MAX5150 Maxim, MAX5150 Datasheet - Page 14

• Manufacturer Part Number: MAX5150
• Description: Low-Power / Dual / 13-Bit Voltage-Output DACs with Serial Interface
• Manufacturer: Maxim

The MAX5150/MAX5151 can be configured for a bipo-
lar output, as shown in Figure 11. The output voltage is
given by the equation (OS_ = AGND):
where NB represents the numeric value of the DAC’s
binary input code. Table 3 shows digital codes and the
corresponding output voltage for Figure 11’s circuit.
In applications where the reference has an AC signal
component, the MAX5150/MAX5151 have multiplying
capabilities within the reference input voltage range
specifications. Figure 12 shows a technique for apply-
ing a sinusoidal input to REF_, where the AC signal is
offset before being applied to REF.
Low-Power, Dual, 13-Bit Voltage-Output DACs
with Serial Interface
14
Table 3. Bipolar Code Table
Figure 11. Bipolar Output Circuit
1 1 1 1 1
1 0 0 0 0
1 0 0 0 0
0 1 1 1 1
0 0 0 0 0
0 0 0 0 0
MSB
TOLERANCES: 10k
REF_
______________________________________________________________________________________
DAC CONTENTS
DAC _
MAX5150
MAX5151
V
1 1 1 1
0 0 0 0
0 0 0 0
1 1 1 1
0 0 0 0
0 0 0 0
OUT
+5V/+3V
± 0.1%
DGND
= V
V
DD
LSB
1 1 1 1
0 0 0 1
0 0 0 0
1 1 1 1
0 0 0 1
0 0 0 0
REF
R
R
AGND
[((2 x NB) / 8192) - 1]
Using an AC Reference
OUT_
OS_
-V
10k
ANALOG OUTPUT
REF
10k
10k
+V
+V
-V
-V
Bipolar Output
REF
REF
REF
REF
4096
4096
0V
4096
4095
4096
V+
V-
10k
4095
4096
4096
1
1
- V
REF
V
OUT
The total harmonic distortion plus noise (THD+N) is typ-
ically less than -78dB at full scale with a 1Vp-p input
swing at 5kHz. The typical -3dB frequency is 300kHz
for both devices, as shown in the Typical Operating
Characteristics.
Figure 13 shows the MAX5150/MAX5151 in a digital
calibration application. With a bright light value applied
to the photodiode (on), the DAC is digitally ramped until
it trips the comparator. The microprocessor stores this
“high” calibration value. Repeat the process with a
dim light (off) to obtain the dark current calibration.
Figure 13. Digital Calibration
Figure 12. AC Reference Input Circuit
REFERENCE
500mVp-p
+5V/
P
+3V
INPUT
AC
DIN
26k
REF_
AGND
DAC _
10k
MAX5150
MAX5151
Harmonic Distortion and Noise
+5V/+3V
+5V/+3V
V
DD
AGND
DAC_
Digital Calibration and
REF
MAX495
DGND
Threshold Selection
R
R
MAX5150
MAX5151
OUT_
OS_
V
DD
GND
V+
R
R
PHOTODIODE
PULLDOWN
R
V+
V-
OS_
OUT
V
OUT