Datasheet

ADS1244
15
SBAS273
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WEIGH SCALE SYSTEM
Figure 19 shows an example of a weigh scale system. OPA1,
OPA2, R
G
, and R
F
form a differential gain stage to amplify the
load cell output. The gain is equal to (1 + 2 R
F
/R
G
). Depend-
ing on the load cell, the typical gain setting is from 100 to 250.
R
I
and C
I
form a single-pole low-pass filter to band-limit the
FIGURE 19. Weigh Scale System.
ADS1244
VREFP
AVDD
SCLK
DRDY/ DOUT
P1.2/TA1
P1.0/TA0
XIN
XOUT/TCLK
CLK
DVDD
VREFN GND
AINP
AVCC
1.8V ~ 3.6V
DVCC
AVSS
MSP430Fx41x
P1.1/TA0/MCLK
AINN
EMI Filter
EMI Filter
EMI Filter
DVSS
EMI Filter
OPA1
(1)
OPA2
(1)
NOTE: (1) OPA2335 or OPA2277 recommended.
5V
R
F
R
F
R
G
C
I
R
I
R
VR2
R
VR1
0.1µF1µF 0.1µF 1µF
0.1µF
32.768kHz
0.1µF
Load Cell
R
I
differential gain stage noise and reduce mechanical vibration
noise from the load cell. The cutoff frequency of the low-pass
filter should be as low as possible to minimize the overall
system noise. The reference voltage is typically generated by
dividing down the supply voltage (R
VR1
, R
VR2
). Use a bypass
capacitor located as close to VREFP as possible.