TOT01 ASIC – First Results (STS prototype chip – first results) Krzysztof Kasiński, Paweł Gryboś,Robert Szczygieł Department of Measurement and Instrumentation AGH – UST Kraków, Poland CBM Collaboration Meeting, Split,

Agenda Chip overview Test set-up First results Future plans

Chip Overview - specification Specification: - UMC 180 nm technology, (Europractice run x3.2mm die) - input charge: 1-16fC (both polarities, much higher charges allowable) - 31 channels (30 regular + 1 test) - Time-over-Threshold (ToT) amplitude measurement method - Low Power (~2.3 mW/channel -> CSA + Discriminator) - Designed for Si Strip Detectors (30pF, 300 um thick, AC-coupled) -Target resolution: 4-6 bits - Noise: ~500 e- TOT01 Chip Layout To be Verified

Chip Overview - Architecture Silicon Strip Detector CSA Switchable FB Const. Current Discharge Discriminator Trim DACs 6-bit Mux Threshold Address Back-End: FPGA Gating Counters PC-Interface Etc. Test Features: - 3 switchable capacitors at the CSA input - 100fC test pulse injection capacitor - 2 test pulse pads (voltage step applied to even / odd channels) - Transfer Gate between CSA and Discriminator - Test Pads for probe-station (CSA out, Discr. Out, Discr. 1st stage, DAC out)

Chip Overview – Architecture 2 CSA: - Folded Cascode - PMOS Input (1.1V) - typ. 500uA current - Source Follower Out - Tuneable Current Feedback: - 20 fC Capacitor (metal-metal) - 2 switchable feedback circuits (for both polarities) - Constant Current discharge circuit (typ. 1 – 10nA) - Tuneable discharge current DAC: - 6-bit DAC / channel - tuneable offset - tuneable range - Registers + Init Value Discriminator: - 2 threshold lines (externally driven) - 1 reference line (Trim DAC driven) - hysteresis - switchable pulse polarity Mux and output buffer: - 5-bit Mux routes the channels to the output - Output buffer is separately powered

TOT01 Chip Layout 1 - pinout 31 detector interface pads (100um pitch) Power supply Address, Data, ControlMux outBias & Switch Odd channel Test Pulse IN Even channel Test Pulse IN Decoupling Capacitors Decoupling Capacitors

TOT01 Chip Layout 2 Mux Output buffer 6-bit TrimDACs Discriminators CSAs Test Pulse Injection caps 3 switchable input caps Address Decoders & Registers Test pads: - CSA output - Discriminator’s first stage outputs - Discriminator output -Trim DAC output * - CSA output after the Transfer-Gate * * 1st channel only Channel pitch: 50um Die size: 1.6 x 3.2 mm Empty space will be filled with: -Threshold DACs, - BandGap Reference etc.

TOT01 Chip Fabrication and Test progress UMC 180 nm Size: 1.6 x 3.2 mm 60 pieces Chip Fabrication: Design Submission: EUROPRACTICE First Chip bonded -> (improvised set-up). Second Chip bonded -> (final PCB set-up)

Test Set-up First Chip bonded -> (improvised set-up) First Check. Second Chip bonded -> (final PCB set-up) Analogue Part Only at the moment

Final Test Set-Up Functionality Test Pulse Ports (SMA, 50 ohm, 24:1 divider) HV detector bias (SMA, Filter, Choke, Ileak measurement ) Ext. Power Supply Internal Power Supp. Analogue: - Low noise 1V VR - Low noise 1.8V VR Digital: - Regular 1.8 VR Back-End (FPGA): -1.2 VR VR VR Biasing resistors: Icsa, Idischarge Icomp, refb, refa (DAC) Single TOT01 Chip (tantalum, ceramic decoupling) Strip Detector Pad (2 x 1.4 cm) External Control Conn. (DAC & MUX ctrl. + TOT read) Threshold set (DAC, External, Trimmer) USB port (PC-link) FPGA (Xilinx Spartan 3, 80Mhz) MEMORY (Fast SRAM 512k x 16)

First Power-Up and Biasing Verification First Check: - Short Circuits Check (O.K.) – no shorts - Power Consumption (O.K.) – no increased power consumption - Bias verification (O.K.) – possible to set the typical bias using expected resistor values - DC voltage levels check (O.K.) – CSA output µ=780mV σ= 20mV - Discriminator operation check (O.K) – varying TH1 and TH2 triggers the discriminator

First Transient Plots 1 Variable current Injection through 100fC capacitor Applied Voltage Step Test Pad): Min: 4,16 mV~ 0,42 fC Max:416,0 mV~41,6 fC Step: 20,8 mV~ 2,1 fC Conditions: Probe placed at CSA output test pad (large capacitive load: 50cm coax cable + 8pF probe) -Vddm, Vcasc = 1.1 V - Vdd = 1.8 V - Vdd_dig, Vdd_comp = 0 V Icomp ~ 800uA Idisch ~ 3nA First Observation of: - Transient response (O.K. ) – as expected -ToT characteristic (O.K.) – seems linear 5us/div

First Transient Plots 2 Changing Discharge current at the fixed input charge Applied Voltage Step: 208mV ~ 20,8fC Varying the discharge current bias (490K ohm -> 590K ohm) First Observation of: -Discharge current control (O.K. ) soon measurements with wider range 5us/div

Plans for the future 1. Run the full-chip set-up (all biases, external config and measurements) 2. Functionality verification of all blocks (esp. Trim DACs) 3. Further measurements using Test Pulses (and the switchable input capacitors) 4. Measurements with the Si Detectors 5. Run the back-end part (FPGA + memory, USB interface)

Summary TOT01 – Time-over-Threshold based Si Strip detector readout Chip Submitted: Fabricated: First-Tests: Tested: To be Tested: Power Consumption- Operation with detector Bias - Trim DAC operation Discriminator Operation - Noise & resolution First transients acquired - ToT Linearity

Thank you for Your attention ? Questions, suggestions, comments? Krzysztof Kasiński, Paweł Gryboś, Robert Szczygieł, AGH University of Science and Technology Kraków, Poland