Some op-amps even include a hardware shutdown control.
The TLV906x series of wideband (10MHz) low voltage, single,
dual, and quad op-amps offer this additional feature, denoted
by versions with an "S" suffix. This is a discrete shutdown
pin that can be invoked to individually disable each op-amp
and so place it in a low-power standby mode, Figure 8a and
Figure 8b. In this mode, the op-amp typically consumes less
than 1μA, which is almost three orders of magnitude less than
its 538μA quiescent current; enable time is 10μsec for full
shutdown of all channels while disable time is 3μs.
Figure 8a and Figure 8b: Each op-amp in the TLV906x series of
single, dual, and quad op-amps comes in two versions: a) no separate
shutdown-control input (here for the dual-channel devices) and b) an
extended package with a control for each internal op-amp.
(Source: Texas Instruments)
The comparator function is so basic and simple that it is easy
to ignore its critical role in many system implementations,
where it functions as a basic overvoltage/undervoltage detector
for out-of-spec conditions, or as a zero-crossing detector.
Comparators are often set up to operate independent of any
software, thus providing an added level of operational integrity
and confidence. The TLV3691 0.9V to 6.5V (or ±0.45V to
±3.25V) nanopower comparator with quiescent current of just
75nA at 25°C increasing to 150nA at 125°C. Its fast 24μsec
response time makes it a good fit for critical alarm situations
such as a bus undervoltage/overvoltage window circuit,
Figure 9, with response shown in Figure 10.
Figure 9: The simplicity of a comparator-based circuit is among its
virtues, as shown by this bus undervoltage/overvoltage window-alarm
configuration using two TLV3691 devices. Source: Texas Instruments
Figure 10: The basic window circuit generates an alert when the input
signal falls below 1.25V or rises above 3.3V, yet requires less than 1µA
from a 5V supply. (Source: Texas Instruments)
15
Conclusion
Basic analog components such as op-amps and
comparators have a large yet sometimes unseen
role in many applications such as IoT sensor
interfaces as well as automotive designs. For these
(and other) designs, it's important to select devices
with low quiescent current—whether to maximize
battery life or minimize vampire power drain—and
stay within tight power budgets.
Fortunately, the newest of these components
have miniscule quiescent current needs while
also offering excellent performance for other
parameters such as bandwidth, noise, offset, and
drift, to cite a few of their many specifications.
