Philips adc0803x DATASHEETS

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 V

•Single 5V supply

•Guaranteed specification with 1MHz clock

PIN CONFIGURATION

1 2 3 4 5 6 7 8 9

20 19 18 17 16 15

N PACKAGES

CS RD

INTR

CLK IN

(+)

(–)

A GND

REF

D GND

CLK R D0 D1 D2 D3 D4 D5 D6 D7

TOP VIEW NOTE: SOL — Released in large SO package only.

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

Supply voltage 6.5 V Logic control input voltages -0.3 to +16 V

All other input voltages

-0.3 to

+0.3)

Operating 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

STG

Storage temperature -65 to +150 °C

SOLD

Lead soldering temperature (10 seconds) 300 °C

Maximum power dissipation T

=25°C (still air)

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

APPLICATIONS

•Transducer-to-microprocessor interface

•Digital thermometer

•Digitally-controlled thermostat

•Microprocessor-based monitoring and control systems

ORDERING INFORMATION

DESCRIPTION

Philips Semiconductors Linear Products Product specification

ADC0803/4-1CMOS 8-bit A/D converters

August 31, 1994

556

BLOCK DIAGRAM

VIN (+) VIN (–)

–

LADDER AND

DECODER

–

AUTO ZERO COMPARATOR

REF

A GND

D GND

SAR

8–BIT

SHIFT REGISTER

INTR

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

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

= 5.0V, f

CLK

= 1MHz, T

MIN

≤ TA ≤ T

MAX

, unless otherwise specified.

ADC0803/4

SYMBOL

PARAMETER

TEST CONDITIONS

Min Typ Max

UNIT

ADC0803 relative accuracy error (adjusted) Full-Scale adjusted 0.50 LSB ADC0804 relative accuracy error (unadjusted) V

REF

/2 = 2.500V

1 LSB

REF

/2 input resistance

VCC = 0V

400 680 Ω

Analog input voltage range

–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%

1/16 LSB

Control inputs

Logical “1” input voltage VCC = 5.25V

2.0 15 V

Logical “0” input voltage VCC = 4.75V

0.8 V

Logical “1” input current VIN = 5V

0.005 1 µA

Logical “0” input current VIN = 0V

–1 –0.005 µA

Clock in and clock R

VT+ Clock in positive-going threshold voltage 2.7 3.1 3.5 V

VT– Clock in negative-going threshold voltage 1.5 1.8 2.1 V

Clock in hysteresis (VT+)–(VT–) 0.6 1.3 2.0 V

Logical “0” clock R output voltage IOL = 360µA, VCC = 4.75V

0.4 V

Logical “1” clock R output voltage IOH = –360µA, VCC = 4.75V

2.4 V

Data output and INTR

Logical “0” output voltage Data outputs IOL = 1.6mA, VCC = 4.75V

0.4 V

INTR outputs IOL = 1.0mA, VCC = 4.75V

0.4 V

IOH = –360µA, VCC = 4.75V

2.4

VOHLogical “1” output voltage

IOH = –10µA, VCC = 4.75V

4.5

OZL

3-state output leakage V

OUT

= 0VDC, CS = logical “1” –3 µA

OZH

3-state output leakage V

OUT

= 5VDC, CS = logical “1” 3 µA

+Output short-circuit current V

OUT

= 0V, TA = 25°C 4.5 12 mA

–Output short-circuit current V

OUT

= VCC, TA = 25°C 9.0 30 mA

Power supply current

CLK

= 1MHz, V

REF

/2 = OPEN,

= Logical “1”, TA = 25°C

3.0 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. V

REF

/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

ADC0803/4

SYMBOL

PARAMETER

FROM

TEST CONDITIONS

Min Typ Max

UNIT

Conversion time f

CLK

=1MHz

66 73 µs

CLK

Clock frequency

0.1 1.0 3.0 MHz

Clock duty cycle

40 60 %

CR Free-running conversion rate

CS=0, f

CLK

=1MHz

INTR

tied to WR

13690 conv/s

tW(WR)L Start pulse width CS=0 30 ns t

ACC

Access time Output RD CS=0, CL=100pF 75 100 ns

t1H, t

3-State control Output RD

CL=10pF, RL=10kΩ

See 3-State test circuit

70 100 ns

tW1, t

INTR delay INTR

or RD

100 150 ns

Logic input=capacitance 5 7.5 pF

OUT

3-State output capacitance 5 7.5 pF

NOTES:

1. Accuracy is guaranteed at f

CLK

=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 [ V

(+)-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 V

IN(+)

and V

IN(-)

, 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 V

IN(+)

input and leaving the V

IN(-)

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 V

IN(+)

input at full scale. This current can be a few microamps, so bypass capacitors should NOT be used at the analog inputs of the V

REF

/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.

+ 9 hidden pages