Rainbow Electronics MAX11043 - Manual (Page 14)

MAX11043
4-Channel, 16-Bit, Simultaneous-Sampling ADCs
with PGA, Filter, and 8-/12-Bit Dual-Stage DAC
14 ______________________________________________________________________________________
Filter coefficients A1 and B1 are always 1. B3 is limited
to -1, 0, and 1.
Filter coefficients A2, A3, and B2 are stored as 16-bit
two’s complement values in the range of -4 to +4.
Gain is limited to the following values 2 4 , 2 2 , 2 0 , 2 -2 , 2 -4 ,
2 -6 , 2 -8 , and 2 -10 . For better gain resolution, adjust the
Fine Gain A/B/C/D Registers at the input of each filter
set. Fine gain adjustment has a resolution of 16 bits and
a gain range of -4 to +4. Set the RECT bit to rectify the
filter output.
Figures 5–8 show the response to a step input of the
default filters used for ADC trimming.
1/A1
-A2
Z -1
-A3
B1
B2
B3
+
+
+
+
OUT
IN
X
Y
RECT
G
ABS
Z -1
Figure 4. Single Programmable 2nd-Order Filter Section
SINC 5 FILTER OUTPUT
MAX11043 fig05
SAMPLE
OUTPUT (LSB)
8 6 4 2
500
1000
1500
2000
2500
0
0 10
Figure 5. Sinc 5 Filter Response to a Step Input