5V, Low-Power, Voltage-Output,
Serial 10-Bit DACs
MAX504/MAX515
DIN
DIN
REFIN
INVERTED
R-2R DAC
REFOUT
2.048V
33µF
AGND DGND
2R
DOUT SCLK
CS
CLR
VOUT
REFIN
INVERTED
R-2R DAC
2R
RFB
VOUT
SCLK
CS
DOUT
MAX504
V
DD
V
SS
0.1µF
0.1µF
2R
BIPOFF CONNECT BIPOFF
TO VOUT FOR G=1,
TO AGND FOR G=2,
OR TO REFIN FOR
+5V
BIPOLAR GAIN
0V to -5V
MAX515
AGND
0.1µF
V
DD
2R
MAX515
ONLY
+5V
Figure 3a. MAX504 Typical Operating Circuit
Figure 3b. MAX515 Typical Operating Circuit
Daisy-Chaining Devices
The serial output, DOUT, allows cascading of two or more
DACs. The data at DIN appears at DOUT, delayed by 16
clock cycles plus one clock width. For low power, DOUT is
a CMOS output that does not require an external pull-up
resistor. DOUT does
not
go into a high-impedance state
when
CS
is high. DOUT changes on SCLK’s falling edge
when
CS
is low. When
CS
is high, DOUT remains in the
state of the last data bit.
Any number of MAX504/MAX515 DACs can be daisy-
chained by connecting the DOUT of one device to the DIN
of the next device in the chain. For proper timing, ensure
that t
CL
(SCLK low) is greater than t
DO
+ t
DS
.
Bipolar Configuration
A bipolar range is set up by connecting BIPOFF to
REFIN and RFB to VOUT, and operating from dual
(±5V) supplies (Figure 8). Table 3 shows the DAC-latch
contents (input) vs. VOUT (output). In this range,
1LSB = V
REFIN
(2
-9
).
Four-Quadrant Multiplication
The MAX504 can be used as a four-quadrant multiplier
by connecting BIPOFF to REFIN and RFB to VOUT, and
using (1) an offset binary digital code, (2) bipolar power
supplies, and (3) a bipolar analog input at REFIN within
the range V
SS
+ 2V to V
DD
- 2V, as shown in Figure 9.
In general, a 10-bit DAC’s output is (D)(V
REFIN)
(G),
where “G” is the gain (1 or 2) and “D” is the binary rep-
resentation of the digital input divided by 2
10
or 1,024.
This formula is precise for unipolar operation. However,
for bipolar, offset binary operation, the MSB is really a
polarity bit. No resolution is lost because the number of
steps is the same. The output voltage, however, has
been shifted from a range of, for example, 0V to 4.096V
(G = 2) to a range of -2.048V to +2.048V.
Keep in mind that when using the DAC as a four-quad-
rant multiplier, the scale is skewed. Negative full scale
is -V
REFIN
, while positive full scale is +V
REFIN
- 1LSB.
Unipolar Configuration
The MAX504 is configured for a gain of 1 (0V to V
REFIN
unipolar output) by connecting BIPOFF and RFB to VOUT
(Figure 6). The converter operates from either single or
dual supplies in this configuration. See Table 1 for the
DAC-latch contents (input) vs. the analog VOUT (output).
In this range, 1LSB = V
REFIN
(2
-10
), where V
REF
is the
voltage on REFIN.
A gain of 2 (0V to 2V
REFIN
unipolar output) is set up by
connecting BIPOFF to AGND and RFB to VOUT (Figure
7). Table 2 shows the DAC-latch contents vs. VOUT. The
MAX504 operates from either single or dual supplies in
this mode. In this range,
1LSB = (2)(V
REFIN
)(2
-10
) = (V
REFIN
)(2
-9
).
The MAX515 is internally configured for unipolar gain of
2 operation.
10
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