Variable-Gain Amplifier Supports High-Speed, Multichannel Data Access In Advanced Cable Equipment
News Release from:
12 February 2008
Analog Devices, Inc. is introducing a general-purpose two-channel, digitally controlled VGA developed with specific features for today's CMTS upstream receiver applications. The two-channel AD8372 VGA enables designers to incorporate more CMTS channels while simultaneously improving modem performance and the quality of upstream cable signals. The new VGA's space-saving design reduces component count and board area by allowing designers to fit more channels into a given space or pack the same number of channels into a smaller area.
For wide-dynamic-range applications, the AD8372 offers a broad 41-dB gain range, with 1-dB steps and 0.2-dB resolution. The gain is programmed through a bidirectional 4-pin, 8-bit serial port, which consists of clock, latch, data input and data output lines for each channel. The 41-dB control range enables designers to keep input signals above the noise floor, while using the full-scale range of a wider variety of ADCs (analog-to-digital converters). The 41-dB gain range makes the AD8372 an essential component for multiple cable applications, including CMTS.
The AD8372, which accepts differential inputs and provides differential outputs, requires no baluns. It provides better than 77-dBc second and third harmonic distortion (HD) and 55-dB common-mode rejection (CMR). Compared to competitive products, the AD8372 delivers 35 percent more gain control range and improved second harmonic distortion in roughly 20 percent of the board space.