Rainbow Electronics MAX5104 - Manual (Page 10)

MAX5104
Low-Power, Dual, Voltage-Output, 12-Bit DAC
with Serial Interface
10 ______________________________________________________________________________________
Serial-Data Output
The serial-data output, DOUT, is the internal shift register’s
output. DOUT allows for daisy chaining of devices and
data readback. The MAX5104 can be programmed to
shift data out of DOUT on SCLK’s falling edge (Mode 0)
or on the rising edge (Mode 1). Mode 0 provides a lag
of 16 clock cycles, which maintains compatibility with
SPI/QSPI and MICROWIRE interfaces. In Mode 1, the
output data lags 15.5 clock cycles. On power-up, the
device defaults to Mode 0.
User-Programmable Logic Output
User-programmable logic output (UPO) allows an external
device to be controlled through the serial interface
(Table 1), thereby reducing the number of microcontroller
I/O pins required. On power-up, UPO is low.
Power-Down Lockout Input
The power-down lockout ( PDL) pin disables software
shutdown when low. When in power-down, transitioning
PDL from high to low wakes up the part with the output
set to the state prior to power-down.
PDL can also be
used to asynchronously wake up the device.
Daisy-Chaining Devices
Any number of MAX5104s can be daisy-chained by
connecting the DOUT pin of one device to the DIN pin
of the following device in the chain (Figure 7).
Since the MAX5104’s DOUT pin has an internal active
pull-up, the DOUT sink/source capability determines the
time required to discharge/charge a capacitive load.
See the digital output V
OH and V OL specifications in the
Electrical Characteristics.
Figure 8 shows an alternate method of connecting several
MAX5104s. In this configuration, the data bus is common
to all devices; data is not shifted through a daisy chain.
More I/O lines are required in this configuration because
a dedicated chip-select input (
CS) is required for each IC.
__________Applications Information
Unipolar Output
Figure 9 shows the MAX5104 configured for unipolar,
rail-to-rail operation with a gain of +2V/V. The MAX5104
can produce a 0 to 4.096V output with a 2.048V reference
(Figure 9). Table 2 lists the unipolar output codes. An
offset to the output can be achieved by connecting a
voltage to OS_, as shown in Figure 10. By applying
V
OS_ = -1V, the output values will range between 1V
and (1V + V REF · 2).
Bipolar Output
The MAX5104 can be configured for a bipolar output
(Figure 11). The output voltage is given by the equation
(OS_ = AGND):
Table 2. Unipolar Code Table (Gain = +2)
MAX5104
DAC_
GAIN = +2V/V
REF_
OUT_
OS_
DGND AGND
+5V/+3V
V DD
R
R
Figure 9. Unipolar Output Circuit (Rail-to-Rail)
MAX5104
DAC _
AGND DGND
REF_
OUT_
OS_
V OS
+5V/+3V
V DD
R
R
ANALOG OUTPUT
1 1 1 1 1 1 1 1 11 1 1 ( 0 )
1 0 0 0 0 0 0 0 00 0 1 ( 0 )
DAC CONTENTS
MSB LSB
1 0 0 0 0 0 0 0 00 0 0 ( 0 )
0 1 1 1 1 1 1 1 11 1 1 ( 0 )
0 0 0 0 0 0 0 0 00 0 0 ( 0 ) 0V
0 0 0 0 0 0 0 0 0 0 0 1 ( 0 )
+V
4095
4096
2 REF

 

⋅
+V
2049
4096
REF

 

⋅
2
+V
2048
4096
V REF REF

 

= ⋅
2
+V
2047
4096
REF

 

⋅
2
+V
1
4096
REF

 

⋅
2
Figure 10. Setting OS_ for Output Offset
Note: ( ) are for the sub-bit.