LTC1540
Nanopower Comparator
with Reference
FEATURES
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DESCRIPTION
The LTC
®
1540 is an ultralow power, single comparator
with built-in reference. The comparator’s features
include less than 0.6µA supply current over the commer-
cial temperature range, a 1.182V
±2%
reference, pro-
grammable hysteresis and TTL/CMOS outputs that sink
and source current. The reference output can drive a
bypass capacitor of up to 0.01µF without oscillation.
The comparator operates from a single 2V to 11V supply
or a dual
±1V
to
±5.5V
supply. Comparator hysteresis is
easily programmed by using two resistors and the HYST
pin. Each comparator’s input operates from the negative
supply to within 1.3V of the positive supply. The compara-
tor output stage can continuously source up to 40mA. By
eliminating the cross-conducting current that normally
occur when the comparator changes logic states, power
supply glitches are eliminated.
The LTC1540 is available in the 8-pin MSOP and SO
packages.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Ultralow Quiescent Current: 0.3
µ
A Typ
Reference Output Drives 0.01
µ
F Capacitor
Adjustable Hysteresis
Wide Supply Range: 2V to 11V
Input Voltage Range Includes the Negative Supply
Reference Output Sources Up to 1mA
TTL/CMOS Compatible Outputs
60µs Propagation Delay with 10mV Overdrive
No Crowbar Current
40mA Continuous Source Current
Pin Compatible with LTC1440, MAX921, MAX931
APPLICATIONS
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Battery-Powered System Monitoring
Threshold Detectors
Window Comparators
Oscillator Circuits
TYPICAL APPLICATION
Nanopower 2.9V V
CC
Threshold Detector
3.3V
0.50
LTC1540 Supply Current vs Temperature
R1
4.32M
1%
R2
3M
1%
7
V
3 IN
+
+
LTC1540
SUPPLY CURRENT (µA)
0.45
0.40
0.35
0.30
0.25
0.20
V
+
= 5V
V
–
= GND = 0V
+
8
OUT
4 IN
–
–
5 HYST
6 REF
V
–
2
GND
1
1540 • TA01
0.15
–40 –20
U
U
U
40
20
60
0
TEMPERATURE (°C)
80
100
1540 • TA02
1
LTC1540
ABSOLUTE
MAXIMUM
RATINGS
Voltage
V
+
to V
–
, V
+
to GND, GND to V
–
...........12V to – 0.3V
IN
+
, IN
–
, HYST ................. (V
+
+ 0.3V) to (V
–
– 0.3V)
REF ................................... (V
+
+ 0.3V) to (V
–
– 0.3V)
OUT ............................... (V
+
+ 0.3V) to (GND – 0.3V)
Current
IN
+
, IN
–
, HYST ................................................. 20mA
REF ................................................................... 20mA
OUT .................................................................. 50mA
OUT Short-Circuit Duration (V
+
≤
5.5V) ...... Continuous
Power Dissipation ............................................. 500mW
Operating Temperature Range
LTC1540C............................................... 0°C to 70°C
LTC1540I ............................................ – 40°C to 85°C
Storage Temperature Range ................ – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
PACKAGE/ORDER INFORMATION
TOP VIEW
GND 1
V
–
2
IN
+
3
IN
–
4
8
7
6
5
OUT
V
+
REF
HYST
ORDER PART
NUMBER
LTC1540CS8
LTC1540IS8
S8 PART MARKING
1540
1540I
GND
V
–
IN
+
IN
–
1
2
3
4
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 125°C,
θ
JA
= 175°C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
Power Supply
V
+
I
CC
Supply Voltage Range
Supply Current
CONDITIONS
V
+
= 5V, V
–
= GND = 0V, T
A
= 25°C unless otherwise noted.
MIN
q
IN
+
= IN
–
= 80mV, HYST = REF, C-Grade
IN
+
= IN
–
= 80mV, HYST = REF, I-Grade
V
CM
= 2.5V
LTC1540CMS8
Comparator
V
OS
Comparator Input Offset Voltage
q
q
q
q
q
I
IN
V
CM
CMRR
PSRR
V
HYST
t
PD
V
OH
V
OL
Input Leakage Current (IN
+
, IN
–
)
Input Leakage Current (HYST)
Comparator Input Common Mode Range
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Hysteresis Input Voltage Range
Propagation Delay
Output High Voltage
Output Low Voltage
V
IN +
= V
IN –
= 2.5V
V
–
to V
+
– 1.3V
V
+
= 2V to 11V
q
REF – 50mV
C
OUT
= 100pF
I
O
= – 13mA
I
O
= 1.8mA
2
U
U
W
W W
U
W
TOP VIEW
8
7
6
5
OUT
V
+
REF
HYST
ORDER PART
NUMBER
LTC1540CMS8
MS8 PART MARKING
LTCE
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 125°C,
θ
JA
= 250°C/ W
TYP
MAX
11.0
UNITS
V
µA
µA
mV
mV
mV
nA
nA
V
mV/V
mV/V
V
µs
µs
V
2.0
0.3
q
q
0.68
0.71
±12
±15
±16
±0.01
±0.02
V
–
0.1
0.1
±1.0
±1.0
V
+
– 1.3V
1
1
REF
Overdrive = 10mV
Overdrive = 100mV
q
q
60
50
V
+
– 0.4V
GND + 0.4V
V
LTC1540
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER
Reference
Reference Voltage
V
REF
CONDITIONS
V
+
= 5V, V
–
= GND = 0V, T
A
= 25°C unless otherwise noted.
MIN
Commercial Temp Range
Industrial Temp Range
q
q
q
q
q
TYP
1.182
1.182
1.182
0.5
0.5
MAX
1.206
1.212
1.208
2.5
1.5
5
UNITS
V
V
V
mV
mV
mV
(SO-8) No Load
LTC1540CMS8
0
≤
I
SOURCE
≤
1mA
0
≤
I
SINK
≤
10µA
1.158
1.152
1.156
∆V
REF
Load Regulation
V
+
= 3V, V
–
= GND = 0V, T
A
= 25°C unless otherwise noted.
SYMBOL PARAMETER
Power Supply
V
+
I
CC
Supply Voltage Range
Supply Current
IN
+
= IN
–
= 80mV, HYST = REF, C-Grade
IN
+
= IN
–
= 80mV, HYST = REF, I-Grade
V
CM
= 2.5V
LTC1540CMS8
I
IN
V
CM
CMRR
PSRR
V
HYST
t
PD
V
OH
V
OL
Reference
V
REF
Reference Voltage
(SO-8) No Load
LTC1540CMS8
∆V
REF
Load Regulation
0
≤
I
SOURCE
≤
1mA
0
≤
I
SINK
≤
10µA
q
q
q
q
q
q
q
q
q
CONDITIONS
MIN
2
TYP
MAX
11
UNITS
V
µA
µA
mV
mV
mV
nA
nA
V
mV/V
mV/V
V
µs
µs
V
0.28
0.61
0.64
±12
±15
±16
Comparator
V
OS
Comparator Input Offset Voltage
Input Leakage Current (IN
+
, IN
–
)
Input Leakage Current (HYST)
Comparator Input Common Mode Range
Common Mode Rejection Ratio
Power Supply Rejection Ratio
Hysteresis Input Voltage Range
Propagation Delay
Output High Voltage
Output Low Voltage
V
IN +
= V
IN –
= 1.5V
±0.01
±0.02
V
–
0.1
0.1
±1
±1
V
+
– 1.3V
1
1
REF
V
–
to V
+
– 1.3V
V
+
= 2V to 11V
q
REF – 50mV
C
OUT
= 100pF
I
O
= – 8mA
I
O
= 0.8mA
Overdrive = 10mV
Overdrive = 100mV
q
q
70
60
V
+
– 0.4V
GND + 0.4V
1.158
1.152
1.156
1.182
1.182
1.182
0.75
0.5
1.206
1.212
1.208
3.5
1.5
5
V
V
V
V
mV
mV
mV
Commercial Temp Range
Industrial Temp Range
q
q
q
q
The
q
denotes specifications which apply over the full operating
temperature range.
Note 1:
MS8 package devices are designed for and intended to meet
commercial temperature range specifications but are not tested at 0°C.
3
LTC1540
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Temperature
0.5
V
–
= GND = 0V
REFERENCE VOLTAGE (V)
V
+
= 5V
0.4
SUPPLY CURRENT (µA)
V
+
= 3V
–
V = GND = 0V
0.3
V
+
= 2V
V
–
= GND = 0V
∆V
REF
(mV)
0.2
0.1
0
– 60 – 40 –20 0 20 40 60
TEMPERATURE (°C)
Reference Voltage
Load Regulation (Source)
5
V
+
= 5V
V
–
= GND = 0V
T
A
= 25°C
OUTPUT VOLTAGE (V)
4
OUTPUT VOLTAGE (V)
∆V
REF
(mV)
3
2
1
0
0
3
2
1
OUTPUT SOURCE CURRENT (mA)
4
1540 G04
Comparator Short-Circuit Current
vs Supply Voltage
200
180
160
140
CURRENT (mA)
T
A
= 25°C
OUTPUT
CONNECTED TO
V
–
= GND = 0V;
SOURCE
CURRENT
OUTPUT
CONNECTED
TO V
+
; SINK
CURRENT
DIFFERENTIAL INPUT VOLTAGE (V)
TIME (µs)
120
100
80
60
40
20
0
0
1
2
3 4 5 6 7 8
SUPPLY VOLTAGE (V)
4
U W
80
1540 G01
Reference Voltage vs Temperature
1.190
1.188
1.186
1.184
1.182
1.180
1.178
1.176
1.174
V
+
= 5V
V
–
= GND = 0V
10
9
8
7
6
5
4
3
2
1
0
Reference Voltage
Load Regulation (Sink)
V
+
= 5V
V
–
= GND = 0V
T
A
= 25°C
100
1.172
20 40 60
– 60 – 40 – 20 0
TEMPERATURE (°C)
80
100
0
5
10 15 20 25 30 35
OUTPUT SINK CURRENT (µA)
40
1540 G02
1540 G03
Comparator Output Voltage (High)
vs Load Current
5
T
A
= 25°C
V
+
= 5V
4
2.0
2.5
Comparator Output Voltage (Low)
vs Load Current
T
A
= 25°C
V
+
= 3V
V
+
= 2V
V
+
= 5V
3
V
+
= 3V
1.5
2
1.0
1
V
+
= 2V
0.5
0
0
10
20 30 40 50 60
LOAD CURRENT (mA)
70
80
0
0
10
20 30 40 50 60
LOAD CURRENT (mA)
70
80
1540 G05
1540 G06
Comparator Response Time
vs Input Overdrive
80
T
A
= 25°C
75 V
+
= 5V
V
–
= GND = 0V
70
65
60
55
50
45
40
35
30
t
PHL
t
PLH
Hysteresis Control
80
60
40
20
0
– 20
– 40
– 60
– 80
0
10
20
30
V
REF
– V
HYST
(mV)
40
50
1540 G09
9
10
10 20 30 40 50 60 70 80 90 100 110
INPUT VOLTAGE (mV)
1540 G08
1540 G07
LTC1540
PIN FUNCTIONS
GND (Pin 1):
Ground. Connect to V
–
for single supply
operation.
V
–
(Pin 2):
Negative Supply. Potential should be more
negative than GND. Connect to ground for single supply
operation.
IN
+
(Pin 3):
Noninverting Comparator Input. Input com-
mon mode range from V
–
to V
+
– 1.3V. Input current
typically 10pA at 25°C.
(Pin 4):
Inverting Comparator Input. Input common
mode range from V
–
to V
+
– 1.3V. Input current typically
10pA at 25°C.
HYST (Pin 5):
Hysteresis Input. Connect to REF if not
used. Input voltage range is from V
REF
to V
REF
– 50mV.
REF (Pin 6):
Reference Output. 1.182V with respect
to V
–
. Can source up to 1mA and sink 10µA at 25°C. Drive
0.01µF bypass capacitor without oscillation.
IN
–
V
+
(Pin 7):
Positive Supply operating voltage is from 2V
to 11V.
OUT (Pin 8):
Comparator CMOS Output. Swings from
GND to V
+
. Output can source up to 40mA and sink 5mA.
APPLICATIONS INFORMATION
The LTC1540 is a nanopower comparator with a built-in
1.182V reference. Features include programmable hyster-
esis, wide supply voltage range (2V to 11V) and the ability
of the reference to drive up to a 0.01µF capacitor without
oscillation. The comparator’s CMOS outputs can source
up to 40mA while supply current glitches that normally
occur when switching logic states, have been eliminated.
Power Supplies
The comparator operates from a single 2V to 11V supply.
The LTC1540 includes a separate ground for the compara-
tor output stage, allowing a split supply ranging from
±1V
to
±5.5V.
Connecting V
–
to GND will allow single supply
operation. If the comparator output is required to source
more than 1mA, or the supply source impedance is high,
V
+
should be bypassed with a 0.1µF capacitor.
Comparator Inputs
The comparator inputs can swing from the negative supply,
V
–
, to within 1.3V (max) of the positive supply V
+
. The
inputs can be forced 300mV below V
–
or above V
+
without
damage and the typical input leakage current is only
±10pA.
Comparator Output
The comparator output swings between GND and V
+
to
assure TTL compatibility with a split supply. The output is
capable of sourcing up to 40mA and sinking up to 5mA
while still maintaining nanoampere quiescent currents.
The output stage does not generate crowbar switching
currents during transitions which helps minimize parasitic
feedback through the supply pins.
Voltage Reference
The internal bandgap reference has a voltage of 1.182V
referenced to V
–
. The reference accuracy is
±2.0%
from
0°C to 70°C. It can source up to 1mA and sink up to 10µA
with a 5V supply. The reference can drive a bypass
capacitor of up to 0.01µF without oscillation and by
inserting a series resistor, capacitance values up to 10µF
can be used (Figure 1).
Figure 2 shows the resistor value required for different
capacitor values to achieve critical damping. Bypassing
the reference can help prevent false tripping of the com-
parators by preventing glitches on V
+
or reference load
transients from disturbing the reference output voltage.
U
W
U
U
U
U
U
1
GND
LTC1540
OUT 8
7
–
2 V
V
+
+
3 IN
+
–
4 IN
–
REF 6
5
HYST
1540 • PD
5
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