Datasheet

AD5203
–11–REV. 0
The data setup and data hold times in the specification table
determine the data valid time requirements. The last eight bits
of the data word entered into the serial register are held when
CS returns high. At the same time CS goes high it gates the
address decoder which enables one of four positive edge trig-
gered RDAC latches, see Figure 36 detail.
RDAC 1
RDAC 2
RDAC 4
AD5203
SDI
CLK
CS
ADDR
DECODE
SERIAL
REGISTER
Figure 36. Equivalent Input Control Logic
The target RDAC latch is loaded with the last six bits of the
serial data word completing one RDAC update. Four separate
8-bit data words must be clocked in to change all four VR
settings.
SERIAL
REGISTER
SDI
CK
RS
D
Q
SHDN
CS
CLK
RS
SDO
Figure 37. Detail, SDO Output Schematic of the AD5203
All digital inputs are protected with a series input resistor and
parallel Zener ESD structure shown in Figure 38. Applies to
digital input pins CS, SDI, SDO, RS, SHDN, CLK.
1kV
LOGIC
Figure 38. Equivalent ESD Protection Circuit
DYNAMIC CHARACTERISTICS
The total harmonic distortion plus noise (THD+N) measures
0.003% using an offset ground with a rail-to-rail OP279 invert-
ing op amp test circuit, see Figure 30. Figure 15 plots THD
versus frequency for both inverting and noninverting amplifier
topologies. Thermal noise is primarily Johnson noise, typically
9 nV/√Hz for the 10 kΩ version measured at 1 kHz. For the
100 kΩ device, thermal noise measures 29 nV/√Hz. Channel-to-
channel crosstalk measures less than –65 dB at f = 100 kHz. To
achieve this isolation, the extra ground pins (AGND) located
between the potentiometer terminals (A, B, W) must be con-
nected to circuit ground. The AGND and DGND pins should
be at the same voltage potential. Any unused potentiometers in
a package should be connected to ground. Power supply rejec-
tion is typically –50 dB at 10 kHz (care is needed to minimize
power supply ripple injection in high accuracy applications).