TSM931 TOUCHSTONE [Touchstone Semiconductor Inc], TSM931 Datasheet - Page 12

• Manufacturer Part Number: TSM931
• Description: Ultra Low-Power Single/Dual-Supply Comparators with Reference
• Manufacturer: TOUCHSTONE [Touchstone Semiconductor Inc]

TSM931-TSM934
THEORY OF OPERATION
The TSM931–TSM934 family of single/dual/quad,
low-voltage,
provide excellent flexibility and performance while
sourcing continuously up to 40mA of current. The
TSM931-TSM934 provide an on-board 1.182V ±2%
reference voltage. To minimize glitches that can
occur with parasitic feedback or a less than optimal
board layout, the design of the TSM931-TSM934
output stage is optimized to eliminate crowbar
glitches as the output switches. To minimize current
consumption
TSM931-TSM933 have an on-board HYST pin in
order to add additional hysteresis.
Power-Supply and Input Signal Ranges
The TSM931-TSM934 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 TSM931 and
the TSM934 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 TSM931 and the TSM934 are compatible
with TTL/CMOS with a ±5V voltage and the TSM932
and the TSM933 are compatible with TTL with a
single +5V supply.
Low-Voltage Operation: V+ = 1.5V (TSM934 Only)
Due to a decrease in propagation delay and a
reduction in output drive, the TSM931-TSM933
cannot be used with a supply voltage much lower
than 2.5V. However, the TSM934 can operate down
to a supply voltage of 2V; however, as the supply
voltage reduces, the TSM934 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
function
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
Page 12
down
micropower
while
to
a
providing
1.5V
analog
supply
flexibility,
comparators
voltage.
the
recommended to evaluate the circuit over the entire
power supply range and temperature.
Comparator Output
The TSM931 and the TSM934 have a GND pin that
allows the output to swing from V+ to GND while the
V- pin can be set to a voltage below GND as long as
the voltage difference between V+ and V- is within
11V. Having a different voltage on V- will not affect
the output swing. For TTL applications, V+ can be
set to +5V±10% and V- can be set anywhere
between 0V and -5V±10%. On the other hand, the
TSM932 and the TSM933 do not have a GND pin;
hence, for TTL applications, V+ needs to be set to a
+5V power supply and V- to 0V. Furthermore, the
output design of the TSM931-TSM934 can source
and sink more than 40mA and 5mA, respectively,
while simultaneously maintaining a quiescent current
in the microampere range. If the power dissipation of
the package is maintained within the max limit, the
output can source pulses of 100mA of current with
V+ set to +5V. In an effort to minimize external
component count needed to address power supply
feedback, the TSM931-TSM934 output does not
produce crowbar switching current as the output
switches. With a 100mV input overdrive, the
propagation delay of the TSM931-TSM934 is 4μs.
Voltage Reference
The TSM931-TSM934 have an on-board 1.182V
reference 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 15μA and 8μA 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 TSM931-TSM934. 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 TSM931-TSM934 produces a
peak-to-peak noise of about 0.3mV
reference voltage produces a peak-to-peak noise of
about 1mV
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.
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. Furthermore, it is important to design
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while the
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