MAX5152 Maxim, MAX5152 Datasheet - Page 15

• Manufacturer Part Number: MAX5152
• Description: Low-Power / Dual / 13-Bit Voltage-Output DACs with Configurable Outputs
• Manufacturer: Maxim

Figure 13 shows the MAX5152/MAX5153 in a digital
calibration application. With a bright value applied to
the photodiode (on), the DAC is digitally ramped up
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. The
microprocessor then programs the DAC to set an out-
put voltage that is the midpoint of the two calibration
values. Applications include tachometers, motion sens-
ing, automatic readers, and liquid clarity analysis.
The two DACs can be used to control the offset and
gain for curve-fitting nonlinear functions, such as trans-
ducer linearization or analog compression/expansion
applications. The input signal is used as the reference
for the gain-adjust DAC, whose output is summed with
the output from the offset-adjust DAC. The relative
weight of each DAC output is adjusted by R1, R2, R3,
and R4 (Figure 14).
Figure 14. Digital Control of Gain and Offset
Low-Power, Dual, 13-Bit Voltage-Output DACs
Digital Control of Gain and Offset
SCLK
V
DIN
V
REF
CS
CL
______________________________________________________________________________________
IN
Digital Calibration and
+5V/+3V
V
DGND
DD
Threshold Selection
DACA
DACB
REFB
REFA
AGND
MAX5152
MAX5153
with Configurable Outputs
FBA
OUT_A
OUT_B
FBB
V
OUT
Figure 13. Digital Calibration
NA IS THE NUMERIC VALUE OF THE INPUT CODE FOR DACA.
NB IS THE NUMERIC VALUE OF THE INPUT CODE FOR DACB.
=
=
[ ]
[
R3
P
R1
(
GAIN
V
IN
DIN
8192
NA
– OFFSET
[
R2
)(
DGND
REF_
R1+R2
DAC _
R2
]
MAX5152
MAX5153
)(
1+
R4
R4
R3
) (
] [
+5V/+3V
V
DD
V
AGND
REF
V
OUT
8192
NB
)( )
R4
R3
FB_
OUT_
]
R
V+
PHOTODIODE
V+
V-
V
OUT
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