Datasheet

GENERAL LAYOUT GUIDELINES
300W
+3V
150W
R
(1)
1
2V V- D
2V+ VD
3V
R
G
INA333
V
O
Ref
1.5V
INPUT PROTECTION
APPLICATION IDEAS
INA333
R /2
G
V
O
LA
RL
RA
10kW
Ref
G=102.8kW
2.8kW
1/2
OPA2333
390kW
390kW
1/2
OPA2333
INA333
SBOS445B – JULY 2008 – REVISED OCTOBER 2008 ..................................................................................................................................................... www.ti.com
Attention to good layout practices is always
recommended. Keep traces short and, when
possible, use a printed circuit board (PCB) ground
plane with surface-mount components placed as
close to the device pins as possible. Place a 0.1 µ F
bypass capacitor closely across the supply pins.
These guidelines should be applied throughout the
analog circuit to improve performance and provide
benefits such as reducing the
electromagnetic-interference (EMI) susceptibility.
(1) R
1
creates proper common-mode voltage, only for low-voltage Instrumentation amplifiers vary in the susceptibility to
operation — see the Single-Supply Operation section.
radio-frequency interference (RFI). RFI can generally
be identified as a variation in offset voltage or dc
Figure 35. Single-Supply Bridge Amplifier
signal levels with changes in the interfering RF signal.
The INA333 has been specifically designed to
minimize susceptibility to RFI by incorporating
passive RC filters with an 8MHz corner frequency at
The input terminals of the INA333 are protected with
the V
IN+
and V
IN –
inputs. As a result, the INA333
internal diodes connected to the power-supply rails.
demonstrates remarkably low sensitivity compared to
These diodes clamp the applied signal to prevent it
previous generation devices. Strong RF fields may
from damaging the input circuitry. If the input signal
continue to cause varying offset levels, however, and
voltage can exceed the power supplies by more than
may require additional shielding.
0.3V, the input signal current should be limited to less
than 10mA to protect the internal clamp diodes. This
current limiting can generally be done with a series
input resistor. Some signal sources are inherently
Additional application ideas are shown in Figure 36 to
current-limited and do not require limiting resistors.
Figure 39 .
Figure 36. ECG Amplifier With Right-Leg Drive
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