ADA4800
Rev. A | Page 12 of 16
POWER SUPPLY BYPASSING
Attention must be paid to bypassing the power supply pin of
the ADA4800. Use high quality capacitors with low equivalent
series resistance (ESR), such as multilayer ceramic capacitors
(MLCCs), to minimize supply voltage ripple and power dissipa-
tion. A large, usually tantalum, 2.2 F to 47 F capacitor located
in close proximity to the ADA4800 is required to provide good
decoupling for lower frequency signals. The actual value is
determined by the circuit transient and frequency requirements. In
addition, 0.1 F MLCC decoupling capacitors should be located
as close to the power supply pin as is physically possible, no more
than ⅛ inch away. The ground returns should terminate imme-
diately into the ground plane. Locating the bypass capacitor
return close to the load return minimizes ground loops and
improves performance.
POWER SEQUENCING
All I/O pins are ESD protected with internal back-to-back
diodes connected to VCC and GND as shown in Figure 24.
With the ADA4800 supply turned off (V
CC
= 0 V), a voltage on
an I/O pin can turn on the protection diodes and cause permanent
damage or destroy the IC. To prevent this condition during
power-on, no voltages should be applied to any I/O pins until
VCC is fully on and settled. During power-off, I/O pin voltages
should be removed or reduced to 0 V before VCC is turned off.
ADA4800
C
EXTERNAL
PIN
09162-030
Figure 24. Simplified Input/Output Circuitry
In the presence of a voltage on an I/O pin with V
CC
= 0 V, the
current should be limited to 5 mA or less by the source or by
adding a series resistor.
