Quad uModule ADCs with Integrated signal conditioning reduce size, power and time-to-market for imaging and base station designs

April 25, 2012 // By Paul Buckley
Linear Technology has introduced a quad 14-bit, 125Msps µModule analog-to-digital converter (ADC) with integrated fixed gain drivers, passive filtering and bypass capacitance.

The LTM9012 integrated µModule converters offer a reduction in board space for high channel-count applications as diverse as medical imaging systems and MIMO (multiple input multiple output) 4G base stations. This high level of integration enables smaller boards with greater density, while eliminating costly layout iterations often required to optimize the driver-to-ADC interface. This results in a significant reduction in design and debug time and faster time to market. Equivalent implementations require five devices and dozens of passive components compared to the LTM9012 in an easy-to-use 15 mm x 11.25 mm BGA µModule package.

Integrating the driver with the ADC simplifies high-speed design, whether the signal originates in an image sensor with CMOS logic outputs or an RF signal chain. CMOS image sensors are used in high-end medical instruments, such as blood cell or molecular microscope cameras, and industrial imaging equipment used for detecting voids in metal objects. Depending on the sensor, many channels of high-speed digitizers are required along with filtering and amplification to translate the sensor output to the ADC input. Filters and amplifiers often consume more than twice the circuit board area as the ADC itself and constitute the key challenge in achieving maximum camera resolution. The LTM9012 amplifiers easily accommodate the single-ended CMOS sensor outputs and translate these levels to differential for the high performance ADC to maximize dynamic range.

Ideal for digitizing high-speed digital signals for imaging applications, the LTM9012 also excels in baseband receiver applications such as cellular infrastructure. Two receiver architectures dominate base station designs: direct conversion and IF-sampling. With the capability of supporting baseband frequencies up to about 90 MHz, the LTM9012 is suitable for both types. Direct conversion demodulates the RF signal and downconverts to DC; therefore a 20 MHz lowpass filter supports 40 MHz signal bandwidth. Low IF-sampling below 90 MHz is also possible with four channels for next generation small base station designs. With 20 dB of gain, the