MCP3421
18-Bit Analog-to-Digital Converter
with I
2
C Interface and On-Board Reference
Features
• 18-bit
ΔΣ
ADC in a SOT-23-6 package
• Differential input operation
• Self calibration of Internal Offset and Gain per
each conversion
• On-board Voltage Reference:
- Accuracy: 2.048V ± 0.05%
- Drift: 5 ppm/°C
• On-board Programmable Gain Amplifier (PGA):
- Gains of 1,2,4 or 8
• On-board Oscillator
• INL: 10 ppm of FSR (FSR = 4.096V/PGA)
• Programmable Data Rate Options:
- 3.75 SPS (18 bits)
- 15 SPS (16 bits)
- 60 SPS (14 bits)
- 240 SPS (12 bits)
• One-Shot or Continuous Conversion Options
• Low current consumption:
- 145 µA typical
(V
DD
= 3V, Continuous Conversion)
- 39 µA typical
(V
DD
= 3V, One-Shot Conversion with 1 SPS)
• Supports I
2
C Serial Interface:
- Standard, Fast and High Speed Modes
• Single Supply Operation: 2.7V to 5.5V
• Extended Temperature Range: -40°C to 125°C
Description
The MCP3421 is a single channel low-noise, high
accuracy
ΔΣ
A/D converter with differential inputs and
up to 18 bits of resolution in a small SOT-23-6 package.
The on-board precision 2.048V reference voltage
enables an input range of ±2.048V differentially
(Δ voltage = 4.096V). The device uses a two-wire I
2
C
compatible serial interface and operates from a single
2.7V to 5.5V power supply.
The MCP3421 device performs conversion at rates of
3.75, 15, 60, or 240 samples per second (SPS)
depending on the user controllable configuration bit
settings using the two-wire I
2
C serial interface. This
device has an on-board programmable gain amplifier
(PGA). The user can select the PGA gain of x1, x2, x4,
or x8 before the analog-to-digital conversion takes
place. This allows the MCP3421 device to convert a
smaller input signal with high resolution. The device
has two conversion modes: (a) Continuous mode and
(b) One-Shot mode. In One-Shot mode, the device
enters a low current standby mode automatically after
one conversion. This reduces current consumption
greatly during idle periods.
The MCP3421 device can be used for various high
accuracy analog-to-digital data conversion applications
where design simplicity, low power, and small footprint
are major considerations.
Block Diagram
V
SS
V
DD
Typical Applications
• Portable Instrumentation
• Weigh Scales and Fuel Gauges
• Temperature Sensing with RTD, Thermistor, and
Thermocouple
• Bridge Sensing for Pressure, Strain, and Force.
Voltage Reference
(2.048V)
Gain = 1, 2, 4, or 8
V
IN
+
PGA
ΔΣ
ADC
Converter
Clock
Oscillator
V
REF
Package Types
SOT-23-6
Top View
V
IN
-
1
2
3
6
5
4
V
IN
+
V
SS
SCL
V
IN
-
V
DD
SDA
I
2
C Interface
SCL
SDA
©
2006 Microchip Technology Inc.
DS22003B-page 1
MCP3421
1.0
ELECTRICAL
CHARACTERISTICS
†Notice:
Stresses above those listed under “Maximum Rat-
ings” may cause permanent damage to the device. This is a
stress rating only and functional operation of the device at
those or any other conditions above those indicated in the
operational listings of this specification is not implied.
Exposure to maximum rating conditions for extended periods
may affect device reliability
.
Absolute Maximum Ratings†
V
DD
...................................................................................7.0V
All inputs and outputs w.r.t V
SS
............... –0.3V to V
DD
+0.3V
Differential Input Voltage ...................................... |V
DD
- V
SS
|
Output Short Circuit Current .................................Continuous
Current at Input Pins ....................................................±2 mA
Current at Output and Supply Pins ............................±10 mA
Storage Temperature.....................................-65°C to +150°C
Ambient Temp. with power applied ...............-55°C to +125°C
ESD protection on all pins
................ ≥
6 kV HBM,
≥
400V MM
Maximum Junction Temperature (T
J
) . .........................+150°C
ELECTRICAL CHARACTERISTICS
Electrical Specifications:
Unless otherwise specified, all parameters apply for T
A
= -40°C to +85°C, V
DD
= +5.0V, V
SS
= 0V,
V
IN
+ = V
IN
- = V
REF
/2. All ppm units use 2*V
REF
as full-scale range.
Parameters
Analog Inputs
Differential Input Range
Common-Mode Voltage Range
(absolute)
(Note 1)
(Note 2)
Sym
Min
—
V
SS
-0.3
Typ
±2.048/PGA
—
2.25/PGA
25
Max
—
V
DD
+0.3
—
—
Units
V
V
MΩ
MΩ
Conditions
V
IN
= V
IN
+ - V
IN
-
Differential Input Impedance
Common Mode input
Impedance
System Performance
Resolution and No Missing
Codes
(Note 8)
Z
IND
(f)
Z
INC
(f)
—
—
During normal mode operation
PGA = 1, 2, 4, 8
12
14
16
18
—
—
—
—
240
60
15
3.75
1.5
—
—
—
—
328
82
20.5
5.1
—
Bits
Bits
Bits
Bits
SPS
SPS
SPS
SPS
µV
RMS
DR = 240 SPS
DR = 60 SPS
DR = 15 SPS
DR = 3.75 SPS
S1,S0 = ‘00’, (12 bits mode)
S1,S0 = ‘01’, (14 bits mode)
S1,S0 = ‘10’, (16 bits mode)
S1,S0 = ‘11’, (18 bits mode)
T
A
= 25°C, DR = 3.75 SPS,
PGA = 1, V
IN
= 0
Data Rate
(Note 3)
DR
176
44
11
2.75
Output Noise
Note 1:
2:
3:
4:
5:
6:
7:
8:
—
Any input voltage below or greater than this voltage causes leakage current through the ESD diodes at the input pins.
This parameter is ensured by characterization and not 100% tested.
This input impedance is due to 3.2 pF internal input sampling capacitor.
The total conversion speed includes auto-calibration of offset and gain.
INL is the difference between the endpoints line and the measured code at the center of the quantization band.
Includes all errors from on-board PGA and V
REF
.
Full Scale Range (FSR) = 2 x 2.048/PGA = 4.096/PGA.
This parameter is ensured by characterization and not 100% tested.
This parameter is ensured by design and not 100% tested.
DS22003B-page 2
©
2006 Microchip Technology Inc.
MCP3421
ELECTRICAL CHARACTERISTICS (CONTINUED)
Electrical Specifications:
Unless otherwise specified, all parameters apply for T
A
= -40°C to +85°C, V
DD
= +5.0V, V
SS
= 0V,
V
IN
+ = V
IN
- = V
REF
/2. All ppm units use 2*V
REF
as full-scale range.
Parameters
Integral Nonlinearity
(Note 4)
Internal Reference Voltage
Gain Error
(Note 5)
Sym
INL
V
REF
Min
—
—
—
—
—
Typ
10
2.048
0.05
0.1
5
15
50
105
110
5
100
Max
35
—
0.35
—
40
40
—
—
—
—
—
Units
Conditions
DR = 3.75 SPS
(Note 6)
PGA = 1, DR = 3.75 SPS
Between any 2 PGA gains
PGA=1, DR=3.75 SPS
Tested at PGA = 1
V
DD
= 5.0V and DR = 3.75 SPS
V
DD
= 5.0V
at DC and PGA =1,
at DC and PGA =8,
T
A
= +25°C
T
A
= +25°C, V
DD
= 2.7V to 5.5V,
PGA = 1
T
A
= +25°C, V
DD
= 2.7V to 5.5V,
PGA = 1
ppm of
FSR
V
%
%
ppm/°C
µV
nV/°C
dB
dB
ppm/V
dB
PGA Gain Error Match
(Note 5)
Gain Error Drift
Offset Error
Offset Drift vs. Temperature
Common-Mode Rejection
(Note
5)
V
OS
—
—
—
—
Gain vs. V
DD
Power Supply Rejection at DC
Power Requirements
Voltage Range
Supply Current during
Conversion
Supply Current during Standby
Mode
High level input voltage
Low level input voltage
Low level output voltage
Hysteresis of Schmitt Trigger
for inputs
(Note 7)
Supply Current when I
2
C bus
line is active
Input Leakage Current
2
—
—
V
DD
I
DDA
I
DDS
2.7
—
—
—
—
155
145
0.1
5.5
190
—
0.5
V
µA
µA
µA
V
DD
= 5.0V
V
DD
= 3.0V
I
2
C Digital Inputs and Digital Outputs
V
IH
V
IL
V
OL
V
HYST
I
DDB
I
ILH
I
ILL
Pin Capacitance and I C Bus Capacitance
Pin capacitance
I
2
C
0.7 V
DD
—
—
0.05V
DD
—
—
-1
—
—
-40
-40
-65
—
—
—
—
—
—
—
—
—
—
—
—
V
DD
0.3V
DD
0.4
—
10
1
—
10
400
+85
+125
+150
V
V
V
V
µA
µA
µA
pF
pF
°C
°C
°C
V
IH
= 5.5V
V
IL
= GND
I
OL
= 3 mA, V
DD
= +5.0V
f
SCL
= 100 kHz
C
PIN
C
b
T
A
T
A
T
A
Bus Capacitance
Thermal Characteristics
Specified Temperature Range
Operating Temperature Range
Storage Temperature Range
Note 1:
2:
3:
4:
5:
6:
7:
8:
Any input voltage below or greater than this voltage causes leakage current through the ESD diodes at the input pins.
This parameter is ensured by characterization and not 100% tested.
This input impedance is due to 3.2 pF internal input sampling capacitor.
The total conversion speed includes auto-calibration of offset and gain.
INL is the difference between the endpoints line and the measured code at the center of the quantization band.
Includes all errors from on-board PGA and V
REF
.
Full Scale Range (FSR) = 2 x 2.048/PGA = 4.096/PGA.
This parameter is ensured by characterization and not 100% tested.
This parameter is ensured by design and not 100% tested.
©
2006 Microchip Technology Inc.
DS22003B-page 3
MCP3421
2.0
Note:
TYPICAL PERFORMANCE CURVES
The graphs and tables provided following this note are a statistical summary based on a limited number of
samples and are provided for informational purposes only. The performance characteristics listed herein
are not tested or guaranteed. In some graphs or tables, the data presented may be outside the specified
operating range (e.g., outside specified power supply range) and therefore outside the warranted range.
Note:
Unless otherwise indicated, T
A
= -40°C to +85°C, V
DD
= +5.0V, V
SS
= 0V, V
IN
+ = V
IN
- = V
REF
/2.
.005
.004
.003
.002
.001
.000
2.5
3
3.5
4
V
DD
(V)
4.5
5
5.5
PGA = 8
PGA = 2
PGA = 4
PGA = 1
Integral Nonlinearity (% of FSR)
10.0
T
A
= +25°C
V
DD
= 5V
PGA = 1
PGA = 2
PGA = 4
Noise (µV, rms)
7.5
5.0
PGA = 8
2.5
0.0
-100 -75
-50
-25
0
25
50
75
100
Input Voltage (% of Full-Scale)
FIGURE 2-1:
(V
DD
).
INL vs. Supply Voltage
FIGURE 2-4:
Noise vs. Input Voltage.
3.0
0.003
Integral Nonlinearity
(% of FSR)
PGA = 1
2.0
Total Error (mV)
1.0
0.0
-1.0
-2.0
-3.0
-100
PGA = 1
PGA = 2
PGA = 4
PGA = 8
0.002
V
DD
= 5 V
0.001
V
DD
= 2.7V
0
-60 -40 -20
0
20 40 60 80 100 120 140
o
-75
-50
-25
0
25
50
75
100
Temperature ( C)
Input Voltage (% of Full-Scale)
FIGURE 2-2:
20
15
Offset Error (µV)
10
5
0
-5
-10
-15
-20
-60 -40 -20
0
PGA = 1
INL vs. Temperature.
FIGURE 2-5:
0.4
Total Error vs. Input Voltage.
V
DD
= 5V
PGA = 4
PGA = 2
PGA = 8
Gain Error (% of FSR)
0.3
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-60 -40 -20
0
20
40
60
PGA = 1
PGA = 2
V
DD
= 5.0V
PGA = 4
PGA = 8
20
40
60
80 100 120 140
80 100 120 140
Temperature (°C)
Temperature (°C)
FIGURE 2-3:
Offset Error vs. Temperature.
FIGURE 2-6:
Gain Error vs. Temperature.
DS22003B-page 4
©
2006 Microchip Technology Inc.
MCP3421
Note:
Unless otherwise indicated, T
A
= -40°C to +85°C, V
DD
= +5.0V, V
SS
= 0V, V
IN
+ = V
IN
- = V
REF
/2.
220
200
V
DD
= 5V
5
I
DDA
(µA)
180
160
140
120
100
V
DD
= 2.7V
Oscillator Drift (%)
4
3
2
1
0
-1
-60 -40 -20
0
20
40
60
80 100 120 140
V
DD
= 2.7V
V
DD
= 5.0V
-60 -40 -20
0
20
40
60
80 100 120 140
Temperature (
o
C)
Temperature (°C)
FIGURE 2-7:
I
DDA
vs. Temperature.
FIGURE 2-10:
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
-110
-120
OSC Drift vs. Temperature.
600
500
I
DDS
(nA)
400
300
200
100
0
-60 -40 -20
0
20 40 60 80 100 120 140
Temperature (
o
C)
V
DD
= 5V
V
DD
= 2.7V
Data Rate = 3.75 SPS
Magnitude (dB)
0.1
0.1
1
1
10
100
1k
Input Signal Frequency (Hz)
10
100
1000
10k
10000
FIGURE 2-8:
I
DDS
vs. Temperature.
FIGURE 2-11:
Frequency Response.
9
8
7
6
5
4
3
2
1
0
V
DD
= 2.7V
V
DD
= 3.3V
V
DD
= 5V
V
DD
= 4.5V
I
DDB
( A)
-60 -40 -20
0
20
40
60
80 100 120 140
Temperature (
o
C)
FIGURE 2-9:
I
DDB
vs. Temperature.
©
2006 Microchip Technology Inc.
DS22003B-page 5
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