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1
LT1394
7ns, Low Power,
Single Supply, Ground-Sensing
Comparator
s
High Speed A/D Converters
s
Zero-Crossing Detectors
s
Current Sense for Switching Regulators
s
Extended Range V/F Coverters
s
Fast Pulse Height/Width Discriminators
s
High Speed Triggers
s
Line Receivers
s
High Speed Sampling Circuits
Propagation Delay vs
Input Overdrive
OVERDRIVE (mV)
0
TIME (ns)
12
10
8
6
4
2
0
10
20
30
40
1394 TA02
50
t
PDLH
t
PDHL
T
A
= 25
C
V
STEP
= 100mV
V
S
=
5V
, LTC and LT are registered trademarks of Linear Technology Corporation.
UltraFast is a trademark of Linear Technology Corporation.
s
UltraFast
TM
: 7ns
s
Low Power: 6mA
s
Low Offset Voltage: 0.8mV
s
Operates Off Single 5V or Dual
5V Supplies
s
Input Common Mode Extends to Negative Supply
s
No Minimum Input Slew Rate Requirement
s
Complementary TTL Outputs
s
Inputs Can Exceed Supplies without Phase Reversal
s
Pin Compatible with LT1016, LT1116 and LT1671
s
Output Latch Capability
s
Available in 8-Lead MSOP and SO Packages
The LT
1394 is an UltraFast
(7ns) comparator with comple-
mentary outputs and latch. The input common mode range
extends from 1.5V below the positive supply down to the
negative supply rail. Like the LT1016, LT1116 and LT1671,
this comparator has complementary outputs designed to
interface directly to TTL or CMOS logic. The LT1394 may
operate from either a single 5V supply or dual
5V supplies.
Low offset voltage specifications and high gain allow the
LT1394 to be used in precision applications.
The LT1394 is designed for improved speed and stability for
a wide range of operating conditions. The output stage
provides active drive in both directions for maximum speed
into TTL, CMOS or passive loads with minimal cross-conduc-
tion current. Unlike other fast comparators, the LT1394
remains stable even for slow transitions through the active
region, which eliminates the need to specify a minimum input
slew rate.
The LT1394 has an internal, TTL/CMOS compatible latch for
retaining data at the outputs. The latch holds data as long as
the LATCH pin is held high. Device parameters such as gain,
offset and negative power supply current are not significantly
affected by variations in negative supply voltage.
45MHz Single Supply Adaptive Trigger
5V
+
A1
LT1227
+
A2
LT1006
INPUT
5V
5V
5V
TRIGGER
OUT
1394 F18
500pF
0.1
F
510
470
470
750
36
1
3
2
4
14
13
15
5
6
12
10
11
2k
10
F
2k
2k
+
0.1
F
0.1
F
0.005
F
0.005
F
100
F
+
Q1, Q2, Q3, Q4 = CA3096 ARRAY:
TIE SUBSTRATE (PIN 16) TO GROUND
= 1N4148
+
LT1394
Q1
Q2
Q3
Q4
3M
3M
FEATURES
DESCRIPTIO
U
APPLICATIO S
U
TYPICAL APPLICATIO
U
2
LT1394
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
T
JMAX
= 150
C,
JA
= 190
C/ W
TOP VIEW
Q OUT
Q OUT
GND
V
+
+IN
IN
V
S8 PACKAGE
8-LEAD PLASTIC SO
1
2
3
4
8
7
6
5
+
LATCH
ENABLE
ORDER PART
NUMBER
S8 PART MARKING
LT1394CS8
LT1394IS8
1394
1394I
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
(Note 1)
Total Supply Voltage (V
+
to V
) ............................... 12V
Positive Supply Voltage ............................................. 7V
Negative Supply Voltage .......................................... 7V
Differential Input Voltage .......................................
12V
Input and Latch Current (Note 2) ........................
10mA
Output Current (Continuous)(Note 2) .................
20mA
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
OS
Input Offset Voltage
R
S
100
(Note 4)
0.8
2.5
mV
q
4.0
mV
V
OS
Input Offset Voltage Drift
q
4
V/
C
T
I
OS
Input Offset Current
0.1
0.5
A
q
0.8
A
I
B
Input Bias Current
(Note 5)
2
4.5
A
q
7.0
A
V
CMR
Input Voltage Range (Note 6)
q
5
3.5
V
Single 5V Supply
q
0
3.5
V
CMRR
Common Mode Rejection Ratio
5V
V
CM
3.5V, T
A
> 0
C
55
100
dB
5V
V
CM
3.3V, T
A
0
C
55
dB
Single 5V Supply
0V
V
CM
3.5V, T
A
> 0
C
55
100
dB
0V
V
CM
3.3V, T
A
0
C
55
dB
PSRR
Power Supply Rejection Ratio
4.6V
V
+
5.4V
q
50
65
dB
7V
V
2V
q
65
100
dB
A
V
Small Signal Voltage Gain
1V
V
OUT
2V
750
1600
V/V
V
OH
Output Voltage Swing High
V
+
4.6V, I
OUT
= 1mA
q
2.7
3.1
V
V
+
4.6V, I
OUT
= 4mA
q
2.4
3.0
V
Operating Temperature Range ................ 40
C to 85
C
Specified Temperature Range (Note 3) ... 40
C to 85
C
Junction Temperature ........................................... 150
C
Storage Temperature Range ................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec).................. 300
C
1
2
3
4
V
+
+IN
IN
V
8
7
6
5
Q OUT
Q OUT
GND
TOP VIEW
MS8 PACKAGE
8-LEAD PLASTIC MSOP
LATCH
ENABLE
T
JMAX
= 150
C,
JA
= 250
C/ W
ORDER PART
NUMBER
MS8 PART MARKING
LT1394CMS8
LTBH
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25
C.
V
+
= 5V, V
= 5V, V
OUT
(Q) = 1.4V, V
LATCH
= V
CM
= 0V unless otherwise noted.
3
LT1394
ELECTRICAL CHARACTERISTICS
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
OL
Output Voltage Swing Low
I
OUT
= 4mA
q
0.3
0.5
V
I
OUT
= 10mA
0.4
V
I
+
Positive Supply Current
6
8.5
mA
q
10.0
mA
I
Negative Supply Current
1.2
2.2
mA
q
2.5
mA
V
IH
LATCH Pin High Input Voltage
q
2
V
V
IL
LATCH Pin Low Input Voltage
q
0.8
V
I
IL
LATCH Pin Current
V
LATCH
= 0V
q
4
10
A
t
PD
Propagation Delay (Note 7)
V
IN
= 100mV, V
OD
= 5mV
7
9
ns
q
14
ns
t
PD
Differential Propagation Delay (Note 7)
V
IN
= 100mV, V
OD
= 5mV
0.5
2.2
ns
t
LPD
Latch Propagation Delay (Note 8)
6
ns
t
SU
Latch Setup Time (Note 8)
0.4
ns
t
H
Latch Hold Time (Note 8)
2
ns
t
PW(D)
Minimum Disable Pulse Width
3
ns
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: This parameter is guaranteed to meet specified perforamnce
through design and characterization. It has not been tested.
Note 3: The LT1394CMS8 and LT1394CS8 are guaranteed to meet
specified performance from 0
C to 70
C and are designed, characterized
and expected to meet these extended temperature limits, but are not tested
at 40
C and 85
C. The LT1394IS8 is guaranteed to meet the extended
temperature limits.
Note 4: Input offset voltage (V
OS
) is defined as the average of the two
voltages measured by forcing first one output, then the other to 1.4V.
Note 5: Input bias current (I
B
) is defined as the average of the two input
currents.
Note 6: Input voltage range is guaranteed in part by CMRR testing and in
part by design and characterization.
Note 7: t
PD
and
t
PD
cannot be measured in automatic handling
equipment with low values of overdrive. The LT1394 is 100% tested with a
100mV step and 20mV overdrive. Correlation tests have shown that t
PD
and
t
PD
limits can be guaranteed with this test, if additional DC tests are
performed to guarantee that all internal bias conditions are correct.
Propagation delay (t
PD
) is measured with the overdrive added to the actual
V
OS
. Differential propagation delay is defined as:
t
PD
= t
PDLH
t
PDHL
Note 8: Latch propagation delay (t
LPD
) is the delay time for the output to
respond when the LATCH pin is deasserted. Latch setup time (t
SU
) is the
interval in which the input signal must remain stable prior to asserting the
latch signal. Latch hold time (t
H
) is the interval after the latch is asserted in
which the input signal must remain stable.
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25
C.
V
+
= 5V, V
= 5V, V
OUT
(Q) = 1.4V, V
LATCH
= V
CM
= 0V unless otherwise noted.
4
LT1394
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
Propagation Delay vs
Input Overdrive
TEMPERATURE (
C)
50
TIME (ns)
12
10
8
6
4
2
0
25
75
1394 G05
25
0
50
100
125
V
S
=
5V
V
STEP
= 100mV
V
OD
= 5mV
t
PDLH
t
PDHL
SOURCE RESISTANCE (k
)
0
0.5
TIME (ns)
1.0
2.0
1.5
2.5
3.0
1394 G04
80
70
60
50
40
30
20
10
0
V
S
=
5V
V
OD
= 20mV
T
A
= 25
C
STEP SIZE = 800mV
400mV
100mV
200mV
Propagation Delay vs
Source Resistance
Propagation Delay vs
Temperature
Input Offset Voltage vs
Temperature
2
1
0
1
2
3
4
5
LT
1394 G06
VOLTAGE (mV)
TEMPERATURE (
C)
50
25
75
25
0
50
100
125
V
S
=
5V
4
3
2
1
0
LT
1394 G07
INPUT BIAS CURRENT (
A)
TEMPERATURE (
C)
50
25
75
25
0
50
100
125
V
S
=
5V
V
CM
= 5V
V
CM
= 0V
V
CM
= 3.5V
Input Bias Current vs
Temperature
TEMPERATURE (
C)
50
VOLTAGE (V)
6
5
4
3
2
1
0
25
75
1394 G08
25
0
50
100
125
V
S
=
5V
Positive Common Mode Limit vs
Temperature
OVERDRIVE (mV)
0
TIME (ns)
12
10
8
6
4
2
0
10
20
30
40
1394 TA02
50
t
PDLH
t
PDHL
T
A
= 25
C
V
STEP
= 100mV
V
S
=
5V
Gain Characteristics
POSITIVE SUPPLY VOLTAGE (V)
4.4
TIME (ns)
12
10
8
6
4
2
0
4.6
4.8
5.0
5.2
5.4
1394 G03
5.6
t
PDHL
t
PDLH
V
= 5V
T
A
= 25
C
V
STEP
= 100mV
OVERDRIVE = 5mV
Propagation Delay vs
Positive Supply Voltage
Propagation Delay vs
Load Capacitance
OUTPUT LOAD CAPACITANCE (pF)
0
TIME (ns)
12
10
8
6
4
2
0
10
20
30
40
1394 G02
50
t
PDLH
t
PDHL
I
OUT
= 0
V
S
=
5V
T
A
= 25
C
V
STEP
= 100mV
OVERDRIVE = 5mV
DIFFERENTIAL INPUT VOLTAGE (mV)
3
OUTPUT VOLTAGE (V)
2
1
0
1
1394 G01
2
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
3
V
S
=
5V
I
OUT
= 0
T
A
= 125
C
T
A
= 25
C
T
A
= 55
C
5
LT1394
Output High Voltage (V
OH
) vs
Output Source Current
Negative Common Mode Limit vs
Temperature
1
0
1
2
3
4
5
6
LT
1394 G09
INPUT VOLTAGE (V)
TEMPERATURE (
C)
50
25
75
25
0
50
100
125
V
S
=
5V
V
S
= SINGLE 5V
OUTPUT SINK CURRENT (mA)
0
2
6
10
14
VOLTAGE (V)
16
1394 G10
4
8
12
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
T
A
= 55
C
T
A
= 125
C
T
A
= 25
C
V
S
=
5V
V
IN
= 30mV
Output Low Voltage (V
OL
) vs
Output Sink Current
OUTPUT SOURCE CURRENT (mA)
0
2
6
10
14
OUTPUT VOLTAGE (V)
16
1394 G11
4
8
12
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
T
A
= 55
C
T
A
= 125
C
T
A
= 25
C
V
S
=
5V
V
IN
= 30mV
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
SUPPLY VOLTAGE (V)
0
CURRENT (mA)
10
9
8
7
6
5
4
3
2
1
0
2
4
5
1394 G12
1
3
6
7
8
T
A
= 55
C
T
A
= 125
C
V
= 0V
V
IN
= 60mV
I
OUT
= 0
T
A
= 25
C
SWITCHING FREQUENCY (MHz)
1
CURRENT (mA)
16
14
12
10
8
6
4
2
0
10
100
1394 G13
T
A
= 55
C
T
A
= 125
C
V
S
=
5V
T
A
= 25
C
Positive Supply Current vs
V
+
Supply Voltage
Positive Supply Current vs
Switching Frequency
NEGATIVE SUPPLY VOLTAGE (V)
8
CURRENT (mA)
0
1394 G14
6
4
2
4
3
2
1
0
7
5
3
1
T
A
= 55
C
T
A
= 125
C
T
A
= 25
C
V
+
= 5V
V
IN
= 60mV
8
7
6
5
4
3
2
1
0
LT
1394 G15
CURRENT (
A)
TEMPERATURE (
C)
50
25
75
25
0
50
100
125
V
S
=
5V
V
LATCH
= 0V
Latch Pin Current vs Temperature
Negative Supply Current vs
V
Supply Voltage
Response to 100MHz
10mV
Sine Wave
0V
Q
OUT
3V
FET PROBES
5ns/DIV
1394 G16
+ IN
20mV
P-P
10mV/DIV
1V/DIV
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