MAX5150 Maxim, MAX5150 Datasheet - Page 15

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

The microprocessor then programs the DAC to set an
output voltage at the midpoint of the two calibrated val-
ues. Applications include tachometers, motion sensing,
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
V
V
REF
IN
Low-Power, Dual, 13-Bit Voltage-Output DACs
SCLK
REFA
REFB
DIN
CS
Digital Control of Gain and Offset
REGISTER
SHIFT
MAX5150
MAX5151
______________________________________________________________________________________
INPUT
REG A
INPUT
REG B
REG A
REG B
DAC
DAC
V
DD
AGND
DACA
DACB
DGND
On power-up, the input and DAC registers clear (set to
zero code). For rated performance, V
least 1.4V below V
4.7µF capacitor in parallel with a 0.1µF capacitor to
AGND. Minimize lead lengths to reduce lead induc-
tance.
Digital and AC transient signals on AGND can create
noise at the output. Connect AGND to the highest quali-
ty ground available. Use proper grounding techniques,
such as a multilayer board with a low-inductance
ground plane. Carefully lay out the traces between
channels to reduce AC cross-coupling and crosstalk.
Wire-wrapped boards and sockets are not recommend-
ed. If noise becomes an issue, shielding may be
required.
R
R
R
R
with Serial Interface
OUTA
OUTB
OSB
Grounding and Layout Considerations
OSA
V
OUT
NA IS THE NUMERIC VALUE OF THE INPUT CODE FOR DACA.
NB IS THE NUMERIC VALUE OF THE INPUT CODE FOR DACB.
R3
R1
=
=
[ ]
[
(
Power-Supply Considerations
GAIN
V
DD
IN
2NA
8192
. Bypass the power supply with a
– OFFSET
R2
[
)(
R1+R2
R2
]
)(
R4
1+
R4
R3
) (
] [
REF_
V
V
OUT
REF
should be at
8192
2NB
)( )
R4
R3
]
15