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Rev C, 4/27/2023

Page 14

© TT electronics plc

FlexSense® I-Series Programmable

Incremental Encoder

FS210/FS310 Datasheet

Quadrature-Track Outputs

Figure 5 below shows the ideal response of the digital quadrature-track output pins (AOUT_P_DIG, AOUT_N_DIG,

BOUT_P_DIG, BOUT_N_DIG) to constant-angular-velocity code-wheel rotation, with the FS210/FS310 configured for digital

quadrature-track output. Four cases are shown: uninterpolated, 2x interpolation, 4x interpolation, and 8x interpolation.

Fully differential outputs are shown in the uninterpolated case, but only the positive-sense signals are shown in the three

interpolated cases. Even though they are not shown for all cases in the figure, when the device is configured for differential

quadrature-track output, AOUT_N_DIG and BOUT_N_DIG are the logical complements of AOUT_P_DIG and BOUT_P_DIG,

respectively, regardless of the configured interpolation factor. When the device is configured for single-ended digital

quadrature-track output, then AOUT_N_DIG and BOUT_N_DIG are placed in a high-impedance state. When the device is

configured for digital quadrature-track output – either differential or single-ended – then the analog quadrature-track

output pins (AOUT_P_ANA, AOUT_N_ANA, BOUT_P_ANA, BOUT_N_ANA) are placed in a high-impedance state. In the

Figure 5 and Figure 6, τCW is the rotational period of the code wheel, and PPR is the number of native pulses per revolution

in the code wheel’s quadrature track.

Figure 6 below shows the ideal response of the positive-sense digital quadrature-track outputs to constant-angular-velocity

code-wheel rotation, with the device configured for digital quadrature-track outputs, for three cases: uninterpolated,

divide-by-2, and divide-by-4.

If the FS210/FS310 is configured for analog quadrature-track outputs, then the digital quadrature-track output pins

(AOUT_P_DIG, AOUT_N_DIG, BOUT_P_DIG, BOUT_N_DIG) are placed in a high-impedance state, and the analog

quadrature-track output (AOUT_P_ANA, AOUT_N_ANA, BOUT_P_ANA, BOUT_N_ANA) waveforms are similar to the

aggregated photocurrent waveforms in the figure, centered at VO:Q ≈ 1.25V and multiplied by a common effective

differential transimpedance.