INTEGRATED CIRCUITS
DATA SHEET
PCF8591
8-bit A/D and D/A converter
Product specification |
1998 Jul 02 |
Supersedes data of 1997 Apr 02
File under Integrated Circuits, IC12
Philips Semiconductors |
Product specification |
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8-bit A/D and D/A converter |
PCF8591 |
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CONTENTS
1FEATURES
2APPLICATIONS
3GENERAL DESCRIPTION
4ORDERING INFORMATION
5BLOCK DIAGRAM
6PINNING
7FUNCTIONAL DESCRIPTION
7.1Addressing
7.2Control byte
7.3D/A conversion
7.4A/D conversion
7.5Reference voltage
7.6Oscillator
8 |
CHARACTERISTICS OF THE I2C-BUS |
8.1Bit transfer
8.2Start and stop conditions
8.3System configuration
8.4Acknowledge
8.5I2C-bus protocol
9LIMITING VALUES
10HANDLING
11DC CHARACTERISTICS
12D/A CHARACTERISTICS
13A/D CHARACTERISTICS
14AC CHARACTERISTICS
15APPLICATION INFORMATION
16PACKAGE OUTLINES
17SOLDERING
17.1Introduction
17.2DIP
17.2.1Soldering by dipping or by wave
17.2.2Repairing soldered joints
17.3SO
17.3.1Reflow soldering
17.3.2Wave soldering
17.3.3Repairing soldered joints
18DEFINITIONS
19LIFE SUPPORT APPLICATIONS
20PURCHASE OF PHILIPS I2C COMPONENTS
1998 Jul 02 |
2 |
Philips Semiconductors |
Product specification |
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8-bit A/D and D/A converter |
PCF8591 |
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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 VSS to VDD
∙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 inputs, one analog output and a serial I2C-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 maximum speed of the I2C-bus.
4 ORDERING INFORMATION
TYPE |
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PACKAGE |
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NUMBER |
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DESCRIPTION |
VERSION |
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PCA8591P |
DIP16 |
plastic dual in-line package; 16 leads (300 mil); long body |
SOT38-1 |
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PCA8591T |
SO16 |
plastic small outline package; 16 leads; body width 7.5 mm |
SOT162-1 |
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1998 Jul 02 |
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_
02 Jul 1998
4
Fig.1 Block diagram.
DIAGRAM BLOCK 5
converter D/A and A/D bit-8
PCF8591
Semiconductors Philips
specification Product
Philips Semiconductors |
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Product specification |
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8-bit A/D and D/A converter |
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PCF8591 |
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6 PINNING |
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SYMBOL |
PIN |
DESCRIPTION |
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AINO |
1 |
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AIN1 |
2 |
analog inputs |
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AIN2 |
3 |
(A/D converter) |
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AIN3 |
4 |
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A0 |
5 |
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A1 |
6 |
hardware address |
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A2 |
7 |
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VSS |
8 |
negative supply voltage |
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SDA |
9 |
I2C-bus data input/output |
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SCL |
10 |
I2C-bus clock input |
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OSC |
11 |
oscillator input/output |
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EXT |
12 |
external/internal switch for oscillator |
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input |
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AGND |
13 |
analog ground |
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VREF |
14 |
voltage reference input |
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AOUT |
15 |
analog output (D/A converter) |
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Fig.2 |
Pinning diagram. |
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VDD |
16 |
positive supply voltage |
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1998 Jul 02 |
5 |
Philips Semiconductors |
Product specification |
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8-bit A/D and D/A converter |
PCF8591 |
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7 FUNCTIONAL DESCRIPTION
7.1Addressing
Each PCF8591 device in an I2C-bus system is activated by 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.
7.2Control 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.
1998 Jul 02 |
6 |
Philips Semiconductors |
Product specification |
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8-bit A/D and D/A converter |
PCF8591 |
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Fig.4 Control byte.
1998 Jul 02 |
7 |
Philips Semiconductors |
Product specification |
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8-bit A/D and D/A converter |
PCF8591 |
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7.3D/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.
1998 Jul 02 |
8 |
Philips Semiconductors |
Product specification |
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8-bit A/D and D/A converter |
PCF8591 |
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Fig.6 DAC data and DC conversion characteristics.
Fig.7 |
D/A conversion sequence. |
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1998 Jul 02 |
9 |
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