AD7151BRMZ Analog Devices Inc, AD7151BRMZ Datasheet - Page 24

• Manufacturer Part Number: AD7151BRMZ
• Description: IC CAP CONV 1CH ULT LP 10MSOP
• Manufacturer: Analog Devices Inc
• Type: Capacitance-to-Digital Converterr

Specifications of AD7151BRMZ

• Input Type: Voltage
• Output Type: Digital
• Interface: 2-Wire Serial
• Current - Supply: 120µA
• Mounting Type: Surface Mount
• Package / Case: 10-MSOP, Micro10™, 10-uMAX, 10-uSOP
• Resolution (bits): 12bit
• Sampling Rate: 100SPS
• Input Channel Type: Single Ended
• Data Interface: 2-Wire, I2C, Serial
• Supply Voltage Range - Analog: 2.7V To 3.6V
• Supply Current: 70µA
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

AD7151
PARASITIC SERIAL RESISTANCE
The AD7151 CDC result is affected by a resistance in series
with the measured capacitance. The total serial resistance (R
R
See Figure 12.
INPUT OVERVOLTAGE PROTECTION
The AD7151 capacitive input has an internal ESD protection.
However, some applications may require an additional
overvoltage protection, depending on the application-specific
requirements. Any additional circuit in the capacitive front end
must be carefully designed, especially with respect to the limits
recommended for maximum capacitance to ground, maximum
serial resistance, maximum leakage, and so on.
S2
in Figure 45) should be on the order of hundreds of Ω.
C
X
R
R
S1
S2
Figure 46. AD7151 CIN Overvoltage Protection
C
X
Figure 45. Parasitic Serial Resistance
EXC
CIN
R
R
S1
S2
EXC
CIN
CDC
CDC
GND
DATA
S1
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+
INPUT EMC PROTECTION
Some applications may require an additional input filter for
improving electromagnetic compatibility (EMC). Any input
filter must be carefully designed, considering the balance between
the system capacitance performance and system electromagnetic
immunity.
Figure 47 shows one of the possible input circuit configurations
significantly improving the system immunity against high
frequency noise and slightly affecting the AD7151 performance
in terms of additional gain and offset error.
POWER SUPPLY DECOUPLING AND FILTERING
The AD7151 has good dc and low frequency power supply
rejection but may be sensitive to higher frequency ripple and
noise, specifically around the excitation frequency and its
harmonics. Figure 48 shows a possible circuit configuration for
improving the system immunity against ripple and noise
coupled to the AD7151 via the power supply.
If the serial interface is connected to the other circuits in the
system, it is better to connect the pull-up resistors on the other
side of the V
AD7151 is used in standalone mode and the serial interface is
not used, it is better to connect the pull-up resistors directly to
the AD7151 V
Figure 48. AD7151 V
DD
C
GND
VDD
DD
X
filter than connect to the AD7151. If the
Figure 47. AD7151 CIN EMC Protection
CDC
.
39kΩ
0.1µF
SDA
SCL
68pF
82kΩ
10kΩ
DD
10µF
Decoupling and Filtering
22pF
47pF
1kΩ
EXC
CIN
1kΩ
GND
CDC
1kΩ
VDD