NSC ADC12038CIWM Self-calibrating 12-bit plus sign serial i/o a/d converters with mux and sample/hold Datasheet

ADC12H030/ADC12H032/ADC12H034/ADC12H038,
ADC12030/ADC12032/ADC12034/ADC12038
Self-Calibrating 12-Bit Plus Sign Serial I/O A/D
Converters with MUX and Sample/Hold
General Description
Applications
The ADC12030, and ADC12H030 families are 12-bit plus
sign successive approximation A/D converters with serial I/O
and configurable input multiplexers. The ADC12032/
ADC12H032, ADC12034/ADC12H034 and ADC12038/
ADC12H038 have 2, 4 and 8 channel multiplexers, respectively. The differential multiplexer outputs and A/D inputs are
available on the MUXOUT1, MUXOUT2, A/DIN1 and A/DIN2
pins. The ADC12030/ADC12H030 has a two channel multiplexer with the multiplexer outputs and A/D inputs internally
connected. The ADC12030 family is tested with a 5 MHz
clock, while the ADC12H030 family is tested with an 8 MHz
clock. On request, these A/Ds go through a self calibration
process that adjusts linearity, zero and full-scale errors to
less than ± 1 LSB each.
The analog inputs can be configured to operate in various
combinations
of
single-ended,
differential,
or
pseudo-differential modes. A fully differential unipolar analog
input range (0V to +5V) can be accommodated with a single
+5V supply. In the differential modes, valid outputs are obtained even when the negative inputs are greater than the
positive because of the 12-bit plus sign output data format.
n Medical instruments
n Process control systems
n Test equipment
The serial I/O is configured to comply with the NSC MICROWIRE. For voltage references see the LM4040 or
LM4041.
Features
Serial I/O (MICROWIRE Compatible)
2, 4, or 8 channel differential or single-ended multiplexer
Analog input sample/hold function
Power down mode
Variable resolution and conversion rate
Programmable acquisition time
Variable digital output word length and format
No zero or full scale adjustment required
Fully tested and guaranteed with a 4.096V reference
0V to 5V analog input range with single 5V power
supply
n No Missing Codes over temperature
n
n
n
n
n
n
n
n
n
n
Key Specifications
j Resolution
12-bit plus sign
j 12-bit plus sign conversion time
– ADC12H30 family
5.5 µs (max)
– ADC12030 family
8.8 µs (max)
j 12-bit plus sign throughput time
– ADC12H30 family
– ADC12030 family
j single supply
j Power consumption
33 mW (max)
– Power down
DS011354
14 µs (max)
± 1 LSB (max)
5V ± 10%
j Integral linearity error
© 2002 National Semiconductor Corporation
8.6 µs (max)
100 µW (typ)
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Self-Calibrating 12-Bit Plus Sign Serial I/O A/D Converters with MUX and Sample/Hold
June 2002
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
ADC12038 Simplified Block Diagram
01135401
Connection Diagrams
16-Pin Wide Body
SO Packages
20-Pin Wide Body
SO Packages
01135406
Top View
01135407
Top View
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2
(Continued)
24-Pin Wide Body
SO, SSOP-EIAJ Packages
28-Pin Wide Body
SO Packages
01135408
Top View
01135409
Top View
Ordering Information
Industrial Temperature Range
Package
−40˚C ≤ TA ≤ +85˚C
ADC12H030CIWM, ADC12030CIWM
M16B
ADC12H032CIWM, ADC12032CIWM
M20B
ADC12H034CIN, ADC12034CIN
N24C
ADC12H034CIWM, ADC12034CIWM
ADC12H034CIMSA
ADC12H038CIWM, ADC12038CIWM
Pin Descriptions
CCLK
SCLK
M24B
MSA24
DI
The clock applied to this input controls the
sucessive approximation conversion time interval and the acquisition time. The rise and
fall times of the clock edges should not exceed 1 µs.
This is the serial data clock input. The clock
applied to this input controls the rate at
which the serial data exchange occurs. The
rising edge loads the information on the DI
pin into the multiplexer address and mode
select shift register. This address controls
which channel of the analog input multiplexer (MUX) is selected and the mode of
operation for the A/D. With CS low the falling
edge of SCLK shifts the data resulting from
the previous ADC conversion out on DO,
with the exception of the first bit of data.
When CS is low continously, the first bit of
the data is clocked out on the rising edge of
EOC (end of conversion). When CS is
toggled the falling edge of CS always clocks
out the first bit of data. CS should be brought
low when SCLK is low. The rise and fall
times of the clock edges should not exceed
DO
EOC
CS
3
M28B
1 µs.
This is the serial data input pin. The data
applied to this pin is shifted by the rising
edge of SCLK into the multiplexer address
and mode select register. Table 2 through
Table 5 show the assignment of the multiplexer address and the mode select data.
The data output pin. This pin is an active
push/pull output when CS is low. When CS
is high, this output is TRI-STATE. The A/D
conversion result (D0–D12) and converter
status data are clocked out by the falling
edge of SCLK on this pin. The word length
and format of this result can vary (see Table
1). The word length and format are controlled by the data shifted into the multiplexer
address and mode select register (see Table
5).
This pin is an active push/pull output and
indicates the status of the ADC12030/2/4/8.
When low, it signals that the A/D is busy with
a conversion, auto-calibration, auto-zero or
power down cycle. The rising edge of EOC
signals the end of one of these cycles.
This is the chip select pin. When a logic low
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Connection Diagrams
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Pin Descriptions
DOR
CONV
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formed while a conversion, Auto-Cal or
Auto-Zero are in progress.
(Continued)
is applied to this pin, the rising edge of SCLK
shifts the data on DI into the address register. This low also brings DO out of
TRI-STATE. With CS low the falling edge of
SCLK shifts the data resulting from the previous ADC conversion out on DO, with the
exception of the first bit of data. When CS is
low continously, the first bit of the data is
clocked out on the rising edge of EOC (end
of conversion). When CS is toggled the falling edge of CS always clocks out the first bit
of data. CS should be brought low when
SCLK is low. The falling edge of CS resets a
conversion in progress and starts the sequence for a new conversion. When CS is
brought back low during a conversion, that
conversion is prematurely terminated. The
data in the output latches may be corrupted.
Therefore, when CS is brought back low during a conversion in progress the data output
at that time should be ignored. CS may also
be left continuously low. In this case it is
imperative that the correct number of SCLK
pulses be applied to the ADC in order to
remain synchronous. After the ADC supply
power is applied it expects to see 13 clock
pulses for each I/O sequence. The number
of clock pulses the ADC expects is the same
as the digital output word length. This word
length can be modified by the data shifted in
on the DO pin. Table 5 details the data
required.
This is the data output ready pin. This pin is
an active push/pull output. It is low when the
conversion result is being shifted out and
goes high to signal that all the data has been
shifted out.
A logic low is required on this pin to program
any mode or change the ADC’s configuration
as listed in the Mode Programming Table 5
such as 12-bit conversion, 8-bit conversion,
Auto Cal, Auto Zero etc. When this pin is
high the ADC is placed in the read data only
mode. While in the read data only mode,
bringing CS low and pulsing SCLK will only
clock out on DO any data stored in the ADCs
output shift register. The data on DI will be
neglected. A new conversion will not be
started and the ADC will remain in the mode
and/or
configuration
previously
programmed. Read data only cannot be per-
PD
This is the power down pin. When PD is high
the A/D is powered down; when PD is low
the A/D is powered up. The A/D takes a
maximum of 250 µs to power up after the
command is given.
CH0–CH7
These are the analog inputs of the MUX. A
channel input is selected by the address information at the DI pin, which is loaded on
the rising edge of SCLK into the address
register (See Tables 2, 3, 4).
The voltage applied to these inputs should
not exceed VA+ or go below GND. Exceeding this range on an unselected channel will
corrupt the reading of a selected channel.
COM
This pin is another analog input pin. It is
used as a pseudo ground when the analog
multiplexer is single-ended.
MUXOUT1,
MUXOUT2
These
are
pins.
the
multiplexer
output
A/DIN1, /DIN2 These are the converter input pins. MUXOUT1 is usually tied to A/DIN1. MUXOUT2
is usually tied to A/DIN2. If external circuitry
is placed between MUXOUT1 and A/DIN1,
or MUXOUT2 and A/DIN2 it may be necessary to protect these pins. The voltage at
these pins should not exceed VA+ or go below AGND (see Figure 5).
This is the positive analog voltage reference
VREF+
input. In order to maintain accuracy, the voltage range of VREF (VREF = VREF+ − VREF−)
is 1 VDC to 5.0 VDC and the voltage at VREF+
cannot exceed VA+. See Figure 6 for recommended bypassing.
The negative voltage reference input. In orVREF−
der to maintain accuracy, the voltage at this
pin must not go below GND or exceed VA+.
(See Figure 6).
These are the analog and digital power supVA+, VD+
ply pins. VA+ and VD+ are not connected
together on the chip. These pins should be
tied to the same power supply and bypassed
separately (see Figure 6). The operating
voltage range of VA+ and VD+ is 4.5 VDC to
5.5 VDC.
DGND
This is the digital ground pin (see Figure 6).
AGND
This is the analog ground pin (see Figure 6).
4
Operating Ratings (Notes 1, 2)
(Notes 1,
2)
Operating Temperature Range
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
ADC12030CIWM,
ADC12H030CIWM,
ADC12032CIWM,
ADC12H032CIWM,
Positive Supply Voltage
(V+ = VA+ = VD+)
6.5V
ADC12034CIN, ADC12034CIWM,
Voltage at Inputs and Outputs
except CH0–CH7 and COM
ADC12H034CIN,
ADC12H034CIWM,
−0.3V to V+ +0.3V
Voltage at Analog Inputs
ADC12H034CIMSA,
ADC12038CIWM,
GND −5V to V+
+5V
CH0–CH7 and COM
|VA+ − VD+|
+
Supply Voltage (V = VA+ = VD+)
± 30 mA
± 120 mA
Package Input Current (Note 3)
Package Dissipation at
TA = 25˚C (Note 4)
−40˚C ≤ TA ≤ +85˚C
ADC12H038CIWM
300 mV
Input Current at Any Pin (Note 3)
TMIN ≤ TA ≤ TMAX
500 mW
+4.5V to +5.5V
|VA+ − VD+|
≤ 100 mV
VREF+
0V to VA+
VREF−
0V to VREF+
VREF (VREF+ − VREF−)
ESD Susceptability (Note 5)
1V to VA+
VREF Common Mode Voltage Range
Human Body Model
1500V
Soldering Information
N Packages (10 seconds)
260˚C
0.1 VA+ to 0.6 VA+
SO Package (Note 6):
Vapor Phase (60 seconds)
215˚C
Infrared (15 seconds)
220˚C
Storage Temperature
A/DIN1, A/DIN2, MUXOUT1
and MUXOUT2 Voltage Range
0V to VA+
A/D IN Common Mode
−65˚C to +150˚C
Voltage Range
0V to VA+
Converter Electrical Characteristics
The following specifications apply for V+ = VA+ = VD+ = +5.0 VDC, VREF+ = +4.096 VDC, VREF− = 0 VDC, 12-bit + sign conversion mode, fCK = fSK = 8 MHz for the ADC12H030, ADC12H032, ADC12H034 and ADC12H038, fCK = fSK = 5 MHz for the
ADC12030, ADC12032, ADC12034 and ADC12038, RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω, fully-differential
input with fixed 2.048V common-mode voltage, and 10(tCK) acquisition time unless otherwise specified. Boldface limits apply
for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (Notes 7, 8, 9)
Symbol
Parameter
Conditions
Typical
(Note 10)
Limits
(Note 11)
Units
(Limits)
12 + sign
Bits (min)
±1
±1
±1
± 3.0
± 3.0
±2
LSB (max)
± 3.5
LSB (max)
STATIC CONVERTER CHARACTERISTICS
Resolution with No
Missing Codes
+ILE
Positive Integral Linearity Error
After Auto-Cal (Notes 12, 18)
−ILE
Negative Integral Linearity Error
After Auto-Cal (Notes 12, 18)
DNL
Differential Non-Linearity
After Auto-Cal
Positive Full-Scale Error
After Auto-Cal (Notes 12, 18)
Negative Full-Scale Error
After Auto-Cal (Notes 12, 18)
Offset Error
After Auto-Cal (Notes 5, 18)
± 1/2
± 1/2
± 1/2
± 1/2
± 1/2
LSB (max)
LSB (max)
LSB (max)
LSB (max)
LSB (max)
VIN(+) = VIN (−) = 2.048V
TUE
DC Common Mode Error
After Auto-Cal (Note 15)
Total Unadjusted Error
After Auto-Cal
±2
±1
LSB
(Notes 12, 13, 14)
Resolution with No
Missing Codes
8-bit + sign mode
8 + sign
5
Bits (min)
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Absolute Maximum Ratings
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Converter Electrical Characteristics
(Continued)
The following specifications apply for V+ = VA+ = VD+ = +5.0 VDC, VREF+ = +4.096 VDC, VREF− = 0 VDC, 12-bit + sign conversion mode, fCK = fSK = 8 MHz for the ADC12H030, ADC12H032, ADC12H034 and ADC12H038, fCK = fSK = 5 MHz for the
ADC12030, ADC12032, ADC12034 and ADC12038, RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω, fully-differential
input with fixed 2.048V common-mode voltage, and 10(tCK) acquisition time unless otherwise specified. Boldface limits apply
for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (Notes 7, 8, 9)
Symbol
Parameter
Conditions
Typical
(Note 10)
Limits
(Note 11)
Units
(Limits)
± 1/2
± 1/2
± 3/4
± 1/2
± 1/2
LSB (max)
± 1/2
LSB (max)
± 3/4
LSB (max)
STATIC CONVERTER CHARACTERISTICS
+INL
Positive Integral Linearity Error
8-bit + sign mode (Note 12)
−INL
Negative Integral Linearity Error
8-bit + sign mode (Note 12)
DNL
Differential Non-Linearity
8-bit + sign mode
Positive Full-Scale Error
8-bit + sign mode (Note 12)
Negative Full-Scale Error
8-bit + sign mode (Note 12)
Offset Error
8-bit + sign mode,
after Auto-Zero (Note 13)
LSB (max)
LSB (max)
LSB (max)
LSB (max)
VIN(+) = VIN(−) = + 2.048V
TUE
Total Unadjusted Error
8-bit + sign mode
after Auto-Zero
(Notes 12, 13, 14)
Multiplexer Channel
to Channel Matching
± 0.05
Power Supply Sensitivity
LSB
V+ = +5V ± 10%
VREF = +4.096V
± 0.5
± 0.5
± 0.5
± 0.5
± 0.5
Offset Error
+ Full-Scale Error
− Full-Scale Error
+ Integral Linearity Error
− Integral Linearity Error
Output Data from
(Note 20)
“12-Bit Conversion of Offset”
±1
± 1.5
± 1.5
LSB (max)
LSB (max)
LSB (max)
LSB
LSB
+10
LSB (max)
−10
LSB (min)
4095
LSB (max)
4093
LSB (min)
(see Table 5)
Output Data from
(Note 20)
“12-Bit Conversion of Full-Scale”
(see Table 5)
UNIPOLAR DYNAMIC CONVERTER CHARACTERISTICS
S/(N+D)
Signal-to-Noise Plus
fIN = 1 kHz, VIN = 5 VPP, VREF+ = 5.0V
69.4
dB
Distortion Ratio
fIN = 20 kHz, VIN = 5 VPP, VREF+ = 5.0V
68.3
dB
fIN = 40 kHz, VIN = 5 VPP, VREF+ = 5.0V
65.7
dB
−3 dB Full Power Bandwidth
VIN = 5 VPP, where S/(N+D) drops 3 dB
31
kHz
77.0
dB
fIN = 20 kHz, VIN = ± 5V, VREF = 5.0V
73.9
dB
fIN = 40 kHz, VIN = ± 5V, VREF+ = 5.0V
67.0
dB
VIN = ± 5V, where S/(N+D) drops 3 dB
40
kHz
DIFFERENTIAL DYNAMIC CONVERTER CHARACTERISTICS
S/(N+D)
Signal-to-Noise Plus
Distortion Ratio
−3 dB Full Power Bandwidth
fIN = 1 kHz, VIN = ± 5V, VREF+ = 5.0V
+
REFERENCE INPUT, ANALOG INPUTS AND MULTIPLEXER CHARACTERISTICS
CREF
Reference Input Capacitance
85
pF
CA/D
A/DIN1 and A/DIN2 Analog
75
pF
Input Capacitance
± 1.0
µA (max)
CH0–CH7 and COM
GND − 0.05
V (min)
Input Voltage
VA+ + 0.05
V (max)
A/DIN1 and A/DIN2 Analog
VIN = +5.0V or
Input Leakage Current
VIN = 0V
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± 0.1
6
(Continued)
The following specifications apply for V+ = VA+ = VD+ = +5.0 VDC, VREF+ = +4.096 VDC, VREF− = 0 VDC, 12-bit + sign conversion mode, fCK = fSK = 8 MHz for the ADC12H030, ADC12H032, ADC12H034 and ADC12H038, fCK = fSK = 5 MHz for the
ADC12030, ADC12032, ADC12034 and ADC12038, RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω, fully-differential
input with fixed 2.048V common-mode voltage, and 10(tCK) acquisition time unless otherwise specified. Boldface limits apply
for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (Notes 7, 8, 9)
Symbol
Parameter
Conditions
Typical
(Note 10)
Limits
(Note 11)
Units
(Limits)
REFERENCE INPUT, ANALOG INPUTS AND MULTIPLEXER CHARACTERISTICS
CCH
CH0–CH7 and COM
Input Capacitance
10
CMUXOUT MUX Output Capacitance
pF
20
Off Channel Leakage (Note 16)
On Channel = 5V and
CH0–CH7 and COM Pins
Off Channel = 0V
On Channel = 0V and
pF
−0.01
−0.3
µA (min)
0.01
0.3
µA (max)
0.01
0.3
µA (max)
−0.01
−0.3
µA (min)
0.01
0.3
µA (max)
850
1150
Ω (max)
Off Channel = 5V
On Channel Leakage (Note 16)
On Channel = 5V and
CH0–CH7 and COM Pins
Off Channel = 0V
On Channel = 0V and
Off Channel = 5V
RON
MUXOUT1 and MUXOUT2
VMUXOUT = 5.0V or
Leakage Current
VMUXOUT = 0V
MUX On Resistance
VIN = 2.5V and
VMUXOUT = 2.4V
RON Matching Channel
VIN = 2.5V and
5
to Channel
VMUXOUT = 2.4V
Channel to Channel Crosstalk
VIN = 5 VPP, fIN = 40 kHz
MUX Bandwidth
%
−72
dB
90
kHz
DC and Logic Electrical Characteristics
The following specifications apply for V+ = VA+ = VD+ = +5.0 VDC, VREF+ = +4.096 VDC, VREF− = 0 VDC, 12-bit + sign conversion mode, fCK = fSK = 8 MHz for the ADC12H030, ADC12H032, ADC12H034 and ADC12H038, fCK = fSK = 5 MHz for the
ADC12030, ADC12032, ADC12034 and ADC12038, RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω,
fully-differential input with fixed 2.048V common-mode voltage, and 10(tCK) acquisition time unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (Notes 7, 8, 9)
Symbol
Parameter
Conditions
Typical
Limits
Units
(Note 10)
(Note 11)
(Limits)
2.0
V (min)
CCLK, CS, CONV, DI, PD AND SCLK INPUT CHARACTERISTICS
VIN(1)
Logical “1” Input Voltage
V+ = 5.5V
+
VIN(0)
Logical “0” Input Voltage
V = 4.5V
0.8
V (max)
IIN(1)
Logical “1” Input Current
VIN = 5.0V
0.005
1.0
µA (max)
IIN(0)
Logical “0” Input Current
VIN = 0V
−0.005
−1.0
µA (min)
DO, EOC AND DOR DIGITAL OUTPUT CHARACTERISTICS
VOUT(1) Logical “1” Output Voltage
VOUT(0) Logical “0” Output Voltage
IOUT
TRI-STATE ®
Output Current
V+ = 4.5V, IOUT = −360 µA
2.4
V (min)
V+ = 4.5V, IOUT = − 10 µA
4.25
V (min)
V+ = 4.5V, IOUT = 1.6 mA
0.4
V (max)
VOUT = 0V
−0.1
−3.0
µA (max)
VOUT = 5V
0.1
3.0
µA (max)
+ISC
Output Short Circuit Source Current
VOUT = 0V
14
6.5
mA (min)
−ISC
Output Short Circuit Sink Current
VOUT = VD+
16
8.0
mA (min)
Digital Supply Current
Awake
1.6
2.5
mA (max)
ADC12030, ADC12032, ADC12034
CS = HIGH, Powered Down, CCLK on
600
POWER SUPPLY CHARACTERISTICS
ID+
7
µA
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Converter Electrical Characteristics
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
DC and Logic Electrical Characteristics
(Continued)
The following specifications apply for V+ = VA+ = VD+ = +5.0 VDC, VREF+ = +4.096 VDC, VREF− = 0 VDC, 12-bit + sign conversion mode, fCK = fSK = 8 MHz for the ADC12H030, ADC12H032, ADC12H034 and ADC12H038, fCK = fSK = 5 MHz for the
ADC12030, ADC12032, ADC12034 and ADC12038, RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω,
fully-differential input with fixed 2.048V common-mode voltage, and 10(tCK) acquisition time unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (Notes 7, 8, 9)
Symbol
Parameter
Conditions
Typical
Limits
Units
(Note 10)
(Note 11)
(Limits)
3.2
mA
POWER SUPPLY CHARACTERISTICS
IA+
IREF
and ADC12038
CS = HIGH, Powered Down, CCLK off
20
Digital Supply Current
Awake
2.3
ADC12H030, ADC12H032,
CS = HIGH, Powered Down, CCLK on
0.9
ADC12H034 and ADC12H038
CS = HIGH, Powered Down, CCLK off
20
Positive Analog Supply Current
Awake
2.7
Reference Input Current
µA
mA
µA
4.0
mA (max)
CS = HIGH, Powered Down, CCLK on
10
µA
CS = HIGH, Powered Down, CCLK off
0.1
µA
Awake
70
µA
CS = HIGH, Powered Down
0.1
µA
AC Electrical Characteristics
The following specifications apply for V+ = VA+ = VD+ = +5.0 VDC, VREF+ = +4.096 VDC, VREF− = 0 VDC, 12-bit + sign conversion mode, tr = tf = 3 ns, fCK = fSK = 8 MHz for the ADC12H030, ADC12H032, ADC12H034 and ADC12H038, fCK = fSK = 5
MHz for the ADC12030, ADC12032, ADC12034 and ADC12038, RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω,
fully-differential input with fixed 2.048V common-mode voltage, and 10(tCK) acquisition time unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (Note 17)
Symbol
fCK
fSK
tC
Parameter
Conditions
Typical
(Note 10)
Conversion Clock
10
(CCLK) Frequency
1
Serial Data Clock
10
SCLK Frequency
0
ADC12H030/2/4/8 ADC12030/2/4/8
Limits
Limits
(Note 11)
(Note 11)
8
5
Units
(Limits)
MHz (max)
MHz (min)
8
5
Conversion Clock
40
40
% (min)
Duty Cycle
60
60
% (max)
Serial Data Clock
40
40
% (min)
Duty Cycle
60
60
% (max)
44(tCK)
(max)
µs (max)
Conversion Time
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MHz (max)
Hz (min)
12-Bit + Sign or 12-Bit
44(tCK)
44(tCK)
5.5
8.8
8-Bit + Sign or 8-Bit
21(tCK)
21(tCK)
21(tCK)
(max)
2.625
4.2
µs (max)
8
(Continued)
The following specifications apply for V+ = VA+ = VD+ = +5.0 VDC, VREF+ = +4.096 VDC, VREF− = 0 VDC, 12-bit + sign conversion mode, tr = tf = 3 ns, fCK = fSK = 8 MHz for the ADC12H030, ADC12H032, ADC12H034 and ADC12H038, fCK = fSK = 5
MHz for the ADC12030, ADC12032, ADC12034 and ADC12038, RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω,
fully-differential input with fixed 2.048V common-mode voltage, and 10(tCK) acquisition time unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (Note 17)
Symbol
Parameter
Acquisition Time
tA
Conditions
Typical
(Note 10)
6 Cycles Programmed
6(tCK)
(Note 19)
10 Cycles Programmed
18 Cycles Programmed
34 Cycles Programmed
tCKAL
Self-Calibration Time
tAZ
Auto-Zero Time
tSYNC
tDOR
10(tCK)
18(tCK)
34(tCK)
ADC12H030/2/4/8 ADC12030/2/4/8
Limits
Limits
(Note 11)
(Note 11)
Units
(Limits)
6(tCK)
6(tCK)
(min)
7(tCK)
7(tCK)
(max)
0.75
1.2
µs (min)
µs (max)
0.875
1.4
10(tCK)
10(tCK)
(min)
11(tCK)
11(tCK)
(max)
1.25
2.0
µs (min)
µs (max)
1.375
2.2
18(tCK)
18(tCK)
(min)
19(tCK)
19(tCK)
(max)
2.25
3.6
µs (min)
2.375
3.8
µs (max)
34(tCK)
34(tCK)
(min)
35(tCK)
35(tCK)
(max)
4.25
6.8
µs (min)
4.375
7.0
µs (max)
4944(tCK)
4944(tCK)
4944(tCK)
(max)
618.0
988.8
µs (max)
76(tCK)
76(tCK)
76(tCK)
(max)
9.5
15.2
µs (max)
2(tCK)
2(tCK)
(min)
or Auto-Zero
Self-Calibration
2(tCK)
3(tCK)
3(tCK)
(max)
Synchronization Time
0.250
0.40
µs (min)
from DOR
0.375
0.60
µs (max)
9(tSK)
9(tSK)
(max)
1.125
1.8
µs (max)
8(tSK)
8(tSK)
(max)
1.0
1.6
µs (max)
DOR High Time
9(tSK)
when CS is Low
Continuously for Read
Data and Software
Power Up/Down
tCONV
CONV Valid Data Time
8(tSK)
AC Electrical Characteristics
The following specifications apply for V+ = VA+ = VD+ = +5.0 VDC, VREF+ = +4.096 VDC, VREF− = 0 VDC, 12-bit + sign conversion mode, tr = tf = 3 ns, fCK = fSK = 8 MHz for the ADC12H030, ADC12H032, ADC12H034 and ADC12H038, fCK = fSK = 5
MHz for the ADC12030, ADC12032, ADC12034 and ADC12038, RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω,
fully-differential input with fixed 2.048V common-mode voltage, and 10(tCK) acquisition time unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (Note 17)
Symbol
tHPU
Parameter
Conditions
Hardware Power-Up Time, Time from
Typical
(Note 10)
Limits
(Note 11)
Units
(Limits)
140
250
µs (max)
140
250
µs (max)
PD Falling Edge to EOC Rising Edge
tSPU
Software Power-Up Time, Time from
Serial Data Clock Falling Edge to
9
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
AC Electrical Characteristics
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
AC Electrical Characteristics
(Continued)
The following specifications apply for V+ = VA+ = VD+ = +5.0 VDC, VREF+ = +4.096 VDC, VREF− = 0 VDC, 12-bit + sign conversion mode, tr = tf = 3 ns, fCK = fSK = 8 MHz for the ADC12H030, ADC12H032, ADC12H034 and ADC12H038, fCK = fSK = 5
MHz for the ADC12030, ADC12032, ADC12034 and ADC12038, RS = 25Ω, source impedance for VREF+ and VREF− ≤ 25Ω,
fully-differential input with fixed 2.048V common-mode voltage, and 10(tCK) acquisition time unless otherwise specified. Boldface limits apply for TA = TJ = TMIN to TMAX; all other limits TA = TJ = 25˚C. (Note 17)
Symbol
Parameter
Conditions
Typical
(Note 10)
Limits
(Note 11)
Units
(Limits)
20
50
ns (max)
30
ns (min)
0
5
ns (min)
40
100
ns (max)
5
15
ns (min)
5
10
ns (min)
25
50
ns (max)
EOC Rising Edge
tACC
Access Time Delay from
tSET-UP
Set-Up Time of CS Falling Edge to
CS Falling Edge to DO Data Valid
Serial Data Clock Rising Edge
tDELAY
Delay from SCLK Falling
Edge to CS Falling Edge
t1H, t0H
Delay from CS Rising Edge to
RL = 3k, CL = 100 pF
DO TRI-STATE
tHDI
DI Hold Time from Serial Data
Clock Rising Edge
tSDI
DI Set-Up Time from Serial Data
tHDO
DO Hold Time from Serial Data
Clock Rising Edge
RL = 3k, CL = 100 pF
Clock Falling Edge
tDDO
Delay from Serial Data Clock
tRDO
DO Rise Time, TRI-STATE to High
5
ns (min)
35
50
ns (max)
Falling Edge to DO Data Valid
RL = 3k, CL = 100 pF
DO Rise Time, Low to High
tFDO
tCD
DO Fall Time, TRI-STATE to Low
RL = 3k, CL = 100 pF
10
30
ns (max)
10
30
ns (max)
ns (max)
12
30
DO Fall Time, High to Low
12
30
ns (max)
Delay from CS Falling Edge
25
45
ns (max)
25
45
ns (max)
to DOR Falling Edge
tSD
Delay from Serial Data Clock Falling
Edge to DOR Rising Edge
CIN
Capacitance of Logic Inputs
10
pF
COUT
Capacitance of Logic Outputs
20
pF
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. For guaranteed specifications and test conditions, see the Electrical Characteristics. The guaranteed
specifications apply only for the test conditions listed. Some performance characteristics may degrade when the device is not operated under the listed test
conditions.
Note 2: All voltages are measured with respect to GND, unless otherwise specified.
Note 3: When the input voltage (VIN) at any pin exceeds the power supplies (VIN < GND or VIN > VA+ or VD+), the current at that pin should be limited to 30 mA.
The 120 mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 30 mA to four.
Note 4: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJmax, θJA and the ambient temperature, TA. The maximum
allowable power dissipation at any temperature is PD = (TJmax − TA)/θJA or the number given in the Absolute Maximum Ratings, whichever is lower. For this device,
TJmax = 150˚C. The typical thermal resistance (θJA) of these parts when board mounted follow:
Thermal
Part Number
Resistance
θJA
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ADC12H030CIWM, ADC12030CIWM
70˚C/W
ADC12H032CIWM, ADC12032CIWM
64˚C/W
ADC12H034CIN, ADC12034CIN
42˚C/W
ADC12H034CIWM, ADC12034CIWM
57˚C/W
ADC12H034CIMSA
97˚C/W
ADC12H038CIWM, ADC12038CIWM
50˚C/W
10
Note 7: Two on-chip diodes are tied to each analog input through a series resistor as shown below. Input voltage magnitude up to 5V above VA+ or 5V below GND
will not damage this device. However, errors in the A/D conversion can occur (if these diodes are forward biased by more than 50 mV) if the input voltage magnitude
of selected or unselected analog input go above VA+ or below GND by more than 50 mV. As an example, if VA+ is 4.5 VDC, full-scale input voltage must be ≤4.55
VDC to ensure accurate conversions.
01135402
Note 8: To guarantee accuracy, it is required that the VA+ and VD+ be connected together to the same power supply with separate bypass capacitors at each V+
pin.
Note 9: With the test condition for VREF (VREF+ − VREF−) given as +4.096V, the 12-bit LSB is 1.0 mV and the 8-bit LSB is 16.0 mV.
Note 10: Typicals are at TJ = TA = 25˚C and represent most likely parametric norm.
Note 11: Tested limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 12: Positive integral linearity error is defined as the deviation of the analog value, expressed in LSBs, from the straight line that passes through positive
full-scale and zero. For negative integral linearity error, the straight line passes through negative full-scale and zero (see Figures 2, 3).
Note 13: Zero error is a measure of the deviation from the mid-scale voltage (a code of zero), expressed in LSB. It is the worst-case value of the code transitions
between 1 to 0 and 0 to +1 (see Figure 4).
Note 14: Total unadjusted error includes offset, full-scale, linearity and multiplexer errors.
Note 15: The DC common-mode error is measured in the differential multiplexer mode with the assigned positive and negative input channels shorted together.
Note 16: Channel leakage current is measured after the channel selection.
Note 17: Timing specifications are tested at the TTL logic levels, VIL = 0.4V for a falling edge and VIH = 2.4V for a rising edge. TRI-STATE output voltage is forced
to 1.4V.
Note 18: The ADC12030 family’s self-calibration technique ensures linearity and offset errors as specified, but noise inherent in the self-calibration process will
result in a maximum repeatability uncertainty of 0.2 LSB.
Note 19: If SCLK and CCLK are driven from the same clock source, then tA is 6, 10, 18 or 34 clock periods minimum and maximum.
Note 20: The “12-Bit Conversion of Offset” and “12-Bit Conversion of Full-Scale” modes are intended to test the functionality of the device. Therefore, the output
data from these modes are not an indication of the accuracy of a conversion result.
01135410
FIGURE 1. Transfer Characteristic
11
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Note 5: The human body model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 6: See AN450 “Surface Mounting Methods and Their Effect on Product Reliability” or the section titled “Surface Mount” found in any post 1986 National
Semiconductor Linear Data Book for other methods of soldering surface mount devices.
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
01135411
FIGURE 2. Simplified Error Curve vs Output Code without Auto-Calibration or Auto-Zero Cycles
01135412
FIGURE 3. Simplified Error Curve vs Output Code after Auto-Calibration Cycle
01135413
FIGURE 4. Offset or Zero Error Voltage
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12
Linearity Error Change
vs Clock Frequency
Linearity Error Change
vs Temperature
01135453
Linearity Error Change
vs Supply Voltage
01135454
Full-Scale Error Change
vs Clock Frequency
01135456
Full-Scale Error Change
vs Reference Voltage
01135455
Full-Scale Error Change
vs Temperature
01135457
Full-Scale Error Change
vs Supply Voltage
01135458
Zero Error Change
vs Clock Frequency
01135460
01135459
Zero Error Change
vs Temperature
Linearity Error Change
vs Reference Voltage
Zero Error Change
vs Reference Voltage
01135462
01135463
13
01135461
Zero Error Change
vs Supply Voltage
01135464
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Typical Performance Characteristics The following curves apply for 12-bit + sign mode after
auto-calibration unless otherwise specified. The performance for 8-bit + sign mode is equal to or better than shown. (Note 9)
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Typical Performance Characteristics The following curves apply for 12-bit + sign mode after
auto-calibration unless otherwise specified. The performance for 8-bit + sign mode is equal to or better than shown. (Note
9) (Continued)
Analog Supply Current
vs Temperature
Digital Supply Current
vs Clock Frequency
01135465
Digital Supply Current
vs Temperature
01135466
Typical Dynamic Performance Characteristics
01135467
The following curves apply for 12-bit + sign
mode after auto-calibration unless otherwise specified.
Bipolar Spectral Response
with 1 kHz Sine Wave Input
Bipolar Spectral Response
with 10 kHz Sine Wave Input
01135468
Bipolar Spectral Response
with 30 kHz Sine Wave Input
01135469
Bipolar Spectral Response
with 40 kHz Sine Wave Input
01135471
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01135472
14
Bipolar Spectral Response
with 20 kHz Sine Wave Input
01135470
Bipolar Spectral Response
with 50 kHz Sine Wave Input
01135473
Bipolar Spurious Free
Dynamic Range
Unipolar Signal-to-Noise Ratio
vs Input Frequency
01135474
Unipolar Signal-to-Noise
+ Distortion Ratio
vs Input Signal Level
01135475
Unipolar Spectral Response
with 1 kHz Sine Wave Input
01135478
01135477
Unipolar Spectral Response
with 20 kHz Sine Wave Input
Unipolar Spectral Response
with 30 kHz Sine Wave Input
01135480
01135481
15
Unipolar Signal-to-Noise
+ Distortion Ratio
vs Input Frequency
01135476
Unipolar Spectral Response
with 10 kHz Sine Wave Input
01135479
Unipolar Spectral Response
with 40 kHz Sine Wave Input
01135482
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Typical Dynamic Performance Characteristics The following curves apply for 12-bit + sign
mode after auto-calibration unless otherwise specified. (Continued)
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Typical Dynamic Performance Characteristics The following curves apply for 12-bit + sign
mode after auto-calibration unless otherwise specified. (Continued)
Unipolar Spectral Response
with 50 kHz Sine Wave Input
01135483
Test Circuits
DO “TRI-STATE” (t1H, tOH)
DO except “TRI-STATE”
01135403
01135404
Leakage Current
01135405
Timing Diagrams
DO Falling and Rising Edge
DO “TRI-STATE” Falling and Rising Edge
01135418
01135419
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16
(Continued)
DI Data Input Timing
01135420
DO Data Output Timing Using CS
01135421
DO Data Output Timing with CS Continuously Low
01135422
17
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Timing Diagrams
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Timing Diagrams
(Continued)
ADC12038 Auto Cal or Auto Zero
01135423
Note: DO output data is not valid during this cycle.
ADC12038 Read Data without Starting a Conversion Using CS
01135424
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18
(Continued)
ADC12038 Read Data without Starting a Conversion with CS Continuously Low
01135425
ADC12038 Conversion Using CS with 8-Bit Digital Output Format
01135426
19
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Timing Diagrams
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Timing Diagrams
(Continued)
ADC12038 Conversion Using CS with 16-Bit Digital Output Format
01135451
ADC12038 Conversion with CS Continuously Low and 8-Bit Digital Output Format
01135428
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20
(Continued)
ADC12038 Conversion with CS Continuously Low and 16-Bit Digital Output Format
01135429
ADC12038 Software Power Up/Down Using CS with 16-Bit Digital Output Format
01135452
21
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Timing Diagrams
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Timing Diagrams
(Continued)
ADC12038 Software Power Up/Down with CS Continuously Low and 16-Bit Digital Output Format
01135431
ADC12038 Hardware Power Up/Down
01135432
Note: Hardware power up/down may occur at any time. If PD is high while a conversion is in progress that conversion will be corrupted and erroneous data will
be stored in the output shift register.
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22
(Continued)
ADC12038 Configuration Modification — Example of a Status Read
01135433
Note: In order for all 9 bits of Status Information to be accessible, the last conversion programmed before Cycle N needs to have a resolution of 8 bits plus
sign, 12 bits, 12 bits plus sign, or greater.
01135434
FIGURE 5. Protecting the MUXOUT1, MUXOUT2, A/DIN1 and A/DIN2 Analog Pins
23
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Timing Diagrams
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
01135435
*Tantalum
**Monolithic Ceramic or better
FIGURE 6. Recommended Power Supply Bypassing and Grounding
Tables
TABLE 1. Data Out Formats
DO Formats
with
Sign
DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 DB8 DB9 DB10 DB11 DB12 DB13 DB14 DB15 DB16
17
X
X
X
X
Sign MSB
10
9
8
7
6
5
4
Sign MSB
10
9
8
7
6
5
4
3
2
1
LSB
Sign MSB
6
5
4
3
2
1
LSB
LSB
1
2
3
4
5
6
7
8
9
10
MSB
Sign
LSB
1
2
3
4
5
6
7
8
9
10
MSB
Sign
LSB
1
2
3
4
5
6
3
2
1
LSB
X
X
X
X
Bits
MSB
13
First Bits
9
Bits
17
Bits
LSB
13
First Bits
9
MSB Sign
Bits
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24
(Continued)
TABLE 1. Data Out Formats (Continued)
DO Formats
without
Sign
DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7 DB8 DB9 DB10 DB11 DB12 DB13 DB14 DB15 DB16
16
0
0
0
0
MSB
10
9
8
7
6
5
4
MSB
10
9
8
7
6
5
4
3
2
1
LSB
MSB
6
5
4
3
2
1
LSB
LSB
1
2
3
4
5
6
7
8
9
10
MSB
LSB
1
2
3
4
5
6
7
8
9
10
MSB
LSB
1
2
3
4
5
6
MSB
3
2
1
LSB
0
0
0
0
Bits
MSB
12
First Bits
8
Bits
16
Bits
LSB
12
First Bits
8
Bits
X = High or Low state.
TABLE 2. ADC12038 Multiplexer Addressing
Analog Channel Addressed
A/D Input
Multiplexer
MUX
and Assignment
Polarity
Output
Address
with A/DIN1 tied to MUXOUT1
Assignment
Channel
and A/DIN2 tied to MUXOUT2
Mode
Assignment
DI0 DI1 DI2 DI3 CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 COM A/DIN1 A/DIN2 MUXOUT1 MUXOUT2
L
L
L
L
L
L
L
H
L
L
H
L
L
L
H
H
L
H
L
L
L
H
L
H
L
H
H
L
L
H
H
H
H
L
L
L
H
L
L
H
H
L
H
L
H
L
H
H
H
H
L
L
H
H
L
H
H
H
H
L
H
H
H
H
+
−
+
−
+
−
+
−
−
+
−
+
−
+
−
+
+
+
+
+
+
+
25
−
CH0
CH1
+
−
CH2
CH3
+
−
CH4
CH5
+
−
CH6
CH7
−
+
CH0
CH1
−
+
CH2
CH3
−
+
CH4
CH5
−
+
CH6
CH7
−
+
−
CH0
COM
−
+
−
CH2
COM
−
+
−
CH4
COM
−
+
−
CH6
COM
−
+
−
CH1
COM
−
+
−
CH3
COM
−
+
−
CH5
COM
−
+
−
CH7
COM
+
+
+
Differential
Single-Ended
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Tables
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
TABLE 3. ADC12034 Multiplexer Addressing
Analog Channel Addressed
A/D Input
Multiplexer
MUX
and Assignment
Polarity
Output
Address
with A/DIN1 tied to MUXOUT1
Assignment
Channel
and A/DIN2 tied to MUXOUT2
DI0
DI1
DI2
CH0
CH1
L
L
L
+
−
L
L
H
L
H
L
L
H
H
H
L
L
H
L
H
H
H
L
H
H
H
−
CH2
CH3
+
−
−
+
Assignment
COM
A/DIN1
A/DIN2
MUXOUT1
MUXOUT2
+
−
CH0
CH1
+
−
CH2
CH3
−
+
CH0
CH1
−
+
CH2
CH3
−
+
−
CH0
COM
−
+
−
CH2
COM
−
+
−
CH1
COM
−
+
−
CH3
COM
+
+
+
+
+
Mode
Differential
Single-Ended
TABLE 4. ADC12032 and ADC12030 Multiplexer Addressing
Analog Channel Addressed
A/D Input
Multiplexer
MUX
and Assignment
Polarity
Output
Address
with A/DIN1 tied to MUXOUT1
Assignment
Mode
Channel
and A/DIN2 tied to MUXOUT2
Assignment
DI0
DI1
CH0
CH1
A/DIN1
A/DIN2
MUXOUT1
L
L
+
−
COM
+
−
CH0
CH1
L
H
−
+
−
+
CH0
CH1
H
L
+
−
+
−
CH0
COM
H
H
−
+
−
CH1
COM
+
MUXOUT2
Differential
Single-Ended
Note: ADC12030 and ADC12H030 do not have A/DIN1, A/DIN2, MUXOUT1
and MUXOUT2 pins.
TABLE 5. Mode Programming
ADC12038
DI0
DI1
DI2
ADC12034
DI0
DI1
DI2
DI0
DI1
DI3
DI4
DI5
DI6
DI7
DI3
DI4
DI5
DI6
Mode Selected
(Current)
DO Format
(next Conversion
Cycle)
DI2
DI3
DI4
DI5
See Tables 2, 3 or Table 4
L
L
L
See Tables 2, 3 or Table 4
L
L
L
L
12 Bit Conversion
12 or 13 Bit MSB First
H
12 Bit Conversion
16 or 17 Bit MSB First
ADC12030
and
ADC12032
See Tables 2, 3 or Table 4
L
L
H
L
8 Bit Conversion
8 or 9 Bit MSB First
L
L
L
H
H
12 Bit Conversion of Full-Scale
12 or 13 Bit MSB First
See Tables 2, 3 or Table 4
L
H
L
L
12 Bit Conversion
12 or 13 Bit LSB First
See Tables 2, 3 or Table 4
L
H
L
H
12 Bit Conversion
16 or 17 Bit LSB First
See Tables 2, 3 or Table 4
L
H
H
L
8 Bit Conversion
8 or 9 Bit LSB First
L
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L
L
L
L
L
L
L
H
H
H
12 Bit Conversion of Offset
12 or 13 Bit LSB First
L
L
L
L
H
L
L
L
Auto Cal
No Change
L
L
L
L
H
L
L
H
Auto Zero
No Change
L
L
L
L
H
L
H
L
Power Up
No Change
L
L
L
L
H
L
H
H
Power Down
No Change
L
L
L
L
H
H
L
L
Read Status Register
No Change
L
L
L
L
H
H
L
H
Data Out without Sign
No Change
H
L
L
L
H
H
L
H
Data Out with Sign
No Change
L
L
L
L
H
H
H
L
Acquisition Time — 6 CCLK Cycles
No Change
L
H
L
L
H
H
H
L
Acquisition Time — 10 CCLK Cycles
No Change
H
L
L
L
H
H
H
L
Acquisition Time — 18 CCLK Cycles
No Change
26
ADC12038
DI0
DI1
DI2
ADC12034
DI0
DI1
DI2
DI0
DI1
H
H
DI3
DI4
DI5
DI6
DI7
DI3
DI4
DI5
DI6
Mode Selected
(Current)
DO Format
(next Conversion
Cycle)
DI2
DI3
DI4
DI5
H
H
H
L
Acquisition Time — 34 CCLK Cycles
No Change
ADC12030
and
ADC12032
L
L
L
L
L
L
H
H
H
H
User Mode
No Change
H
X
X
X
H
H
H
H
Test Mode
No Change
(CH1–CH7 become Active Outputs)
Note: The A/D powers up with no Auto Cal, no Auto Zero, 10 CCLK acquisition time, 12-bit + sign conversion, power up, 12- or 13-bit MSB first, and user mode.
X = Don’t Care
TABLE 6. Conversion/Read Data Only Mode Programming
CS
CONV
PD
Mode
L
L
L
See Table 5 for Mode
Read Only (Previous DO Format). No Conversion.
L
H
L
H
X
L
Idle
X
X
H
Power Down
X = Don’t Care
TABLE 7. Status Register
Status Bit
DB0
DB1
DB2
DB3
DB4
PD
Cal
8 or 9
12 or 13
DB5
DB6
DB7
DB8
16 or 17
Sign
Justification
Test Mode
Location
Status Bit
PU
Device Status
Function
“High”
indicates a
Power Up
Sequence
is in
progress
“High”
indicates a
Power
Down
Sequence
is in
progress
“High”
indicates
an
Auto-Cal
Sequence
is in
progress
DO Output Format Status
“High”
indicates
an 8 or 9
bit format
“High”
indicates a
12 or 13
bit format
“High”
indicates a
16 or 17
bit format
“High”
indicates
that the
sign bit is
included.
When
“Low” the
sign bit is
not
included.
When “High”
the
conversion
result will be
output MSB
first. When
“Low” the
result will be
output LSB
first.
When “High”
the device is
in test mode.
When “Low”
the device is
in user
mode.
since the Auto Cal procedure modifies the data in the output
shift register. To retrieve the status information, an additional
read status instruction is issued to the A/D. At this time the
status data is available on DO. If the Cal signal in the status
word, is low Auto Cal has been completed. Therefore, the
next instruction issued can start a conversion. The data
output at this time is again status information. To keep noise
from corrupting the A/D conversion, status can not be read
during a conversion. If CS is strobed and is brought low
during a conversion, that conversion is prematurely ended.
EOC can be used to determine the end of a conversion or
the A/D controller can keep track in software of when it would
be appropriate to comnmunicate to the A/D again. Once it
has been determined that the A/D has completed a conversion, another instruction can be transmitted to the A/D. The
data from this conversion can be accessed when the next
instruction is issued to the A/D.
Note, when CS is low continuously it is important to transmit
the exact number of SCLK cycles, as shown in the timing
diagrams. Not doing so will desynchronize the serial communication to the A/D. (See Section 1.3.)
Application Hints
1.0 DIGITAL INTERFACE
1.1 Interface Concepts
The example in Figure 7 shows a typical sequence of events
after the power is applied to the ADC12030/2/4/8:
01135436
FIGURE 7. Typical Power Supply Power Up Sequence
The first instruction input to the A/D via DI initiates Auto Cal.
The data output on DO at that time is meaningless and is
completely random. To determine whether the Auto Cal has
been completed, a read status instruction is issued to the
A/D. Again the data output at that time has no significance
27
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
TABLE 5. Mode Programming (Continued)
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
If erroneous SCLK pulses desynchronize the communications, the simplest way to recover is by cycling the power
supply to the device. Not being able to easily resynchronize
the device is a shortcoming of leaving CS low continuously.
(Continued)
1.2 Changing Configuration
The configuration of the ADC12030/2/4/8 on power up defaults to 12-bit plus sign resolution, 12- or 13-bit MSB First,
10 CCLK acquisition time, user mode, no Auto Cal, no Auto
Zero, and power up mode. Changing the aquisition time and
turning the sign bit on and off requires an 8-bit instruction to
be issued to the ADC. This instruction will not start a conversion. The instructions that select a multiplexer address
and format the output data do start a conversion. Figure 8
describes an example of changing the configuration of the
ADC12030/2/4/8.
During I/O sequence 1, the instruction on DI configures the
ADC12030/2/4/8 to do a conversion with 12-bit +sign resolution. Notice that when the 6 CCLK Acquisition and Data
Out without Sign instructions are issued to the ADC, I/O
sequences 2 and 3, a new conversion is not started. The
data output during these instructions is from conversion N
which was started during I/O sequence 1. The Configuration
Modification timing diagram describes in detail the sequence
of events necessary for a Data Out without Sign, Data Out
with Sign, or 6/10/18/34 CCLK Acquisition time mode selection. Table 5 describes the actual data necessary to be input
to the ADC to accomplish this configuration modification. The
next instruction, shown in Figure 8, issued to the A/D starts
conversion N+1 with 8 bits of resolution formatted MSB first.
Again the data output during this I/O cycle is the data from
conversion N.
The number of SCLKs applied to the A/D during any conversion I/O sequence should vary in accord with the data out
word format chosen during the previous conversion I/O sequence. The various formats and resolutions available are
shown in Table 1. In Figure 8, since 8-bit without sign MSB
first format was chosen during I/O sequence 4, the number
of SCLKs required during I/O sequence 5 is 8. In the following I/O sequence the format changes to 12-bit without sign
MSB first; therefore the number of SCLKs required during
I/O sequence 6 changes accordingly to 12.
The number of clock pulses required for an I/O exchange
may be different for the case when CS is left low continuously vs the case when CS is cycled. Take the I/O sequence
detailed in Figure 7 (Typical Power Supply Sequence) as an
example. The table below lists the number of SCLK pulses
required for each instruction:
Instruction
13 SCLKs
8 SCLKs
Read Status
13 SCLKs
8 SCLKs
Read Status
13 SCLKs
8 SCLKs
12-Bit + Sign Conv 1
13 SCLKs
8 SCLKs
12-Bit + Sign Conv 2
13 SCLKs
13 SCLKs
1.4 Analog Input Channel Selection
The data input on DI also selects the channel configuration
for a particular A/D conversion (see Tables 2, 3, 4 and Table
5). In Figure 8 the only times when the channel configuration
could be modified would be during I/O sequences 1, 4, 5 and
6. Input channels are reselected before the start of each new
conversion. Shown below is the data bit stream required on
DI, during I/O sequence number 4 in Figure 8, to set CH1 as
the positive input and CH0 as the negative input for the
different versions of ADCs:
Part
DI Data
Number
DI0 DI1 DI2 DI3 DI4 DI5 DI6 DI7
ADC12H030
ADC12H032
ADC12H038
12-Bit MSB or LSB First
16-Bit MSB or LSB first
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9
SIGN OFF
12
SIGN ON
13
SIGN OFF
16
SIGN ON
17
L
H
L
X
X
L
H
L
L
H
L
X
X
L
H
L
L
L
H
L
X
L
H
L
L
L
L
H
L
ADC12038
Where X can be a logic high (H) or low (L).
1.5 Power Up/Down
The ADC may be powered down at any time by taking the
PD pin HIGH or by the instruction input on DI (see Tables 5,
6, and the Power Up/Down timing diagrams). When the ADC
is powered down in this way, the circuitry necessary for an
A/D conversion is deactivated. The circuitry necessary for
digital I/O is kept active. Hardware power up/down is controlled by the state of the PD pin. Software power-up/down is
controlled by the instruction issued to the ADC. If a software
power up instruction is issued to the ADC while a hardware
power down is in effect (PD pin high) the device will remain
in the power-down state. If a software power down instruction is issued to the ADC while a hardware power up is in
effect (PD pin low), the device will power down. When the
device is powered down by software, it may be powered up
by either issuing a software power up instruction or by taking
PD pin high and then low. If the power down command is
issued during an A/D conversion, that conversion is disrupted. Therefore, the data output after power up cannot be
relied upon.
Expected
8
L
ADC12034
SCLKs
SIGN ON
H
ADC12032
Number of
SIGN OFF
L
ADC12030
1.3 CS Low Continuously Considerations
When CS is continuously low, it is important to transmit the
exact number of SCLK pulses that the ADC expects. Not
doing so will desynchronize the serial communications to the
ADC. When the supply power is first applied to the ADC, it
will expect to see 13 SCLK pulses for each I/O transmission.
The number of SCLK pulses that the ADC expects to see is
the same as the digital output word length. The digital output
word length is controlled by the Data Out (DO) format. The
DO format maybe changed any time a conversion is started
or when the sign bit is turned on or off. The table below
details out the number of clock periods required for different
DO formats:
8-Bit MSB or LSB First
CS Strobed
Auto Cal
ADC12H034
DO Format
CS Low
Continuously
28
(Continued)
01135437
FIGURE 8. Changing the ADC’s Conversion Configuration
1.6 User Mode and Test Mode
1.7 Reading the Data Without Starting a Conversion
An instruction may be issued to the ADC to put it into test
mode. Test mode is used by the manufacturer to verify
complete functionality of the device. During test mode
CH0–CH7 become active outputs. If the device is inadvertently put into the test mode with CS continuously low, the
serial communications may be desynchronized. Synchronization may be regained by cycling the power supply voltage
to the device. Cycling the power supply voltage will also set
the device into user mode. If CS is used in the serial interface, the ADC may be queried to see what mode it is in. This
is done by issuing a “read STATUS register” instruction to the
ADC. When bit 9 of the status register is high, the ADC is in
test mode; when bit 9 is low the ADC, is in user mode. As an
alternative to cycling the power supply, an instruction sequence may be used to return the device to user mode. This
instruction sequence must be issued to the ADC using CS.
The following table lists the instructions required to return the
device to user mode:
The data from a particular conversion may be accessed
without starting a new conversion by ensuring that the
CONV line is taken high during the I/O sequence. See the
Read Data timing diagrams. Table 6 describes the operation
of the CONV pin.
Instruction
2.0 DESCRIPTION OF THE ANALOG MULTIPLEXER
For the ADC12038, the analog input multiplexer can be
configured with 4 differential channels or 8 single ended
channels with the COM input as the zero reference or any
combination thereof (see Figure 9). The difference between
the voltages on the VREF+ and VREF− pins determines the
input voltage span (VREF). The analog input voltage range is
0 to VA+. Negative digital output codes result when VIN− >
VIN+. The actual voltage at VIN− or VIN+ cannot go below
AGND.
4 Differential
Channels
DI Data
DI0 DI1 DI2 DI3 DI4 DI5 DI6 DI7
TEST MODE
H
X
X
X
H
H
H
H
Reset
Test Mode
Instructions
L
L
L
L
H
H
H
L
L
L
L
L
H
L
H
L
L
L
L
L
H
L
H
H
USER MODE
L
L
L
L
H
H
H
H
Power Up
L
L
L
L
H
L
H
L
L
L
L
H
H
L
H
Set DO with
H
or without
or
Sign
L
01135438
Set
H
H
Acquisition
or
or
Time
L
L
8 Single-Ended Channels
with COM
as Zero Reference
L
L
Start
H
H
H
H
a
or
or
or
or
Conversion
L
L
L
L
H
H
H
L
H
H
H
L
or
or
or
L
L
L
X = Don’t Care
After returning to user mode with the user mode instruction
the power up, data with or without sign, and acquisition time
instructions need to be resent to ensure that the ADC is in
the required state before a conversion is started.
01135439
FIGURE 9.
29
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
With the single-ended multiplexer configuration CH0 through
CH7 can be assigned to the MUXOUT1 pin. The COM pin is
always assigned to the MUXOUT2 pin. A/DIN1 is assigned
as the positve input; A/DIN2 is assigned as the negative
input. (See Figure 10).
(Continued)
CH0, CH2, CH4, and CH6 can be assigned to the MUXOUT1 pin in the differential configuration, while CH1, CH3,
CH5, and CH7 can be assigned to the MUXOUT2 pin. In the
differential configuration, the analog inputs are paired as
follows: CH0 with CH1, CH2 with CH3, CH4 with CH5 and
CH6 with CH7. The A/DIN1 and A/DIN2 pins can be assigned positive or negative polarity.
Differential
Configuration
Single-Ended
Configuration
01135440
01135441
A/DIN1 and A/DIN2 can be assigned as the + or − input
A/DIN1 is + input
A/DIN2 is − input
FIGURE 10.
The Multiplexer assignment tables for the ADC12030,2,4,8
(Tables 2, 3, 4) summarize the aforementioned functions for
the different versions of A/Ds.
2.1 Biasing for Various Multiplexer Configurations
Figure 11 is an example of biasing the device for
single-ended operation. The sign bit is always low. The
digital output range is 0 0000 0000 0000 to 0 1111 1111 1111.
One LSB is equal to 1 mV (4.1V/4096 LSBs).
01135446
FIGURE 11. Single-Ended Biasing
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30
periods, the input biasing resistor needs to be 600Ω or less.
Notice though that the input coupling capacitor needs to be
made fairly large to bring down the high pass corner. Increasing the acquisition time to 34 clock periods (with a
5 MHz CCLK frequency) would allow the 600Ω to increase to
6k, which with a 1 µF coupling capacitor would set the high
pass corner at 26 Hz. Increasing R, to 6k would allow R2 to
be 2k.
(Continued)
For pseudo-differential signed operation, the biasing circuit
shown in Figure 12 shows a signal AC coupled to the ADC.
This gives a digital output range of −4096 to +4095. With a
2.5V reference, as shown, 1 LSB is equal to 610 µV. Although, the ADC is not production tested with a 2.5V reference, linearity error typically will not change more than 0.1
LSB (see the curves in the Typical Electrical Characteristics
Section). With the ADC set to an acquisition time of 10 clock
01135447
FIGURE 12. Pseudo-Differential Biasing with the Signal Source AC Coupled Directly into the ADC
An alternative method for biasing pseudo-differential operation is to use the +2.5V from the LM4040 to bias any amplifier circuits driving the ADC as shown in Figure 13. The value
of the resistor pull-up biasing the LM4040-2.5 will depend
upon the current required by the op amp biasing circuitry.
In the circuit of Figure 13 some voltage range is lost since
the amplifier will not be able to swing to +5V and GND with
a single +5V supply. Using an adjustable version of the
LM4041 to set the full scale voltage at exactly 2.048V and a
lower grade LM4040D-2.5 to bias up everything to 2.5V as
shown in Figure 14 will allow the use of all the ADC’s digital
output range of −4096 to +4095 while leaving plenty of head
room for the amplifier.
Fully differential operation is shown in Figure 15. One LSB
for this case is equal to (4.1V/4096) = 1 mV.
31
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
(Continued)
01135448
FIGURE 13. Alternative Pseudo-Differential Biasing
01135449
FIGURE 14. Pseudo-Differential Biasing without the Loss of Digital Output Range
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32
(Continued)
01135450
FIGURE 15. Fully Differential Biasing
varies between very specific voltage limits, a time and temperature stable voltage source can be connected to the
reference inputs. Typically, the reference voltage’s magnitude will require an initial adjustment to null reference voltage induced full-scale errors.
3.0 REFERENCE VOLTAGE
The difference in the voltages applied to the VREF+ and
VREF− defines the analog input span (the difference between
the voltage applied between two multiplexer inputs or the
voltage applied to one of the multiplexer inputs and analog
ground), over which 4095 positive and 4096 negative codes
exist. The voltage sources driving VREF+ or VREF− must have
very low output impedance and noise. The circuit in Figure
16 is an example of a very stable reference appropriate for
use with the device.
Below are recommended references along with some key
specifications.
Part Number
Output
Temperature
Voltage
Coefficient
Tolerance
LM4041CI-Adj
LM4040AI-4.1
LM4120AI-4.1
LM4121AI-4.1
LM4050AI-4.1
LM4030AI-4.1
LM4031AI
LM4031AC
01135442
*Tantalum
LM4140AC-4.1
Circuit of Figure 16
FIGURE 16. Low Drift Extremely
Stable Reference Circuit
± 0.5%
± 0.1%
± 0.2%
± 0.2%
± 0.1
± 0.05%
± 2.2
± 0.4
± 0.1%
Adjustable
± 100ppm/˚C
± 100ppm/˚C
± 50ppm/˚C
± 50ppm/˚C
± 50ppm/˚C
± 10ppm/˚C
± 26ppm/˚C
± 46ppm/˚C
± 3.0ppm/˚C
± 2ppm/˚C
The reference voltage inputs are not fully differential. The
ADC12030/2/4/8 will not generate correct conversions or
comparisons if VREF+ is taken below VREF−. Correct conversions result when VREF+ and VREF− differ by 1V and remain,
at all times, between ground and VA+. The VREF common
mode range, (VREF+ + VREF−)/2 is restricted to (0.1 x VA+) to
(0.6 x VA+). Therefore, with VA+ = 5V the center of the
reference ladder should not go below 0.5V or above 3.0V.
Figure 17 is a graphic representation of the voltage restrictions on VREF+ and VREF−.
The ADC 12030/2/4/8 can be used in either ratiometric or
absolute reference applications. In ratiometric systems, the
analog input voltage is proportional to the voltage used for
the ADC’s reference voltage. When this voltage is the system power supply, the VREF+ pin is connected to VA+ and
VREF− is connected to ground. This technique relaxes the
system reference stability requirements because the analog
input voltage and the ADC reference voltage move together.
This maintains the same output code for given input conditions. For absolute accuracy, where the analog input voltage
33
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
applied, the source impedance and the internal multiplexer
switch on resistance. With MUXOUT1 tied to A/DIN1 and
MUXOUT2 tied to A/DIN2 the internal multiplexer switch on
resistance is typically 1.6 kΩ. The A/DIN1 and A/DIN2 mux
on resistance is typically 750Ω.
(Continued)
6.0 INPUT SOURCE RESISTANCE
For low impedance voltage sources ( < 600Ω), the input
charging current will decay, before the end of the S/H’s
acquisition time of 2 µs (10 CCLK periods with fC = 5 MHz),
to a value that will not introduce any conversion errors. For
high source impedances, the S/H’s acquisition time can be
increased to 18 or 34 CCLK periods. For less ADC resolution
and/or slower CCLK frequencies the S/H’s acquisition time
may be decreased to 6 CCLK periods. To determine the
number of clock periods (Nc) required for the acquisition time
with a specific source impedance for the various resolutions
the following equations can be used:
12 Bit + Sign NC = [RS + 2.3] x fC x 0.824
8 Bit + Sign NC = [RS + 2.3] x fC x 0.57
Where fC is the conversion clock (CCLK) frequency in MHz
and RS is the external source resistance in kΩ. As an example, operating with a resolution of 12 Bits+sign, a 5 MHz
clock frequency and maximum acquistion time of 34 conversion clock periods the ADC’s analog inputs can handle a
source impedance as high as 6 kΩ. The acquisition time may
also be extended to compensate for the settling or response
time of external circuitry connected between the MUXOUT
and A/DIN pins.
The acquisition time tA is started by a falling edge of SCLK
and ended by a rising edge of CCLK (see timing diagrams).
If SCLK and CCLK are asynchronous one extra CCLK clock
period may be inserted into the programmed acquisition time
for synchronization. Therefore with asnychronous SCLK and
CCLKs the acquisition time will change from conversion to
conversion.
01135445
FIGURE 17. VREF Operating Range
4.0 ANALOG INPUT VOLTAGE RANGE
The ADC12030/2/4/8’s fully differential ADC generate a
two’s complement output that is found by using the equations shown below:
for (12-bit) resolution the Output Code =
7.0 INPUT BYPASS CAPACITANCE
for (8-bit) resolution the Output Code =
External capacitors (0.01 µF–0.1 µF) can be connected
between the analog input pins, CH0–CH7, and analog
ground to filter any noise caused by inductive pickup associated with long input leads. These capacitors will not degrade the conversion accuracy.
Round off to the nearest integer value between −4096 to
4095 for 12-bit resolution and between −256 to 255 for 8-bit
resolution if the result of the above equation is not a whole
number.
Examples are shown in the table below:
8.0 NOISE
The leads to each of the analog multiplexer input pins should
be kept as short as possible. This will minimize input noise
and clock frequency coupling that can cause conversion
errors. Input filtering can be used to reduce the effects of the
noise sources.
Digital
VREF+
VREF−
VIN+
VIN−
Output
+2.5V
+1V
+1.5V
0V
0,1111,1111,1111
+4.096V
0V
+3V
0V
0,1011,1011,1000
+4.096V
0V
+4.096V
0V
9.0 POWER SUPPLIES
Noise spikes on the VA+ and VD+ supply lines can cause
conversion errors; the comparator will respond to the noise.
The ADC is especially sensitive to any power supply spikes
that occur during the auto-zero or linearity correction. The
minimum power supply bypassing capacitors recommended
are low inductance tantalum capacitors of 10 µF or greater
paralleled with 0.1 µF monolithic ceramic capacitors. More or
different bypassing may be necessary depending on the
overall system requirements. Separate bypass capacitors
should be used for the VA+ and VD+ supplies and placed as
close as possible to these pins.
Code
+2.499V +2.500V
0V
1,1111,1111,1111
+4.096V 1,0000,0000,0000
5.0 INPUT CURRENT
At the start of the acquisition window (tA) a charging current
flows into or out of the analog input pins (A/DIN1 and
A/DIN2) depending on the input voltage polarity. The analog
input pins are CH0–CH7 and COM when A/DIN1 is tied to
MUXOUT1 and A/DIN2 is tied to MUXOUT2. The peak value
of this input current will depend on the actual input voltage
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34
point, either the power supply ground or at the pins of the
ADC. This greatly reduces the occurence of ground loops
and noise.
(Continued)
10.0 GROUNDING
The ADC12030/2/4/8’s performance can be maximized
through proper grounding techniques. These include the use
of separate analog and digital ground planes. The digital
ground plane is placed under all components that handle
digital signals, while the analog ground plane is placed under
all components that handle analog signals. The digital and
analog ground planes are connected together at only one
Shown in Figure 18 is the ideal ground plane layout for the
ADC12038 along with ideal placement of the bypass capacitors. The circuit board layout shown in Figure 18 uses three
bypass capacitors: 0.01 µF (C1) and 0.1 µF (C2) surface
mount capacitors and 10 µF (C3) tantalum capacitor.
01135443
FIGURE 18. Ideal Ground Plane
11.0 CLOCK SIGNAL LINE ISOLATION
The ADC12030/2/4/8’s performance is optimized by routing
the analog input/output and reference signal conductors as
far as possible from the conductors that carry the clock
signals to the CCLK and SCLK pins. Ground traces parallel
to the clock signal traces can be used on printed circuit
boards to reduce clock signal interference on the analog
input/output pins.
13.0 THE AUTO-ZERO CYCLE
To correct for any change in the zero (offset) error of the A/D,
the auto-zero cycle can be used. It may be necessary to do
an auto-zero cycle whenever the ambient temperature or the
power supply voltage change significantly. (See the curves
titled “Zero Error Change vs Ambient Temperature” and
“Zero Error Change vs Supply Voltage” in the Typical Performance Characteristics.)
12.0 THE CALIBRATION CYCLE
A calibration cycle needs to be started after the power supplies, reference, and clock have been given enough time to
stabilize after initial turn-on. During the calibration cycle,
correction values are determined for the offset voltage of the
sampled data comparator and any linearity and gain errors.
These values are stored in internal RAM and used during an
analog-to-digital conversion to bring the overall full-scale,
offset, and linearity errors down to the specified limits.
Full-scale error typically changes ± 0.4 LSB over temperature and linearity error changes even less; therefore it should
be necessary to go through the calibration cycle only once
after power up if the Power Supply Voltage and the ambient
temperature do not change significantly (see the curves in
the Typical Performance Characteristics).
14.0 DYNAMIC PERFORMANCE
Many applications require the A/D converter to digitize AC
signals, but the standard DC integral and differential nonlinearity specifications will not accurately predict the A/D converter’s performance with AC input signals. The important
specifications for AC applications reflect the converter’s ability to digitize AC signals without significant spectral errors
and without adding noise to the digitized signal. Dynamic
characteristics such as signal-to-noise (S/N), signal-tonoise
+ distortion ratio (S/(N + D)), effective bits, full power bandwidth, aperture time and aperture jitter are quantitative measures of the A/D converter’s capability.
An A/D converter’s AC performance can be measured using
Fast Fourier Transform (FFT) methods. A sinusoidal waveform is applied to the A/D converter’s input, and the transform is then performed on the digitized waveform. S/(N + D)
and S/N are calculated from the resulting FFT data, and a
spectral plot may also be obtained. Typical values for S/N
35
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
and the effective number of Bits (ENOB) is defined as:
(Continued)
are shown in the table of Electrical Characteristics, and
spectral plots of S/(N + D) are included in the typical performance curves.
The A/D converter’s noise and distortion levels will change
with the frequency of the input signal, with more distortion
and noise occurring at higher signal frequencies. This can be
seen in the S/(N + D) versus frequency curves.
Effective number of bits can also be useful in describing the
A/D’s noise performance. An ideal A/D converter will have
some amount of quantization noise, determined by its resolution, which will yield an optimum S/N ratio given by the
following equation:
As an example, this device with a differential signed 5V,
1 kHz sine wave input signal will typically have a S/(N + D) of
77 dB, which is equivalent to 12.5 effective bits.
15.0 AN RS232 SERIAL INTERFACE
Shown on the following page is a schematic for an RS232
interface to any IBM and compatible PCs. The DTR, RTS,
and CTS RS232 signal lines are buffered via level translators and connected to the ADC12038’s DI, SCLK, and DO
pins, respectively. The D flip flop drives the CS control line.
S/N = (6.02 x n + 1.76) dB
where n is the A/D’s resolution in bits.
S/(N + D) (or SINAD) is a combination of S/N (or SNR) and
distortion and is considered to be an overall measure of an
A/D converter performance. S/(N + D) is defined as:
01135444
Note: VA+, VD+, and VREF+ on the ADC12038 each have 0.01 µF and 0.1 µF chip caps, and 10 µF tantalum caps. All logic devices are bypassed with 0.1 µF
caps.
The assignment of the RS232 port is shown below
COM1 Input Address
Output Address
B7
B6
B5
B4
B3
B2
B1
B0
3FE
X
X
X
CTS
X
X
X
X
3FC
X
X
X
0
X
X
RTS
DTR
A sample program, written in Microsoft QuickBasic, is shown
on the next page. The program prompts for data mode select
instruction to be sent to the A/D. This can be found from the
Mode Programming table shown earlier. The data should be
entered in “1”s and “0”s as shown in the table with DI0 first.
Next the program prompts for the number of SCLKs required
for the programmed mode select instruction. For instance, to
send all “0”s to the A/D, selects CH0 as the +input, CH1 as
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the −input, 12-bit conversion, and 13-bit MSB first data
output format (if the sign bit was not turned off by a previous
instruction). This would require 13 SCLK periods since the
output data format is 13 bits. The part powers up with No
Auto Cal, No Auto Zero, 10 CCLK Acquisition Time, 12-bit
conversion, data out with sign, power up, 12- or 13-bit MSB
first, and user mode. Auto Cal, Auto Zero, Power Up and
36
(Continued)
Power Down instructions do not change these default settings. The following power up sequence should be followed:
1.
2.
Run the program
Prior to responding to the prompt apply the power to the
ADC12038
3. Respond to the program prompts
It is recommended that the first instruction issued to the
ADC12038 be Auto Cal (see Section 1.1).
’variables DOL=Data Out word length,
⇒ DI=Data string for A/D DI input,
’
DO=A/D result string
’SET CS# HIGH
OUT
&H3FC, (&H2 OR INP (&H3FC))
’set
⇒ RTS HIGH
OUT
&H3FC, (&HFE AND INP(&H3FC))
’set
⇒ DTR LOW
OUT
&H3FC, (&HFD AND INP(&H3FC))
’set
⇒ RTS LOW
OUT
&H3FC, (&HEF AND INP(&H3FC))
’set
⇒ B4 low
10
LINE INPUT <&ldquo>DI data for ADC12038 (see
⇒ Mode Table on data sheet)”; DI$
INPUT <&ldquo>ADC12038 output word length
⇒ (8,9,12,13,16 or 17)”; DOL
20
’SET CS# HIGH
OUT
&H3FC, (&H2 OR INP (&H3FC))
’set
⇒ RTS HIGH
OUT
&H3FC, (&HFE AND INP(&H3FC))
’set
⇒ DTR LOW
OUT
&H3FC, (&HFD AND INP(&H3FC))
’set
⇒ RTS LOW
’SET CS# LOW
OUT
&H3FC, (&H2 OR INP (&H3FC))
’set
⇒ RTS HIGH
OUT
&H3FC, (&H1 OR INP(&H3FC))
’set
⇒ DTR HIGH
OUT
&H3FC, (&HFD AND INP(&H3FC))
’set
⇒ RTS LOW
DO$=
⇒ <&ldquo> ”
⇒ DO variable
OUT &H3FC, (&H1 OR INP(&H3FC))
’SET
⇒ DTR HIGH
OUT &H3FC, (&HFD AND
⇒ INP(&H3FC))
’SCLK low
FOR N=1 TO 8
Temp$=MID$(DI$,N,1)
IF Temp$=<&ldquo>0” THEN
OUT &H3FC,(&H1 OR INP(&H3FC))
ELSE OUT &H3FC, (&HFE AND INP(&H3FC))
END IF
’out
⇒ DI
OUT &H3FC, (&H2 OR
⇒ INP(&H3FC))
’SCLK high
IF (INP(&H3FE) AND 16)=16 THEN
DO$=DO$+<&ldquo>0”
ELSE
DO$=DO$+<&ldquo>1”
END
⇒ IF
’input
⇒ DO
OUT &H3FC, (&H1 OR INP(&H3FC))
’SET
⇒ DTR HIGH
OUT &H3FC, (&HFD AND
⇒ INP(&H3FC))
’SCLK low
NEXT N
IF DOL>8 THEN
FOR N=9 TO DOL
OUT &H3FC, (&H1 OR INP(&H3FC))
’SET
⇒ DTR HIGH
OUT &H3FC, (&HFD AND
⇒ INP(&H3FC))
’SCLK low
OUT &H3FC, (&H2 OR
⇒ INP(&H3FC))
’SCLK high
IF (INP(&H3FE) AND &H10)=&H10 THEN
DO$=DO$+<&ldquo>0”
ELSE
DO$=DO$+<&ldquo>1”
END IF
NEXT N
END IF
OUT
&H3FC, (&HFA AND
⇒ INP(&H3FC))
’SCLK low and DI high
FOR N=1 TO 500
NEXT N
PRINT DO$
INPUT <&ldquo>Enter <&ldquo>C” to convert
⇒ else <&ldquo>RETURN” to alter DI data”; s$
IF s$=<&ldquo>C” OR s$=<&ldquo>c” THEN
’reset GOTO 20
ELSE
GOTO 10
END IF
END
37
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Application Hints
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Physical Dimensions
inches (millimeters)
unless otherwise noted
Order Number ADC12030CIWM or ADC12H030CIWM
NS Package Number M16B
Order Number ADC12032CIWM or ADC12H032CIWM
NS Package Number M20B
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38
ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
Order Number ADC12034CIWM or ADC12H034CIWM
NS Package Number M24B
Order Number ADC12H034CIMSA
NS Package Number MSA24
39
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Physical Dimensions
inches (millimeters) unless otherwise noted (Continued)
Order Number ADC12038CIWM or ADC12H038CIWM
NS Package Number M28B
Order Number ADC12034CIN or ADC12H034CIN
NS Package Number N24C
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40
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ADC12H030/ADC12H032/ADC12H034/ADC12H038, ADC12030/ADC12032/ADC12034/ADC12038
Self-Calibrating 12-Bit Plus Sign Serial I/O A/D Converters with MUX and Sample/Hold
Notes