THS6101

The THS6101 is a Class-A amplifier designed specifically for driving the upstream data path in Data Over Cable System Interface Specification (DOCSIS)-compliant cable modem applications. The DOCSIS places demanding constraints on the upstream drive amplifier, and the THS6101 is designed for full compliance with this industry standard.

Using only a single 5-V power supply, the THS6101 meets all of the DOCSIS distortion requirements. Differential signal paths throughout the device maintain signal integrity. An external 2:1 balun transformer converts the differential output signal to a single-ended output signal.

The THS6101 architecture results in a very low third-harmonic distortion of 64 dBc at 29.3 MHz and an output power level of 56 dBmV. Signal linearity is maintained at maximum output levels, providing a third-harmonic distortion of 58 dBc at 29.3 MHz and an output power level of 62 dBmV. The THS6101 also exhibits an IP3 of 83 dBmV at a frequency of 65 MHz and an output power level of 60 dBmV, for two-tone intermodulation effects.

Output noise from the THS6101 is very low. At minimum gain, the device produces less than 10 nV//Hz of noise at its output. This translates to a level of 47 dBmV at the lowest symbol rate, which is lower than that required by DOCSIS. The THS6101 exhibits a disable-mode output noise of 2 nV//Hz or 61 dBmV.

The THS6101 output power level range exceeds the 58 dBmV required by DOCSIS. Its 62-dBmV RMS drive readily compensates for typical losses associated with the output transformer and tuner duplexer. The THS6101 provides a gain range of 54 dB, from 32 dB down to 22 dB in 6-dB steps. The gain is programmable through an SPI-compatible serial interface with a 4-bit control word.

The stringent power requirements of cable telephony and VOIP systems will greatly benefit from the low, industry-leading power consumption of the THS6101. With a typical 10% transmit duty-cycle, the 15-mW disable-mode power consumption of the THS6101 results in an average power consumption of 94 mW. Furthermore, the advanced architecture of the THS6101 reduces this average power consumption to 15 mW when transmitting at minimum gain.