1. AIDA ASIC Davide Braga Steve Thomas ASIC Design Group 14 October 2010

2. 2 Input comparator: Now that the original diodes have been replaced by diode-connected pass transistors (not as fast or low impedance) the active-link circuit must take most of the input current. To avoid the build up of a large input voltage now that the passive link is slower, the active link must respond faster Necessary to optimize the input comparator

3. 14 October 20103 Input comparator speed Vin (d=100ns) -with input diode-connected transistors -without Vin (d=200ns) no significant difference between the two, the diode- connected transistors don’t conduce Vin (d=300ns) 6.7ns13ns New comparator: appreciably faster across all corners old comparator NB: speed function of input voltage. In this simulation Vin=Vt hreshold ±100mV, t rise =t fall =10ns 5.5ns3.3ns -80%~ -50%

4. 14 October 20104 High ref, Qin=900pC (~18GeV) (1): link charge (d=100ns-200ns-300ns) Q_input Q_HEC Q_input Q_HEC Q_input Q_HEC LEC charge

5. 14 October 20105 High ref, Qin=900pC (~18GeV) (2): link charge (detail) (d=100ns-200ns-300ns) Q_input Q_HEC Q_input Q_HEC Q_input Q_HEC

6. 14 October 20106 new comp old comp new comp old comp new comp old comp High ref, Qin=900pC (~18GeV) (3): The new comparator is generally faster and loses less charge for very fast inputs

7. 14 October 20107 old comp new comp High ref, Qin=900pC (~18GeV) (4): Significant improvement for slower signals too. (NB: old and new configurations in these presentation have the same link, the only difference is the input comparator) d=100ns d=200ns d=300ns

8. 14 October 20108 Low ref, Qin=900pC (~18GeV) (1): Q_input Q_HEC_new Q_HEC_old Q_HEC_new Q_HEC_old Q_HEC_new Q_HEC_old

9. 14 October 20109 Low ref, Qin=900pC (~18GeV) (2): new old new old new old Vin

10. 14 October 201010 Low ref, Qin=900pC (~18GeV) (3): new old new old new old Vin

11. 14 October 201011 Low ref, Qin=900pC (~18GeV) (3): new old new old new old Current: fast (~ns) feature, total current comparable (NB: absolute value in this graph due to ancillary circuits in the schematic)

12. 14 October 201012 Link leakage current: [pA] [fA] low_ref (0.4V), comparator thresh=0.35V high_ref (1.6V), comparator thresh=1.65V T= -10°C ÷ +50°C Vdd= 3.0V ÷ 3.6V V offset_preAmps =±1.2mV Sample of the current through the HEC/LEC link for high-low input references, different process corners. The concern was that a possible offset between the amplifiers’ references could cause significant current. The current is <30 pA in the worst case so it will be easily handled by the feedback compensation circuit

13. 14 October 201013