LT6703-3 Linear Technology Corporation, LT6703-3 Datasheet - Page 10

• Manufacturer Part Number: LT6703-3
• Description: Micropower, Low Voltage Comparator With 400mv Reference
• Manufacturer: Linear Technology Corporation

LT6703-2/LT6703-3
APPLICATIONS INFORMATION
The LT6703-2/LT6703-3 devices are micropower compara-
tors with a built-in 400mV reference. Features include wide
supply voltage range (1.4V to 18V), Over-The-Top input and
output range, 2% accurate rising input threshold voltage
and 6.5mV typical built-in hysteresis.
Internal Reference
Each comparator has one input available externally. The two
versions of the part differ by the polarity of the available
input (i.e., inverting or noninverting). The other comparator
input is connected internally to the 400mV reference. The
rising input threshold voltage of the comparator is designed
to be equal to that of the reference (i.e., ≈400mV). The
reference voltage is established with respect to the device
GND connection.
Hysteresis
Each comparator has built-in 6.5mV (typical) of hysteresis
to simplify designs, to insure stable operation in the pres-
ence of noise at the inputs, and to reject supply rail noise
that might be induced by state change load transients. The
hysteresis is designed such that the falling input threshold
voltage is nominally 393.5mV. External positive feedback
10
V
THRESHOLD EQUATIONS:
V
V
IN
IN
IN
(L TO H) = (400mV) • (R1) •
(H TO L) = (393mV) • (R1) •
R1
Figure 1. Additional Hysteresis Circuit
R2
+IN
(
(
R1
R1
1
1
+
+
R2
R2
LT6703-3
1
1
GND
+
+
R3
V
S
R3
R3 + R4
1
)
1
)
670323 F01
–
OUT
(
R3 + R4
V
S
• R1
R4
)
V
OUT
circuitry can be employed to increase effective hysteresis
if desired, but such circuitry will provide an apparent effect
on both the rising and falling input thresholds (the actual
internal thresholds remain unaffected).
Comparator Input
The comparator input can range from ground to 18V,
regardless of the supply voltage used. The typical input
current for inputs well above the threshold (i.e., >800mV)
is a few pA leaking into the input. With decreasing input
voltage, a small bias current begins to be drawn out of
the input, reaching a few nA when at ground potential.
The input may be forced 100mV below ground without
causing an improper output, though some additional bias
current will begin to fl ow from the ESD input protection
diode. Inputs driven further negative than 100mV below
ground will not cause damage provided the current is
limited to 10mA.
Comparator Output
The comparator output is open collector and capable of
sinking 40mA typical. Load currents are directed out of
the GND pin of the part. The output off-state voltage may
range between –0.3V and 18V with respect to ground,
regardless of the supply voltage used. As with any open-
collector device, the outputs of multiple comparators may
be tied together to implement wire-AND logic functions.
Power Supplies
The comparator circuitry operates from a single 1.4V
to 18V supply. A minimum 0.1μF bypass capacitor is
required between the V
load is connected to the supply rail near the part and the
output is sinking more than 5mA, a 1μF bypass capacitor is
recommended. In instances where the supply is relatively
“soft” (such as with small batteries) and susceptible to
load steps, an additional 47Ω series decoupling resistor
can further improve isolation of supply transients from
the V
S
pin.
S
pin and GND. When an output
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