Bias Card RevD to RevE changes

Low-noise Bias lines

Low noise bias lines are meant to be used as TES bias lines. Bias Card Rev. E provides 12 independent bipolar low-noise bias lines (LN_BIAS) in addition to the 32 regular biases. The 12th low-noise bias is what was called det_bias in Rev. D cards. Rev. D cards shared a DAC between two outputs called Heater and det_bias.

Note that the low-noise bias line in Rev. D was unipolar with 0 to +5V range, while low-noise bias lines in Rev. F are bipolar from -5V to +5V. At powerup, the output voltage is 0V, equivalent to an input pattern of 0x8000.

10V supply

Vah or 10V supply is not used by Rev. F cards anymore. The reference voltage for the DACs is generated from pVa or 6.2V supply instead.

Vah is used in Rev. D cards to provide the reference voltage for the DACs.

Faster Bias lines

In order to allow fast switching of the 32 regular biases (<1MHz), the output opamp (U10) is replaced with a faster opamp and the 10kHz output filter is removed (compared to Rev. D). This allows Rev. F cards to be used for switching SQ2FB lines at row-visit rate.

Software considerations

To make the 12 bias lines commandable, set $hw_rev["bc"] = "revE" (or greater) in mce.cin . This will add a op_xor entry in mce.cfg file to make a 2's complement interpretation of values entered so that wb bc2 bias 0 is aligned with 0V and wb bc2 bias 32767 with +5V.

in experiment.cfg, set hardware_fast_sq2 accordingly

Firmware consideration

The FPGA pins assigned to control lines for ln_bias DACs are not compatible with Rev. D nor Rev. F cards. Therefore, special RevE firmware is needed to be able to excercise ln_bias DACs (bias command).