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pcf8591
DATASHEETS
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Philips pcf8591 DATASHEETS

INTEGRATED CIRCUITS
DATA SH EET
PCF8591
8-bit A/D and D/A converter
Product specification Supersedes data of 1997 Apr 02 File under Integrated Circuits, IC12
1998 Jul 02
Philips Semiconductors Product specification
8-bit A/D and D/A converter PCF8591
CONTENTS
1 FEATURES 2 APPLICATIONS 3 GENERAL DESCRIPTION 4 ORDERING INFORMATION 5 BLOCK DIAGRAM 6 PINNING 7 FUNCTIONAL DESCRIPTION
7.1 Addressing
7.2 Control byte
7.3 D/A conversion
7.4 A/D conversion
7.5 Reference voltage
7.6 Oscillator 8 CHARACTERISTICS OF THE I2C-BUS
8.1 Bit transfer
8.2 Start and stop conditions
8.3 System configuration
8.4 Acknowledge
8.5 I2C-bus protocol 9 LIMITING VALUES 10 HANDLING 11 DC CHARACTERISTICS 12 D/A CHARACTERISTICS 13 A/D CHARACTERISTICS 14 AC CHARACTERISTICS 15 APPLICATION INFORMATION 16 PACKAGE OUTLINES 17 SOLDERING
17.1 Introduction
17.2 DIP
17.2.1 Soldering by dipping or by wave
17.2.2 Repairing soldered joints
17.3 SO
17.3.1 Reflow soldering
17.3.2 Wave soldering
17.3.3 Repairing soldered joints 18 DEFINITIONS 19 LIFE SUPPORT APPLICATIONS 20 PURCHASE OF PHILIPS I2C COMPONENTS
Philips Semiconductors Product specification
8-bit A/D and D/A converter PCF8591

1 FEATURES

• Single power supply
• Operating supply voltage 2.5 V to 6 V
• Low standby current
• Serial input/output via I2C-bus
• Address by 3 hardware address pins
• Sampling rate given by I2C-bus speed
• 4 analog inputs programmable as single-ended or
differential inputs
• Auto-incremented channel selection
• Analog voltage range from V
SS
to V
DD
• On-chip track and hold circuit
• 8-bit successive approximation A/D conversion
• Multiplying DAC with one analog output.

2 APPLICATIONS

• Closed loop control systems
• Low power converter for remote data acquisition
• Battery operated equipment
• Acquisition of analog values in automotive, audio and
TV applications.

3 GENERAL DESCRIPTION

The PCF8591 is a single-chip, single-supply low power 8-bit CMOS data acquisition device with four analog
2
inputs, one analog output and a serial I
C-bus interface. Three address pins A0, A1 and A2 are used for programming the hardware address, allowing the use of up to eight devices connected to the I2C-bus without additional hardware. Address, control and data to and from the device are transferred serially via the two-line bidirectional I2C-bus.
The functions of the device include analog input multiplexing, on-chip track and hold function, 8-bit analog-to-digital conversion and an 8-bit digital-to-analog conversion. The maximum conversion rate is given by the
2
maximum speed of the I
C-bus.

4 ORDERING INFORMATION

TYPE
NUMBER
NAME DESCRIPTION VERSION
PACKAGE
PCA8591P DIP16 plastic dual in-line package; 16 leads (300 mil); long body SOT38-1 PCA8591T SO16 plastic small outline package; 16 leads; body width 7.5 mm SOT162-1
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1998 Jul 02 4

5 BLOCK DIAGRAM

8-bit A/D and D/A converter PCF8591
Philips Semiconductors Product specification
Fig.1 Block diagram.
Philips Semiconductors Product specification
8-bit A/D and D/A converter PCF8591

6 PINNING

SYMBOL PIN DESCRIPTION
AINO 1 AIN1 2 AIN2 3 AIN3 4 A0 5
A2 7 V
SS
SDA 9 I SCL 10 I OSC 11 oscillator input/output EXT 12 external/internal switch for oscillator
AGND 13 analog ground V
REF
AOUT 15 analog output (D/A converter) V
DD
analog inputs (A/D converter)
hardware addressA1 6
8 negative supply voltage
2
C-bus data input/output
2
C-bus clock input
input
14 voltage reference input
16 positive supply voltage
Fig.2 Pinning diagram.
Philips Semiconductors Product specification
8-bit A/D and D/A converter PCF8591

7 FUNCTIONAL DESCRIPTION

7.1 Addressing

Each PCF8591 device in an I sending a valid address to the device. The address consists of a fixed part and a programmable part. The programmable part must be set according to the address pins A0, A1 and A2. The address always has to be sent as the first byte after the start condition in the I2C-bus protocol. The last bit of the address byte is the read/write-bit which sets the direction of the following data transfer (see Figs 3, 15 and 16).
Fig.3 Address byte.
2
C-bus system is activated by

7.2 Control byte

The second byte sent to a PCF8591 device will be stored in its control register and is required to control the device function.
The upper nibble of the control register is used for enabling the analog output, and for programming the analog inputs as single-ended or differential inputs. The lower nibble selects one of the analog input channels defined by the upper nibble (see Fig.4). If the auto-increment flag is set the channel number is incremented automatically after each A/D conversion.
If the auto-increment mode is desired in applications where the internal oscillator is used, the analog output enable flag in the control byte (bit 6) should be set. This allows the internal oscillator to run continuously, thereby preventing conversion errors resulting from oscillator start-up delay. The analog output enable flag may be reset at other times to reduce quiescent power consumption.
The selection of a non-existing input channel results in the highest available channel number being allocated. Therefore, if the auto-increment flag is set, the next selected channel will be always channel 0. The most significant bits of both nibbles are reserved for future functions and have to be set to 0. After a Power-on reset condition all bits of the control register are reset to 0. The D/A converter and the oscillator are disabled for power saving. The analog output is switched to a high-impedance state.
Philips Semiconductors Product specification
8-bit A/D and D/A converter PCF8591
Fig.4 Control byte.
Philips Semiconductors Product specification
8-bit A/D and D/A converter PCF8591

7.3 D/A conversion

The third byte sent to a PCF8591 device is stored in the DAC data register and is converted to the corresponding analog voltage using the on-chip D/A converter. This D/A converter consists of a resistor divider chain connected to the external reference voltage with 256 taps and selection switches. The tap-decoder switches one of these taps to the DAC output line (see Fig.5).
The analog output voltage is buffered by an auto-zeroed unity gain amplifier. This buffer amplifier may be switched on or off by setting the analog output enable flag of the control register. In the active state the output voltage is held until a further data byte is sent.
The on-chip D/A converter is also used for successive approximation A/D conversion. In order to release the DAC for an A/D conversion cycle the unity gain amplifier is equipped with a track and hold circuit. This circuit holds the output voltage while executing the A/D conversion.
The output voltage supplied to the analog output AOUT is given by the formula shown in Fig.6. The waveforms of a D/A conversion sequence are shown in Fig.7.
Fig.5 DAC resistor divider chain.
Philips Semiconductors Product specification
8-bit A/D and D/A converter PCF8591
Fig.6 DAC data and DC conversion characteristics.
Fig.7 D/A conversion sequence.
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