TS9002
than 3µA. 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 components
needed to address power supply feedback, the
TS9002 output does not produce crowbar switching
current as the output switches. At a power supply
voltage of 3V, the propagation delay of the TS9002
is 6μs when the output switches from high-to-low
and low-to-high.
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 TS9002. 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 TS9002 produces a peak-to-peak noise of
about 0.3mVPP while the reference voltage produces
a peak-to-peak noise of about 1mvPP. 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.
Voltage Reference
The TS9002 has an on-board +1.182V voltage
reference with an accuracy of ±0.75%. The REF pin
is able to source and sink 20μA and 10μA of current,
voltage and an IN+ is varied. If the input signals
were reversed, the figure would be the same with an
inverted output. Hysteresis can be generated with
two external resistors using positive feedback as
shown in Figure 2. Resistor R1 is connected
between REF and HYST and R2 is connected
between HYST and V-. This will increase the trip
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
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,
hysteresis effectively forces one comparator input to
move quickly past the other input, moving the input
out of the region where oscillation occurs. Figure 1
illustrates the case in which an IN- input is a fixed
Figure 2. Programming the HYST Pin
point for the rising input voltage, VTHR, and decrease
the trip point for the falling input voltage, VTHF, by the
same amount. If no hysteresis is required, connect
HYST to REF. The hysteresis band, VHB, is voltage
across the REF and HYST pin multiplied by a factor
of 2. The HYST pin can accept a voltage between
REF and REF-50mV, where a voltage of REF-50mV
generates the maximum voltage across R1 and
thus, the maximum hysteresis and hysteresis band
of 50mV and 100mV, respectively. To design the
circuit for a desired hysteresis band, consider the
equations below to acquire the values for resistors
R1 and R2:
Figure 1. Threshold Hysteresis Band
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TS9002DS r1p0
RTFDS
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