Broadcom ACPL-C740 User Manual page 7

ACPL-C740 Evaluation Kit Board User Guide
Figure 4: Measurement Setup
Lab bench test: Apply input voltage signal from a function generator with one shunt resistor mounted on the input of

evaluation board.
A more accurate method to measure the performance of the ACPL-C740 evaluation board is to connect a 1-shunt
resistor, then supply the voltage signal from a function generator that can drive sufficient current through the 1-shunt
resistor until an input signal level of ±200 mV is reached. One such function generator is the ultra low distortion DS360
function generator from Standford Research Systems.
Table 3 shows the SNR/SNDR performance using this method.
Table 3: SNR/SNDR Performance
Filter
Configuration SNR(dB)
Sinc3 DR = 64 not enough sampling sinewave cycles
Sinc3 DR = 128
Sinc3 DR = 256
If such a function generator is not available, it is best to connect an actual shunt resistor and connect to the current-sensing
system directly.
Broadcom
Signal Freq. = 500 Hz
SNDR(dB)
81 77
82 78
Signal Source from Audio Jack of Laptop
Signal Freq. = 1000 Hz
SNR(dB)
75
79
82
Signal Freq. = 2000 Hz
SNDR(dB) SNR(dB)
72 72
76 79
78 81
Isolated Sigma-Delta Modulator
SNDR(dB)
71
76
77
ACPL-C740-EvalKit-UG100
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