Datasheet

OPA140
OPA2140, OPA4140
www.ti.com SBOS498A –JULY 2010–REVISED AUGUST 2010
PHASE-REVERSAL PROTECTION Although the output current is limited by internal
protection circuitry, accidental shorting of one or more
The OPA140, OPA2140, and OPA4140 family has
output channels of a device can result in excessive
internal phase-reversal protection. Many FET- and
heating. For instance, when an output is shorted to
bipolar-input op amps exhibit a phase reversal when
mid-supply, the typical short-circuit current of 36mA
the input is driven beyond its linear common-mode
leads to an internal power dissipation of over 600mW
range. This condition is most often encountered in
at a supply of ±18V.
noninverting circuits when the input is driven beyond
the specified common-mode voltage range, causing In the case of a dual OPA2140 in an MSOP-8
the output to reverse into the opposite rail. The input package (thermal resistance q
JA
= 180°C/W), such
circuitry of the OPA140, OPA2140, and OPA4140 power dissipation would lead the die temperature to
prevents phase reversal with excessive be 220°C above ambient temperature, when both
common-mode voltage; instead, the output limits into channels are shorted. This temperature increase
the appropriate rail (see Figure 22). significantly decreases the operating life of the
device.
OUTPUT CURRENT LIMIT
In order to prevent excessive heating, the OPAx140
series has an internal thermal shutdown circuit, which
The output current of the OPAx140 series is limited
shuts down the device if the die temperature exceeds
by internal circuitry to +36mA/–30mA
approximately +180°C. Once this thermal shutdown
(sourcing/sinking), to protect the device if the output
circuit activates, a built-in hysteresis of 15°C ensures
is accidentally shorted. This short-circuit current
that the die temperature must drop to approximately
depends on temperature, as shown in Figure 32.
+165°C before the device switches on again.
POWER DISSIPATION AND THERMAL
Additional consideration should be given to the
PROTECTION
combination of maximum operating voltage,
maximum operating temperature, load, and package
The OPAx140 series of op amps are capable of
type. Figure 36 and Figure 37 show several practical
driving 2kΩ loads with power-supply voltages of up to
considerations when evaluating the OPA2140 (dual
±18V over the specified temperature range. In a
version) and the OPA4140 (quad version).
single-supply configuration, where the load is
connected to the negative supply voltage, the
As an example, the OPA4140 has a maximum total
minimum load resistance is 2.8kΩ at a supply voltage
quiescent current of 10.8mA (2.7mA/channel) over
of +36V. For lower supply voltages (either
temperature. The TSSOP-14 package has a typical
single-supply or symmetrical supplies), a lower load
thermal resistance of 135°C/W. This parameter
resistance may be used, as long as the output current
means that because the junction temperature should
does not exceed 13mA; otherwise, the device
not exceed +150°C in order to ensure reliable
short-circuit current protection circuit may activate.
operation, either the supply voltage must be reduced,
or the ambient temperature should remain low
Internal power dissipation increases when operating
enough so that the junction temperature does not
at high supply voltages. Copper leadframe
exceed +150°C. This condition is illustrated in
construction used in the OPA140, OPA2140, and
Figure 36 for various package types. Moreover,
OPA4140 series devices improves heat dissipation
resistive loading of the output causes additional
compared to conventional materials. Printed circuit
power dissipation and thus self-heating, which also
board (PCB) layout can also help reduce a possible
must be considered when establishing the maximum
increase in junction temperature. Wide copper traces
supply voltage or operating temperature. To this end,
help dissipate the heat by acting as an additional
Figure 37 shows the maximum supply voltage versus
heatsink. Temperature rise can be further minimized
temperature for a worst-case dc load resistance of
by soldering the devices directly to the PCB rather
2kΩ.
than using a socket.
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