Parameters of the Beetle chip

This appendix lists the parameters of the Beetle chip as described in the original work by S. Löchner and M. Schmelling (The Beetle Reference Manual, LHCb-2005-105).

Table A-1Beetle parameters and default values
Name Range Step Nominal Reg. content Description
Itp 0-2 mA 7.8 μA 0 μA 0x00 test pulse bias current
Ipre 0-2 mA 7.8 μA 600 μA 0x4C preamplifier bias current
Isha 0-2 mA 7.8 μA 80 μA 0x0A shaper bias current
Ibuf 0-2 mA 7.8 μA 80 μA 0x0A front-end buffer bias current
Vfp 0-2.5 V 9.8 mV 0 mV 0x00 preamplifier feedback voltage
Vfs 0-2.5 V 9.8 mV 0 mV 0x00 shaper feedback voltage
Icomp 0-2 mA 7.8 μA 40 μA 0x05 comparator bias current
Ithdelta 0-2 mA 7.8 μA -- -- current defining incremental comparator threshold
Ithmain 0-2 mA 7.8 μA -- -- current defining common comparator threshold
Vrc 0-1.25 V 4.9 mV 0 mV 0x00 comparator RC time constant
Ipipe 0-2 mA 7.8 μA 100 μA 0x0D pipeamp bias current
Vd 0-2.5 V 9.8 mV 1275 mV 0x82 pipeamp reset potential
Vdcl 0-2.5 V 9.8 mV 1030 mV 0x69 pipeamp reference voltage
Ivoltbuf 0-2 mA 7.8 μA 160 μA 0x14 pipeamp buffer bias current
Isf 0-2 mA 7.8 μA 200 μA 0x1A multiplexer buffer bias current
Icurrbuf 0-2 mA 7.8 μA 800 μA 0x66 output buffer bias current
Latency 10-160 -- 160 0xA0 trigger latency
ROCtrl -- -- cf. table C.11 readout control
RclkDiv 0-255 -- 0 0x00 ratio between Rclk and Sclk
CompCtrl -- -- See Table A-2 comparator control
CompChTh 0-31 -- -- -- comparator channel threshold shift register implementation and Beetle revision Id.
CompMask -- -- 0 0x00 comparator mask shift register implementation
TpSelect -- -- 0 0x00 test pulse selection shift register implementation
SEUcounts 0-255 -- -- -- sum of Single Event Upsets

The following table describes the bits in the CompCtrl reagister

Table A-2Bits in the CompCtrl register
Bit Function Description
0 DisableCompLVDS 0: enable comparator LVDS output ports 1: disable comparator LVDS output ports
1 CompPolarity 0: inverting 1: non-inverting
2 PipelineMode 0: analogue readout 1: binary readout
3 CompDisable 0: enable comparator 1: disable comparator
4 CompMode 0: track mode 1: pulse mode
5-7 not used --