinear XR34350 multiprotocol transceiver is not capable of regulating the RS-232 output voltage with varying load capacitance and data rate and as a result, output voltage drop can be observed when load capacitance and/or data rate increases.

A comparison of output voltage for RS-232 between TI’s THVD4431 and Maxlinear’s XR34350 is shown in Figure 2-1 and Figure 2-2. Figure 2-1 shows output voltage v.s. data rate and Figure 2-2 shows output voltage v.s. load capacitance. The high output voltage for RS-232 signaling of the THVD4431 multiprotocol transceiver enables high signal-to-noise ratio (SNR) which is beneficial for noisy industrial environments.

Figure 2-1 THVD4431 RS-232 Output Voltage vs Data Rate

Figure 2-2 THVD4431 RS-232 Output Voltage vs Load Capacitance