MAX5650/MAX5651/MAX5652
16-Bit, Parallel-Input, Voltage-Output DACs
with Internal Reference
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The MAX5650/MAX5651/MAX5652 provide an asyn-
chronous clear input (CLR). Asserting CLR resets the
input and DAC registers and DAC output to midscale if
the MID/ZERO input is high and to zero scale when
MID/ZERO is low.
Power-On Reset (POR)
The MAX5650/MAX5651/MAX5652 provide an internal
POR circuit. On power-up, the input and DAC registers
and DAC output are set to 0000 hex if MID/ZERO is low
or 8000 hex if MID/ZERO is high. Wait 10µs after
power-up before pulling CSMSB or CSLSB low.
Internal Scaling Resistors
The MAX5650/MAX5651/MAX5652 include two internal
scaling resistors of 12.4kΩ(typ) each that are matched
to 0.05% or better. Use these resistors with a precision
external op amp to generate a bipolar output swing
(see the Bipolar Operation section). The free ends of
these resistors are accessible at INA and INB while the
midpoint is accessible at MTAP. Connect INB to the
output of the op amp and INA to REF for bipolar opera-
tion. Negative voltages are only allowed at INB (see the
Absolute Maximum Ratings section).
Applications Information
Unipolar Buffered/Unbuffered Operation
Unbuffered operation reduces power consumption as
well as the offset error contributed by the external out-
put buffer (see Figure 1). The R2R DAC output is avail-
able directly at OUT, allowing 16-bit performance from
+VREF to GND without degradation at zero scale.
The typical application circuit (Figure 2) shows the
MAX5650/MAX5651/MAX5652 configured for a
buffered unipolar voltage-output operation. Use the
integrated precision matched resisters for op-amp
input impedance matching. Table 2 shows digital
codes and corresponding output voltages for unipolar
buffered or unbuffered operation.
Bipolar Operation
For bipolar voltage-output operation, use an external op
amp (such as the MAX400) in conjunction with the
internal scaling resistors (see Figure 3). Connect the
free end of the internal resistor (INB) to the output of the
external op amp and the free end of the other resistor
(INA) to REF. Connect the midpoint of the resistors to
the inverting input of the op amp. Connect the output of
the DAC to the noninverting input of the external op
amp. The resulting transfer function is as follows:
where D is the decimal value of the DACs binary input
code. Table 3 shows digital codes and corresponding
output voltages for bipolar operation.
Power-Supply and Layout Considerations
Careful PC board layout is important for optimal system
performance. Wire-wrapped boards, sockets, and
breadboards are not recommended. Keep analog and
digital signals separate to reduce noise injection and
digital feedthrough. Connect AGND and DGND to the
highest quality ground available. Star-connect all
ground return paths back to AGND or use a multilayer
board with a low-inductance ground plane. Connect
analog and digital ground planes together at a low-
impedance power-supply source. For the MAX5652,
keep the trace between the reference source to the ref-
erence input short and low impedance. Bypass each
supply with a 0.1µF capacitor as close as possible to
the IC for optimal 16-bit performance.
Chip Information
PROCESS: BiCMOS
Table 2. Unipolar Code Table
Table 3. Bipolar Code Table