MAX5181/MAX5184
10-Bit, 40MHz, Current/Voltage-Output DACs
8 _______________________________________________________________________________________
Detailed Description
The MAX5181/MAX5184 are 10-bit digital-to-analog con-
verters (DACs) capable of operating with clock speeds
up to 40MHz. Each converter consists of separate input
and DAC registers, followed by a current source array
capable of generating up to 1.5mA full-scale output cur-
rent (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 charac-
teristics. The MAX5184’s voltage output operation fea-
tures matched 400Ω on-chip resistors that convert the
current-array current into a voltage.
Internal Reference and
Control Amplifier
The MAX5181/MAX5184 provide an integrated 50ppm/°C,
+1.2V, low-noise bandgap reference that can be dis-
abled and overridden by an external reference voltage.
REFO serves either as an external reference input or an
integrated reference output. If REN is connected to
DGND, the internal reference is selected and REFO
provides a +1.2V output. Due to its limited 10µA output
drive capability, REFO must be buffered with an exter-
nal amplifier, if heavier loading is required.
The MAX5181/MAX5184 also employ a control amplifier
designed to regulate simultaneously the full-scale out-
put current (I
FS
) for both outputs of the devices. 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 on the MAX5181 (Figure 2).
This current is mirrored into the current source array,
where it is equally distributed between matched current
segments and summed to valid output current readings
for the DACs.
The MAX5184 converts this output current into a differ-
ential output voltage (V
OUT
) with two internal, ground-
referenced 400Ω load resistors. Using the internal
+1.2V reference voltage, the MAX5184’s integrated
RESISTORS FOR MAX5184 ONLY.
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