Datasheet

AD5551/AD5552
Rev. A | Page 13 of 16
REFERENCE AND GROUND
As the input impedance is code-dependent, the reference pin
should be driven from a low-impedance source. The AD5551/
AD5552 operate with a voltage reference ranging from 2 V to
V
DD
. Although DAC’s full-scale output voltage is determined by
the reference, references below 2 V results in reduced accuracy.
Table 6 and Table 7 outline the analog output voltage for
particular digital codes. For optimum performance, Kelvin
sense connections are provided on the AD5552.
If the application does not require separate force and sense
lines, they should be tied together close to the package to
minimize voltage drops between the package leads and the
internal die. ADR291 and ADR293 are suitable references
for this product.
POWER-ON RESET
These parts have a power-on reset function to ensure the output
is at a known state upon power-up. After power-up, the DAC
register contains all zeros, until data is loaded from the serial
register. However, the serial register is not cleared on power-up,
so its contents are undefined. When loading data initially to the
DAC, 14 bits or more should be loaded to prevent erroneous
data appearing on the output. If more than 14 bits are loaded,
only the last 14 are kept, and if fewer than 14 are loaded, bits
remain from the previous word. If the AD5551/AD5552 needs
to be interfaced with data shorter than 14 bits, the data should
be padded with zeros at the LSBs.
POWER SUPPLY AND REFERENCE BYPASSING
For accurate high-resolution performance, it is recommended
that the reference and supply pins be bypassed with a 10 F
tantalum capacitor in parallel with a 0.1 F ceramic capacitor.