Rainbow Electronics MAX5184 - Manual (Page 8)

MAX5181/MAX5184
10-Bit, 40MHz, Current/Voltage-Output DACs
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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 400
Ω 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 400
Ω load resistors. Using the internal
+1.2V reference voltage, the MAX5184’s integrated
9.6k*
REFR
REFO
1.2V REF
REN
CURRENT-
SOURCE ARRAY
DAC SWITCHES
400 Ω*
OUTP
OUTN
400 Ω*
MSB
DECODE
CLK
OUTPUT
LATCHES
OUTPUT
LATCHES
INPUT
LATCHES
*INTERNAL 400 Ω AND 9.6kΩ
RESISTORS FOR MAX5184 ONLY.
INPUT
LATCHES
AV DD AGND CS DACEN PD
DV
DD
DGND
CREF
MAX5181
MAX5184
MSB
DECODE
D9–D0
Figure 1. Functional Diagram