Datasheet

IN+

IN-

GAIN

2.2kW

10nF

SENSE+

SENSE-

=47mA

(1.4V – 0.7V)

15W

OPA

XTR300

I/VOUT

V+

V-

47nF

15W

100nF

1N4002

DRV

XTR300

SBOS336C –JUNE 2005– REVISED JUNE 2011

www.ti.com

OUTPUT PROTECTION

The XTR300 is intended to operate in a harsh industrial environment. Therefore, a robust semiconductor process

was chosen for this design. However, some external protection is still required.

The instrumentation amplifier inputs can be protected by external resistors that limit current into the protection

cell behind the IC-pins, as shown in Figure 44. This cell conducts to the power-supply connection through a

diode as soon as the input voltage exceeds the supply voltage. The circuit configuration example shows how to

arrange these two external resistors.

The bias current is best cancelled if both resistors are equal. The additional capacitor reduces RF noise in the

input signal to the IA.

Figure 44. Current-Limiting Resistors

The load connection to the DRV output must be low impedance; therefore, external protection diodes may be

necessary to handle excessive currents, as shown in Figure 45. The internal protection diodes start to conduct

earlier than a normal external PN-type diode because they are affected by the higher die temperature. Therefore,

either Schottky diodes are required, or an additional resistor (R

) can be placed in series with the input. An

example of this protection is shown in Figure 45. Assuming the standard diodes limit the voltage to 1.4V and the

internal diodes clamp at 0.7V, this resistor can limit the current into the internal protection diodes to 50mA:

(7)

is also part of the recommended loop compensation. C

helps protect the output against RFI and high-voltage

spikes.

Figure 45. Example for DRV Output Protection