ADC0831-N, ADC0832-N, ADC0834-N, ADC0838-N
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ADC0831-N/ADC0832-N/ADC0834-N/ADC0838-N 8-Bit Serial I/O A/D Converters with
Multiplexer Options
Check for Samples: ADC0831-N, ADC0832-N, ADC0834-N, ADC0838-N
FEATURES
KEY SPECIFICATIONS
•
•
•
•
•
•
1
2
•
•
•
•
•
•
•
•
•
•
•
TI MICROWIRE Compatible—Direct Interface to
COPS Family Processors
Easy Interface to All Microprocessors, or
Operates “Stand-Alone”
Operates Ratiometrically or with 5 VDC Voltage
Reference
No Zero or Full-Scale Adjust Required
2-, 4- or 8-Channel Multiplexer Options with
Address Logic
Shunt Regulator Allows Operation with High
Voltage Supplies
0V to 5V Input Range with Single 5V Power
Supply
Remote Operation with Serial Digital Data Link
TTL/MOS Input/Output Compatible
0.3 in. Standard Width, 8-, 14- or 20-Pin PDIP
Package
20 Pin PLCC Package (ADC0838-N Only)
SOIC Package
Resolution: 8 Bits
Total Unadjusted Error: ±½ LSB and ±1 LSB
Single Supply: 5 VDC
Low Power: 15 mW
Conversion Time: 32 μs
DESCRIPTION
The ADC0831 series are 8-bit successive
approximation A/D converters with a serial I/O and
configurable input multiplexers with up to 8 channels.
The serial I/O is configured to comply with the TI
MICROWIRE serial data exchange standard for easy
interface to the COPS family of processors, and can
interface with standard shift registers or μPs.
The 2-, 4- or 8-channel multiplexers are software
configured for single-ended or differential inputs as
well as channel assignment.
The differential analog voltage input allows increasing
the common-mode rejection and offsetting the analog
zero input voltage value. In addition, the voltage
reference input can be adjusted to allow encoding
any smaller analog voltage span to the full 8 bits of
resolution.
Typical Application
1
2
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 1999–2013, Texas Instruments Incorporated
ADC0831-N, ADC0832-N, ADC0834-N, ADC0838-N
SNAS531B – AUGUST 1999 – REVISED MARCH 2013
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Connection Diagrams
Figure 4. ADC0831-N Single Differential Input
PDIP Package (P) Top View
Figure 1. ADC0838-N 8-Channel Mux SOIC/PDIP
Package (DW or NFH) Top View
COM internally connected to GND.
VREF internally connected to VCC.
Top View
Figure 5. ADC0832-N 2-Channel MUX PDIP
Package (P) Top View
Figure 2. ADC0832-N 2-Channel MUX
SOIC Package (NPA) Top View
Figure 6. ADC0831-N Single Differential Input
SOIC Package (NPA) Top View
COM internally connected to A GND
Top View
Figure 3. ADC0834-N 4-Channel MUX SOIC/PDIP
(NPA or NFF) Top View
Figure 7. ADC0838-N 8-Channel MUX
PLCC Package (FN)
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
2
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SNAS531B – AUGUST 1999 – REVISED MARCH 2013
Absolute Maximum Ratings (1) (2) (3)
Current into V+ (4)
15 mA
Supply Voltage, VCC (4)
6.5V
Voltage
Logic Inputs
−0.3V to VCC + 0.3V
Analog Inputs
−0.3V to VCC + 0.3V
Pin
Input Current per
(5)
±5 mA
Package
±20 mA
−65°C to +150°C
Storage Temperature
Package Dissipation
at TA = 25°C (Board Mount)
Lead Temperature (Soldering 10 sec.)
PDIP Package
260°C
Vapor Phase (60 sec.)
215°C
PLCC Package
0.8W
Infrared (15 sec.)
220°C
ESD Susceptibility (6)
(1)
(2)
(3)
(4)
(5)
(6)
2000V
All voltages are measured with respect to the ground plugs.
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not
apply when operating the device beyond its specified operating conditions.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
Internal zener diodes (6.3 to 8.5V) are connected from V+ to GND and VCC to GND. The zener at V+ can operate as a shunt regulator
and is connected to VCC via a conventional diode. Since the zener voltage equals the A/D's breakdown voltage, the diode insures that
VCC will be below breakdown when the device is powered from V+. Functionality is therefore ensured for V+ operation even though the
resultant voltage at VCC may exceed the specified Absolute Max of 6.5V. It is recommended that a resistor be used to limit the max
current into V+. (See Figure 24 in Functional Description)
When the input voltage (VIN) at any pin exceeds the power supply rails (VIN < V− or VIN > V+) the absolute value of current at that pin
should be limited to 5 mA or less. The 20 mA package input current limits the number of pins that can exceed the power supply
boundaries with a 5 mA current limit to four.
Human body model, 100 pF discharged through a 1.5 kΩ resistor.
Operating Ratings (1) (2)
Supply Voltage, VCC
4.5 VDC to 6.3 VDC
Temperature Range (TMIN ≤ TA ≤ TMAX)
ADC0832/8CIWM ADC0834BCN, ADC0838BCV,
ADC0831/2/4/8CCN, ADC0838CCV
ADC0831/2/4/8CCWM
(1)
(2)
−40°C to +85°C
0°C to +70°C
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not
apply when operating the device beyond its specified operating conditions.
All voltages are measured with respect to the ground plugs.
Copyright © 1999–2013, Texas Instruments Incorporated
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Converter and Multiplexer Electrical Characteristics
The following specifications apply for VCC = V+ = VREF = 5V, VREF ≤ VCC +0.1V, TA = Tj = 25°C, and fCLK = 250 kHz unless
otherwise specified. Boldface limits apply from TMIN to TMAX.
BCV, CCV, CCWM, BCN
and CCN Devices
CIWM Devices
Parameter
Conditions
Tested
Limit (2)
Design
Limit (3)
ADC0838BCV
±½
±½
ADC0834BCN
±½
±½
ADC0838CCV
±1
±1
±1
±1
±1
±1
Typ (1)
Tested
Limit (2)
Design
Limit (3)
Typ (1)
Units
CONVERTER AND MULTIPLEXER CHARACTERISTICS
Total
Unadjusted
Error
ADC0831/2/4/8CCN
VREF = 5.00 V (4)
ADC0831/2/4/8CCWM
ADC0832/8CIWM
LSB (Max)
±1
Minimum Reference Input
Resistance (5)
3.5
1.3
3.5
1.3
1.3
kΩ
Maximum Reference Input
Resistance (5)
3.5
5.9
3.5
5.4
5.9
kΩ
Maximum Common-Mode Input
Range (6)
VCC
+0.05
VCC
+0.05
VCC+0.05
V
Minimum Common-Mode Input
Range (6)
GND
−0.05
GND
−0.05
GND
−0.05
V
±¼
±¼
LSB
1
1
1
LSB
6.3
6.3
6.3
8.5
8.5
V
±¼
±¼
LSB
−0.2
−1
μA
+0.2
+1
μA
−0.2
−1
μA
+0.2
+1
μA
DC Common-Mode Error
±1/16
Change in zero error from VCC=5V
to internal zener operation (7)
VZ, internal diode
breakdown (at V+) (7)
15 mA into V+, VCC =
N.C.,
VREF = 5V
MIN 15 mA into V+
MAX
Power Supply Sensitivity
On Channel = 5V
ION, On Channel Leakage Current (8)
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
4
±1/16
8.5
VCC = 5V ± 5%
IOFF, Off Channel Leakage
Current (8)
±¼
±1/16
±¼
±¼
±1/16
−0.2
Off Channel = 0V
−1
On Channel = 0V
+0.2
Off Channel = 5V
+1
On Channel = 0V
−0.2
Off Channel = 5V
−1
On Channel = 5V
+0.2
Off Channel = 0V
+1
Typicals are at 25°C and represent most likely parametric norm.
Tested limits are ensured to TI's AOQL (Average Outgoing Quality Level).
Ensured but not 100% production tested. These limits are not used to calculate outgoing quality levels.
Total unadjusted error includes offset, full-scale, linearity, and multiplexer errors.
Cannot be tested for ADC0832-N.
For VIN(−) ≥ VIN(+) the digital output code will be 0000 0000. Two on-chip diodes are tied to each analog input (see Functional Block
Diagram) which will forward conduct for analog input voltages one diode drop below ground or one diode drop greater than the VCC
supply. Be careful, during testing at low VCC levels (4.5V), as high level analog inputs (5V) can cause this input diode to
conduct—especially at elevated temperatures, and cause errors for analog inputs near full-scale. The spec allows 50 mV forward bias of
either diode. This means that as long as the analog VIN or VREF does not exceed the supply voltage by more than 50 mV, the output
code will be correct. To achieve an absolute 0 VDC to 5 VDC input voltage range will therefore require a minimum supply voltage of 4.950
VDC over temperature variations, initial tolerance and loading.
Internal zener diodes (6.3 to 8.5V) are connected from V+ to GND and VCC to GND. The zener at V+ can operate as a shunt regulator
and is connected to VCC via a conventional diode. Since the zener voltage equals the A/D's breakdown voltage, the diode insures that
VCC will be below breakdown when the device is powered from V+. Functionality is therefore ensured for V+ operation even though the
resultant voltage at VCC may exceed the specified Absolute Max of 6.5V. It is recommended that a resistor be used to limit the max
current into V+. (See Figure 24 in Functional Description)
Leakage current is measured with the clock not switching.
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Converter and Multiplexer Electrical Characteristics (continued)
The following specifications apply for VCC = V+ = VREF = 5V, VREF ≤ VCC +0.1V, TA = Tj = 25°C, and fCLK = 250 kHz unless
otherwise specified. Boldface limits apply from TMIN to TMAX.
CIWM Devices
Parameter
Conditions
Typ (1)
Tested
Limit (2)
Design
Limit (3)
BCV, CCV, CCWM, BCN
and CCN Devices
Typ (1)
Tested
Limit (2)
Design
Limit (3)
Units
DIGITAL AND DC CHARACTERISTICS
VIN(1), Logical “1” Input Voltage (Min) VCC = 5.25V
2.0
2.0
2.0
V
VIN(0), Logical “0” Input Voltage
(Max)
0.8
0.8
0.8
V
VCC = 4.75V
IIN(1), Logical “1” Input Current (Max) VIN = 5.0V
0.005
1
0.005
1
1
μA
IIN(0), Logical “0” Input Current (Max) VIN = 0V
−0.005
−1
−0.00
5
−1
−1
μA
VCC = 4.75V
VOUT(1), Logical “1” Output Voltage
(Min)
IOUT = −360 μA
2.4
2.4
2.4
V
IOUT = −10 μA
4.5
4.5
4.5
V
VOUT(0), Logical “0” Output Voltage
(Max)
VCC = 4.75V,
IOUT = 1.6 mA
0.4
0.4
0.4
V
IOUT, TRI-STATE Output Current
(Max)
VOUT = 0V
−0.1
−3
−0.1
−3
−3
μA
VOUT = 5V
0.1
3
0.1
+3
+3
μA
ISOURCE, Output Source Current
(Min)
VOUT = 0V
−14
−6.5
−14
−7.5
−6.5
mA
ISINK, Output Sink Current (Min)
VOUT = VCC
16
8.0
16
9.0
8.0
mA
0.9
2.5
0.9
2.5
2.5
mA
2.3
6.5
2.3
6.5
6.5
mA
ICC, Supply Current
(Max)
ADC0832-N
ADC0831-N,
ADC0834-N,
ADC0838-N
Includes Ladder
Current
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AC Characteristics
The following specifications apply for VCC = 5V, tr = tf = 20 ns and 25°C unless otherwise specified.
Parameter
Conditions
Typ (1)
Min
fCLK, Clock Frequency
Tested
Limit (2)
10
Max
tC, Conversion Time
Design
Limit (3)
kHz
400
Not including MUX Addressing Time
Limit
Units
8
kHz
1/fCLK
Min
40
%
Max
60
%
tSET-UP, CS Falling Edge or Data Input Valid
to CLK Rising Edge
250
ns
tHOLD, Data Input Valid after CLK Rising
Edge
90
ns
Clock Duty Cycle (4)
CL=100 pF
tpd1, tpd0—CLK Falling Edge to Output Data
Valid (5)
t1H, t0H,—Rising Edge of CS to Data Output
and SARS Hi–Z
Data MSB First
650
1500
ns
Data LSB First
250
600
ns
CL=10 pF, RL=10k (See TRI-STATE
Test Circuits and Waveforms)
125
250
ns
CL=100 pf, RL=2k
500
ns
CIN, Capacitance of Logic Input
5
pF
COUT, Capacitance of Logic Outputs
5
pF
(1)
(2)
(3)
(4)
(5)
6
Typicals are at 25°C and represent most likely parametric norm.
Tested limits are ensured to TI's AOQL (Average Outgoing Quality Level).
Ensured but not 100% production tested. These limits are not used to calculate outgoing quality levels.
A 40% to 60% clock duty cycle range insures proper operation at all clock frequencies. In the case that an available clock has a duty
cycle outside of these limits, the minimum, time the clock is high or the minimum time the clock is low must be at least 1 μs. The
maximum time the clock can be high is 60 μs. The clock can be stopped when low so long as the analog input voltage remains stable.
Since data, MSB first, is the output of the comparator used in the successive approximation loop, an additional delay is built in (see
ADC0838-N Functional Block Diagram) to allow for comparator response time.
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Typical Performance Characteristics
Unadjusted Offset Error vs. VREF Voltage
Linearity Error vs. VREFVoltage
Figure 8.
Figure 9.
Linearity Error vs. Temperature
Linearity Error vs. fCLK
Figure 10.
Figure 11.
Power Supply Current vs.
Temperature (ADC0838-N, ADC0831-N, ADC0834-N)
Output Current vs. Temperature
Note: For ADC0832-N add IREF.
Figure 12.
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Figure 13.
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Typical Performance Characteristics (continued)
Power Supply Current vs. fCLK
Figure 14.
Leakage Current Test Circuit
TRI-STATE Test Circuits and Waveforms
8
t1H
t1H
t0H
t0H
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Timing Diagrams
Figure 15. Data Input Timing
Figure 16. Data Output Timing
Figure 17. ADC0831-N Start Conversion Timing
*LSB first output not available on ADC0831-N.
Figure 18. ADC0831-N Timing
Figure 19. ADC0832-N Timing
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Figure 20. ADC0834-N Timing
10
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*Make sure clock edge #18 clocks in the LSB before SE is taken low
Figure 21. ADC0838-N Timing
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ADC0838-N Functional Block Diagram
*Some of these functions/pins are not available with other options.
Note 1: For the ADC0834-N, D1 is input directly to the D input of SELECT 1. SELECT 0 is forced to a “1”. For the ADC0832-N, DI is input directly to the DI input of
ODD/SIGN. SELECT 0 is forced to a “0” and SELECT 1 is forced to a “1”.
12
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Functional Description
Multiplexer Addressing
The design of these converters utilizes a sample-data comparator structure which provides for a differential
analog input to be converted by a successive approximation routine.
The actual voltage converted is always the difference between an assigned “+” input terminal and a “−” input
terminal. The polarity of each input terminal of the pair being converted indicates which line the converter expects
to be the most positive. If the assigned “+” input is less than the “−” input the converter responds with an all zeros
output code.
A unique input multiplexing scheme has been utilized to provide multiple analog channels with softwareconfigurable single-ended, differential, or a new pseudo-differential option which will convert the difference
between the voltage at any analog input and a common terminal. The analog signal conditioning required in
transducer-based data acquisition systems is significantly simplified with this type of input flexibility. One
converter package can now handle ground referenced inputs and true differential inputs as well as signals with
some arbitrary reference voltage.
A particular input configuration is assigned during the MUX addressing sequence, prior to the start of a
conversion. The MUX address selects which of the analog inputs are to be enabled and whether this input is
single-ended or differential. In the differential case, it also assigns the polarity of the channels. Differential inputs
are restricted to adjacent channel pairs. For example channel 0 and channel 1 may be selected as a different
pair but channel 0 or 1 cannot act differentially with any other channel. In addition to selecting differential mode
the sign may also be selected. Channel 0 may be selected as the positive input and channel 1 as the negative
input or vice versa. This programmability is best illustrated by the MUX addressing codes shown in the following
tables for the various product options.
The MUX address is shifted into the converter via the DI line. Because the ADC0831-N contains only one
differential input channel with a fixed polarity assignment, it does not require addressing.
The common input line on the ADC0838-N can be used as a pseudo-differential input. In this mode, the voltage
on this pin is treated as the “−” input for any of the other input channels. This voltage does not have to be analog
ground; it can be any reference potential which is common to all of the inputs. This feature is most useful in
single-supply application where the analog circuitry may be biased up to a potential other than ground and the
output signals are all referred to this potential.
Table 1. Multiplexer/Package Options Single-Ended MUX Mode
Number of Analog Channels
Part Number
Number of Package Pins
Single-Ended
Differential
ADC0831-N
1
1
8
ADC0832-N
2
1
8
ADC0834-N
4
2
14
ADC0838-N
8
4
20
Table 2. MUX Addressing: ADC0838-N Single-Ended MUX Mode
MUX Address
Analog Single-Ended Channel #
SGL/
ODD/
DIF
SIGN
SELECT
0
1
0
0
0
1
0
0
1
1
0
1
0
1
0
1
1
1
1
0
0
1
1
0
1
1
1
1
0
1
1
1
1
1
1
2
3
4
5
6
7
COM
0
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−
+
−
+
−
+
−
+
−
+
−
+
−
+
+
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Table 3. MUX Addressing: ADC0838-N Differential MUX Mode
MUX Address
Analog Differential Channel-Pair #
SGL/
ODD/
SELECT
0
DIF
SIGN
1
0
0
1
0
0
0
0
+
−
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
0
0
1
0
1
0
1
1
0
0
1
1
1
−
1
2
2
3
+
−
3
4
5
+
−
6
7
+
−
−
+
+
−
+
−
+
Table 4. MUX Addressing: ADC0834-N Single-Ended MUX Mode
MUX Address
Channel #
SELECT
SGL / DIF
ODD / SIGN
1
0
0
1
0
1
1
1
0
1
1
1
1
0
1
2
3
+
+
+
+
Table 5. MUX Addressing: ADC0834-N Differential MUX Mode
MUX Address
Channel #
SELECT
SGL / DIF
ODD / SIGN
0
0
0
0
0
1
0
1
0
0
1
1
1
0
1
+
−
−
+
2
3
+
−
−
+
Table 6. MUX Addressing: ADC0832-N Single-Ended MUX Mode
MUX Address
Channel #
SGL / DIF
ODD / SIGN
0
1
0
+
1
1
1
+
Table 7. MUX Addressing: ADC0832-N Differential MUX Mode
MUX Address
Channel #
SGL / DIF
ODD / SIGN
0
1
0
0
+
−
0
1
−
+
Since the input configuration is under software control, it can be modified, as required, at each conversion. A
channel can be treated as a single-ended, ground referenced input for one conversion; then it can be
reconfigured as part of a differential channel for another conversion. Figure 22 illustrates the input flexibility which
can be achieved.
The analog input voltages for each channel can range from 50 mV below ground to 50 mV above VCC (typically
5V) without degrading conversion accuracy.
14
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THE DIGITAL INTERFACE
A most important characteristic of these converters is their serial data link with the controlling processor. Using a
serial communication format offers two very significant system improvements; it allows more function to be
included in the converter package with no increase in package size and it can eliminate the transmission of low
level analog signals by locating the converter right at the analog sensor; transmitting highly noise immune digital
data back to the host processor.
To understand the operation of these converters it is best to refer to the Timing Diagrams and Functional Block
Diagram and to follow a complete conversion sequence. For clarity a separate diagram is shown of each device.
1. A conversion is initiated by first pulling the CS (chip select) line low. This line must be held low for the entire
conversion. The converter is now waiting for a start bit and its MUX assignment word.
2. A clock is then generated by the processor (if not provided continuously) and output to the A/D clock input.
8 Single-Ended
8 Pseudo-Differential
4 Differential
Mixed Mode
Figure 22. Analog Input Multiplexer Options for the ADC0838-N
3. On each rising edge of the clock the status of the data in (DI) line is clocked into the MUX address shift
register. The start bit is the first logic “1” that appears on this line (all leading zeros are ignored). Following the
start bit the converter expects the next 2 to 4 bits to be the MUX assignment word.
4. When the start bit has been shifted into the start location of the MUX register, the input channel has been
assigned and a conversion is about to begin. An interval of ½ clock period (where nothing happens) is
automatically inserted to allow the selected MUX channel to settle. The SAR status line goes high at this time to
signal that a conversion is now in progress and the DI line is disabled (it no longer accepts data).
5. The data out (DO) line now comes out of TRI-STATE and provides a leading zero for this one clock period of
MUX settling time.
6. When the conversion begins, the output of the SAR comparator, which indicates whether the analog input is
greater than (high) or less than (low) each successive voltage from the internal resistor ladder, appears at the
DO line on each falling edge of the clock. This data is the result of the conversion being shifted out (with the
MSB coming first) and can be read by the processor immediately.
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7. After 8 clock periods the conversion is completed. The SAR status line returns low to indicate this ½ clock
cycle later.
8. If the programmer prefers, the data can be provided in an LSB first format [this makes use of the shift enable
(SE) control line]. All 8 bits of the result are stored in an output shift register. On devices which do not include the
SE control line, the data, LSB first, is automatically shifted out the DO line, after the MSB first data stream. The
DO line then goes low and stays low until CS is returned high. On the ADC0838-N the SE line is brought out and
if held high, the value of the LSB remains valid on the DO line. When SE is forced low, the data is then clocked
out LSB first. The ADC0831-N is an exception in that its data is only output in MSB first format.
9. All internal registers are cleared when the CS line is high. If another conversion is desired, CS must make a
high to low transition followed by address information.
The DI and DO lines can be tied together and controlled through a bidirectional processor I/O bit with one wire.
This is possible because the DI input is only “looked-at” during the MUX addressing interval while the DO line is
still in a high impedance state.
Reference Considerations
The voltage applied to the reference input to these converters defines the voltage span of the analog input (the
difference between VIN(MAX) and VIN(MIN)) over which the 256 possible output codes apply. The devices can be
used in either ratiometric applications or in systems requiring absolute accuracy. The reference pin must be
connected to a voltage source capable of driving the reference input resistance of typically 3.5 kΩ. This pin is the
top of a resistor divider string used for the successive approximation conversion.
In a ratiometric system, the analog input voltage is proportional to the voltage used for the A/D reference. This
voltage is typically the system power supply, so the VREF pin can be tied to VCC (done internally on the ADC0832N). This technique relaxes the stability requirements of the system reference as the analog input and A/D
reference move together maintaining the same output code for a given input condition.
For absolute accuracy, where the analog input varies between very specific voltage limits, the reference pin can
be biased with a time and temperature stable voltage source. The LM385 and LM336 reference diodes are good
low current devices to use with these converters.
The maximum value of the reference is limited to the VCC supply voltage. The minimum value, however, can be
quite small (see Typical Performance Characteristics) to allow direct conversions of transducer outputs providing
less than a 5V output span. Particular care must be taken with regard to noise pickup, circuit layout and system
error voltage sources when operating with a reduced span due to the increased sensitivity of the converter (1
LSB equals VREF/256).
a) Ratiometric
b) Absolute with a reduced Span
Figure 23. Reference Examples
16
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The Analog Inputs
The most important feature of these converters is that they can be located right at the analog signal source and
through just a few wires can communicate with a controlling processor with a highly noise immune serial bit
stream. This in itself greatly minimizes circuitry to maintain analog signal accuracy which otherwise is most
susceptible to noise pickup. However, a few words are in order with regard to the analog inputs should the input
be noisy to begin with or possibly riding on a large common-mode voltage.
The differential input of these converters actually reduces the effects of common-mode input noise, a signal
common to both selected “+” and “−” inputs for a conversion (60 Hz is most typical). The time interval between
sampling the “+” input and then the “−” input is ½ of a clock period. The change in the common-mode voltage
during this short time interval can cause conversion errors. For a sinusoidal common-mode signal this error is:
where
•
•
•
fCM is the frequency of the common-mode signal
VPEAK is its peak voltage value
fCLK, is the A/D clock frequency
(1)
For a 60 Hz common-mode signal to generate a ¼ LSB error (≈5 mV) with the converter running at 250 kHz, its
peak value would have to be 6.63V which would be larger than allowed as it exceeds the maximum analog input
limits.
Due to the sampling nature of the analog inputs short spikes of current enter the “+” input and exit the “−” input at
the clock edges during the actual conversion. These currents decay rapidly and do not cause errors as the
internal comparator is strobed at the end of a clock period. Bypass capacitors at the inputs will average these
currents and cause an effective DC current to flow through the output resistance of the analog signal source.
Bypass capacitors should not be used if the source resistance is greater than 1 kΩ.
This source resistance limitation is important with regard to the DC leakage currents of input multiplexer as well.
The worst-case leakage current of ±1 μA over temperature will create a 1 mV input error with a 1 kΩ source
resistance. An op amp RC active low pass filter can provide both impedance buffering and noise filtering should
a high impedance signal source be required.
Optional Adjustments
Zero Error
The zero of the A/D does not require adjustment. If the minimum analog input voltage value, VIN(MIN), is not
ground a zero offset can be done. The converter can be made to output 0000 0000 digital code for this minimum
input voltage by biasing any VIN (−) input at this VIN(MIN) value. This utilizes the differential mode operation of the
A/D.
The zero error of the A/D converter relates to the location of the first riser of the transfer function and can be
measured by grounding the VIN(−) input and applying a small magnitude positive voltage to the VIN(+) input. Zero
error is the difference between the actual DC input voltage which is necessary to just cause an output digital
code transition from 0000 0000 to 0000 0001 and the ideal ½ LSB value (½ LSB=9.8 mV for VREF=5.000 VDC).
Full-Scale
The full-scale adjustment can be made by applying a differential input voltage which is 1 ½ LSB down from the
desired analog full-scale voltage range and then adjusting the magnitude of the VREF input (or VCC for the
ADC0832) for a digital output code which is just changing from 1111 1110 to 1111 1111.
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Adjusting for an Arbitrary Analog Input Voltage Range
If the analog zero voltage of the A/D is shifted away from ground (for example, to accommodate an analog input
signal which does not go to ground), this new zero reference should be properly adjusted first. A VIN (+) voltage
which equals this desired zero reference plus ½ LSB (where the LSB is calculated for the desired analog span,
using 1 LSB= analog span/256) is applied to selected “+” input and the zero reference voltage at the
corresponding “−” input should then be adjusted to just obtain the 00HEX to 01HEX code transition.
The full-scale adjustment should be made [with the proper VIN(−) voltage applied] by forcing a voltage to the
VIN(+) input which is given by:
where
•
•
VMAX = the high end of the analog input range
VMIN = the low end (the offset zero) of the analog range. (Both are ground referenced.)
(2)
The VREF (or VCC) voltage is then adjusted to provide a code change from FEHEX to FFHEX. This completes the
adjustment procedure.
Power Supply
A unique feature of the ADC0838-N and ADC0834-N is the inclusion of a zener diode connected from the V+
terminal to ground which also connects to the VCC terminal (which is the actual converter supply) through a
silicon diode, as shown in Figure 24 (1).
Figure 24. An On-Chip Shunt Regulator Diode
This zener is intended for use as a shunt voltage regulator to eliminate the need for any additional regulating
components. This is most desirable if the converter is to be remotely located from the system power source.
Figure 25 and Figure 27 illustrate two useful applications of this on-board zener when an external transistor can
be afforded.
An important use of the interconnecting diode between V+ and VCC is shown in Figure 26 and Figure 28. Here,
this diode is used as a rectifier to allow the VCC supply for the converter to be derived from the clock. The low
current requirements of the A/D and the relatively high clock frequencies used (typically in the range of 10k–400
kHz) allows using the small value filter capacitor shown to keep the ripple on the VCC line to well under ¼ of an
LSB. The shunt zener regulator can also be used in this mode. This requires a clock voltage swing which is in
excess of VZ. A current limit for the zener is needed, either built into the clock generator or a resistor can be used
from the CLK pin to the V+ pin.
(1)
18
Internal zener diodes (6.3 to 8.5V) are connected from V+ to GND and VCC to GND. The zener at V+ can operate as a shunt regulator
and is connected to VCC via a conventional diode. Since the zener voltage equals the A/D's breakdown voltage, the diode insures that
VCC will be below breakdown when the device is powered from V+. Functionality is therefore ensured for V+ operation even though the
resultant voltage at VCC may exceed the specified Absolute Max of 6.5V. It is recommended that a resistor be used to limit the max
current into V+. (See Figure 24 in Functional Description)
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APPLICATIONS
*4.5V ≤ VCC ≤ 6.3V
Figure 25. Operating with a Temperature
Compensated Reference
Figure 26. Generating VCC from the Converter
Clock
*4.5V ≤ VCC ≤ 6.3V
Figure 27. Using the A/D as
the System Supply Regulator
Figure 28. Remote Sensing—
Clock and Power on 1 Wire
Figure 29. Digital Link and Sample Controlling Software for the Serially Oriented COP420 and the Bit
Programmable I/O INS8048
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Cop Coding Example
Mnemonic
LEI
SC
OGI
CLR A
AISC 1
XAS
LDD
NOP
XAS
XAS
XIS
CLER A
RC
XAS
XIS
OGI
LEI
Instruction
ENABLES SIO's INPUT AND OUTPUT
C = 1
G0 = 0 (CS = 0)
CLEARS ACCUMULATOR
LOADS ACCUMULATOR WITH 1
EXCHANGES SIO WITH ACCUMULATOR
AND STARTS SK CLOCK
LOADS MUX ADDRESS FROM RAM
INTO ACCUMULATOR
LOADS MUX ADDRESS FROM
ACCUMULATOR
↑
8 INSTRUCTIONS
↓
READS HIGH ORDER NIBBLE (4 BITS)
INTO ACCUMULATOR
PUTS HIGH ORDER NIBBLE INTO RAM
CLEARS ACCUMULATOR
C = 0
READS LOW ORDER NIBBLE INTO
ACCUMULATOR AND STOPS SK
PUTS LOW ORDER NIBBLE INTO RAM
G0 = 1 (CS = 1)
DISABLES SIO's INPUT AND OUTPUT
8048 Coding Example
Mnemonic
START:
ANL
MOV
MOV
LOOP 1: RRC
JC
ZERO:
ANL
JMP
ONE:
CONT:
ORL
CALL
DJNZ
CALL
LOOP 2:
MOV
CALL
IN
RRC
RRC
MOV
RLC
MOV
DJNZ
Instruction
P1, #0F7H ;SELECT A/D (CS = 0)
B, #5
;BIT COUNTER←5
A, #ADDR
;A←MUX ADDRESS
A
;CY←ADDRESS BIT
ONE
;TEST BIT
;BIT=0
P1, #0FEH ;DI←0
CONT
;CONTINUE
;BIT=1
P1, #1
;DI←1
PULSE
;PULSE SK 0→1→0
B, LOOP 1 ;CONTINUE UNTIL
DONE
PULSE
;EXTRA CLOCK FOR
SYNC
B, #8
;BIT COUNTER←8
PULSE
;PULSE SK 0→1→0
A, P1
;CY←DO
A
A
A, C
;A←RESULT
A
;A(0)←BIT AND SHIFT
C, A
;C←RESULT
B, LOOP 2 ;CONTINUE UNTIL
DONE
RETR
PULSE:
20
ORL
NOP
ANL
RET
P1, #04
P1, #0FBH
;PULSE SUBROUTINE
;SK←1
;DELAY
;SK←0
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*Pinouts shown for ADC0838-N.
For all other products tie to
pin functions as shown.
Figure 30. A “Stand-Alone” Hook-Up for ADC0838-N Evaluation
Figure 31. Low-Cost Remote Temperature Sensor
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Figure 32. Digitizing a Current Flow
*VIN(−) = 0.15 VCC
15% of VCC ≤ VXDR ≤ 85% of VCC
Figure 33. Operating with Ratiometric Transducers
Figure 34. Span Adjust: 0V≤VIN≤3V
22
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Figure 35. Zero-Shift and Span Adjust: 2V ≤ VIN ≤ 5V
Figure 36. Obtaining Higher Resolution - 9-Bit A/D
Controller performs a routine to determine which input polarity (9-bit example) or which channel pair (10-bit example)
provides a non-zero output code. This information provides the extra bits.
Figure 37. Obtaining Higher Resolution - 10-Bit A/D
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Diodes are 1N914
Figure 38. Protecting the Input
DO = all 1s if +VIN > −VIN
DO = all 0s if +VIN < −VIN
Figure 39. High Accuracy Comparators
24
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SNAS531B – AUGUST 1999 – REVISED MARCH 2013
•Uses one more wire than load cell itself
•Two mini-DIPs could be mounted inside load cell for digital output transducer
•Electronic offset and gain trims relax mechanical specs for gauge factor and offset
•Low level cell output is converted immediately for high noise immunity
Figure 40. Digital Load Cell
•All power supplied by loop
•1500V isolation at output
Figure 41. 4 mA-20 mA Current Loop Converter
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•No power required remotely
•1500V isolation
Figure 42. Isolated Data Converter
26
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Figure 43. Two Wire Interface for 8 Channels
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Figure 44. Two Wire 1-Channels Interface
28
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SNAS531B – AUGUST 1999 – REVISED MARCH 2013
REVISION HISTORY
Changes from Revision A (March 2013) to Revision B
•
Page
Changed layout of National Data Sheet to TI format .......................................................................................................... 28
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29
PACKAGE OPTION ADDENDUM
www.ti.com
3-Sep-2022
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
Samples
(4/5)
(6)
ADC0831CCN/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 85
ADC
0831CCN
Samples
ADC0831CCWM/NOPB
ACTIVE
SOIC
NPA
14
50
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0831
CCWM
Samples
ADC0831CCWMX/NOPB
ACTIVE
SOIC
NPA
14
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0831
CCWM
Samples
ADC0832CCN/NOPB
ACTIVE
PDIP
P
8
40
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 85
ADC
0832CCN
Samples
ADC0832CCWM/NOPB
ACTIVE
SOIC
NPA
14
50
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0832
CCWM
Samples
ADC0832CCWMX/NOPB
ACTIVE
SOIC
NPA
14
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0832
CCWM
Samples
ADC0834CCN/NOPB
ACTIVE
PDIP
N
14
25
RoHS & Green
NIPDAU
Level-1-NA-UNLIM
-40 to 85
ADC0834CCN
Samples
ADC0834CCWM/NOPB
ACTIVE
SOIC
NPA
14
50
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0834
CCWM
Samples
ADC0834CCWMX/NOPB
ACTIVE
SOIC
NPA
14
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0834
CCWM
Samples
ADC0838CCWM/NOPB
ACTIVE
SOIC
DW
20
36
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0838
CCWM
Samples
ADC0838CCWMX/NOPB
ACTIVE
SOIC
DW
20
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0838
CCWM
Samples
ADC0838CIWM/NOPB
ACTIVE
SOIC
DW
20
36
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0838
CIWM
Samples
ADC0838CIWMX/NOPB
ACTIVE
SOIC
DW
20
1000
RoHS & Green
SN
Level-3-260C-168 HR
-40 to 85
ADC0838
CIWM
Samples
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
Addendum-Page 1
PACKAGE OPTION ADDENDUM
www.ti.com
3-Sep-2022
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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