Datasheet

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1
2
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DAC8574
V
OUTA
V
OUTB
V
REFH
V
DD
V
REFL
GND
V
OUTC
V
OUTD
A3
A2
A1
A0
IOV
DD
SDA
SCL
L
DAC
SDA
SCL
I
2
C Pullup Resistors
1 kΩ to 10 kΩ (typical)
IOV
DD
Microcontroller or
Microprocessor With
I
2
C Port
NOTE: DAC8574 power and input/output connections are omitted for clarity, except I

C Inputs.
USING GPIO PORTS FOR I
2
C
DAC8574
SLAS377B – JANUARY 2003 – REVISED DECEMBER 2004
APPLICATION INFORMATION (continued)
Figure 56. Typical DAC8574 Connections
The DAC8574 interfaces directly to standard mode, fast mode and high-speed mode I
2
C controllers. Any
microcontroller's I
2
C peripheral, including master-only and non-multiple-master I
2
C peripherals, work with the
DAC8574. The DAC8574 does not perform clock-stretching (i.e., it never pulls the clock line low), so it is not
necessary to provide for this unless other devices are on the same I
2
C bus.
Pullup resistors are necessary on both the SDA and SCL lines because I
2
C bus drivers are open-drain. The size
of the these resistors depend on the bus operating speed and capacitance on the bus lines. Higher-value
resistors consume less power, but increase the transition times on the bus, limiting the bus speed. Lower-value
resistors allow higher speed at the expense of higher power consumption. Long bus lines have higher
capacitance and require smaller pullup resistors to compensate. If the pullup resistors are too small the bus
drivers may not be able to pull the bus line low.
Most microcontrollers have programmable input/output pins that can be set in software to act as inputs or
outputs. If an I
2
C controller is not available, the DAC8574 can be connected to GPIO pins, and the I
2
C bus
protocol simulated, or bit-banged, in software. An example of this for a single DAC8574 is shown in Figure 57 .
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