The DAC1220 is a 20-bit digital-to-analog (D/A) converter offering 20-bit monotonic performance over the specified temperature range

DAC1220

Manufacturer Part NumberDAC1220
DescriptionThe DAC1220 is a 20-bit digital-to-analog (D/A) converter offering 20-bit monotonic performance over the specified temperature range
ManufacturerTexas Instruments
DAC1220 datasheet
 


Specifications of DAC1220

Resolution(bits)20Dac: Channels1
InterfaceSerial SPIOutput TypeVoltage
Output Range Max.(v Or Ma)5.5Settling Time(µs)10000
Reference: TypeExtPower Consumption(typ)(mw)2.5
Dnl(max)(+/-lsb)1Inl(max)(+/-lsb)1
Pin/package16SSOP/QSOP  
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DAC1220
SBAS082G – FEBRUARY 1998 – REVISED SEPTEMBER
Layout Recommendations
The DAC1220 is a high-precision analog component
incorporating
digital
elements.
precision is not difficult, but achieving excellent
precision may require several attempts.
It is critical to supply a guard ring, or fill, around the
C
and C
pins. The guard ring should be connected
1
2
to the voltage reference. These nodes are very
sensitive, and are good places for noise to couple
through to the output. A ground fill on the opposite
side of the board, or a ground plane, is also a good
idea.
The capacitors themselves should be placed as near
the pins as possible. In particular, the traces leading
from C
and C
should be kept very short. The traces
1
2
leading to V
and V
can be longer.
OUT
REF
It is also very important to route digital traces away
from analog traces, so that their associated return
currents will not couple into the analog side.
If a crystal is used, do not route the traces connecting
the crystal to the device through vias, if possible,
because this will increase the trace inductance and
may affect startup and reliability. Keep the traces
short, and place the crystal close to the device. Keep
in mind that extra ground planes and trace lengths
increase parasitic capacitance, and this should be
deducted from the load capacitor values.
Software Considerations
A key to communicating successfully with the
DAC1220 is observing the delays in the interface
timing diagrams. A violation of these delays, at best,
results in lack of correct output; at worse, violating the
delays can corrupt communications entirely.
18
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APPLICATION INFORMATION
Note that the delays are slightly different if chip-select
(CS) is not being used.
Timing delays from the beginning of an SPI byte
Achieving
good
transmission
microcontroller firmware that uses an SPI peripheral.
Be sure that any delay routine begins once a byte
has completed transmission, or add the byte
transmission time to the delay time.
Some programmers may find that bit-banging, or
direct manipulation of microcontroller I/O pins, is the
easiest way to communicate with the DAC1220,
because of the delays and direction changes
required.
Write-Only Interfacing
In some situations, such as isolated interfacing, it is
inconvenient to use the DAC1220 bidirectionally,
since the SDIO pin changes direction for readback.
The DAC1220 can be used write-only. The following
considerations apply:
When used write-only, it is not possible to verify
that the DAC1220 is operating using its serial
interface alone. The operation of the DAC is
open-loop.
It may be helpful to wait at least 150ms-200ms
after startup. This ensures that, in case the reset
was a result of firmware problems and not
power-up, any previous communication with the
DAC has been cancelled by the I/O recovery
timeout.
When applying the SCLK reset pattern, which can
be done in place of the above steps, allow time for
the oscillator to start before applying the pattern.
The pattern is detected based on oscillator cycles,
so it will not be detected if the oscillator is not yet
running.
Product Folder Link(s):
DAC1220
www.ti.com
are
a
common
problem
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