  A readout electronic with high time and energy resolution performance is
designed for the SDD (Silicon Drift Detector) signals readout, which is aimed
for X-ray pulsar based navigation (XNAV). For time measurement, the input
signal is fed into a fast shaping and Constant Fraction Discrimination (CFD)
circuit, and then be digitalized by a Time-to-Digital Converter (TDC)
implemented in an Field Programmable Gate Array (FPGA), which is designed with
a bin size of 2.5 ns. For energy measurement, a slow shaping and analog peak
detection circuit is employed to acquire the energy information of input
signals, which is then digitalized by a 14-bit Analog-to-Digital Converter
(ADC). Both the time and energy measurement results are buffered and packaged
in FPGA and then transmitted to Data Processing (DP) system. Test results
indicate that the time resolution is about 3 ns, while the FWHM (Full Width at
Half Maximum) of energy spectrum is better than 160 eV @ 5.9 keV, with the
energy dynamic range from 1 keV to 10 keV. Meanwhile, the linearity test shows
that the residual is less than 1.5% with different coming photons.
