SLAU443 Datasheet, PDF (46/68 Pages) Texas Instruments – EEG Front-End Performance Demonstration Kit

Test Options on the EVM
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8.3 Noise with Common Reference on Negative Inputs
There is an option in ADS1299 to connect all the channels negative inputs to a common reference. This
can be accomplished by giving a signal on SRB1 pin and setting the bit SRB1 bit in MISC1 register. There
is an option on board to test out the channel noise performance with this setting. On JP81 a jumper on (3-
4) and (5-6) is needed. On JP8 a jumper (1-2) is required. These settings routes the common mode
voltage VCM on BIAS_ELEC to all the positive inputs. It also connects BIAS_ELEC to REF_ELEC via R11
(5K). REF_ELEC is connected to SRB1 pin on ADS1299. The noise in this test includes noise of two 5K
resistors and the channel noise. The SRB1 control switch must be set as shown in Figure 55.The
snapshot of the scope in the analysis tab is shown in Figure 56. The average peak-to-peak noise for this
test is 1.28µV.
Figure 55. MISC1 Register Setting for SRB1
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EEG Front-End Performance Demonstration Kit
Copyright © 2012, Texas Instruments Incorporated
SLAU443 – May 2012
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