Linear Technology DC1010A-A - LTC2493 24-Bit 4/2-ch I²C Delta Sigma ADC (Req. DC590) DC1010A-A DC1010A-A Fiche De Données
Codes de produits
DC1010A-A
QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 1010
2/4 CHANNEL 24,16,16/PGA-BIT ADC WITH I2C
4
EXPERIMENTS
INPUT NOISE
Solder a short wire between the CH0 and CH1 tur-
rets. Connect the inputs to ground through a short
wire and start taking data. LTC2493 Noise should
be approximately 0.12ppm of 5V (600nV RMS.) The
electrical noise of the LTC2489 is also 600nV RMS,
however this is masked by the 76.3µV quantization
level. If the input is well between code transitions,
the noise level will read zero. If the input is exactly
between two codes such that the two adjacent out-
put codes have equal probability, the noise level will
be approximately 7.9ppm. The input noise of the
LTC2487 is apparent at very high gain settings (128
or 256.) Note that with a 5V reference and gain set
to 256, 1LSB is equal to 298nV – which is lower
than the 600nVRMS electrical noise of the input
stage.
rets. Connect the inputs to ground through a short
wire and start taking data. LTC2493 Noise should
be approximately 0.12ppm of 5V (600nV RMS.) The
electrical noise of the LTC2489 is also 600nV RMS,
however this is masked by the 76.3µV quantization
level. If the input is well between code transitions,
the noise level will read zero. If the input is exactly
between two codes such that the two adjacent out-
put codes have equal probability, the noise level will
be approximately 7.9ppm. The input noise of the
LTC2487 is apparent at very high gain settings (128
or 256.) Note that with a 5V reference and gain set
to 256, 1LSB is equal to 298nV – which is lower
than the 600nVRMS electrical noise of the input
stage.
COMMON MODE REJECTION
Tie the two inputs (still connected together from
previous experiment) to ground through a short
wire and note the indicated voltage. Tie the inputs
previous experiment) to ground through a short
wire and note the indicated voltage. Tie the inputs
to REF+; the difference should be less than 0.5
µV
due to the 140 dB+ CMRR of the LTC2493. The
LTC2489 will produce less than 1LSB difference.
LTC2489 will produce less than 1LSB difference.
INPUT NORMAL MODE REJECTION
The LTC2493 and LTC2487 SINC4 digital filter can
be software selected to reject 50Hz, 60Hz by 110dB,
or both 50 and 60Hz by 87dB. The LTC2489’s
SINC4 filter is fixed at 50/60Hz. To measure input
normal mode rejection, connect COM to a 2.5 volt
source such as an LT1790-2.5 reference or a power
supply. Connect any other input (CH0 – CH3) to the
same supply through a 10k
be software selected to reject 50Hz, 60Hz by 110dB,
or both 50 and 60Hz by 87dB. The LTC2489’s
SINC4 filter is fixed at 50/60Hz. To measure input
normal mode rejection, connect COM to a 2.5 volt
source such as an LT1790-2.5 reference or a power
supply. Connect any other input (CH0 – CH3) to the
same supply through a 10k
Ω resistor. Apply a 10
Hz, 2V peak-to-peak sine wave to the input through
a 1uF capacitor.
a 1uF capacitor.
Set the rejection frequency to 55Hz (LTC2493 only)
and start taking data. The input noise will be quite
large, and the graph of output vs. time should show
large variations.
and start taking data. The input noise will be quite
large, and the graph of output vs. time should show
large variations.
Next, slowly increase the frequency to 55 Hz. The
noise should be almost undetectable in the graph.
noise should be almost undetectable in the graph.