The VATAGP8 is an integrated circuit that allows one to measure the charge from radiation sensors. The ASIC has 128 channels with low-noise and low-power buffered pre-amplifiers, shapers with sample-and-hold, and multiplexed analogue readout. Each channel has a level-comparator that generates a trigger signal when the pulse-height exceeds the programmable threshold. Depending on the mode of operation, the chip sends out the pulse height value and the address of the triggering channels, from all channels or from selected channels. An internal circuit automatically compensates for detector leakage currents.
The VATAGP8 is a successor of the VATAGP3 and it is pad compatible with VATAGP3.
The VATAGP8 was designed for use in systems employing many chips in parallel, sharing some control lines and all output lines. The VATAGP8 has a test channel that allows one to probe the fast shaper output. The trigger threshold is programmable by 5-bit global threshold DAC. Each channel has an additional 4-bit trim DAC that allows fine adjustment of the trigger threshold.
The chip requires positive and negative supply voltages (-2V, +1.5V) and generates all bias currents internally. However, one can also apply bias currents externally, if needed. The total power is 280mW maximum, depending on the readout rate. The chip has a 926-bit configuration register that allows one to program various features, and allows one to test and measure its gain by injection of an external calibrated charge. All amplifier inputs are protected by diodes against over-voltage and electro-static discharge (ESD).
|Application||Imaging, Spectroscopy, Calorimetry|
|Number of inputs||128|
|Input charge range||-250 fC to +250 fC|
|Shaping time||0.5 μs|
|Nominal capacitive load||6 pF|
|Equivalent Noise Charge (ENC)||398e + 5e/pF|
|Trigger outputs||Common trigger output for all channels|
|Outputs||Multiplexed pulse height|
|Test and calibration||Internal calibration circuit|
|Power consumption||2.2 mW / channel|