TSM971/72/73/82/84
V- pin can be set to a voltage below GND as long as
the voltage difference between V+ and V- is within
11V. The TSM971 and the TSM984 sink current to
GND. By having open-drain outputs, the
TSM971/972/973/982/984 can be used in wire-
OREd and level-shifting applications. On the other
hand, the TSM972, TSM973, and the TSM982 do
not have a GND pin so the outputs sink current to V-
. With a 100mV input overdrive, the propagation
delay of the TSM971/972/973/982/984 is 4μs.
THEORY OF OPERATION
The
TSM971/972/973/982/984
family
of
single/dual/quad, low-voltage, micropower analog
comparators provide excellent flexibility and
performance while sourcing continuously up to
40mA of current. The TSM971, TSM973, TSM982,
and the TSM984 provide an on-board 1.182V
reference voltage. To minimize current consumption
while providing flexibility, the TSM971, TSM973, and
the TSM982 have an on-board HYST pin in order to
add additional hysteresis.
Voltage Reference
The TSM971/972/973 have an on-board 1.182V
reference voltage with an accuracy of ±1% while the
TSM982/984 have an on-board 1.182V reference
Power-Supply and Input Signal Ranges
The TSM971/972/973/982/984 can operate from a
single supply voltage range of +2.5V to +11V,
provide a wide common mode input voltage range of
V- to V+-1.3V, and accept input signals ranging from
V- to V+ - 1V. The inputs can accept an input as
much as 300mV above the below the power supply
rails without damage to the part. While the TSM971
and the TSM984 are able to operate from a single
supply voltage range, a GND pin is available that
allows for a dual supply operation with a range of
±1.25V to ±5.5V. If a single supply operation is
desired, the GND pin needs to be tied to V-. In a
dual supply mode, the TSM971 and the TSM984 are
compatible with TTL/CMOS with a ±5V voltage and
the TSM972, TSM973, and TSM982 are compatible
with TTL with a single +5V supply.
voltage with an accuracy of ±2% across
a
temperature range of 0°C to +70°C. The REF pin is
able to source and sink 25μA and 15μA of current,
respectively. The REF pin is referenced to V- and it
should not be bypassed.
Noise Considerations
Noise can play a role in the overall performance of
the TSM971/972/973/982/984. Despite having a
large gain, if the input voltage is near or equal to the
input offset voltage, the output will randomly switch
HIGH
and
LOW.
As
a
result,
the
TSM971/972/973/982/984 produces a peak-to-peak
noise of about 0.3mV while the reference voltage
produces a peak-to-peak noise of about 1mV.
Furthermore, it is important to design a layout that
minimizes capacitive coupling from a given output to
the reference pin as crosstalk can add noise and as
a result, degrade performance.
Low-Voltage Operation: V+ = 1.5V (TSM984 Only)
Due to a decrease in propagation delay and a
reduction in output drive, the TSM971/972/973/982
cannot be used with a supply voltage much lower
than 2.5V. However, the TSM984 can operate down
to a supply voltage of 2V; furthermore, as the supply
voltage reduces, the TSM984 supply current drops
and the performance is degraded. When the supply
voltage drops to 2.2V, the reference voltage will no
longer function; however, the comparators will
APPLICATIONS INFORMATION
Hysteresis
As a result of circuit noise or unintended parasitic
feedback, many analog comparators often break into
oscillation within their linear region of operation
especially when the applied differential input voltage
approaches 0V (zero volt). Externally-introduced
function down to
a
1.5V supply voltage.
Furthermore, the input voltage range is extended to
just below 1V the positive supply rail. For
applications with a sub-2.5V power supply, it is
recommended to evaluate the circuit over the entire
power supply range and temperature.
hysteresis is
a
well-established technique to
stabilizing analog comparator behavior and requires
external components. As shown in Figure 1, adding
comparator hysteresis creates two trip points: VTHR
(for the rising input voltage) and VTHF (for the falling
input voltage). The hysteresis band (VHB) is defined
as the voltage difference between the two trip points.
When a comparator’s input voltages are equal,
Comparator Output
The TSM971 and the TSM984 have a GND pin that
allows the output to swing from V+ to GND while the
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RTFDS
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