ADC10154/ADC10158
10-Bit Plus Sign 4 µs ADCs with 4- or 8-Channel MUX,
Track/Hold and Reference
General Description
The ADC10154 and ADC10158 are CMOS 10-bit plus sign
successive approximation A/D converters with versatile ana-
log input multiplexers, track/hold function and a 2.5V
band-gap reference. The 4-channel or 8-channel multiplex-
ers can be software configured for single-ended, differential
or pseudo-differential modes of operation.
The input track/hold is implemented using a capacitive array
and sampled-data comparator.
Resolution can be programmed to be 8-bit, 8-bit plus sign,
10-bit or 10-bit plus sign. Lower-resolution conversions can
be performed faster.
The variable resolution output data word is read in two bytes,
and can be formatted left justified or right justified, high byte
first.
Applications
nProcess control
nInstrumentation
nTest equipment
Features
n4- or 8- channel configurable multiplexer
nAnalog input track/hold function
n0V to 5V analog input range with single +5V power
supply
n−5V to +5V analog input voltage range with ±5V
supplies
nFully tested in unipolar (single +5V supply) and bipolar
(dual ±5V supplies) operation
nProgrammable resolution/speed and output data format
nRatiometric or Absolute voltage reference operation
nNo zero or full scale adjustment required
nNo missing codes over temperature
nEasy microprocessor interface
Key Specifications
nResolution 10-bit plus sign
nIntegral linearity error ±1 LSB (max)
nUnipolar power dissipation 33 mW (max)
nConversion time (10-bit + sign) 4.4 µs (max)
nConversion time (8-bit) 3.2 µs (max)
nSampling rate (10-bit + sign) 166 kHz
nSampling rate (8-bit) 207 kHz
nBand-gap reference 2.5V ±2.0% (max)
ADC10158 Simplified Block Diagram
DS011225-1
November 1999
ADC10154/ADC10158 10-Bit Plus Sign 4 µs ADCs with 4- or 8-Channel MUX, Track/Hold and
Reference
© 2001 National Semiconductor Corporation DS011225 www.national.com
Connection Diagrams
Pin Descriptions
AV
+
This is the positive analog supply. This pin
should be bypassed with a 0.1 µF ceramic ca-
pacitor and a 10 µF tantalum capacitor to the
system analog ground.
DV
+
This is the positive digital supply. This supply
pin also needs to be bypassed with 0.1 µF
ceramic and 10 µF tantalum capacitors to the
system digital ground. AV
+
and DV
+
should be
bypassed separately and tied to same power
supply.
DGND This is the digital ground. All logic levels are
referred to this ground.
V
−
This is the negative analog supply. For unipolar
operation this pin may be tied to the system
analog ground or to a negative supply source.
It should not go above DGND by more than
50 mV. When bipolar operation is required, the
voltage on this pin will limit the analog input’s
negative voltage level. In bipolar operation this
supply pin needs to be bypassed with 0.1 µF
ceramic and 10 µF tantalum capacitors to the
system analog ground.
V
REF+
,
V
REF−
These are the positive and negative reference
inputs. The voltage difference between V
REF+
and V
REF−
will set the analog input voltage
span.
V
REF
Out This is the internal band-gap voltage reference
output. For proper operation of the voltage ref-
erence, this pin needs to be bypassed with a
330 µF tantalum or electrolytic capacitor.
CS This is the chip select input. When a logic low
is applied to this pin the WR and RD pins are
enabled.
RD This is the read control input. When a logic low
is applied to this pin the digital outputs are
enabled and the INT output is reset high.
WR This is the write control input. The rising edge
of the signal applied to this pin selects the
multiplexer channel and initiates a conversion.
INT This is the interrupt output. A logic low at this
output indicates the completion of a conver-
sion.
CLK This is the clock input. The clock frequency
directly controls the duration of the conversion
time (for example, in the 10-bit bipolar mode
t
C
= 22/f
CLK
) and the acquisition time (t
A
=
6/f
CLK
).
DB0(MA0)
–DB7 (L/R) These are the digital data inputs/outputs. DB0
is the least significant bit of the digital output
word; DB7 is the most significant bit in the
digital output word (see the Output Data Con-
figuration table). MA0 through MA4 are the
digital inputs for the multiplexer channel selec-
tion (see the Multiplexer Addressing tables).
U/S (Unsigned/Signed), 8/10, (8/10-bit resolu-
tion) and L/R (Left/Right justification) are the
digital input bits that set the A/D’s output word
format and resolution (see the Output Data
Configuration table). The conversion time is
modified by the chosen resolution (see Electri-
cal AC Characteristics table). The lower the
resolution, the faster the conversion will be.
CH0–CH7 These are the analog input multiplexer chan-
nels. They can be configured as single-ended
inputs, differential input pairs, or
pseudo-differential inputs (see the Multiplexer
Addressing tables for the input polarity
assignments).
Dual-in-Line and SO Packages
DS011225-2
Top View
Order Number ADC10154
NS Package Number M24B
Dual-in-Line and SO Packages
DS011225-3
Top View
Order Number ADC10158
NS Package Numbers
M28B or N28B
ADC10154/ADC10158
www.national.com 2
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.
Positive Supply Voltage
(V
+
=AV
+
=DV
+
) 6.5V
Negative Supply Voltage (V
−
) −6.5V
Total Supply Voltage (V
+
−V
−
) 13V
Total Reference Voltage
(V
REF+
−V
REF−
) 6.6V
Voltage at Inputs and
Outputs V
−
− 0.3V to V
+
+ 0.3V
Input Current at Any Pin (Note 4) ±5mA
Package Input Current (Note 4) ±20 mA
Package Dissipation at
T
A
= 25˚C (Note 5) 500 mW
ESD Susceptibility (Note 6) 2000V
Soldering Information
N Packages (10 Sec) 260˚C
J Packages (10 Sec) 300˚C
SO Package (Note 7):
Vapor Phase (60 Sec) 215˚C
Infrared (15 Sec) 220˚C
Storage Temperature
Ceramic DIP Packages
Plastic DIP and SO Packages −65˚C to +150˚C
−40˚C to +150˚C
Operating Ratings (Notes 2, 3)
Temperature Range T
MIN
≤T
A
≤T
MAX
ADC10154CIWM,
ADC10158CIN,
ADC10158CIWM −40˚C ≤T
A
≤+85˚C
Positive Supply
Voltage
(V
+
=AV
+
=DV
+
) 4.5 V
DC
to 5.5 V
DC
Unipolar Negative
Supply Voltage
(V
−
) DGND
Bipolar Negative
Supply Voltage
(V
−
) −4.5V to −5.5V
V
+
−V
−
11V
V
REF+
AV
+
+ 0.05 V
DC
to V
−
− 0.05 V
DC
V
REF−
AV
+
+ 0.05 V
DC
to V
−
− 0.05 V
DC
V
REF
(V
REF+
−V
REF−
) 0.5 V
DC
to V
+
Electrical Characteristics
The following specifications apply for V
+
=AV
+
=DV
+
= + 5.0 V
DC
,V
REF+
= 5.000 V
DC
,V
REF−
= GND, V
−
= GND for unipolar
operation or V
−
= −5.0 V
DC
for bipolar operation, and f
CLK
= 5.0 MHz unless otherwise specified. Boldface limits apply for T
A
=T
J
=T
MIN
to T
MAX
;all other limits T
A
=T
J
= 25˚C. (Notes 8, 9, 12)
Symbol Parameter Conditions Typical
(Note 10) CIN and CIWM Units
(Limit)
Suffixes
Limits
(Note 11)
UNIPOLAR CONVERTER AND MULTIPLEXER STATIC CHARACTERISTICS
Resolution 10 + Sign Bits
Unipolar Integral V
REF+
= 2.5V ±0.5 LSB
Linearity Error V
REF+
= 5.0V ±1LSB (Max)
Unipolar Full-Scale Error V
REF+
= 2.5V ±0.5 LSB
V
REF+
= 5.0V ±1.5 LSB (Max)
Unipolar Offset Error V
REF+
= 2.5V ±1 LSB
V
REF+
= 5.0V ±2LSB (Max)
Unipolar Total Unadjusted V
REF+
= 2.5V ±1.5 LSB
Error (Note 13) V
REF+
= 5.0V ±2.5 LSB (Max)
Unipolar Power Supply V
+
= +5V ±10%
Sensitivity V
REF+
= 4.5V
Offset Error ±0.25 ±1LSB (Max)
Full-Scale Error ±0.25 ±1LSB (Max)
Integral Linearity Error ±0.25 LSB
BIPOLAR CONVERTER AND MULTIPLEXER STATIC CHARACTERISTICS
Resolution 10 + Sign Bits
Bipolar Integral V
REF+
= 5.0V ±1LSB (Max)
Linearity Error
Bipolar Full-Scale Error V
REF+
= 5.0V ±1.25 LSB (Max)
ADC10154/ADC10158
www.national.com3
Electrical Characteristics (Continued)
The following specifications apply for V
+
=AV
+
=DV
+
= + 5.0 V
DC
,V
REF+
= 5.000 V
DC
,V
REF−
= GND, V
−
= GND for unipolar
operation or V
−
= −5.0 V
DC
for bipolar operation, and f
CLK
= 5.0 MHz unless otherwise specified. Boldface limits apply for T
A
=T
J
=T
MIN
to T
MAX
;all other limits T
A
=T
J
= 25˚C. (Notes 8, 9, 12)
Symbol Parameter Conditions Typical
(Note 10) CIN and CIWM Units
(Limit)
Suffixes
Limits
(Note 11)
BIPOLAR CONVERTER AND MULTIPLEXER STATIC CHARACTERISTICS
Bipolar Negative Full-Scale V
REF+
= 5.0V
Error with Positive-Full ±1.25 LSB (Max)
Scale Adjusted
Bipolar Offset Error V
REF+
= 5.0V ±2.5 LSB (Max)
Bipolar Total Unadjusted V
REF+
= 5.0V ±3LSB (Max)
Error (Note 13)
Bipolar Power Supply
Sensitivity Offset Error V
+
= +5V ±10% ±0.5 ±2.5 LSB (Max)
Full-Scale Error V
REF+
= 4.5V ±0.5 ±1.5 LSB (Max)
Integral Linearity Error ±0.25 LSB
Offset Error V
−
= −5V ±10% ±0.25 ±0.75 LSB (Max)
Full-Scale Error V
REF+
= 4.5V ±0.25 ±0.75 LSB (Max)
Integral Linearity Error ±0.25 LSB
UNIPOLAR AND BIPOLAR CONVERTER AND MULTIPLEXER STATIC CHARACTERISTICS
Missing Codes 0
DC Common Mode V
IN+
=V
IN−
Error (Note 14) = V
IN
where
Bipolar +5.0V ≥V
IN
≥−5.0V ±0.25 ±0.75 LSB (Max)
Unipolar +5.0V ≥V
IN
≥0V ±0.25 ±0.5 LSB (Max)
R
REF
Reference Input Resistance 7 4.5 kΩ(Max)
9.5 kΩ(Max)
C
REF
Reference Input Capacitance 70 pF
V
AI
Analog Input Voltage (V
+
+0.05) V (Max)
(V
−
−0.05) V (Min)
C
AI
Analog Input Capacitance 30 pF
Off Channel Leakage On Channel = 5V −400 −1000 nA (Max)
Current Off Channel = 0V
(Note 15) On Channel = 0V 400 1000 nA (Max)
Off Channel = 5V
Electrical Characteristics
The following specifications apply for V
+
=AV
+
=DV
+
= + 5.0 V
DC
,V
REF+
= 5.000 V
DC
,V
REF−
= GND, V
−
= GND for unipolar
operation or V
−
= −5.0 V
DC
for bipolar operation, and f
CLK
= 5.0 MHz unless otherwise specified. Boldface limits apply for T
A
=T
J
=T
MIN
to T
MAX
;all other limits T
A
=T
J
= 25˚C. (Notes 8, 9, 12)
Symbol Parameter Conditions Typical Limits
(Note 11) Units
(Limit)
(Note 10)
DYNAMIC CONVERTER AND MULTIPLEXER CHARACTERISTICS
S/(N+D) Unipolar Signal-to-Noise+ f
IN
= 10 kHz, V
IN
= 4.85 V
p–p
60 dB
Distortion Ratio f
IN
= 150 kHz, V
IN
= 4.85 V
p-p
58 dB
S/(N+D) Bipolar Signal-to-Noise+ f
IN
= 10 kHz, V
IN
=±4.85V 60 dB
Distortion Ratio f
IN
= 150 kHz, V
IN
=±4.85V 58 dB
ADC10154/ADC10158
www.national.com 4
Electrical Characteristics (Continued)
The following specifications apply for V
+
=AV
+
=DV
+
= + 5.0 V
DC
,V
REF+
= 5.000 V
DC
,V
REF−
= GND, V
−
= GND for unipolar
operation or V
−
= −5.0 V
DC
for bipolar operation, and f
CLK
= 5.0 MHz unless otherwise specified. Boldface limits apply for T
A
=T
J
=T
MIN
to T
MAX
;all other limits T
A
=T
J
= 25˚C. (Notes 8, 9, 12)
Symbol Parameter Conditions Typical Limits
(Note 11) Units
(Limit)
(Note 10)
DYNAMIC CONVERTER AND MULTIPLEXER CHARACTERISTICS
−3 dB Unipolar Full V
IN
= 4.85 V
p–p
200 kHz
Power Bandwidth
−3 dB Bipolar Full V
IN
=±4.85V 200 kHz
Power Bandwidth
REFERENCE CHARACTERISTICS (Unipolar Operation V
−
= GND Only)
VREFOut Reference Output Voltage 2.5 ±1% 2.5 ±2% V (Max)
∆V
REF
/∆t VREFOut Temperature Coefficient 40 ppm/˚C
∆V
REF
/∆I
L
Load Regulation Sourcing 0 mA ≤I
L
≤+4 mA 0.003 0.1 %/mA (Max)
Sinking 0 mA ≥I
L
≥−1 mA 0.2 0.6 %/mA (Max)
Line Regulation 4.5V ≤V
+
≤5.5V 0.5 6mV (Max)
I
SC
Short Circuit Current VREFOut = 0V 14 25 mA (Max)
∆V
REF
/∆t Long-Term Stability 200 ppm/1 kHr
t
SU
Start-Up Time C
L
= 330 µF 20 ms
DIGITAL AND DC CHARACTERISTICS
V
IN(1)
Logical “1” Input Voltage V
+
= 5.5V 2.0 V (Min)
V
IN(0)
Logical “0” Input Voltage V
+
= 4.5V 0.8 V (Max)
I
IN(1)
Logical “1” Input Current V
IN
= 5.0V 0.005 2.5 µA (Max)
I
IN(0)
Logical “0” Input Current V
IN
= 0V −0.005 −2.5 µA (Max)
V
OUT(1)
Logical “1” Output Voltage V
+
= 4.5V: I
OUT
= −360 µA 2.4 V (Min)
I
OUT
= −10 µA 4.25 V (Min)
V
OUT(0)
Logical “0” Output Voltage V
+
= 4.5V 0.4 V (Max)
I
OUT
= 1.6 mA
I
OUT
TRI-STATE Output Current V
OUT
= 0V −0.01 −3 µA (Max)
V
OUT
= 5V 0.01 3µA (Max)
+I
SC
Output Short Circuit Source Current V
OUT
= 0V −40 −10 mA (Min)
−I
SC
Output Short Circuit V
OUT
=DV
+
30 10 mA (Min)
Sink Current
DI+ Digital Supply Current CS = HIGH 0.75 2mA (Max)
CS = HIGH, f
CLK
=0Hz 0.15 mA (Max)
AI
+
Analog Supply Current CS = HIGH 3 4.5 mA (Max)
CS = HIGH, f
CLK
=0Hz 3 mA (Max)
I
−
Negative Supply Current CS = HIGH 3.5 4.5 mA (Max)
CS = HIGH, f
CLK
=0Hz 3.5 mA (Max)
I
REF
Reference Input Current V
REF+
= 5V 0.7 1.1 mA (Max)
ADC10154/ADC10158
www.national.com5
Electrical Characteristics
The following specifications apply for V
+
=AV
+
=DV
+
= + 5.0 V
DC
,V
REF+
= 5.000 V
DC
,V
REF−
= GND, V
−
= GND for unipolar
operation or V
−
= −5.0 V
DC
for bipolar operation, and f
CLK
= 5.0 MHz unless otherwise specified. Boldface limits apply for T
A
=T
J
=T
MIN
to T
MAX
;all other limits T
A
=T
J
= 25˚C. (Note 16)
Symbol Parameter Conditions Typical Limits
(Note 11) Units
(Limit)
(Note 10)
AC CHARACTERISTICS
f
CLK
Clock Frequency 8 5.0 MHz (Max)
10 kHz (Min)
Clock Duty Cycle 20 % (Min)
80 % (Max)
t
C
Conversion 8-Bit Unipolar Mode 16 1/f
CLK
Time f
CLK
= 5.0 MHz 3.2 µs (Max)
8-Bit Bipolar Mode 18 1/f
CLK
f
CLK
= 5.0 MHz 3.6 µs (Max)
10-Bit Unipolar Mode 20 1/f
CLK
f
CLK
= 5.0 MHz 4.0 µs (Max)
10-Bit Bipolar Mode 22 1/f
CLK
f
CLK
= 5.0 MHz 4.4 µs (Max)
t
A
Acquisition Time 61/f
CLK
f
CLK
= 5.0 MHz 1.2 µs
t
CR
Delay between Falling Edge of 0 5ns (Min)
CS and Falling Edge of RD
t
RC
Delay betwee Rising Edge 0 5ns (Min)
RD and Rising Edge of CS
t
CW
Delay between Falling Edge 0 5ns (Min)
of CS and Falling Edge of WR
t
WC
Delay between Rising Edge 0 5ns (Min)
of WR and Rising Edge of CS
t
RW
Delay between Falling Edge 0 5ns (Min)
of RD and Falling Edge of WR
t
W(WR)
WR Pulse Width 25 50 ns (Min)
t
WS
WR High to CLK÷2 Low Set-Up Time 5ns (Max)
t
DS
Data Set-Up Time 6 15 ns (Max)
t
DH
Data Hold Time 0 5ns (Max)
t
WR
Delay from Rising Edge 0 5ns (Min)
of WR to Rising Edge RD
t
ACC
Access Time (Delay from Falling C
L
= 100 pF 25 45 ns (Max)
Edge of RD to Output Data Valid)
t
WI
,t
RI
Delay from Falling Edge C
L
= 100 pF 25 40 ns (Max)
of WR or RD to Reset of INT
t
INTL
Delay from Falling Edge of CLK÷2 to
Falling Edge of INT 40 ns
t
1H
,t
0H
TRI-STATE Control (Delay from C
L
= 10 pF, R
L
=1kΩ20 35 ns (Max)
Rising Edge of RD to Hi-Z State)
t
RR
Delay between Successive 25 50 ns (Min)
RD Pulses
t
P
Delay between Last Rising Edge
of RD and the Next Falling 20 50 ns (Min)
Edge of WR
C
IN
Capacitance of Logic Inputs 5 pF
C
OUT
Capacitance of Logic Outputs 5 pF
ADC10154/ADC10158
www.national.com 6
Electrical Characteristics (Continued)
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, 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 3: All voltages are measured with respect to GND, unless otherwise specified.
Note 4: When the input voltage (VIN) at any pin exceeds the power supplies (VIN <V−or VIN >AV+or DV+), 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.
Note 5: 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=(T
Jmax −T
A
)/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:ADC10154 with BIN and CIN suffixes 65˚C/W, ADC10154 with BIJ,
CIJ and CMJ suffixes 49˚C/W, ADC10154 with BIWM and CIWM suffixes 72˚C/W, ADC10158 with BIN and CIN suffixes 59˚C/W, ADC10158 with BIJ, CIJ, and CMJ
suffixes 46˚C/W, ADC10158 with BIWM and CIWM suffixes 68˚C/W.
Note 6: Human body model, 100 pF capacitor discharged through a 1.5 kΩresistor.
Note 7: See AN-450 “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.
Note 8: Two on-chip diodes are tied to each analog input as shown below. They will forward-conduct for analog input voltages one diode drop below V−supply or
one diode drop greater than V+supply. Be careful during testing at low V+levels (4.5V), as high level analog inputs (5V) can cause an input diode to conduct,
especially at elevated temperatures, which 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 VIN 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. This means that if AV+and DV+are minimum (4.5 VDC) and V−is a maximum (−4.5 VDC) full scale must be
≤±4.55 VDC.
Note 9: A diode exists between AV+and DV+as shown below.
Note 10: Typicals are at TJ=T
A= 25˚C and represent most likely parametric norm.
Note 11: Tested limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 12: One LSB is referenced to 10 bits of resolution.
Note 13: Total unadjusted error includes offset, full-scale, linearity, multiplexer, and hold step errors.
Note 14: For DC Common Mode Error the only specification that is measured is offset error.
Note 15: Channel leakage current is measured after the channel selection.
Note 16: All the timing specifications are tested at the TTL logic levels, VIL = 0.8V for a falling edge and VIH = 2.0V for a rising.
DS011225-4
DS011225-5
To guarantee accuracy, it is required that the AV+and DV+be connected together to a power supply with separate bypass filter at each V+pin.
ADC10154/ADC10158
www.national.com7
Electrical Characteristics (Continued)
Ordering Information
Industrial −40˚C ≤T
A
≤85˚C Package
ADC10154CIWM M24B
ADC10158CIN N28B
ADC10158CIWM M28B
DS011225-6
FIGURE 1. Transfer Characteristic
DS011225-7
FIGURE 2. Simplified Error Curve vs Output Code
ADC10154/ADC10158
www.national.com 8
Typical Converter Performance Characteristics
Total Positive Supply
Current (DI
+
+AI
+
)
vs Temperature
DS011225-27
Total Positive Power
Supply Current (DI
+
+AI
+
)
vs Clock Frequency
DS011225-28
Offset Error
vs Temperature
DS011225-29
Offset Error vs
Reference Voltage
DS011225-30
Linearity Error
vs Temperature
DS011225-31
Linearity Error vs
Reference Voltage
DS011225-32
Linearity Error vs
Clock Frequency
DS011225-33
Spectral Response with
50 kHz Sine Wave
DS011225-34
10-Bit Unsigned
Signal-to-Noise + THD Ratio
vs Input Signal Level
DS011225-35
ADC10154/ADC10158
www.national.com9
Typical Reference Performance Characteristics
Leakage Current Test Circuit
Load Regulation
DS011225-36
Line Regulation
(3 Typical Parts)
DS011225-37
Output Drift
vs Temperature
(3 Typical Parts)
DS011225-38
Available
Output Current
vs Supply Voltage
DS011225-39
DS011225-10
ADC10154/ADC10158
www.national.com 10
TRI-STATE Test Circuits and Waveforms
Timing Diagrams
DS011225-11
DS011225-12
DS011225-13
DS011225-14
DS011225-15
DIAGRAM 1. Starting a Conversion with New MUX Channel and Output Configuration
ADC10154/ADC10158
www.national.com11
Timing Diagrams (Continued)
DS011225-16
DIAGRAM 2. Starting a Conversion without Changing the MUX Channel or Output Configuration
DS011225-17
DIAGRAM 3. Reading the Conversion Result
ADC10154/ADC10158
www.national.com 12
Multiplexer Addressing and Output Data Configuration Tables
TABLE 1. ADC10154 and ADC10158 Output Data Configuration
Output
Data Format Control Input Data Bus Output Assignment
Resolution Data
8/10 U/S L/R DB7 DB6 DB5 DB4 DB3 DB2 DB1 DB0
10-Bits + Sign Right-Justified L L L Sign Sign Sign Sign Sign Sign MSB 9 First Byte Read
8765432LSBSecond Byte Read
10-Bits + Sign Left-Justified L L H Sign MSB 987654First Byte Read
32LSBLLLLLSecond Byte Read
10-Bits Right-Justified L H L LLLLLLMSB9First Byte Read
8765432LSBSecond Byte Read
10-Bits Left-Justified L H H MSB 9876543First Byte Read
2LSBLLLLLLSecond Byte Read
8-Bits + Sign Right-Justified H L L Sign Sign Sign Sign Sign Sign Sign Sign First Byte Read
MSB765432LSBSecond Byte Read
8-Bits + Sign Left-Justified H L H Sign MSB 765432First Byte Read
LSBLLLLLLLSecond Byte Read
8-Bits Right-Justified H H L LLLLLLLLFirst Byte Read
MSB765432LSBSecond Byte Read
8-Bits Left-Justified H H H MSB 765432LSBFirst Byte Read
LLLLLLLLSecond Byte Read
TABLE 2. ADC10158 Multiplexer Addressing
MUX Address CS WR RD Channel Number MUX
Mode
MA4 MA3 MA2 MA1 MA0 CH0 CH1 CH2 CH3 CH4 CH5 CH6 CH7 V
REF−
XLLLLL H+−
XLLLHL H−+
XLLHLL H +−
XLLHHL
L
H − + Differential
XLHLLL H +−
XLHLHL H −+
XLHHLL H +−
XLHHHL H −+
LHLLLL H+ −
LHLLHL H + −
LHLHLL H + −
LHLHHL
L
H + − Single-Ended
LHHLLL H + −
LHHLHL H + −
LHHHLL H + −
LHHHHL H + −
HHLLLL H+ −
HHLLHL H + −
HHLHLL H + −
HHLHHL
L
H + − Pseudo-Differential
HHHLLL H + −
HHHLHL H + −
HHHHLL H +−
XXXXXL
L
L Previous Channel Configuration
ADC10154/ADC10158
www.national.com13
Multiplexer Addressing and Output Data Configuration Tables (Continued)
TABLE 3. ADC10154 Multiplexer Addressing
MUX Address CS WR RD Channel Number MUX
Mode
MA4 MA3 MA2 MA1 MA0 CH0 CH1 CH2 CH3 V
REF−
XXLLLL H+−
XXLLHL
L
H − + Differential
XXLHLL H +−
XXLHHL H −+
XLHLLL H+ −
XLHLHL
L
H + − Single-Ended
XLHHLL H + −
XLHHHL H + −
XHHLLL H+ −
XHHLHL
L
H + − Pseudo-Differential
XHHHLL H +−
XXXXXL
L
L Previous Channel Configuration
ADC10154/ADC10158
www.national.com 14
Detailed Block Diagram
DS011225-18
ADC10154/ADC10158
www.national.com15
1.0 Functional Description
The ADC10154 and ADC10158 use successive approxima-
tion to digitize an analog input voltage. Additional logic has
been incorporated in the devices to allow for the program-
mability of the resolution, conversion time and digital output
format.Acapacitive array and a resistive ladder structure are
used in the DAC portion of the A/D converters. The structure
of the DAC allows a very simple switching scheme to provide
a very versatile analog input multiplexer. Also, inherent in
this structure is a sample/hold. A 2.5V CMOS band-gap
reference is also provided on the ADC10154 and
ADC10158.
1.1 DIGITAL INTERFACE
The ADC10154 and ADC10158 have eight digital outputs
(DB0–DB8) and can be easily interfaced to an 8-bit data bus.
Taking CS and WR low simultaneously will strobe the data
word on the data-bus into the input latch. This word will be
decoded to determine the multiplexer channel selection, the
A/D conversion resolution and the output data format. The
following table shows the input word data-bit assignment.
DB0 through DB4 are assigned to the multiplexer address
data bits zero through four (MA0–MA4).
Tables 2, 3
describe
the multiplexer address assignment. DB5 selects unsigned
or signed (U/S) operation. DB6 selects 8- or 10-bit resolu-
tion. DB7 selects left or right justification of the output data.
Refer to
Table 1
for the effect the Control Input Data has on
the digital output word.
The conversion process is started by the rising edge of WR,
which sets the “start conversion” bit inside theADC. If this bit
is set, the converter will start acquiring the input voltage on
the next falling edge of the internal CLK÷2 signal. The ac-
quisition period is 3 CLK÷2 periods, or 6 CLK periods. Im-
mediately after the acquisition period the input signal is held
and the actual conversion begins. The number of clocks
required for a conversion is given in the following table:
Conversion Type CLK÷2 CLK
Cycles Cycles (N)
8-Bit 8 16
8-Bit + Sign 9 18
10-Bit 10 20
10-Bit + Sign 11 22
Since the CLK÷2 signal is internal to the ADC, it is initially
impossible to know which falling edge of CLK corresponds to
the falling edge of CLK÷2. For the first conversion, the rising
edge of WR should occur at least t
WS
ns before any falling
edge of CLK. If this edge happens to be on the rising edge of
CLK÷2, this will add 2 CLK cycles to the total conversion
time. The phase of the CLK÷2 signal can be determined at
the end of the first conversion, when INT goes low. INT
always goes low on the falling edge of the CLK÷2 signal.
From the first falling edge of INT onward, every other falling
edge of CLK will correspond to the falling edge of CLK÷2.
With the phase of CLK÷2 now known, the conversion time
can be minimized by taking WR high at least t
WS
ns before
the falling edge of CLK÷2.
Upon completion of the conversion, INT goes low to signal
theA/D conversion result is ready to be read. Taking CS and
RD low will enable the digital output buffer and put byte 1 of
the conversion result on DB0 through DB7. The falling edge
of RD resets the INT output high. Taking CS and RD low a
second time will put byte 2 of the conversion result on
DB7–DB0.
Table 1
defines the DB0–DB7 assignment for
different Control Input Data. The second read does not have
to be completed before a new conversion is started.
Taking CS, WR and RD low simultaneously will start a con-
version without changing the multiplexer channel assign-
ment or output configuration and resolution. The timing dia-
gram in
Figure 3
shows the sequence of events that
implement this function. Refer to Diagrams 1, 2, and 3 in the
Timing Diagrams section for the timing constraints that must
be met.
DS011225-44
DS011225-19
FIGURE 3. Starting a Conversion without Updating the Channel Configuration, Resolution, or Data Format
ADC10154/ADC10158
www.national.com 16
1.0 Functional Description (Continued)
Digital Interface Hints:
•Reads and writes can be completely asynchronous to
CLK.
•In addition to the timing indicated in Diagrams 1–3, CS
can be tied low permanently or taken low for entire
conversions, eliminating all the CS guardbands (t
CR
,t
RC
,
t
CW
,t
WC
).
•If CS is used as shown in Diagrams 1–-3, the CS guard-
bands (t
CR
,t
RC
,t
CW
,t
WC
) between CS and the RD and
WR signals can safely be ignored as long as the follow-
ing two conditions are met:
1) When initiating a write, CS and WR must be simulta-
neously low for at least t
W(WR)
ns (see Diagram 1). The
“start” conversion” bit will be set on the rising edge of WR
or CS, whichever is first.
2) When reading data, understand that data will not be valid
until t
ACC
ns after
both
CS and RD go low. The output
data will enter TRI-STATE t
1H
ns or t
0H
ns after
either
CS
or RD goes high (see Diagrams 2 and 3).
1.2 ARCHITECTURE
Before a conversion is started, during the analog input sam-
pling period, the sampled data comparator is zeroed. As the
comparator is being zeroed the channel assigned to be the
positive input is connected to the A/D’s input capacitor. (See
the Digital Interface section for a description of the assign-
ment procedure.) This charges the input 32C capacitor of the
DAC to the positive analog input voltage. The switches
shown in the DAC portion of the detailed block diagram are
set for this zeroing/acquisition period. The voltage at the
input and output of the comparator are at equilibrium at this
point in time. When the conversion is started the comparator
feedback switches are opened and the 32C input capacitor
is then switched to the assigned negative input voltage.
When the comparator feedback switch opens a fixed amount
of charge is trapped on the common plates of the capacitors.
The voltage at the input of the comparator moves away from
equilibrium when the 32C capacitor is switched to the as-
signed negative input voltage, causing the output of the
comparator to go high (“1”) or low (“0”). The SAR next goes
through an algorithm, controlled by the output state of the
comparator, that redistributes the charge on the capacitor
array by switching the voltage on one side of the capacitors
in the array. The objective of the SAR algorithm is to return
the voltage at the input of the comparator as close as pos-
sible to equilibrium.
The switch position information at the completion of the
successive approximation routine is a direct representation
of the digital output. This information is then manipulated by
the Digital Output decoder to the programmed format. The
reformatted data is then available to be strobed onto the data
bus (DB0–DB7) via the digital output buffers by taking CS
and RD low.
2.0 Applications Information
2.1 MULTIPLEXER CONFIGURATION
The design of these converters utilizes a sampled-data com-
parator structure which allows a differential analog input to
be converted by the successive approximation routine.
The actual voltage converted is always the difference be-
tween an assigned “+” input terminal and a “−” input terminal.
The polarity of each input terminal or pair of input terminals
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 when configured for unsigned operation. When config-
ured for signed operation the A/D responds with the appro-
priate output digital code.
A unique input multiplexing scheme has been utilized to
provide multiple analog channels. The input channels can be
software configured into three modes: differential,
single-ended, or pseudo-differential.
Figure 4
shows the
three modes using the 4-channel MUX of the ADC10154.
The eight inputs of the ADC10158 can also be configured in
any of the three modes. The single-ended mode has
CH0–CH3 assigned as the positive input with the negative
input being the V
REF−
of the device. In the differential mode,
the ADC10154 channel inputs are grouped in pairs, CH0
with CH1 and CH2 with CH3. The polarity assignment of
each channel in the pair is interchangeable. Finally, in the
pseudo-differential mode CH0–CH2 are positive inputs re-
ferred to CH3 which is now a pseudo-ground. This
pseudo-ground input can be set to any potential within the
input common-mode range of the converter. The analog
signal conditioning required in transducer-based data acqui-
sition systems is significantly simplified with this type of input
flexibility. One converter package can now handle
ground-referred inputs and true differential inputs as well as
signals referred to a specific voltage.
The analog input voltages for each channel can range from
50 mV below V
−
(typically ground for unipolar operation or
−5V for bipolar operation) to 50 mV above V
+
=DV
+
=AV
+
(typically 5V) without degrading conversion accuracy. If the
voltage on an unselected channel exceeds these limits it
may corrupt the reading of the selected channel.
ADC10154/ADC10158
www.national.com17
2.0 Applications Information (Continued)
2.2 REFERENCE CONSIDERATIONS
The voltage difference between the V
REF+
and V
REF
− inputs
defines the analog input voltage span (the difference be-
tween V
IN
(Max) and V
IN
(Min)) over which the 2
n
(where n is
the programmed resolution) possible output codes apply. In
the pseudo-differential and differential modes the actual volt-
age applied to V
REF+
and V
REF−
can lie anywhere between
theAV
+
and V
−
. Only the difference voltage is of importance.
When using the single-ended multiplexer mode the voltage
at V
REF−
has a dual function. It simultaneously determines
the “zero” reference voltage and, with V
REF+
, the analog
voltage span.
The value of the voltage on the V
REF+
or V
REF−
inputs can be
anywhere betweenAV
+
+ 50 mV and V
−
− 50 mV, so long as
V
REF+
is greater than V
REF−
. TheADC10154 andADC10158
can be used in either ratiometric applications or in systems
requiring absolute accuracy. The reference pins must be
connected to a voltage source capable of driving the mini-
mum reference input resistance of 4.5 kΩ.
The internal 2.5V bandgap reference in the ADC10154 and
ADC10158 is available as an output on the VREFOut pin. To
ensure optimum performance this output needs to be by-
passed to ground with 330 µF aluminum electrolytic or tan-
talum capacitor. The reference output is unstable with ca-
pacitive loads greater than 100 pF and less than 100 µF.Any
capacitive loads ≤100 pF or ≥100 µF will not cause the
reference to oscillate. Lower output noise can be obtained by
increasing the output capacitance. The 330 µF capacitor will
yield a typical noise floor of 200 nVrms/ .
The 2.5V reference output is referred to the negative supply
pin (V
−
). Therefore, the voltage at VREFOut will always be
2.5V greater than the voltage applied to V
−
.Applying this
voltage to V
REF+
with V
REF−
tied to V
−
will yield an analog
voltage span of 2.5V. In bipolar operation the voltage at
VREFOut will be at −2.5V when V
−
is tied to −5V. For the
single-ended multiplexer mode the analog input voltage
range will be from −5V to −2.5V. The pseudo-differential and
differential multiplexer modes allow for more flexibility in the
analog input voltage range since the “zero” reference volt-
age is set by the actual voltage applied to the assigned
negative input pin. The drawback of using the internal refer-
ence in the bipolar mode is that any noise on the −5V tied to
the V
−
pin will affect the conversion result. The bandgap
reference is specified and tested in unipolar operation with
V
−
tied to the system ground.
In a ratiometric system (
Figure 5
(a)), the analog input volt-
age is proportional to the voltage used for theA/D reference.
This voltage may also be the system power supply, so V
REF+
can also be tied to AV
+
. This technique relaxes the stablity
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 (
Figure 5
(b)), where the analog input
varies between very specific voltage limits, the reference pin
can be biased with a time- and temperature-stable voltage
source that has excellent initial accuracy. The LM4040 and
LM185 references are suitable for use with the ADC10154
and ADC10158.
4 Single-Ended
DS011225-40
2 Differential
DS011225-41
3 Pseudo-Differential
DS011225-42
2 Single Ended and 1 Differential
DS011225-43
FIGURE 4. Analog Input Multiplexer Options
ADC10154/ADC10158
www.national.com 18
2.0 Applications Information (Continued)
The minimum value of V
REF
(V
REF
=V
REF+
−V
REF−
) can be
quite small (see Typical Performance Characteristics) to al-
low direct conversion 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 volt-
age sources when operating with a reduced span due to the
increased sensitivity of the converter (1 LSB equals V
REF
/
2
n
).
2.3 THE ANALOG INPUTS
Due to the sampling nature of the analog inputs, at the clock
edges short duration spikes of current will be seen on the
selected assigned negative input. Input bypass capacitors
should not be used if the source resistance is greater than
1kΩsince they will average the AC current and cause an
effective DC current to flow through the analog input source
resistance. An op amp RC active lowpass filter can provide
both impedance buffering and noise filtering should a high
impedance signal source be required. Bypass capacitors
may be used when the source impedance is very low without
any degradation in performance.
In a true differential input stage, a signal that is common to
both “+” and “−” inputs is cancelled. For the ADC10154 and
ADC10158, the positive input of a selected channel pair is
only sampled once before the start of a conversion during
the acquisition time (t
A
). The negative input needs to be
stable during the complete conversion sequence because it
is sampled before each decision in the SAR sequence.
Therefore, any AC common-mode signal present on the
analog inputs will not be completely cancelled and will cause
some conversion errors. For a sinusoid common-mode sig-
nal this error is:
V
error
(Max) = V
PEAK
(2πf
CM
)(t
C
)
where f
CM
is the frequency of the common-mode signal,
V
PEAK
is its peak voltage value, and t
C
is theA/D’s maximum
conversion time (t
C
= 22/f
CLK
for 10-bit plus sign resolution).
For example, for a 60 Hz common-mode signal to generate
a
1
⁄
4
LSB error (1.24 mV) with a 4.5 µs conversion time, its
peak value would have to be approximately 731 mV.
2.4 OPTIONAL ADJUSTMENTS
2.4.1 Zero Error
The zero error of the A/D converter relates to the location of
the first riser of the transfer function (see
Figure 1
) and can
be measured by grounding the minus input and applying a
small magnitude positive or negative voltage to the plus
input. Zero error is the difference between actual DC input
DS011225-21
a. Ratiometric Using the Internal Reference
DS011225-22
b. Absolute Using a 4.096V Span
FIGURE 5. Different Reference Configurations
ADC10154/ADC10158
www.national.com19
2.0 Applications Information
(Continued)
voltage which is necessary to just cause an output digital
code transition from 000 0000 0000 to 000 0000 0001
(10-bits plus sign) and the ideal
1
⁄
2
LSB value (
1
⁄
2
LSB = 2.44
mV for V
REF
= + 5.000V and 10-bit plus sign resolution).
The zero error of the A/D does not require adjustment. If the
minimum analog input voltage value, V
IN
(Min), is not ground,
the effetive “zero” voltage can be adjusted to a convenient
value. The converter can be made to output an all zeros
digital code for this minimum input voltage by biasing any
minus input to V
IN
(Min). This is useful for either the differen-
tial or pseudo-differential input channel configurations.
2.4.2 Full-Scale
The full-scale adjustment can be made by applying a differ-
ential input voltage which is 1
1
⁄
2
LSB down from the desired
analog full-scale voltage range and then adjusting the V
REF
voltage (V
REF
=V
REF+
−V
REF−
) for a digital output code
changing from 011 1111 1110 to 011 1111 1111. In bipolar
signed operation this only adjusts the positive full scale error.
The negative full-scale error will be as specified in the Elec-
trical Characteristics after a positive full-scale adjustment.
2.4.3 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 plus input voltage which
equals this desired zero reference plus
1
⁄
2
LSB (where the
LSB is calculated for the desired analog span, using 1 LSB =
analog span/2
n
, n being the programmed resolution) is ap-
plied to selected plus input and the zero reference voltage at
the corresponding minus input should then be adjusted to
just obtain the 000
HEX
to 001
HEX
code transition.
The full-scale adjustment should be made [with the proper
minus input voltage applied] by forcing a voltage to the plus
input which is given by:
where V
MAX
equals the high end of the ananlog input range,
V
MIN
equals the low end (the offset zero) of the analog range
and n equals the programmed resolution. Both V
MAX
and
V
MIN
are ground referred. The V
REF
(V
REF
=V
REF+
−V
REF−
)
voltage is then adjusted to provide a code change from
3FE
HEX
to 3FF
HEX
. Note, when using a pseudo-differential
or differential multiplexer mode where V
REF+
and V
REF
− are
placed within the V
+
and V
−
range, the individual values of
V
REF+
and V
REF−
do not matter, only the difference sets the
analog input voltage span. This completes the adjustment
procedure.
2.5 INPUT SAMPLE-AND-HOLD
The ADC10154/8’s sample/hold capacitor is implemented in
the capacitor array. After the channel address is loaded, the
array is switched to sample the selected positive analog
input. The rising edge of WR loads the multiplexer address-
ing information. The sampling period for the assigned posi-
tive input is maintained for the duration of the acquisition
time (t
A
), i.e., approximately 6 to 8 clock cycles after the
rising edge of WR.
An acquisition window of 6 clock cycles is available to allow
the voltage on the capacitor array to settle to the positive
analog input voltage. Any change in the analog voltage on a
selected positive input before or after the acquisition window
will not effect the A/D conversion result.
In the simplest case, the array’s acquisition time is deter-
mined by the R
ON
(9 kΩ) of the multiplexer switches, the
stray input capacitance C
S1
(3.5 pF) and the total array (C
L
)
and stray (C
S2
) capacitance (C
L
+C
S2
= 48 pF). For a large
source resistance the analog input can be modeled as an
RC network as shown in
Figure 6
. The values shown yield an
acquisition time of about 1.1 µs for 10-bit unipolar or 10-bit
plus sign bipolar accuracy with a zero-to-full-scale change in
the input voltage. External source resistance and capaci-
tance will lengthen the acquisition time and should be ac-
counted for. Slowing the clock will lengthen the acquisition
time, thereby allowing a larger external source resistance.
The curve “Signal to Noise Ratio vs. Output Frequency”
(
Figure 7
) gives an indication of the usable bandwidth of the
ADC10154/ADC10158. The signal-to-noise ratio of an ideal
A/D is the ratio of the RMS value of the full scale input signal
amplitude to the value of the total error amplitude (including
noise) caused by the transfer function of the A/D. An ideal
10-bit plus signA/D converter with a total unadjusted error of
0 LSB would have a signal-to-noise ratio of about 68 dB,
which can be derived from the equation:
S/N = 6.02(n) + 1.76
where S/N is in dB and n is the number of bits.
Figure 3
shows the signal-to-noise ratio vs. input frequency of a typi-
cal ADC10154/ADC10158 with
1
⁄
2
LSB total unadjusted er-
ror. The dotted lines show signal-to-noise ratios for an ideal
(noiseless) 10-bit A/D with 0 LSB error and an A/D with a 1
LSB error.
DS011225-23
FIGURE 6. Analog Input Model
SNR vs Input Frequency
DS011225-24
FIGURE 7. ADC10154/ADC10158
Signal-to-Noise Ratio vs Input Frequency
ADC10154/ADC10158
www.national.com 20
2.0 Applications Information
(Continued)
The sample-and-hold error specifications are included in the
error and timing specifications of the A/D. The hold step and
gain error sample/hold specs are included in theADC10154/
ADC10158’s total unadjusted, linearity, gain and offset error
specifications, while the hold settling time is included in the
A/D’s maximum conversion time specification. The hold
droop rate can be thought of as being zero since an unlim-
ited amount of time can pass between a conversion and the
reading of data. The data is lost after a new conversion has
been completed.
Protecting the Analog Inputs
DS011225-25
Diodes are 1N914.
The protection diodes should be able to withstand the output current of the op amp under current limit.
Zero-Shift and Span-Adjust for Signed or Unsigned, Unipolar, Single-Ended
Multiplexer Assignment, Analog Input Range of 2V ≤V
IN
≤4.5V
DS011225-26
*1% resistors
ADC10154/ADC10158
www.national.com21
Physical Dimensions inches (millimeters) unless otherwise noted
Dual-In-Line Package (M)
Order Number ADC10154CIWM
NS Package Number M24B
Dual-In-Line Package (M)
Order Number ADC10158CIWM
NS Package Number M28B
ADC10154/ADC10158
www.national.com 22
Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
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into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
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www.national.com
Dual-In-Line Package (N)
Order Number ADC10158BIN or ADC10158CIN
NS Package Number N28B
ADC10154/ADC10158 10-Bit Plus Sign 4 µs ADCs with 4- or 8-Channel MUX, Track/Hold and
Reference
National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
