Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
555
August 31, 1994 853-0034 13721
DESCRIPTION
The ADC0803 family is a series of three CMOS 8-bit successive
approximation A/D converters using a resistive ladder and
capacitive array together with an auto-zero comparator. These
converters are designed to operate with microprocessor-controlled
buses using a minimum of external circuitry. The 3-State output data
lines can be connected directly to the data bus.
The differential analog voltage input allows for increased
common-mode rejection and provides a means to adjust the
zero-scale offset. Additionally, the voltage reference input provides a
means of encoding small analog voltages to the full 8 bits of
resolution.
FEATURES
•Compatible with most microprocessors
•Differential inputs
•3-State outputs
•Logic levels TTL and MOS compatible
•Can be used with internal or external clock
•Analog input range 0V to VCC
•Single 5V supply
•Guaranteed specification with 1MHz clock
PIN CONFIGURATION
1
2
3
4
5
6
7
8
9
10 11
12
13
14
20
19
18
17
16
15
D1, N PACKAGES
CS
RD
WR
INTR
CLK IN
VIN(+)
VIN(–)
A GND
VREF/2
D GND
VCC
CLK R
D0
D1
D2
D3
D4
D5
D6
D7
TOP VIEW
NOTE:
SOL — Released in large SO package only.
APPLICATIONS
•Transducer-to-microprocessor interface
•Digital thermometer
•Digitally-controlled thermostat
•Microprocessor-based monitoring and control systems
ORDERING INFORMATION
DESCRIPTION
TEMPERATURE RANGE ORDER CODE DWG #
20-Pin Plastic Dual In-Line Package (DIP) -40 to +85°C ADC0803/04-1 LCN 0408B
20-Pin Plastic Dual In-Line Package (DIP) 0 to 70°C ADC0803/04-1 CN 0408B
20-Pin Plastic Small Outline (SO) Package 0 to 70°C ADC0803/04-1 CD 1021B
20-Pin Plastic Small Outline (SO) Package -40 to 85°C ADC0803/04-1 LCD 1021B
ABSOLUTE MAXIMUM RATINGS
SYMBOL PARAMETER RATING UNIT
VCC Supply voltage 6.5 V
Logic control input voltages -0.3 to +16 V
All other input voltages -0.3 to
(VCC +0.3) V
TAOperating temperature range
ADC0803/04-1 LCD -40 to +85 °C
ADC0803/04-1 LCN -40 to +85 °C
ADC0803/04-1 CD 0 to +70 °C
ADC0803/04-1 CN 0 to +70 °C
TSTG Storage temperature -65 to +150 °C
TSOLD Lead soldering temperature (10 seconds) 300 °C
PDMaximum power dissipation
TA=25°C (still air)1
N package 1690 mW
D package 1390 mW
NOTES:
1. Derate above 25°C, at the following rates: N package at 13.5mW/°C; D package at 11.1mW/°C
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 556
BLOCK DIAGRAM
M
VIN (+) VIN (–)
76
+–
LADDER AND
DECODER
+
–
AUTO ZERO
COMPARATOR
VREF/2
A GND
9
8
VCC 20
10
D GND
WR
CS
RD
3
1
2
SAR
8–BIT
SHIFT REGISTER
INTR
FF
CLOCK
OUTPUT
LATCHES
LE OE
D7 (MSB) (11)
D6 (12)
D5 (13)
D4 (14)
D3 (15)
D2 (16)
D1 (17)
D0 (LSB) (18)
INTR CLK IN CLK R
S
R Q
5 4 19
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 557
DC ELECTRICAL CHARACTERISTICS
VCC = 5.0V, fCLK = 1MHz, TMIN ≤ TA ≤ TMAX, unless otherwise specified.
SYMBOL
PARAMETER
TEST CONDITIONS
ADC0803/4
UNIT
SYMBOL
PARAMETER
TEST CONDITIONS
Min Typ Max
UNIT
ADC0803 relative accuracy error (adjusted) Full-Scale adjusted 0.50 LSB
ADC0804 relative accuracy error (unadjusted) VREF/2 = 2.500VDC 1 LSB
RIN VREF/2 input resistance3VCC = 0V2400 680 Ω
Analog input voltage range3–0.05 VCC+0.05 V
DC common-mode error Over analog input voltage
range 1/16 1/8 LSB
Power supply sensitivity VCC = 5V ±10%11/16 LSB
Control inputs
VIH Logical “1” input voltage VCC = 5.25VDC 2.0 15 VDC
VIL Logical “0” input voltage VCC = 4.75VDC 0.8 VDC
IIH Logical “1” input current VIN = 5VDC 0.005 1 µADC
IIL Logical “0” input current VIN = 0VDC –1 –0.005 µADC
Clock in and clock R
VT+Clock in positive-going threshold voltage 2.7 3.1 3.5 VDC
VT–Clock in negative-going threshold voltage 1.5 1.8 2.1 VDC
VHClock in hysteresis (VT+)–(VT–) 0.6 1.3 2.0 VDC
VOL Logical “0” clock R output voltage IOL = 360µA, VCC = 4.75VDC 0.4 VDC
VOH Logical “1” clock R output voltage IOH = –360µA, VCC = 4.75VDC 2.4 VDC
Data output and INTR
VOL Logical “0” output voltage
Data outputs IOL = 1.6mA, VCC = 4.75VDC 0.4 VDC
INTR outputs IOL = 1.0mA, VCC = 4.75VDC 0.4 VDC
VOH
Logical “1” output voltage
IOH = –360µA, VCC = 4.75VDC 2.4
VDC
VOH
Logical “1” output voltage
IOH = –10µA, VCC = 4.75VDC 4.5
VDC
IOZL 3-state output leakage VOUT = 0VDC, CS = logical “1” –3 µADC
IOZH 3-state output leakage VOUT = 5VDC, CS = logical “1” 3 µADC
ISC +Output short-circuit current VOUT = 0V, TA = 25°C 4.5 12 mADC
ISC –Output short-circuit current VOUT = VCC, TA = 25°C 9.0 30 mADC
ICC Power supply current fCLK = 1MHz, VREF/2 = OPEN,
CS = Logical “1”, TA = 25°C3.0 3.5 mA
NOTES:
1. Analog inputs must remain within the range: –0.05 ≤ VIN ≤ VCC + 0.05V.
2. See typical performance characteristics for input resistance at VCC = 5V.
3. VREF/2 and VIN must be applied after the VCC has been turned on to prevent the possibility of latching.
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 558
AC ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
TO
FROM
ADC0803/4
UNIT
SYMBOL
PARAMETER
TO
FROM
Min Typ Max
UNIT
Conversion time fCLK=1MHz166 73 µs
fCLK Clock frequency10.1 1.0 3.0 MHz
Clock duty cycle140 60 %
CR Free-running conversion rate CS=0, fCLK=1MHz
INTR tied to WR 13690 conv/s
tW(WR)L Start pulse width CS=0 30 ns
tACC Access time Output RD CS=0, CL=100pF 75 100 ns
t1H, t0H 3-State control Output RD CL=10pF, RL=10kΩ
See 3-State test circuit 70 100 ns
tW1, tR1 INTR delay INTR WD
or RD 100 150 ns
CIN Logic input=capacitance 5 7.5 pF
COUT 3-State output capacitance 5 7.5 pF
NOTES:
1. Accuracy is guaranteed at fCLK=1MHz. Accuracy may degrade at higher clock frequencies.
FUNCTIONAL DESCRIPTION
These devices operate on the Successive Approximation principle.
Analog switches are closed sequentially by successive
approximation logic until the input to the auto-zero comparator
[ VIN(+)-VIN(-) ] matches the voltage from the decoder. After all bits
are tested and determined, the 8-bit binary code corresponding to
the input voltage is transferred to an output latch. Conversion begins
with the arrival of a pulse at the WR input if the CS input is low. On
the High-to-Low transition of the signal at the WR or the CS input,
the SAR is initialized, the shift register is reset, and the INTR output
is set high. The A/D will remain in the reset state as long as the CS
and WR inputs remain low. Conversion will start from one to eight
clock periods after one or both of these inputs makes a Low-to-High
transition. After the conversion is complete, the INTR pin will make a
High-to-Low transition. This can be used to interrupt a processor, or
otherwise signal the availability of a new conversion result. A read
(RD) operation (with CS low) will clear the INTR line and enable the
output latches. The device may be run in the free-running mode as
described later. A conversion in progress can be interrupted by
issuing another start command.
Digital Control Inputs
The digital control inputs (CS, WR, RD) are compatible with
standard TTL logic voltage levels. The required signals at these
inputs correspond to Chip Select, START Conversion, and Output
Enable control signals, respectively. They are active-Low for easy
interface to microprocessor and microcontroller control buses. For
applications not using microprocessors, the CS input (Pin 1) can be
grounded and the A/D START function is achieved by a
negative-going pulse to the WR input (Pin 3). The Output Enable
function is achieved by a logic low signal at the RD input (Pin 2),
which may be grounded to constantly have the latest conversion
present at the output.
ANALOG OPERATION
Analog Input Current
The analog comparisons are performed by a capacitive charge
summing circuit. The input capacitor is switched between VIN(+)4
and VIN(-), while reference capacitors are switched between taps on
the reference voltage divider string. The net charge corresponds to
the weighted difference between the input and the most recent total
value set by the successive approximation register.
The internal switching action causes displacement currents to flow
at the analog inputs. The voltage on the on-chip capacitance is
switched through the analog differential input voltage, resulting in
proportional currents entering the VIN(+) input and leaving the VIN(-)
input. These transient currents occur at the leading edge of the
internal clock pulses. They decay rapidly so do not inherently cause
errors as the on-chip comparator is strobed at the end of the clock
period.
Input Bypass Capacitors and Source Resistance
Bypass capacitors at the input will average the charges mentioned
above, causing a DC and an AC current to flow through the output
resistance of the analog signal sources. This charge pumping action
is worse for continuous conversions with the VIN(+) input at full
scale. This current can be a few microamps, so bypass capacitors
should NOT be used at the analog inputs of the VREF/2 input for
high resistance sources (> 1kΩ). If input bypass capacitors are
desired for noise filtering and a high source resistance is desired to
minimize capacitor size, detrimental effects of the voltage drop
across the input resistance can be eliminated by adjusting the full
scale with both the input resistance and the input bypass capacitor
in place. This is possible because the magnitude of the input current
is a precise linear function of the differential voltage.
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 559
Large values of source resistance where an input bypass capacitor
is not used will not cause errors as the input currents settle out prior
to the comparison time. If a low pass filter is required in the system,
use a low valued series resistor (< 1kΩ) for a passive RC section or
add an op amp active filter (low pass). For applications with source
resistances at or below 1kΩ, a 0.1µF bypass capacitor at the inputs
will prevent pickup due to series lead inductance or a long wire. A
100Ω series resistor can be used to isolate this capacitor (both the
resistor and capacitor should be placed out of the feedback loop)
from the output of the op amp, if used.
Analog Differential Voltage Inputs and Common-
Mode Rejection
These A/D converters have additional flexibility due to the analog
differential voltage input. The VIN(-) input (Pin 7) can be used to
subtract a fixed voltage from the input reading (tare correction). This
is also useful in a 4/20mA current loop conversion. Common-mode
noise can also be reduced by the use of the differential input.
The time interval between sampling VIN(+) and VIN(-) is 4.5 clock
periods. The maximum error due to this time difference is given by:
V(max)=(VP) (2fCM) (4.5/fCLK),
where:
V=error voltage due to sampling delay
VP=peak value of common-mode voltage
fCM=common mode frequency
For example, with a 60Hz common-mode frequency, fcm, and a
1MHz A/D clock, FCLK, keeping this error to 1/4 LSB (about 5mV)
would allow a common-mode voltage, VP, which is given by:
VP
[V(max) (fCLK)
(2fCM)(4.5)
or
VP(5 x 103) (104)
(6.28) (60) (4.5) 2.95V
The allowed range of analog input voltages usually places more
severe restrictions on input common-mode voltage levels than this,
however.
An analog input span less than the full 5V capability of the device,
together with a relatively large zero offset, can be easily handled by
use of the differential input. (See Reference Voltage Span Adjust).
Noise and Stray Pickup
The leads of the analog inputs (Pins 6 and 7) should be kept as
short as possible to minimize input noise coupling and stray signal
pick-up. Both EMI and undesired digital signal coupling to these
inputs can cause system errors. The source resistance for these
inputs should generally be below 5kΩ to help avoid undesired noise
pickup. Input bypass capacitors at the analog inputs can create
errors as described previously. Full scale adjustment with any input
bypass capacitors in place will eliminate these errors.
Reference Voltage
For application flexibility, these A/D converters have been designed
to accommodate fixed reference voltages of 5V to Pin 20 or 2.5V to
Pin 9, or an adjusted reference voltage at Pin 9. The reference can
be set by forcing it at VREF/2 input, or can be determined by the
supply voltage (Pin 20). Figure 1 indicates how this is accomplished.
Reference Voltage Span Adjust
Note that the Pin 9 (VREF/2) voltage is either 1/2 the voltage applied
to the VCC supply pin, or is equal to the voltage which is externally
forced at the VREF/2 pin. In addition to allowing for flexible
references and full span voltages, this also allows for a ratiometric
voltage reference. The internal gain of the VREF/2 input is 2, making
the full-scale differential input voltage twice the voltage at Pin 9.
For example, a dynamic voltage range of the analog input voltage
that extends from 0 to 4V gives a span of 4V (4-0), so the VREF/2
voltage can be made equal to 2V (half of the 4V span) and full scale
output would correspond to 4V at the input.
On the other hand, if the dynamic input voltage had a range of 0.5 to
3.5V, the span or dynamic input range is 3V (3.5-0.5). To encode
this 3V span with 0.5V yielding a code of zero, the minimum
expected input (0.5V, in this case) is applied to the VIN(-) pin to
account for the offset, and the VREF/2 pin is set to 1/2 the 3V span,
or 1.5V. The A/D converter will now encode the VIN(+) signal
between 0.5 and 3.5V with 0.5V at the input corresponding to a code
of zero and 3.5V at the input producing a full scale output code. The
full 8 bits of resolution are thus applied over this reduced input
voltage range. The required connections are shown in Figure 2.
Operating Mode
These converters can be operated in two modes:
1) absolute mode
2) ratiometric mode
In absolute mode applications, both the initial accuracy and the
temperature stability of the reference voltage are important factors in
the accuracy of the conversion. For VREF/2 voltages of 2.5V, initial
errors of ±10mV will cause conversion errors of ±1 LSB due to the
gain of 2 at the VREF/2 input. In reduced span applications, the initial
value and stability of the VREF/2 input voltage become even more
important as the same error is a larger percentage of the VREF/2
nominal value. See Figure 3.
In ratiometric converter applications, the magnitude of the reference
voltage is a factor in both the output of the source transducer and
the output of the A/D converter, and, therefore, cancels out in the
final digital code. See Figure 4.
Generally, the reference voltage will require an initial adjustment.
Errors due to an improper reference voltage value appear as
full-scale errors in the A/D transfer function.
ERRORS AND INPUT SPAN ADJUSTMENTS
There are many sources of error in any data converter, some of
which can be adjusted out. Inherent errors, such as relative
accuracy, cannot be eliminated, but such errors as full-scale and
zero scale offset errors can be eliminated quite easily. See Figure 2.
Zero Scale Error
Zero scale error of an A/D is the difference of potential between the
ideal 1/2 LSB value (9.8mV for VREF/2=2.500V) and that input
voltage which just causes an output transition from code 0000 0000
to a code of 0000 0001.
If the minimum input value is not ground potential, a zero offset can
be made. The converter can be made to output a digital code of
0000 0000 for the minimum expected input voltage by biasing the
VIN(-) input to that minimum value expected at the VIN(-) input to
that minimum value expected at the VIN(+) input. This uses the
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 560
differential mode of the converter. Any offset adjustment should be
done prior to full scale adjustment.
Full Scale Adjustment
Full scale gain is adjusted by applying any desired offset voltage to
VIN(-), then applying the VIN(+) a voltage that is 1-1/2 LSB less than
the desired analog full-scale voltage range and then adjusting the
magnitude of VREF/2 input voltage (or the VCC supply if there is no
VREF/2 input connection) for a digital output code which just
changes from 1111 1110 to 1111 1111. The ideal VIN(+) voltage for
this full-scale adjustment is given by:
VIN())+VIN(*)*1.5 x VMAX *VMIN
255
where:
VMAX=high end of analog input range (ground referenced)
VMIN=low end (zero offset) of analog input (ground referenced)
CLOCKING OPTION
The clock signal for these A/Ds can be derived from external
sources, such as a system clock, or self-clocking can be
accomplished by adding an external resistor and capacitor, as
shown in Figure 6.
Heavy capacitive or DC loading of the CLK R pin should be avoided
as this will disturb normal converter operation. Loads less than 50pF
are allowed. This permits driving up to seven A/D converter CLK IN
pins of this family from a single CLK R pin of one converter. For
larger loading of the clock line, a CMOS or low power TTL buffer or
PNP input logic should be used to minimize the loading on the CLK
R pin.
Restart During a Conversion
A conversion in process can be halted and a new conversion began
by bringing the CS and WR inputs low and allowing at least one of
them to go high again. The output data latch is not updated if the
conversion in progress is not completed; the data from the
previously completed conversion will remain in the output data
latches until a subsequent conversion is completed.
Continuous Conversion
To provide continuous conversion of input data, the CS and RD
inputs are grounded and INTR output is tied to the WR input. This
INTR/WR connection should be momentarily forced to a logic low
upon power-up to insure circuit operation. See Figure 5 for one way
to accomplish this.
DRIVING THE DATA BUS
This CMOS A/D converter, like MOS microprocessors and
memories, will require a bus driver when the total capacitance of the
data bus gets large. Other circuitry tied to the data bus will add to
the total capacitive loading, even in the high impedance mode.
There are alternatives in handling this problem. The capacitive
loading of the data bus slows down the response time, although DC
specifications are still met. For systems with a relatively low CPU
clock frequency, more time is available in which to establish proper
logic levels on the bus, allowing higher capacitive loads to be driven
(see Typical Performance Characteristics).
At higher CPU clock frequencies, time can be extended for I/O
reads (and/or writes) by inserting wait states (8880) or using
clock-extending circuits (6800, 8035).
Finally, if time is critical and capacitive loading is high, external bus
drivers must be used. These can be 3-State buffers (low power
Schottky is recommended, such as the N74LS240 series) or special
higher current drive products designed as bus drivers. High current
bipolar bus drivers with PNP inputs are recommended as the PNP
input offers low loading of the A/D output, allowing better response
time.
POWER SUPPLIES
Noise spikes on the VCC line can cause conversion errors as the
internal comparator will respond to them. A low inductance filter
capacitor should be used close to the converter VCC pin and values
of 1µF or greater are recommended. A separate 5V regulator for the
converter (and other 5V linear circuitry) will greatly reduce digital
noise on the VCC supply and the attendant problems.
WIRING AND LAYOUT PRECAUTIONS
Digital wire-wrap sockets and connections are not satisfactory for
breadboarding this (or any) A/D converter. Sockets on PC boards
can be used. All logic signal wires and leads should be grouped or
kept as far as possible from the analog signal leads. Single wire
analog input leads may pick up undesired hum and noise, requiring
the use of shielded leads to the analog inputs in many applications.
A single-point analog ground separate from the logic or digital
ground points should be used. The power supply bypass capacitor
and the self-clocking capacitor, if used, should be returned to digital
ground. Any VREF/2 bypass capacitor, analog input filter capacitors,
and any input shielding should be returned to the analog ground
point. Proper grounding will minimize zero-scale errors which are
present in every code. Zero-scale errors can usually be traced to
improper board layout and wiring.
APPLICATIONS
Microprocessor Interfacing
This family of A/D converters was designed for easy microprocessor
interfacing. These converters can be memory mapped with
appropriate memory address decoding for CS (read) input. The
active-Low write pulse from the processor is then connected to the
WR input of the A/D converter, while the processor active-Low read
pulse is fed to the converter RD input to read the converted data. If
the clock signal is derived from the microprocessor system clock,
the designer/programmer should be sure that there is no attempt to
read the converter until 74 converter clock pulses after the start
pulse goes high. Alternatively, the INTR pin may be used to interrupt
the processor to cause reading of the converted data. Of course, the
converter can be connected and addressed as a peripheral (in I/O
space), as shown in Figure 7. A bus driver should be used as a
buffer to the A/D output in large microprocessor systems where the
data leaves the PC board and/or must drive capacitive loads in
excess of 100pF. See Figure 9.
Interfacing the SCN8048 microcomputer family is pretty simple, as
shown in Figure 8. Since the SCN8048 family has 24 I/O lines, one
of these (shown here as bit 0 or port 1) can be used as the chip
select signal to the converter, eliminating the need for an address
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 561
decoder. The RD and WR signals are generated by reading from
and writing to a dummy address.
Digitizing a Transducer Interface Output
Circuit Description
Figure 10 shows an example of digitizing transducer interface output
voltage. In this case, the transducer interface is the NE5521, an
LVDT (Linear Variable Differential Transformer) Signal Conditioner.
The diode at the A/D input is used to insure that the input to the A/D
does not go excessively beyond the supply voltage of the A/D. See
the NE5521 data sheet for a complete description of the operation of
that part.
Circuit Adjustment
To adjust the full scale and zero scale of the A/D, determine the
range of voltages that the transducer interface output will take on.
Set the LVDT core for null and set the Zero Scale Scale Adjust
Potentiometer for a digital output from the A/D of 1000 000. Set the
LVDT core for maximum voltage from the interface and set the Full
Scale Adjust potentiometer so the A/D output is just barely 1111
1111.
A Digital Thermostat
Circuit Description
The schematic of a Digital Thermostat is shown in Figure 11. The
A/D digitizes the output of the LM35, a temperature transducer IC
with an output of 10mV per °C. With VREF/2 set for 2.56V, this 10mV
corresponds to 1/2 LSB and the circuit resolution is 2°C. Reducing
VREF/2 to 1.28 yields a resolution of 1°C. Of course, the lower
VREF/2 is, the more sensitive the A/D will be to noise.
The desired temperature is set by holding either of the set buttons
closed. The SCC80C451 programming could cause the desired
(set) temperature to be displayed while either button is depressed
and for a short time after it is released. At other times the ambient
temperature could be displayed.
The set temperature is stored in an SCN8051 internal register. The
A/D conversion is started by writing anything at all to the A/D with
port pin P10 set high. The desired temperature is compared with the
digitized actual temperature, and the heater is turned on or off by
clearing setting port pin P12. If desired, another port pin could be
used to turn on or off an air conditioner.
The display drivers are NE587s if common anode LED displays are
used. Of course, it is possible to interface to LCD displays as well.
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 562
TYPICAL PERFORMANCE CHARACTERISTICS
fCLK = 1MHz
CS = H
3.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8 –50 –25 0 25 50 75 100 125
AMBIENT TEMPERATURE (Co)
POWER SUPPLY CURRENT (mA)
10.0
8.0
6.0
4.0
2.0
1.0
0.8
0.6
0.4
0.2
0.110 20 40 60 80100 200 400 6001000
CLOCK CAP (pF)
CLOCK FRQ (MHz)
MAX.
TYP.
MIN.
VCC =
5.0V
TA = 25oC
5
4
3
2
1
0
–1
–2
–3
–4
–5 0 1 2 3 4 5
f (mA)
REF/2
APPLIED VREF/2 (V)
1.70
1.60
1.50
1.40
1.304.50 4.75 5.00 5.25 5.50
–55oC
+25oC
+125oC
LOGIC INPUT (V)
VCC SUPPLY VOLTAGE (V)
–55oC < TA 125oC
VT+
VT
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
4.50 4.75 5.00 5.25 5.50
CLK–IN THRESHOLD VOLTAGE (V)
VCC SUPPLY VOLTAGE (V)
18
16
14
12
10
8
6–50 –25 0 25 50 75 100 125
AMBIENT TEMPERATURE (oC)
OUTPUT CURRENT (mA)
VCC = 5.0V
VO = 2.5V
VO = 0.4V
VCC = 5.0V
VREF/2 =
2.5V
4
3
2
1
00 20 40 60 80 100 120
CONVERSION TIME (µs)
ERROR (LSB)
VCC =
5.0V
TA = 25oC
350
300
250
200
150
100
50
00 200 400 600 800 1000
LOAD CAPACITANCE (pF)
DEALY (ns)
Power Supply Current vs
Temperature Clock Frequency vs
Clock Capacitor Input Current vs
Applied Voltage at VREF/2 Pin
Logic Input Threshold
Voltage vs Supply Voltage CLK–IN Threshold Voltage vs
Supply Voltage Output Current vs
Temperature
Full Scale Error vs
Conversion Time
Delay From RD Falling
Edge to Data Valid vs
Load Capacitance
5.5V
5.0V
4.5V
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 563
3-STATE TEST CIRCUITS AND WAVEFORMS (ADC0801-1)
tr90%
50%
10%
t0H
10%
VCC
GND
VOH
GND
RD
DATA
OUTPUT
CL
VCC
DATA
OUTPUT
10K
CL
CS
RD
tr90%
50%
10%
t1H
90%
VCC
GND
VOH
GND
RD
DATA
OUTPUT
VCC
10K
CS
RD DATA
OUTPUT
VCC
20ns
10pF
tOH
t1H
10pF
TIMING DIAGRAMS (All timing is measured from the 50% voltage points)
START
CONVERSION
CS
WR
tWI tW(WR)L
ACTUAL INTERNAL
STATUS OF THE
CONVERTER (LAST DATA WAS READ)
(LAST DATA WAS NOT READ)
INTR
INTR
CS
RD
DATA
OUTPUTS
INTR RESET
tRI
tACC t1H, t0H
THREE–STATE
1 TO 8 X 1/fCLK
”NOT BUSY”
”BUSY”
INTERNAL TC
DATA IS VALID IN
OUTPUT LATCHES
INT ASSERTED
1/2 TCLK
NOTE
NOTE:
Read strobe must occur 8 clock periods (8/fCLK) after assertion of interrupt to guarantee reset of INTR.
Output Enable and Reset INTR
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 564
NOTE:
The VREF/2 voltage is either 1/2 the VCC voltage or is that which is forced at Pin 9.
Figure 1. Internal Reference Design
VREF/2
VCC
20 VREF
R
R
DIGITAL
CIRCUITS
ANALOG
CIRCUITS
8 10
9
Figure 2. Offsetting the Zero Scale and Adjusting
the Input Range (Span)
(5V)
VREF
FS
OFFSET
ADJUST
ZS
OFFSET
ADJUST
330
0.1µFTO VREF/2
TO VIN(–)
+
–
VOLTAGE
REFERENCE
VREF/2
a. Fixed Reference b. Fixed Reference Derived from VCC c. Optional Full
Scale Adjustment
VIN(+)
VIN(–)
VCC
+5V
+
VREF/2
10µF
A/D
A/D
VIN(+)
VIN(–)
VCC
VREF/2
+10µF
+5V
2k
2k
+5V
2k
2k
100
Figure 3. Absolute Mode of Operation
A/D
VIN(+)
VIN(–)
VCC
VREF/2
+10µF2k
2k
100 FULL SCALE
OPTIONAL
TRANSDUCER
VCC
Figure 4. Ratiometric Mode of Operation with Optional
Full Scale Adjustment
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 565
CLK IN
A GND
VREF/2
VIN(–)
A/D
+5V
10K 2.7k
10k 47µF TO
100µF56pF
10k
CS 1
2
3
4
5
6
7
8
9
10
RD
INTR
WR
VIN(+)
D GND
20
CLK R
18
17
16
15
14
13
12
11
VCC
D0 DB0
D1
D2
D3
D4
D5
D6
D7
DB1
DB2
DB3
DB4
DB5
DB6
DB7
+5V
19
Figure 5. Connection for Continuous Conversion
R
CLK IN 4
C
CLK
A/D
fCLK = 1/1.7 R C
R = 10K
CLK R19
Figure 6. Self-Clocking the Converter
D GND
VREF/2
CLK IN
A GND
VIN(–)
A/D
10k
CS 1
2
3
4
5
6
7
8
9
10
RD
INTR
WR
VIN(+)
20
CLK R
18
17
16
15
14
13
12
11
VCC
D0 DB0
D1
D2
D3
D4
D5
D6
D7
DB1
DB2
DB3
DB4
DB5
DB6
DB7
+5V
19
ADDRESS
DECODE
LOGIC
INT
I/O WR
I/O RD
ANALOG
INPUTS
56pF
Figure 7. Interfacing to 8080A Microprocessor
20
VCC
D GND
VREF/2
A GND
A/D
CS
1
2
3
4
5
6
7
8
17 RD
INTO
WR
VIN(+)
VCC D0
D1
D2
D3
D4
D5
D6
D7
+5V
40
16
12
39
P1.0
P1.1
P1.2
P1.3
P1.4
P1.5
P1.6
P1.7
P0.0
SCN8051
OR
SCN80C51
18
17
16
15
14
13
12
11
2
3
5
1
RD
INTR
WR
19 CLK R
10k
4 CLK IN
6
7
ANALOG
INPUTS
12
11
Figure 8. SCN8051 Interfacing
56pF
18
17
16
15
14
13
12
11
D0
D1
D2
D3
D4
D5
D6
D7
A/D
OE
DATA
BUS
8–BIT
BUFFER
N74LS241
N74LS244
N74LS541
Figure 9. Buffering the A/D Output to Drive High
Capacitance Loads and for Driving Off-Board Loads
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 566
A/D
4.7k
1.5k
1µF
4.7k 0.47µF22k
470
Ct
18k
+5V
NE5521
LVDT
IN4148
VIN(–)
3.3k
2k
VCC
VIN(+)
2k
+5V
100
2k
FULL
SCALE
ADJUST
820
VREF/2
Figure 10. Digitizing a Transducer Interface Output
Philips Semiconductors Linear Products Product specification
ADC0803/4-1CMOS 8-bit A/D converters
August 31, 1994 567
SCC80C51
A/D
CS
18
17
16
15
14
13
12
11
8 RD
INT
WR
D0
D1
D2
D3
D4
D5
D6
D7
10
6
27
DB0
DB1
DB2
DB3
DB4
DB5
DB6
DB7
P10
18
17
16
15
14
13
12
11
2
3
5
1
RD
INTR
WR
LOWER
P15
RAISE
P16
13 14
1/4
HEF4071
20 GND29 P12
+V
2N3906
1N4148 TO HEATER
1/4
HEF4071
6
2
1
7
3
6
2
1
7
3
RBI 5
NE587
NE587
RBO 4
RBI 5
7
8
10K
7
8
10K
20
19
+5V
VCC
CLK R
10K
CLK IN
56pF
4
+10µF
VIN(–)
VIN(+)
7
D GND 10 8 AGND
LM35
6
Figure 11. Digital Thermostat