ADC08131/ADC08134/ADC08138
8-Bit High-Speed Serial I/O A/D Converters with
Multiplexer Options, Voltage Reference, and Track/Hold
Function
General Description
The ADC08131/ADC08134/ADC08138 are 8-bit successive
approximation A/D converters with serial I/O and config-
urable input multiplexers with up to 8 channels. The serial
I/O is configured to comply with the NSC MICROWIRE
TM
se-
rial data exchange standard for easy interface to the
COPS
TM
family of controllers, and can easily interface with
standard shift registers or microprocessors.
All three devices provide a 2.5V band-gap derived reference
with guaranteed performance over temperature.
A track/hold function allows the analog voltage at the positive
input to vary during the actual A/D conversion.
The analog inputs can be configured to operate in various
combinations
of
single-ended,
differential,
or
pseudo-differential modes. In addition, input voltage spans
as small as 1V can be accommodated.
Applications
n
Digitizing automotive sensors
n
Process control/monitoring
n
Remote sensing in noisy environments
n
Embedded diagnostics
Features
n
Serial digital data link requires few I/O pins
n
Analog input track/hold function
n
4- or 8-channel input multiplexer options with address
logic
n
On-chip 2.5V band-gap reference (
2% over
temperature guaranteed)
n
No zero or full scale adjustment required
n
TTL/CMOS input/output compatible
n
0V to 5V analog input range with single 5V power
supply
Key Specifications
n
Resolution
8 Bits
n
Conversion time (f
C
= 1 MHz)
8 s (Max)
n
Power dissipation
20 mW (Max)
n
Single supply
5 V
DC
(
5%)
n
Total unadjusted error
1
/
2
LSB and
1 LSB
n
Linearity Error (V
REF
= 2.5V)
1
/
2
LSB
n
No missing codes (over temperature)
n
On-board Reference
+2.5V
1.5% (Max)
Ordering Information
Industrial
Package
(-40C
T
A
+85C)
ADC08131CIWM
M14B
ADC08134CIWM
M14B
ADC08138CIWM
M20B
TRI-STATE
is a registered trademark of National Semiconductor Corporation.
COPS
TM
microcontrollers and MICROWIRE
TM
are trademarks of National Semiconductor Corporation.
June 1999
ADC08131/ADC08134/ADC08138
8-Bit
High-Speed
Serial
I/O
A/D
Converters
with
Multiplexer
Options,
V
oltage
Reference,
and
T
rack/Hold
Function
1999 National Semiconductor Corporation
DS010749
www.national.com
Absolute Maximum Ratings
(Notes 1, 3)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage (V
CC
)
6.5V
Voltage at Inputs and Outputs
-0.3V to V
CC
+ 0.3V
Input Current at Any Pin (Note 4)
5 mA
Package Input Current (Note 4)
20 mA
Power Dissipation at T
A
= 25C
(Note 5)
800 mW
ESD Susceptibility (Note 6)
1500V
Soldering Information
N Package (10 sec.)
SO Package:
Vapor Phase (60 sec.)
Infrared (15 sec.) (Note 7)
260C
215C
220C
Storage Temperature
-65C to +150C
Operating Ratings
(Notes 2, 3)
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
+85C
Supply Voltage (V
CC
)
4.5 V
DC
to 6.3 V
DC
Electrical Characteristics
The following specifications apply for V
CC
= +5 V
DC
, V
REF
= +2.5 V
DC
and f
CLK
= 1 MHz unless otherwise specified. Bold-
face limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other limits T
A
= T
J
= 25C.
Symbol
Parameter
Conditions
Typical
(Note 8)
Limits
(Note 9)
Units
(Limits)
CONVERTER AND MULTIPLEXER CHARACTERISTICS
Linearity Error
V
REF
= +2.5 V
DC
1
LSB (max)
Full Scale Error
V
REF
= +2.5 V
DC
1
LSB (max)
Zero Error
V
REF
= +2.5 V
DC
1
LSB (max)
Total Unadjusted Error
V
REF
= +5 V
DC
(Note 10)
1
LSB (max)
Differential Linearity
V
REF
= +2.5 V
DC
8
Bits (min)
R
REF
Reference Input Resistance
(Note 11)
3.5
k
1.3
k
(min)
6.0
k
(max)
V
IN
Analog Input Voltage
(Note 12)
(V
CC
+ 0.05)
V (max)
(GND - 0.05)
V (min)
DC Common-Mode Error
V
REF
= 2.5 V
DC
1
/
2
LSB (max)
Power Supply Sensitivity
V
CC
= +5V
5%,
1
/
4
LSB (max)
V
REF
= +2.5 V
DC
On Channel Leakage Current
(Note 13)
On Channel = 5V,
0.2
A (max)
Off Channel = 0V
1
On Channel = 0V,
-0.2
A (max)
Off Channel = 5V
-1
Off Channel Leakage Current
(Note 13)
On Channel = 5V,
-0.2
A (max)
Off Channel = 0V
-1
On Channel = 0V,
0.2
A (max)
Off Channel = 5V
1
DIGITAL AND DC CHARACTERISTICS
V
IN(1)
Logical "1" Input Voltage
V
CC
= 5.25V
2.0
V (min)
V
IN(0)
Logical "0" Input Voltage
V
CC
= 4.75V
0.8
V (max)
I
IN(1)
Logical "1" Input Current
V
IN
= 5.0V
1
A (max)
I
IN(0)
Logical "0" Input Current
V
IN
= 0V
-1
A (max)
V
CC
= 4.75V:
V
OUT(1)
Logical "1" Output Voltage
I
OUT
= -360 A
2.4
V (min)
I
OUT
= -10 A
4.5
V (min)
V
OUT(0)
Logical "0" Output Voltage
V
CC
= 4.75V
0.4
V (max)
I
OUT
= 1.6 mA
I
OUT
TRI-STATE
Output Current
V
OUT
= 0V
-3.0
A (max)
V
OUT
= 5V
3.0
A (max)
I
SOURCE
Output Source Current
V
OUT
= 0V
-6.5
mA (min)
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3
Electrical Characteristics
(Continued)
The following specifications apply for V
CC
= +5 V
DC
, V
REF
= +2.5 V
DC
and t
r
= t
f
= 20 ns unless otherwise specified. Boldface
limits apply for T
A
= T
J
= T
MIN
to T
MAX
; all other limits T
A
= T
J
= 25C.
Symbol
Parameter
Conditions
Typical
(Note 8)
Limits
(Note 9)
Units
(Limits)
T
C
Conversion Time (Not Including
f
CLK
= 1 MHz
8
1/f
CLK
(max)
MUX Addressing Time)
8
s (max)
t
CA
Acquisition Time
1
/
2
1/f
CLK
(max)
t
SELECT
CLK High while CS is High
50
ns
t
SET-UP
CS Falling Edge or Data Input
25
ns (min)
Valid to CLK Rising Edge
t
HOLD
Data Input Valid after CLK Rising
Edge
20
ns (min)
t
pd1
, t
pd0
CLK Falling Edge to Output Data
Valid (Note 15)
C
L
= 100 pF:
Data MSB First
250
ns (max)
Data LSB First
200
ns (max)
t
1H
, t
0H
TRI-STATE Delay from Rising Edge
of CS to Data Output and SARS
Hi-Z
C
L
= 10 pF, R
L
= 10 k
50
ns
(see TRI-STATE Test Circuits)
C
L
= 100 pF, R
L
= 2 k
180
ns (max)
C
IN
Capacitance of Logic Inputs
5
pF
C
OUT
Capacitance of Logic Outputs
5
pF
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur.
Note 2: Operating Ratings indicate conditions for which the device is functional. These ratings do not guarantee specific performance limits. For guaranteed speci-
fications and test conditions, see the Electrical Characteristics. The guaranteed specifications apply only for the test conditions listed. Some performance character-
istics may degrade when the device is not operated under the listed test conditions.
Note 3: All voltages are measured with respect to AGND = DGND = 0 V
DC
, unless otherwise specified.
Note 4: When the input voltage (V
IN
) at any pin exceeds the power supplies (V
IN
<
(AGND or DGND) or V
IN
>
AV
CC
) the current at that pin should be limited to
5 mA. The 20 mA maximum package input current rating limits the number of pins that can safely exceed the power supplies with an input current of 5 mA to four
pins.
Note 5: The maximum power dissipation must be derated at elevated temperatures and is dictated by T
JMAX
,
JA
and the ambient temperature, T
A
. The maximum
allowable power dissipation at any temperature is P
D
= (T
JMAX
- T
A
)/
JA
or the number given in the Absolute Maximum Ratings, whichever is lower. For these devices
T
JMAX
= 125C. The typical thermal resistances (
JA
) of these parts when board mounted for the ADC 08131 and the ADC08134 is 140C/W and 91C/W for the
ADC08138.
Note 6: Human body model, 100 pF capacitor discharged through a 1.5 k
resistor.
Note 7: See AN450 "Surface Mounting Methods and Their Effect on Product Reliability" or Linear Data Book section "Surface Mount" for other methods of soldering
surface mount devices.
Note 8: Typicals are at T
J
= 25C and represent the most likely parametric norm.
Note 9: Guaranteed to National's AOQL (Average Outgoing Quality Level).
Note 10: Total unadjusted error includes zero, full-scale, linearity, and multiplexer error. Total unadjusted error with V
REF
= +5V only applies to the ADC08134 and
ADC08138. See (Note 16).
Note 11: Cannot be tested for the ADC08131.
Note 12: For V
IN(-)
V
IN(+)
the digital code will be 0000 0000. Two on-chip diodes are tied to each analog input (see Block Diagram) which will forward-conduct for
analog input voltages one diode drop below ground or one diode drop greater than V
CC
supply. During testing at low V
CC
levels (e.g., 4.5V), high level analog inputs
(e.g., 5V) can cause an input diode to conduct, especially at elevated temperatures. This will cause errors for analog inputs near full-scale. The specification allows
50 mV forward bias of either diode; this means that as long as the analog V
IN
does not exceed the supply voltage by more than 50 mV, the output code will be correct.
Exceeding this range on an unselected channel will corrupt the reading of a selected channel. Achievement of an absolute 0 V
DC
to 5 V
DC
input voltage range will
therefore require a minimum supply voltage of 4.950 V
DC
over temperature variations, initial tolerance and loading.
Note 13: Channel leakage current is measured after a single-ended channel is selected and the clock is turned off. For off channel leakage current the following two
cases are considered: one, with the selected channel tied high (5 V
DC
) and the remaining seven off channels tied low (0 V
DC
), total current flow through the off chan-
nels is measured; two, with the selected channel tied low and the off channels tied high, total current flow through the off channels is again measured. The two cases
considered for determining on channel leakage current are the same except total current flow through the selected channel is measured.
Note 14: A 40% to 60% 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 low must be at least 450 ns. The maximum time the clock can be high or low is 100 s.
Note 15: Since data, MSB first, is the output of the comparator used in the successive approximation loop, an additional delay is built in (see Block Diagram) to allow
for comparator response time.
Note 16: For the ADC08131 V
REF
IN is internally tied to the on chip 2.5V band-gap reference output; therefore, the supply current is larger because it includes the
reference current (700 A typical, 2 mA maximum).
Note 17: Load regulation test conditions and specifications for the ADC08131 differ from those of the ADC08134 and ADC08138 because the ADC08131 has the
on-board reference as a permanent load.
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5
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