New Comparators Feature Micropower Operation
Under All Conditions – Design Note 137
Jim Williams
Some micropower comparators have operating modes
that allow excessive current drain. In particular, poorly
designed devices can conduct large transient currents
during switching. Such behavior causes dramatically
increased power drain with rising frequency, or when
the inputs are nearly balanced, as in battery monitoring
applications. resulting in greatly reduced power consumption versus
frequency, or when the inputs are nearly balanced. Figure 2’s
plot contrasts the LTC1440’s power consumption versus
frequency with that of another comparator specified as a
micropower component. The LTC1440 has about 200 times
lower current consumption at higher frequencies, while
maintaining a significant advantage below 1kHz. Figure 1 shows a popular micropower comparator’s current
consumption during switching. Trace A is the input pulse,
trace B is the output response and trace C is the supply
current. The device, specified for micropower level supply drain, pulls 40mA during switching. This undesirable
surprise can upset a design’s power budget or interfere
with associated circuitry’s operation. Table 1 shows some LTC1440 family characteristics. A voltage reference and programmable hysteresis are included
in some versions, with 5Вµs response time for all devices. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks
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