A TDC integrated circuit for drift chamber readout

A custom integrated circuit for the measurement of the signal drift-time coming from the KLOE chamber developed by INFN Sezione di Roma is presented. The circuit is a multichannel common start/stop TDC, with 32 channels per chip. The TDC integrated circuit will be developed as a full-custom device in 0.5 μm CMOS technology, with 1 ns LSB realized using a Gray counter working at the frequency of 1 GHz. The circuit is capable of detecting rising/falling edges, with a double edge resolution of 8 ns; the hits are recorded as 16 bit words, hits older than a programmable time window are discarded, if not confirmed by a stop signal. The chip has four event-buffers, which are used only if at least one hit is present in one of the 32 channels. The readout of the data passes through the I/O port at a speed of 33 MHz; empty channels are automatically skipped during the readout phase.