FEATURES
s
s
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LT1394
7ns, Low Power,
Single Supply, Ground-Sensing
Comparator
DESCRIPTIO
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.
UltraFast
TM
: 7ns
Low Power: 6mA
Low Offset Voltage: 0.8mV
Operates Off Single 5V or Dual
±5V
Supplies
Input Common Mode Extends to Negative Supply
No Minimum Input Slew Rate Requirement
Complementary TTL Outputs
Inputs Can Exceed Supplies without Phase Reversal
Pin Compatible with LT1016, LT1116 and LT1671
Output Latch Capability
Available in 8-Lead MSOP and SO Packages
APPLICATIO S
s
s
s
s
s
s
s
s
High Speed A/D Converters
Zero-Crossing Detectors
Current Sense for Switching Regulators
Extended Range V/F Coverters
Fast Pulse Height/Width Discriminators
High Speed Triggers
Line Receivers
High Speed Sampling Circuits
, LTC and LT are registered trademarks of Linear Technology Corporation.
UltraFast is a trademark of Linear Technology Corporation.
TYPICAL APPLICATIO
45MHz Single Supply Adaptive Trigger
2k
3
Q1
5V
2
0.005µF
5V
12
6
1
5
4
Q2
3M
TIME (ns)
+
A1
LT1227
500pF
5V
–
13
2k
5V
36Ω
750Ω
510Ω
Q3
15
0.1µF
2k
14 12
11
10
Q4
0.005µF
3M
A2
LT1006
Q1, Q2, Q3, Q4 = CA3096 ARRAY:
TIE SUBSTRATE (PIN 16) TO GROUND
= 1N4148
470Ω
10µF
0.1µF
100µF
INPUT
–
470Ω
0.1µF
+
+
+
LT1394
U
+
–
U
U
Propagation Delay vs
Input Overdrive
T
A
= 25°C
V
STEP
= 100mV
V
S
=
±5V
10
8
t
PDLH
6
4
2
0
t
PDHL
0
10
TRIGGER
OUT
1394 F18
20
30
OVERDRIVE (mV)
40
50
1394 TA02
1
LT1394
ABSOLUTE
MAXIMUM
RATINGS
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
PACKAGE/ORDER INFORMATION
TOP VIEW
V
+
+IN
–IN
V
–
1
2
3
4
8
7
6
5
Q OUT
Q OUT
GND
LATCH
ENABLE
ORDER PART
NUMBER
LT1394CMS8
MS8 PART MARKING
LTBH
+IN 2
–IN 3
V
–
4
MS8 PACKAGE
8-LEAD PLASTIC MSOP
T
JMAX
= 150°C,
θ
JA
= 250°C/ W
S8 PACKAGE
8-LEAD PLASTIC SO
T
JMAX
= 150°C,
θ
JA
= 190°C/ W
Consult factory for Military grade parts.
ELECTRICAL CHARACTERISTICS
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.
SYMBOL
V
OS
∆V
OS
∆T
I
OS
I
B
V
CMR
CMRR
PARAMETER
Input Offset Voltage
Input Offset Voltage Drift
Input Offset Current
q
CONDITIONS
R
S
≤
100Ω (Note 4)
q
q
Input Bias Current
Input Voltage Range (Note 6)
(Note 5)
q
q
q
Single 5V Supply
Common Mode Rejection Ratio
– 5V
≤
V
CM
≤
3.5V, T
A
> 0°C
– 5V
≤
V
CM
≤
3.3V, T
A
≤
0°C
Single 5V Supply
0V
≤
V
CM
≤
3.5V, T
A
> 0°C
0V
≤
V
CM
≤
3.3V, T
A
≤
0°C
PSRR
A
V
V
OH
Power Supply Rejection Ratio
Small Signal Voltage Gain
Output Voltage Swing High
4.6V
≤
V
+
≤
5.4V
– 7V
≤
V
–
≤
– 2V
1V
≤
V
OUT
≤
2V
V
+
≥
4.6V, I
OUT
= 1mA
V
+
≥
4.6V, I
OUT
= 4mA
2
–
+
U
U
W
W W
U
W
(Note 1)
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
TOP VIEW
V
+
1
8 Q OUT
7 Q OUT
6 GND
5
LATCH
ENABLE
ORDER PART
NUMBER
LT1394CS8
LT1394IS8
S8 PART MARKING
1394
1394I
MIN
TYP
0.8
4
0.1
2
MAX
2.5
4.0
UNITS
mV
mV
µV/°C
0.5
0.8
4.5
7.0
3.5
3.5
µA
µA
µA
µA
V
V
dB
dB
dB
dB
dB
dB
V/V
V
V
–5
0
55
55
55
55
100
100
65
100
1600
3.1
3.0
q
q
50
65
750
2.7
2.4
q
q
LT1394
ELECTRICAL CHARACTERISTICS
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.
SYMBOL
V
OL
I
+
I
–
V
IH
V
IL
I
IL
t
PD
∆t
PD
t
LPD
t
SU
t
H
t
PW(D)
PARAMETER
Output Voltage Swing Low
Positive Supply Current
q
CONDITIONS
I
OUT
= – 4mA
I
OUT
= – 10mA
q
MIN
TYP
0.3
0.4
6
1.2
MAX
0.5
8.5
10.0
2.2
2.5
0.8
UNITS
V
V
mA
mA
mA
mA
V
V
µA
ns
ns
ns
ns
ns
ns
ns
Negative Supply Current
q
LATCH Pin High Input Voltage
LATCH Pin Low Input Voltage
LATCH Pin Current
Propagation Delay (Note 7)
Differential Propagation Delay (Note 7)
Latch Propagation Delay (Note 8)
Latch Setup Time (Note 8)
Latch Hold Time (Note 8)
Minimum Disable Pulse Width
V
LATCH
= 0V
∆V
IN
= 100mV, V
OD
= 5mV
q
q
q
q
2
–4
7
0.5
6
– 0.4
2
3
– 10
9
14
2.2
∆V
IN
= 100mV, V
OD
= 5mV
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.
3
LT1394
TYPICAL PERFORMANCE CHARACTERISTICS
Gain Characteristics
5.0
4.5
4.0
OUTPUT VOLTAGE (V)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
–3
–2
0
1
2
–1
DIFFERENTIAL INPUT VOLTAGE (mV)
3
0
0
12
T
A
= 125°C
T
A
= 25°C
V
S
=
±5V
I
OUT
= 0
TIME (ns)
TIME (ns)
T
A
= –55°C
Propagation Delay vs
Input Overdrive
12
10
8
T
A
= 25°C
V
STEP
= 100mV
V
S
=
±5V
TIME (ns)
TIME (ns)
t
PDLH
6
4
2
0
t
PDHL
TIME (ns)
0
10
20
30
OVERDRIVE (mV)
Input Offset Voltage vs
Temperature
2
V
S
=
±5V
1
INPUT BIAS CURRENT (µA)
0
VOLTAGE (mV)
–1
–2
–3
–4
–5
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
0
3
4
2
V
CM
= –5V
V
CM
= 0V
VOLTAGE (V)
4
U W
1394 G01
Propagation Delay vs
Load Capacitance
12
10
t
PDLH
8
6
4
2
t
PDHL
Propagation Delay vs
Positive Supply Voltage
10
8
6
4
2
0
V
–
= –5V
T
A
= 25°C
V
STEP
= 100mV
OVERDRIVE = 5mV
4.4
t
PDHL
t
PDLH
I
OUT
= 0
V
S
=
±5V
T
A
= 25°C
V
STEP
= 100mV
OVERDRIVE = 5mV
10
20
30
40
OUTPUT LOAD CAPACITANCE (pF)
50
1394 G02
4.6
4.8
5.0
5.2
5.4
POSITIVE SUPPLY VOLTAGE (V)
5.6
1394 G03
Propagation Delay vs
Source Resistance
80
70
60
50
40
30
20
10
0
40
50
1394 TA02
Propagation Delay vs
Temperature
V
S
=
±5V
V
OD
= 20mV
T
A
= 25°C
12
10
8
t
PDHL
6
4
200mV
2
0
–50 –25
V
S
=
±5V
V
STEP
= 100mV
V
OD
= 5mV
t
PDLH
400mV
STEP SIZE = 800mV
100mV
0
0.5
2.5
1.0
1.5
2.0
SOURCE RESISTANCE (kΩ)
3.0
1394 G04
50
25
75
0
TEMPERATURE (°C)
100
125
1394 G05
Input Bias Current vs
Temperature
6
V
S
=
±5V
5
4
3
2
1
V
CM
= 3.5V
1
Positive Common Mode Limit vs
Temperature
V
S
=
±5V
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
LT1394
G06
LT1394
G07
1394 G08
LT1394
TYPICAL PERFORMANCE CHARACTERISTICS
Negative Common Mode Limit vs
Temperature
1
0
INPUT VOLTAGE (V)
–1
VOLTAGE (V)
0.8
V
S
= SINGLE 5V
OUTPUT VOLTAGE (V)
–2
–3
–4
–5
–6
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
V
S
=
±5V
Positive Supply Current vs
V
+
Supply Voltage
10
9
8
7
V
–
= 0V
V
IN
= –60mV
I
OUT
= 0
16
14
12
CURRENT (mA)
CURRENT (mA)
6
5
4
3
2
1
0
0
10
T
A
= 125°C
8
6
4
2
0
1
10
SWITCHING FREQUENCY (MHz)
100
1394 G13
T
A
= 125°C
CURRENT (mA)
T
A
= 25°C
T
A
= –55°C
1
2
4
6
5
3
SUPPLY VOLTAGE (V)
Latch Pin Current vs Temperature
8
7
6
CURRENT (µA)
5
4
3
2
0V
1
0
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
V
S
=
±5V
V
LATCH
= 0V
+ IN
20mV
P-P
3V
Q
OUT
U W
LT1394
G09
Output Low Voltage (V
OL
) vs
Output Sink Current
5.0
V
S
=
±5V
∆V
IN
= 30mV
0.7
0.6
0.5
T
A
= 125°C
0.4
0.3
0.2
0.1
0
0
2
8
6
10 12 14
4
OUTPUT SINK CURRENT (mA)
16
T
A
= –55°C
T
A
= 25°C
Output High Voltage (V
OH
) vs
Output Source Current
4.5
4.0
T
A
= 125°C
3.5
T
A
= 25°C
3.0
T
A
= –55°C
2.5
2.0
1.5
1.0
0
2
8
6
10 12 14
4
OUTPUT SOURCE CURRENT (mA)
16
V
S
=
±5V
∆V
IN
= –30mV
1394 G10
1394 G11
Positive Supply Current vs
Switching Frequency
V
S
=
±5V
Negative Supply Current vs
V
–
Supply Voltage
4
V
+
= 5V
∆V
IN
= –60mV
3
T
A
= 25°C
2
T
A
= 125°C
T
A
= 25°C
T
A
= –55°C
1
T
A
= –55°C
7
8
0
–8
–7 –6 –5 –4 –3 –2 –1
NEGATIVE SUPPLY VOLTAGE (V)
0
1394 G12
1394 G14
Response to 100MHz
±10mV
Sine Wave
10mV/DIV
1V/DIV
FET PROBES
5ns/DIV
1394 G16
LT1394
G15
5
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