Datasheet

MUX1[2:0]=000
BIAS_SENSP[0]=1
BIAS_SENSN[0]=1
MUX2[2:0]=000
MUX3[2:0]=000
MUX8[2:0]=010
BIAS_MEAS=1
AND
Low-Noise
PGA1
BIAS_SENSP[1]=1
BIAS_SENSN[1]=1
Low-Noise
PGA2
BIAS_SENSP[2]=1
BIAS_SENSN[2]=1
Low-Noise
PGA3
BIAS_AMP
BIAS_SENSP[7]=0
BIAS_SENSN[7]=0
Low-Noise
PGA8
BIASOUT BIASINVBIASREFBIASIN
Filteror
Feedthrough
Device
¼ ¼
IN1P
IN1N
MUX
¼
IN2N
IN3N
IN8N
IN2P
IN3P
IN8P
MUX8[2:0]=111
1MW
(1)
1.5nF
(1)
BIASREF_INT=1
BIASREF_INT=0
(AVDD+AVSS)
2
ADS1299
www.ti.com SBAS499A –JULY 2012–REVISED AUGUST 2012
INPUT MULTIPLEXER (Measuring the BIAS Drive Signal)
Also, the BIASOUT signal can be routed to a channel (that is not used for the calculation of BIAS) for
measurement. Figure 47 shows the register settings to route the BIASIN signal to channel 8. The measurement
is done with respect to the voltage on the BIASREF pin. If BIASREF is chosen to be internal, it would be at
[(AVDD + AVSS) / 2]. This feature is useful for debugging purposes during product development.
(1) Typical values for example only.
Figure 47. BIASOUT Signal Configured to be Read Back by Channel 8
Copyright © 2012, Texas Instruments Incorporated Submit Documentation Feedback 49
Product Folder Link(s): ADS1299