The AD8488 is a 128-channel analog front end designed for use in high performance digital X-ray systems. The analog channels consist of an integrator followed by a gain selectable single-ended to low impedance differential output. The analog channel converts the charge acquired by X-ray or photodiode detectors to a voltage. The channels are composed of CMOS transistors, using typical high input impedance CMOS gates. The integrators generate charge dependent voltages using a range of selectable capacitance values that accommodate a broad range of input charge values. The integrators are followed by single-ended input to differential output voltage amplifiers where offset and low frequency noise voltages are subtracted from the input voltages. A 128:1 channel differential MUX follows the buffers and drives the analog output buffer. Switch drivers and certain digital timing functions are included, and all are mounted on a 255-lead BGA substrate. Charge conversion for all 128 channels is simultaneous followed by a sequential voltage output read of the channels using a 7-bit address code. The sequence occurs twice, sampling all 128 channels. Logic control inputs, CS_A and CS_B select the lower and upper 64-blocks of channel addresses.

The AD8488 is packaged in a 17 mm × 17 mm 255-lead RoHS compliant ball grid array (BGA). The operating temperature range is 0°C to 85°C ambient. 

Applications

• High performance digital X-ray systems
• Medical X-ray
• Security (baggage scanner) systems

At least one model within this product family is in production and available for purchase. The product is appropriate for new designs but newer alternatives may exist.