DS4402 View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated
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DS4402 Datasheet PDF : 8 Pages
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Two/Four-Channel, I2C Adjustable Current DAC
Detailed Description
The DS4402/DS4404 contain two/four I2C adjustable
current sources (Figure 1) that are each capable of
sinking and sourcing current. Each output has 31 sink
and 31 source settings that are programmed through
the I2C interface. The full-scale ranges (and corre-
sponding step sizes) of the outputs are determined by
external resistors that adjust the output currents over a
4:1 range. The formula to determine the external resis-
tor values (RFS) for each of the outputs is given by:
Equation 1:
RFS = (VREF / IFS) x (31 / 4)
where IFS = desired full-scale current
On power-up, the DS4402/DS4404 output zero current.
This is done to prevent it from sinking or sourcing an
incorrect current before the system host controller has
had a chance to modify the device’s setting.
As a source for biasing instrumentation or other cir-
cuits, the DS4402/DS4404 provide a simple and inex-
pensive current source with an I2C interface for control.
The adjustable full-scale range allows the application to
get the most out of its 5-bit sink or source resolution.
When used in adjustable power-supply applications
(see the Typical Operating Circuit), the DS4402/DS4404
do not affect the initial power-up supply voltage because
it defaults to providing zero output current on power-up.
As it sources or sinks current into the feedback voltage
node, it changes the amount of output voltage required
by the regulator to reach its steady state operating point.
By using the external resistor to set the output current
range, the devices provide flexibility for adjusting the
impedances of the feedback network or the range over
which the power supply can be controlled or margined.
I2C Slave Address
The DS4402/DS4404 respond to one of nine I2C slave
addresses determined by the two tri-level address
inputs. The three input states are connected to VCC,
connected to ground, or disconnected. To sense the
disconnected state (Figure 2), the address inputs have
weak internal resistors that pull the pins to mid-supply.
VCC
RIN
A1
A0
RIN
RIN
I2C
ADDRESS
DECODE
RIN
Figure 2. I2C Address Inputs
Table 1 lists the slave address determined by the
address input combinations.
Table 1. Slave Addresses
A1
GND
GND
VCC
VCC
N.C.
N.C.
GND
VCC
N.C.
A0
GND
VCC
GND
VCC
GND
VCC
N.C.
N.C.
N.C.
SLAVE ADDRESS
(HEXADECIMAL)
90h
92h
94h
96h
98h
9Ah
9Ch
9Eh
A0h
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