DA C
Austin Semiconductor, Inc.
DETAILED DESCRIPTION
The AS5181 is a 10-bit digital-to-analog converters (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 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.
AS5181
selected and provides a +1.2V output. Due to its limited 10µA
output drive capability, REFO must be buffered with an external
amplifier, if heavier loading is required.
The AS5181 also employ a control amplifier designed to
regulate simultaneously the full-scale output 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
AS5181 (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.
Internal Reference and Control Amplifier
The AS5181 provide an integrated 50ppm/°C, 1.2V,
low-noise bandgap reference that can be disabled 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
FIGURE 1: Functional Diagram
AS5181
Rev. 0.3 6/05
Austin Semiconductor, Inc. reserves the right to change products or specifications without notice.
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AUSTIN [ AUSTIN SEMICONDUCTOR ]
