ADC121C021/ADC121C027 I
2
C-Compatible, 12-Bit Analog-to-Digital Converter (ADC) with Alert
January 17, 2008
ADC121C021/ADC121C027
I
2
C-Compatible, 12-Bit Analog-to-Digital Converter (ADC)
with Alert Function
General Description
The ADC121C021 is a low-power, monolithic, 12-bit, analog-
to-digital converter(ADC) that operates from a +2.7 to 5.5V
supply. The converter is based on a successive approxima-
tion register architecture with an internal track-and-hold circuit
that can handle input frequencies up to 11MHz. The
ADC121C021 operates from a single supply which also
serves as the reference. The device features an
I
2
C-compatible serial interface that operates in all three speed
modes, including high speed mode (3.4MHz).
The ADC's Alert feature provides an interrupt that is activated
when the analog input violates a programmable upper or low-
er limit value. The device features an automatic conversion
mode, which frees up the controller and I
2
C interface. In this
mode, the ADC continuously monitors the analog input for an
"out-of-range" condition and provides an interrupt if the mea-
sured voltage goes out-of-range.
The ADC121C021 comes in a small TSOT-6 package with an
alert output. The ADC121C027 comes in a small TSOT-6
package with an address selection input. The ADC121C027
provides three pin-selectable addresses. Pin-compatible al-
ternatives are available with additional address options.
Normal power consumption using a +3V or +5V supply is
0.26mW or 0.78mW, respectively. The automatic power-
down feature reduces the power consumption to less than
1µW while not converting. Operation over the industrial tem-
perature range of −40°C to +105°C is guaranteed. Their low
power consumption and small packages make this family of
ADCs an excellent choice for use in battery operated equip-
ment.
The ADC121C021 and ADC121C027 are part of a family of
pin-compatible ADCs that also provide 8 and 10 bit resolution.
For 8-bit ADCs see the ADC081C021 and ADC081C027. For
10-bit ADCs see the ADC101C021 and ADC101C027.
Features
■
I
2
C-Compatible 2-wire Interface which supports standard
■
■
■
■
■
■
(100kHz), fast (400kHz), and high speed (3.4MHz) modes
Extended power supply range (+2.7V to +5.5V)
Up to four pin-selectable chip addresses
Out-of-range Alert Function
Automatic Power-down mode while not converting
Very small 6-pin TSOT packages
±8kV HBM ESD protection (SDA, SCL)
Key Specifications
■
■
■
■
■
Resolution
12 bits; no missing codes
Conversion Time
1µs (typ)
INL & DNL
±1 LSB (max) (up to 22kSPS)
Throughput Rate
188.9kSPS (max)
Power Consumption (at 22kSPS)
0.26 mW (typ)
—
3V Supply
0.78 mW (typ)
—
5V Supply
Applications
■
■
■
■
■
System Monitoring
Peak Detection
Portable Instruments
Medical Instruments
Test Equipment
Pin-Compatible Alternatives
All devices are fully pin and function compatible.
Resolution
ALERT Output
ADDR Input
12-bit
10-bit
8-bit
ADC121C021
ADC101C021
ADC081C021
ADC121C027
ADC101C027
ADC081C027
Connection Diagrams
30020901
30020902
I2C
®
is a registered trademark of Phillips Corporation.
© 2008 National Semiconductor Corporation
300209
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ADC121C021/ADC121C027
Ordering Information
Order Code
ADC121C021CIMK
ADC121C021CIMKX
ADC121C027CIMK
ADC121C027CIMKX
Option
Alert pin
Alert pin
Address pin
Address pin
Shipped with the ADC121C021.
Also compatible with the
ADC121C027 option.
Please order samples.
Package
TSOT-6
TSOT-6 Tape-and-Reel
TSOT-6
TSOT-6 Tape-and-Reel
Top Mark
X30C
X30C
X31C
X31C
ADC121C021EB
Evaluation Board
Block Diagram
30020903
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2
ADC121C021/ADC121C027
Pin Descriptions
Symbol
V
A
GND
V
IN
ALERT
Type
Supply
Ground
Analog Input
Digital Output
See
Figure 4
Equivalent Circuit
Description
Power and unbufferred reference voltage. V
A
must be free
of noise and decoupled to GND.
Ground for all on-chip circuitry.
Analog input. This signal can range from GND to V
A
.
Alert output. Can be configured as active high or active
low. This is an open drain data line that must be pulled to
the supply (V
A
) with an external pull-up resistor.
Serial Clock Input. SCL is used together with SDA to
control the transfer of data in and out of the device. This is
an open drain data line that must be pulled to the supply
(V
A
) with an external pull-up resistor. This pin's extended
ESD tolerance( 8kV HBM) allows extension of the I
2
C bus
across multiple boards without extra ESD protection.
Serial Data bi-directional connection. Data is clocked into
or out of the internal 16-bit register with SCL. This is an
open drain data line that must be pulled to the supply
(V
A
) with an external pull-up resistor. This pin's extended
ESD tolerance( 8kV HBM) allows extension of the I
2
C bus
across multiple boards without extra ESD protection.
SCL
Digital Input
SDA
Digital
Input/Output
ADDR
Digital Input,
three levels
Tri-level Address Selection Input. Sets Bits A0 & A1 of the
7-bit slave address. (see
Table 1)
Package Pinouts
V
A
ADC121C021
TSOT-6
ADC121C027
TSOT-6
1
1
GND
2
2
V
IN
3
3
ALERT
4
N/A
SCL
5
5
SDA
6
6
ADDR
N/A
4
3
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ADC121C021/ADC121C027
Absolute Maximum Ratings
(Notes 1, 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage, V
A
Voltage on any Analog Input Pin to
GND
Voltage on any Digital Input Pin to
GND
Input Current at Any Pin (Note 3)
Package Input Current (Note 3)
Power Dissipation at T
A
= 25°C
ESD Susceptibility (Note 5)
VA, GND, VIN, ALERT,
ADDR pins:
Human Body Model
Machine Model
Charged Device Model (CDM)
SDA, SCL pins:
Human Body Model
Machine Model
Junction Temperature
Storage Temperature
-0.3V to +6.5V
−0.3V to (V
A
+0.3V)
−0.3V to 6.5V
±15 mA
±20 mA
See (Note 4)
2500V
250V
1250V
8000V
400V
+150°C
−65°C to +150°C
Operating Ratings
(Notes 1, 2)
Operating Temperature Range
Supply Voltage, V
A
Analog Input Voltage, V
IN
Digital Input Voltage (Note 7)
Sample Rate
−40°C
≤
T
A
≤
+105°C
+2.7V to 5.5V
0V to V
A
0V to 5.5V
up to 188.9 kSPS
Package Thermal Resistances
Package
6-Lead TSOT
θ
JA
250°C/W
Soldering
process
must
comply
with
National
Semiconductor's Reflow Temperature Profile specifications.
Refer to www.national.com/packaging. (Note 6)
Electrical Characteristics
The following specifications apply for V
A
= +2.7V to +5.5V, GND = 0V, f
SCL
up to 3.4MHz, f
IN
= 1kHz for f
SCL
up to 400kHz,
f
IN
= 10kHz for f
SCL
= 3.4MHz unless otherwise noted.
Boldface limits apply for T
A
= T
MIN
to T
MAX
: all other limits T
A
= 25°C
unless otherwise noted.
Symbol
Parameter
Conditions
Typical
(Note 9)
Limits
(Note 9)
12
V
A
= +2.7V to +3.6V
f
SCL
up to 400kHz (Note 13)
V
A
= +2.7V to +5.5V. f
SCL
up to 3.4MHz
V
A
= +2.7V to +3.6V
f
SCL
up to 400kHz (Note 13)
V
A
= +2.7V to +5.5V. f
SCL
up to 3.4MHz
V
A
= +2.7V to +3.6V
f
SCL
up to 400kHz (Note 13)
V
A
= +2.7V to +5.5V. f
SCL
up to 3.4MHz
GE
Gain Error
V
A
= +2.7V to +3.6V
V
A
= +3.6V to +5.5V
V
A
= +2.7V to +3.6V
V
A
= +3.6V to +5.5V
V
A
= +2.7V to +3.6V
V
A
= +3.6V to +5.5V
V
A
= +2.7V to +3.6V
V
A
= +3.6V to +5.5V
DYNAMIC CONVERTER CHARACTERISTICS
ENOB
SNR
THD
SINAD
Effective Number of Bits
Signal-to-Noise Ratio
Total Harmonic Distortion
Signal-to-Noise Plus Distortion Ratio
11.7
11.5
72.5
71
−92
−87
72.6
71
70
−78
70.4
11.3
Bits (min)
Bits (min)
dB (min)
dB (min)
dB (max)
dB (max)
dB (min)
dB (min)
±0.5
+1.2
−0.9
+0.5
−0.5
+1.3
−0.9
+0.1
+1.4
-0.8
±6
±1.6
+1
−0.9
±1
Units (Limits)
STATIC CONVERTER CHARACTERISTICS
Resolution with No Missing Codes
Integral Non-Linearity (End Point
Method)
Bits
LSB (max)
LSB
LSB
LSB (max)
LSB (min)
LSB
LSB
LSB (max)
LSB
LSB (max)
INL
DNL
Differential Non-Linearity
V
OFF
Offset Error
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4
ADC121C021/ADC121C027
Symbol
SFDR
Parameter
Spurious-Free Dynamic Range
Conditions
V
A
= +2.7V to +3.6V
V
A
= +3.6V to +5.5V
V
A
= +3.0V,
f
a
= 1.035 kHz, f
b
= 1.135 kHz
V
A
= +5.0V,
f
a
= 1.035 kHz, f
b
= 1.135 kHz
V
A
= +3.0V,
f
a
= 1.035 kHz, f
b
= 1.135 kHz
V
A
= +5.0V,
f
a
= 1.035 kHz, f
b
= 1.135 kHz
V
A
= +3.0V
V
A
= +5.0V
Typical
(Note 9)
90
87
−89
−91
−88
−88
8
11
0 to V
A
Limits
(Note 9)
76
Units (Limits)
dB (min)
dB (min)
dB
dB
dB
dB
MHz
MHz
V
Intermodulation Distortion, Second
Order Terms (IMD
2
)
IMD
Intermodulation Distortion, Third
Order Terms (IMD
3
)
FPBW
Full Power Bandwidth (−3dB)
ANALOG INPUT CHARACTERISTICS
V
IN
I
DCL
C
INA
Input Range
DC Leakage Current (Note 10)
Input Capacitance
Track Mode
Hold Mode
30
3
0.7 x V
A
0.3 x V
A
±1
3
0.1 x V
A
V
A
- 0.5V
0.5
±1
I
SINK
= 3 mA
I
SINK
= 6 mA
0.4
0.6
±1
±1
µA (max)
pF
pF
V (min)
V (max)
µA (max)
pF
V (min)
V (min)
V (max)
µA (max)
V (max)
V (max)
µA (max)
SERIAL INTERFACE INPUT CHARACTERISTICS (SCL, SDA)
V
IH
V
IL
I
IN
C
IN
V
HYST
V
IH
V
IL
I
IN
Input High Voltage
Input Low Voltage
Input Current (Note 10)
Input Pin Capacitance
Input Hysteresis
Input High Voltage
Input Low Voltage
Input Current (Note 10)
ADDRESS SELECTION INPUT CHARACTERISTICS (ADDR)
LOGIC OUTPUT CHARACTERISTICS, OPEN-DRAIN (SDA, ALERT)
V
OL
I
OZ
Output Low Voltage
High-Impedence Output
Leakage Current (Note 10)
Output Coding
Straight (Natural) Binary
5
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