LT1011IS8#TRPBF Linear Technology, LT1011IS8#TRPBF Datasheet - Page 7

• Manufacturer Part Number: LT1011IS8#TRPBF
• Description: IC VOLTAGE COMPARATOR 5V 8-SOIC
• Manufacturer: Linear Technology
• Type: General Purposer

Specifications of LT1011IS8#TRPBF

• Number Of Elements: 1
• Output Type: Open Collector
• Voltage - Supply: 3 V ~ 36 V, ±1.5 V ~ 18 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

APPLICATIONS INFORMATION
of the compara tor, but require a minimum input sig-
nal slew rate to be effective. DC hysteresis works for
all input slew rates, but creates a shift in offset volt-
age dependent on the previous condition of the input
signal. The circuit shown in Figure 1 is an excellent
compromise between AC and DC hysteresis.
This circuit is especially useful for general purpose
comparator applications because it does not force
any signals directly back onto the input signal source.
Instead, it takes advantage of the unique proper-
ties of the BALANCE pins to provide extremely fast,
clean output switching even with low frequency input
signals in the millivolt range. The 0.003μF capacitor
from Pin 6 to Pin 8 generates AC hysteresis because
the voltage on the BALANCE pins shifts slightly,
depending on the state of the output. Both pins move
about 4mV. If one pin (6) is bypassed, AC hysteresis
is created. It is only a few millivolts referred to the
inputs, but is suffi cient to switch the output at nearly
the maximum speed of which the comparator is ca-
pable. To prevent problems from low values of input
slew rate, a slight amount of DC hysteresis is also
used. The sensitivity of the BALANCE pins to current
is about 0.5mV input referred offset for each micro-
ampere of BALANCE pin current. The 15M resistor
tied from OUTPUT to Pin 5 generates 0.5mV DC
hysteresis. The combination of AC and DC hysteresis
creates clean oscillation-free switching with very
small input errors. Figure 2 plots input referred error
versus switching frequency for the circuit as shown.
Note that at low frequencies, the error is simply the
DC hysteresis, while at high frequencies, an additional
TANT
INPUTS
2μF
Figure 1. Comparator with Hysteresis
–15V
+
15V
3
2
–
+
LT1011
8
4
0.1μF
6
C1
0.003μF
1
5
7
15M
R2
R
L
OUTPUT
1011 F01
Input Protection
The inputs to the LT1011 are particularly suited to general
purpose comparator applications because large differential
and/or common mode voltages can be tolerated without
damage to the comparator. Either or both inputs can be
raised 40V above the negative supply, independent of the
positive supply voltage. Internal forward biased diodes
will conduct when the inputs are taken below the negative
supply. In this condition, input current must be limited to
1mA. If very large (fault) input voltages must be accom-
modated, series resistors and clamp diodes should be
used (see Figure 3).
error is created by the AC hysteresis. The high
frequency error can be reduced by reducing C
lower values may not provide clean switching with
very low slew rate input signals.
Figure 2. Input Offset Voltage vs Time to Last Transition
INPUTS
**
*
D1 TO D4: 1N4148
MAY BE ELIMINATED FOR I
SELECT ACCORDING TO ALLOWABLE
FAULT CURRENT AND POWER DISSIPATION
–1
–2
Figure 3. Limiting Fault Input Currents
8
7
6
5
4
3
2
1
0
1
R1**
R2**
C8 TO C6 = 0.003μF
(50kHz)
D1
D3
TIME/FREQUENCY (μs)
10
LT1011/LT1011A
FAULT
D2
D4
OUTPUT “LO” TO “HI”
OUTPUT “HI” TO “LO”
≤ 1mA
300Ω 3
300Ω
R3*
R4*
(5kHz)
100
2
–
+
LT1011
1011 F02
V
V
1000
+
–
8
4
1011 F03
H
, but
1011afc
7