CAT5171_13 Datasheet, PDF (8/12 Pages) ON Semiconductor – 256‐position I2C Compatible Digital Potentiometer (POT)

CAT5171
ESD Protection
Digital
Input
LOGIC
GND
W, A, B
Potentiometer
GND
Figure 12. ESD Protection Networks
Terminal Voltage Operating Range
The CAT5171 V_DD and GND power supply define the
limits for proper 3-terminal digital potentiometer operation.
Signals or potentials applied to terminals A, B or the wiper
must remain inside the span of V_DD and GND. Signals
which attempt to go outside these boundaries will be
clamped by the internal forward biased diodes.
V_DD
Power-up Sequence
Because ESD protection diodes limit the voltage
compliance at terminals A, B, and W (see Figure 12), it is
recommended that V_DD/GND be powered before applying
any voltage to terminals A, B, and W. The ideal power−up
sequence is: GND, V_DD, digital inputs, and then V_A/B/W. The
order of powering V_A, V_B, V_W, and the digital inputs is not
important as long as they are powered after V_DD/GND.
Power Supply Bypassing
Good design practice employs compact, minimum lead
length layout design. Leads should be as direct as possible.
It is also recommended to bypass the power supplies with
quality low ESR Ceramic chip capacitors of 0.01 mF to
0.1 mF. Low ESR 1 mF to 10 mF tantalum or electrolytic
capacitors can also be applied at the supplies to suppress
transient disturbances and low frequency ripple. As a further
precaution digital ground should be joined remotely to the
analog ground at one point to minimize the ground bounce.
V_DD
+
C₃
10 mF
C₁
0.1 mF
V_DD
CAT5171
GND
Figure 14. Power Supply Bypassing
W, A, B
LOGIC
CAT5171
GND
Figure 13.
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