Broadcom ACPL-C799 User Manual page 7

ACPL-C799 Evaluation Kit Board
User Guide
Table 2 SNR/SNDR Comparison
Audio Signal from Dell Lattitude E7440 Laptop
ACPL-C799 Board signal freq=1kHz
SNDR(dB)
Clock freq = 10MHz 67.55
Lab bench test: Apply input voltage signal from a function generator with 1 shunt resistor mounted on the input of

evaluation board.
When a voltage signal is sourced from a function generator to the evaluation board without a shunt resistor connected as
shown in Figure 8, input bias current of about 0.18mA from the ACPL-C799 will cause a 9mV offset on the function generator
output due to the 50 source impedance of the function generator.
Figure 8 Sourcing the Voltage Signal from a Function Generator to the Evaluation Board without a Shunt Resistor Connected
A more accurate method to measure the performance of the ACPL-C799 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 ±50mV 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
ACPL-C799 Board
Clock freq = 10MHz 74.53
If such a function generator is not available, it is best to connect an actual shunt resistor and connect to customer's current sensing
system directly.
SNR(dB) SNDR(dB)
68.44 66.27
DS360 Stanford Research Systems Ultra Low Distortion Function
signal freq=1kHz
SNDR(dB) SNR(dB)
77.42
signal freq =500Hz
SNR(dB)
68.06 72.31
Generator
signal freq =500Hz
SNDR(dB)
74.97 78.35
Broadcom
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Audio Signal from Samsung Galaxy S6
signal freq =1kHz
SNDR(dB) SNR(dB)
74.26
SNR(dB)
Measurement
signal freq =500Hz
SNDR(dB) SNR(dB)
72.05 74.76