Lo w -P o w e r, Du a l, 1 2 -Bit Vo lt a g e -Ou t p u t DACs
w it h S e ria l In t e rfa c e
Table 3. Bipolar Code Table
+5V/
+3V
+5V/+3V
DAC CONTENTS
ANALOG OUTPUT
26k
AC
MSB
LSB
MAX495
REFERENCE
INPUT
2047
+V
1 1 1 1 1 1 1 1 1 1 1 1 (0 )
REF
2048
10k
V
DD
REF
R
500mVp-p
1
OS_
1 0 0 0 0 0 0 0 0 0 0 1 (0 )
1 0 0 0 0 0 0 0 0 0 0 0 (0 )
0 1 1 1 1 1 1 1 1 1 1 1 (0 )
+V
REF
2048
R
DGND
V+
0V
OUT_
DAC_
1
-V
REF
2048
MAX5154
MAX5155
2047
0 0 0 0 0 0 0 0 0 0 0 1 (0 )
-V
REF
AGND
2048
2048
-V
= - V
REF
0 0 0 0 0 0 0 0 0 0 0 0 (0 )
REF
4/MAX15
2048
Figure 12. AC Reference Input Circuit
Note: ( ) are for the sub bit.
+5V/+3V
REF_
PHOTODIODE
REF_
+5V/+3V
10k
10k
V+
OS_
V
DD
OS_
V
DD
R
R
V+
MAX5154
MAX5155
R
R
MAX5154
MAX5155
V
OUT
OUT_
10k
V
OUT
DAC _
AGND
µP
DAC _
V-
OUT_
DIN
DGND
10k
R
PULLDOWN
V-
DGND
AGND
Figure 13. Digital Calibration
Figure 11. Bipolar Output Circuit
ing a sinusoidal input to REF_, where the AC signal is
offset before being applied to the reference input.
Bip o la r Ou t p u t
The MAX5154/MAX5155 can be configured for a bipo-
lar output, as shown in Figure 11. The output voltage is
given by the equation (OS_ = AGND):
Ha rm o n ic Dis t o rt io n a n d No is e
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.
V
OUT
= V
[((2 x NB) / 4096) - 1]
REF
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.
Us in g a n AC Re fe re n c e
In applications where the reference has an AC signal
component, the MAX5154/MAX5155 have multiplying
capabilities within the reference input voltage range
specifications. Figure 12 shows a technique for apply-
Dig it a l Ca lib ra t io n a n d
Th re s h o ld S e le c t io n
Figure 13 shows the MAX5154/MAX5155 in a digital
calibration application. With a bright light value applied
to the photodiode (on), the DAC is digitally ramped until
14 ______________________________________________________________________________________
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
