MCP3903-I/SS Microchip Technology, MCP3903-I/SS Datasheet - Page 21

• Manufacturer Part Number: MCP3903-I/SS
• Description: IC AFE 24BIT 64KSPS 28SSOP
• Manufacturer: Microchip Technology
• Series: -r

Specifications of MCP3903-I/SS

• Featured Product: MCP3903 Six Channel ΔΣ A/D Converter
• Number Of Bits: 24
• Number Of Channels: 6
• Power (watts): -
• Voltage - Supply, Analog: 4.5 V ~ 5.5 V
• Voltage - Supply, Digital: 2.7 V ~ 3.6 V
• Package / Case: 28-SSOP (0.209", 5.30mm Width)
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

4.16
The crosstalk is defined as the perturbation caused by
one ADC channel on the other ADC channel. It is a
measurement of the isolation between the six ADCs
present in the chip.
This measurement is a two-step procedure:
1.
2.
The crosstalk is then the ratio between the output
power of the ADC when the perturbation is present and
when it is not divided by the power of the perturbation
signal.
A lower crosstalk value implies more independence
and isolation between the six channels.
The measurement of this signal is performed under the
following conditions:
• GAIN = 1,
• PRESCALE = 1,
• OSR = 256,
• MCLK = 4 MHz
Step 1
• CH0+=CH0-=AGND
• CHn+=CHn-=AGND, n different than 0
Step 2
• CH0+=CH0-=AGND
• CHn+ - CHn-=1V
The crosstalk is then calculated with the following
formula:
EQUATION 4-10:
4.17
This is the ratio between a change in the power supply
voltage and the ADC output codes. It measures the
influence of the power supply voltage on the ADC
outputs.
The PSRR specification can be DC (the power supply
is taking multiple DC values) or AC (the power supply
is a sinewave at a certain frequency with a certain
common mode). In AC, the amplitude of the sinewave
is representing the change in the power supply.
It is defined as:
© 2011 Microchip Technology Inc.
wave)
Measure one ADC input with no perturbation on
any other ADC (ADC inputs shorted).
Measure
perturbation sine wave signal on the other ADC
at a certain predefined frequency.
CTalk dB
Crosstalk
PSRR
(
the
)
P-P
=
same
10
@ 50/60 Hz (Full-scale sine
log
⎛
⎝
Δ
-------------------------------- -
Δ
ADC
CH0Power
CHnPower
input
⎞
⎠
with
a
EQUATION 4-11:
Where V
output code translates to with the ADC transfer
function. In the MCP3903 specification, AV
from 4.5V to 5.5V, and for AC PSRR a 50/60 Hz
sinewave is chosen, centered around 5V with a
maximum 500 mV amplitude. The PSRR specification
is measured with
4.18
This is the ratio between a change in the
Common-Mode input voltage and the ADC output
codes. It measures the influence of the Common-Mode
input voltage on the ADC outputs.
The
common-mode input voltage is taking multiple DC
values) or AC (the common-mode input voltage is a
sinewave at a certain frequency with a certain common
mode). In AC, the amplitude of the sinewave is
representing the change in the power supply.
It is defined as:
EQUATION 4-12:
Where V
input voltage and V
that the output code translates to with the ADC transfer
function. In the MCP3903 specification, VCM varies
from -1V to +1V, and for AC specification a 50/60 Hz
sinewave is chosen centered around 0V with a 500 mV
amplitude.
4.19
ADC Reset mode (called also soft reset mode) can only
be entered through setting high the RESET<5:0> bits in
the configuration register. This mode is defined as the
condition where the converters are active but their
output is forced to 0.
The registers are not affected in this reset mode and
retain their values.
The ADCs can immediately output meaningful codes
after leaving reset mode (and after the sinc filter settling
time of 3/DRCLK). This mode is both entered and
exited through setting of bits in the configuration
register.
Each converter can be placed in soft reset mode
independently. The configuration registers are not
modified by the soft reset mode.
CMRR
CM
CMRR
ADC Reset Mode
OUT
CMRR dB
PSRR dB
= (CHn+ + CHn-)/2 is the Common-Mode
is the equivalent input voltage that the
specification
(
DV
(
OUT
)
DD
)
=
=
is the equivalent input voltage
= 3.3V.
20
20
log
log
MCP3903
⎛
⎝
⎛
⎝
------------------ -
Δ
Δ
can
Δ
-----------------
Δ
AV
V
V
V
OUT
OUT
CM
DD
DS25048B-page 21
be
⎞
⎠
⎞
⎠
DC
DD
varies
(the