MAX5182/MAX5185
Dual, 10-Bit, 40MHz Current/Voltage
Alternate-Phase Output DACs
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Detailed Description
The MAX5182/MAX5185 are dual, 10-bit digital-to-ana-
log converters (DACs) capable of operating with clock
speeds up to 40MHz. Each of these dual converters
consists of separate input and DAC registers, followed
by a current-source array capable of generating up to
1.5mA full-scale output current (Figure 1). An integrated
+1.2V voltage reference and control amplifier determine
the data converters’ full-scale output currents/voltages.
Careful reference design ensures close gain matching
and excellent drift characteristics. The MAX5185, with
its voltage output operation, features matched 400Ω on-
chip resistors that convert the current from the current
array into a voltage.
Internal Reference and Control Amplifier
The MAX5182/MAX5185 provide an integrated
50ppm/°C, +1.2V, low-noise bandgap reference, which
can be disabled and overridden by an external refer-
ence voltage. REFO serves either as an input for an
external reference or as an output for the integrated ref-
erence. If REN is connected to DGND, the internal ref-
erence is selected and REFO provides a +1.2V output.
Due to its limited 10µA output drive capability, the
REFO pin must be buffered with an external amplifier if
heavier loading is required.
The MAX5182/MAX5185 also employ a control amplifier
designed to simultaneously regulate the full-scale out-
put current IFS for both outputs of the ICs. The output
current is calculated as follows:
I
FS
= 8 ✕ I
REF
where I
REF
is the reference output current (I
REF
=
V
REFO
/R
SET
), and I
FS
is the full-scale output current.
R
SET
is the reference resistor that determines the
amplifier’s output current (Figure 2) on the MAX5182.
This current is mirrored into the current-source array,
where it is equally distributed between matched current
segments, and summed to valid output current read-
ings for the DACs.
Inside the MAX5185, each output current (DAC1 and DAC2)
is converted to an output voltage (V
OUT1
, V
OUT2
) with two
internal, ground-referenced 400Ω load resistors. Using the
internal +1.2V reference voltage, the MAX5185’s integrated
reference output current resistor (R
SET
= 9.6kΩ), sets I
REF
to 125µA and I
FS
to 1mA.
RESISTORS FOR MAX5185 ONLY.
