MCP3422A1-E/MS Microchip Technology, MCP3422A1-E/MS Datasheet - Page 31

• Manufacturer Part Number: MCP3422A1-E/MS
• Description: 18-Bit, Multi-Channel Delta-Sigma ADC w/ I2C Interface and On-Board Reference ; 8L MSOP 3x3mm
• Manufacturer: Microchip Technology

6.0
The MCP3422/3/4 devices can be used for various pre-
cision analog-to-digital converter applications. These
devices operate with very simple connections to the
application circuit. The following sections discuss the
examples of the device connections and applications.
6.1
6.1.1
For an accurate measurement, the application circuit
needs a clean supply voltage and must block any noise
signal to the MCP3422/3/4 devices.
an example of using two bypass capacitors (a 10 µF
tantalum capacitor and a 0.1 µF ceramic capacitor) on
the V
helpful to filter out any high frequency noises on the
V
extra currents when the device needs from the supply.
These capacitors should be placed as close to the V
pin as possible (within one inch). If the application
circuit has separate digital and analog power supplies,
the V
reside on the analog plane.
6.1.2
The SCL and SDA pins of the MCP3422/3/4 are
open-drain configurations. These pins require a pull-up
resistor as shown in
pull-up resistors depends on the operating speed (stan-
dard, fast, and high speed) and loading capacitance of
the I
consumes less power, but increases the signal transi-
tion time (higher RC time constant) on the bus. There-
fore, it can limit the bus operating speed. The lower
value of resistor, on the other hand, consumes higher
power, but allows higher operating speed. If the bus
line has higher capacitance due to long bus line or high
number of devices connected to the bus, a smaller
pull-up resistor is needed to compensate the long RC
time constant. The pull-up resistor is typically chosen
between 5 kΩ and 10 kΩ ranges for standard and fast
modes, and less than 1 kΩ for high speed mode
depending on the presence of bus loading capacitance.
© 2008 Microchip Technology Inc.
DD
line and also provide the momentary bursts of
2
DD
DD
C bus line. Higher value of pull-up resistor
and V
BASIC APPLICATION
CONFIGURATION
Connecting to the Application
Circuits
line of the MCP3424. These capacitors are
BYPASS CAPACITORS ON V
CONNECTING TO I
PULL-UP RESISTORS
SS
of the MCP3422/3/4 devices should
Figure
6-1. The value of these
2
C BUS USING
Figure 6-1
DD
shows
PIN
DD
6.1.3
The user can tie the Adr0 and Adr1 pins to V
or left floating. See more details in Section 5.3.2
“Device Address Bits (A2, A1, A0) and Address
Selection Pins (MCP3423 and MCP3424)”.
FIGURE 6-1:
Figure 6-2
nections. The I
as the number of device connected to the I
increases. The bus loading capacitance affects on the
bus operating speed. For example, the highest bus
operating speed for the 400 pF bus capacitance is
1.7 MHz, and 3.4 MHz for 100 pF. Therefore, the user
needs to consider the relationship between the maxi-
mum operation speed versus. the number of I
devices that are connected to the I
FIGURE 6-2:
Connection on I
Signal 1
Input
Signal 2
Input
Rp is the pull-up resistor:
C1: 0.1 µF, Ceramic capacitor
C2: 10 µF, Tantalum capacitor
5 kΩ - 10 kΩ for f
Microcontroller
C
(PIC16F876)
~700Ω for f
C
1
2
shows an example of multiple device con-
I
(
2
MCP3423
MCP3424
C ADDRESS SELECTION PINS
2
C bus loading capacitance increases
4
5
6
2
7
1
3
R
2
P
C Bus.
SCL
SCL
CH1+
CH1-
CH2+
SDA
V
V
CH2-
SS
MCP3422/3/4
DD
MCP3424
Typical Connection.
Example of Multiple Device
AND
=
=
SDA SCL
100 kHz to 400 kHz
3.45 MHz
CH3+
CH4+
CH4-
CH3-
MCP3424
Adr1
Adr0
SCL
14
13
12
11
10
9
8
R
2
C bus line.
MCP3422
MCP3423
P
DS22088B-page 31
MCP4725
)
(MASTER)
I
Selection
Pins
T
2
2
Input
Signal 4
Signal 3
O
C bus line
C Address
Input
MCU
SS
V
DD
, V
DD
2
C
,