Page 1
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
EL5285C - Preliminary
Features
• 4ns typ. propagation delay
• 5V to 12V input supply
• +2.7V to +5V output supply
• True-to-ground input
• Rail-to-rail outputs
• Separate analog and digital
supplies
• Active low latch
• Single available (EL5185C)
• Quad available (EL5485C &
EL5486C)
• Pin-compatible 6ns family
available (EL5x81C, EL5283C &
EL5482C)
Applications
• Threshold detection
• High speed sampling circuits
• High speed triggers
• Line receivers
• PWM circuits
• High speed V/F converters
General Description
The EL5285C comparator is designed for operation in single supply
and dual supply applications with 5V to 12V between VS+ and VS-.
For single supplies, the inputs can operate from 0.1V below ground for
use in ground sensing applications.
The output side of the comparators can be supplied from a single supply of 2.7V to 5V. The rail-to-rail output swing enables direct
connection of the comparator to both CMOS and TTL logic circuits.
The latch input of the EL5285C can be used to hold the comparator
output value by applying a low logic level to the pin. The EL5285C
features two separate comparators
The EL5285C is available in the 14-pin SO package and is specified
for operation over the full -40°C to +85°C temperature range. Also
available are a single (EL5185C) and quad versions (EL5485C and
EL5486C.)
Pin Configurations
Ordering Information
Part No. Package Tape & Reel Outline #
EL5285CS 14-Pin SOIC - MDP0027
EL5285CS-T7 14-Pin SOIC 7” MDP0027
EL5285CS-T13 14-Pin SOIC 13” MDP0027
Note: All information contained in this data sheet has been carefully checked and is believed to be accurate as of the date of publication; however, this data sheet cannot be a “controlled document”. Current revisions, if any, to these
specifications are maintained at the factory and are available upon your request. We recommend checking the revision level before finalization of your design documentation.
© 2001 Elantec Semiconductor, Inc.
VS+
INA+
INA-
INB-
INB+
VS-
1
2
+
-
3
4
NC
5
+
6
-
7
EL5285C
(14-Pin SO)
14
13
12
11
10
9
8
VSD
OUTA
LATCHA
NC
LATCHB
OUTB
GND
September 7, 2001
Page 2
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
Absolute Maximum Ratings (T
Absolute maximum ratings are those values beyond which the device
could be permanently damaged. Absolute maximum ratings are stress
ratings only and functional device operation is not implied.
Analog Supply Voltage (VS+ to VS-) +12V
EL5285C - Preliminary
Digital Supply Voltage (VSD to GND) +7V
Differential Input Voltage [(VS-) -0.2V] to [(VS+) +0.2V]
Common-mode Input Voltage [(VS-) -0.2V] to [(VS+) +0.2V]
= 25°C)
A
Latch Input Voltage -0.2V to [VSD+0.2V]
Storage Temperature Range -65°C to +150°C
Ambient operating Temperature -40°C to +85°C
Operating Junction Temperature 125°C
Power Dissipation TBDmW
ESD Voltage 2kV
Important Note:
All parameters having Min/Max specifications are guaranteed. Typ values are for information purposes only. Unless otherwise noted, all tests are at the
specified temperature and are pulsed tests, therefore: TJ = TC = TA.
Electrical Characteristics
VS = ±5V, VSD = 5V, R
Parameter Description Condition Min Typ Max Unit
V
OS
I
B
C
IN
I
OS
V
CM
A
VO
CMRR Common-mode Rejection Ratio -5V < V
PSRR Power Supply Rejection Ratio 60 dB
V
OH
V
OL
V
LH
V
LL
I
LH
I
LL
IS+ Positive Analog Supply Current (per comparator) 10.5 mA
IS- Negative Analog Supply Current (per comparator) 7.5 mA
I
DD
td+ Positive Going Delay Time V
td- Negative Going Delay Time V
tpd+ Latch Disable to High Delay 6 ns
tpd- Latch Disable to Low Delay 8 ns
t
s
t
h
tpw(D) Minimum Latch Disable Pulse
= 2.3kΩ, C
L
Input Offset Voltage V
= 15pF, TA = 25°C, unless otherwise specified.
L
= 0V, VO = 2.5V 2 4 mV
CM
Input Bias Current 8 15 µA
Input Capacitance 5 pF
Input Offset Current V
= 0V, VO = 2.5V 100 500 nA
CM
Input Voltage Range (VS-) - 0.1 (VS+) - 2V V
Large Signal Voltage Gain 5000 V/V
< +2.75V, VO = 2.5V 80 dB
CM
Output High Voltage V
Output Low Voltage V
> 250mV VSD - 0.5V VSD - 0.4V V
IN
> 250mV GND + 0.4V GND + 0.5V V
IN
Latch Input Voltage High 2.0 V
Latch Input Voltage Low 0.8 V
Latch Input Current High V
Latch Input Current Low V
= 3V 1 20 µA
LH
= 0.3V 40 80 µA
LL
Digital Supply Current (per comparator) 6 mA
= 5mV, CL = 15pF, I O= 2mA 4 6 ns
OD
= 5mV, CL = 15pF, IO = 2mA 4 6 ns
OD
Minimum Setup Time 2 ns
Minimum Hold Time 1 ns
Width
5 ns
2
Page 3
Typical Performance Curves
EL5285C - Preliminary
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
Supply Current vs Supply Voltage
(per comparator)
10
VIN=50mV
RL=2.2k
8
6
(mA)
S
I
4
2
0
0 1 2 3 4 5 6
Offset Voltage vs Temperature
3
2.5
2
(mV)
1.5
OS
V
1
0.5
0
-50 -30 10 30 50 70 90
IS+
IS-
±VS (V)
-10
Temperature (°C)
Output High Voltage vs Temperature
4.832
4.83
4.828
4.826
(V)
OH
V
4.824
4.822
4.82
4.818
-50 -30 10 30 50 70 90
Input Bias Current vs Temperature
8
7
6
5
4
IB (µA)
3
2
1
0
-50 -30 30 50 90
-10
Temperature (°C)
-10
10 70
Temperature (°C)
Output Low Voltage vs Temperature
0.285
0.275
0.265
(V)
OL
V
0.255
0.245
0.235
-50 -30 10 30 50 70 90
-10
Temperature (°C)
Supply Current vs Temperature
(per comparator)
12
11
10
9
8
Supply Current (mA)
7
6
-50 10 70 90
IS+
IS-
-30
Temperature (°C)
50
30-10
3
Page 4
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
Typical Performance Curves
Propagation Delay vs Overdrive
VIN=5V
EL5285C - Preliminary
Delay Time (ns)
Delay Time (ns)
STEP
7.8
7.6
7.4
7.2
7
6.8
6.6
6.4
6.8
6.6
6.4
6.2
6
5.8
5.6
TPD-
TPD+
0.2 0.6 1 1.4 1.8 2.2 2.6
VOD (V)
Propagation Delay vs Supply Voltage
TPD-
TPD+
4 4.2 4.8 5.2 5.4 5.6 6
4.4
54.6 5.8
±VS (V)
VS=±5V
VSD=5V
RL=2.2k
VSD=VS+
VOD=50mV
RL=2.2k
Propagation Delay vs Source Resistance
VIN=1V
STEP
15
VS=±5V
VSD=5V
VOD=50mV
13
RL=2.2k
11
9
Delay Time (ns)
7
5
0 1.6 2
Digital Supply Current vs Switching Frequency
(per comparator)
25
VS=±5V
TA=25°C
20
15
(mA)
SD
I
10
5
0
0 20 40 50
TPD-
0.4 1.20.8
Source Resistance (kΩ)
VSD=5V
10
Frequency (MHz)
TPD+
VSD=3V
30
Propagation Delay vs Overdrive
VIN=1V
STEP
6.1
6
5.9
5.8
5.7
5.6
Delay Time (ns)
5.5
5.4
5.3
5.2
50 100 250 300 400 500 600
150
TPD-
TPD+
350 450 550200
VOD (mV)
VS=±5V
VSD=5V
RL=2.2k
Propagation Delay vs Overdrive
VIN=3V
STEP
8
7.5
7
6.5
Delay Time (ns)
6
5.5
5
0.2 0.6 0.8 1.2 1.6 2
TPD-
TPD+
1 1.4 1.80.4
VOD (mV)
VS=±5V
VSD=5V
RL=2.2k
4
Page 5
Typical Performance Curves
EL5285C - Preliminary
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
Propagation Delay vs Load Capacitance
VIN=1V
STEP
9
VS=±5V
8.5
VSD=5V
VOD=50mV
8
RL=2.2k
7.5
7
6.5
Delay Time (ns)
6
5.5
5
0 10 30 40 50 80 100
Output with 50MHz Input
VIN=1V
P-P
Output
(5ns/div,
2V/div)
Input
(5ns/div,
0.5V/div)
TPD-
TPD+
20
60 9070
C
(pF)
LOAD
Package Power Dissipation vs Ambient Temp.
JEDEC JESD51-3 Low Effective Thermal Conductivity Test Board
0.9
0.8
833mW
0.7
0.6
0.5
0.4
0.3
Power Dissipation (W)
0.2
0.1
0
0 100755025
Output with 50MHz Input
VIN=3V
Output
(5ns/div,
2V/div)
Input
(5ns/div,
2V/div)
P-P
S
O
1
1
4
2
0
°
C
/
W
Ambient Temperature (°C)
85
125
5
Page 6
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
Pin Descriptions
Pin Number Pin Name Function Equivalent Circuit
EL5285C - Preliminary
1 VS+ Positive supply current
2 INA+ Positive input, channel A
VS+
IN+IN-
3 INA- Negative input, channel A (Reference Circuit 1)
4, 11 NC Not connected
5 INB+ Negative input, channel B (Reference Circuit 1)
6 INB- Positive input, channel B (Reference Circuit 1)
7 VS- Negative supply voltage
8 GND Ground
9 OUTB Output, channel B
10 LATCHB Latch input, channel B
LATCH
12 LATCHA Latch input, channel A (Reference Circuit 3)
13 OUTA Output, channel A (Reference Circuit 2)
14 VSD Digital supply voltage
Circuit 1
V
SD
VS+
VS-
Circuit 2
VS+
VS-
Circuit 3
V
SD
VS-
OUT
6
Page 7
Timing Diagram
EL5285C - Preliminary
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
Latch
Enable
Input
Latch
Differential
Input
Voltage
Comparator
Output
Compare
Latch Latch
t
t
h
s
V
IN
V
OD
tpd-
Compare
tpw(D)
1.4V
V
OS
td+
2.4V
Definition of Terms
Term Definition
V
OS
V
IN
V
OD
tpd+ Input to Output High Delay - The propagation delay measured from the time the input signal crosses the input offset voltage to the CMOS
tpd- Input to Output Low Delay - The propagation delay measured from the time the input signal crosses the input offset voltage to the CMOS
td+ Latch Disable to Output High Delay - The propagation delay measured from the latch signal crossing the CMOS threshold in a low to high
td- Latch Disable to Output Low Delay - The propagation delay measured from the latch signal crossing the CMOS threshold in a low to high
t
s
t
h
tpw (D) Minimum Latch Disable Pulse Width - The minimum time that the latch signal must remain high in order to acquire and hold an input signal
Input Offset Voltage - Voltage applied between the two input terminals to obtain CMOS logic threshold at the output
Input Voltage Pulse Amplitude - Usually set to 1V for comparator specifications
Input Voltage Overdrive - Usually set to 50mV and in opposite polarity to VIN for comparator specifications
logic threshold of an output low to high transition
logic threshold of an output high to low transition
transition to the point of the output crossing CMOS threshold in a low to high transition
transition to the point of the output crossing CMOS threshold in a high to low transition
Minimum Setup Time - The minimum time before the negative transition of the latch signal that an input signal change must be present in
order to be acquired and held at the outputs
Minimum Hold Time - The minimum time after the negative transition of the latch signal that an input signal must remain unchanged in
order to be acquired and held at the output
change
7
Page 8
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
Applications Information
Power Supplies and Circuit Layout
The EL5285C comparator operates with single and dual
EL5285C - Preliminary
supply with 5V to 12V between VS+ and VS-. The output side of the comparator is supplied by a single supply
from 2.7V to 5V. The rail to rail output swing enables
direct connection of the comparator to both CMOS and
TTL logic circuits. As with many high speed devices,
the supplies must be well bypassed. Elantec recommends a 4.7µF tantalum in parallel with a 0.1µF
ceramic. These should be placed as close as possible to
the supply pins. Keep all leads short to reduce stray
capacitance and lead inductance. This will also minimize unwanted parasitic feedback around the
comparator. The device should be soldered directly to
the PC board instead of using a socket. Use a PC board
with a good, unbroken low inductance ground plane.
Good ground plane construction techniques enhance stability of the comparators.
Input Voltage Considerations
The EL5285C’s input range is specified from 0.1V
below VS- to 2.25V below VS+. The criterion for the
input limit is that the output still responds correctly to a
small differential input signal. The differential input
stage is a pair of PNP transistors, therefore, the input
bias current flows out of the device. When either input
signal falls below the negative input voltage limit, the
parasitic PN junction formed by the substrate and the
base of the PNP will turn on, resulting in a significant
increase of input bias current. If one of the inputs goes
above the positive input voltage limit, the output will
still maintain the correct logic level as long as the other
input stays within the input range. However, the propagation delay will increase. When both inputs are outside
the input voltage range, the output becomes unpredictable. Large differential voltages greater than the supply
voltage should be avoided to prevent damages to the
input stage.
imum slew rate requirements. In some applications, it
may be helpful to apply some positive feedback (hysteresis) between the output and the positive input. The
hysteresis effectively causes one comparator's input
voltage to move quickly past the other, thus taking the
input out of the region where oscillation occurs. For the
EL5285C, the propagation delay increases when the
input slew rate increases for low overdrive voltages.
With high overdrive voltages, the propagation delay
does not change much with the input slew rate.
Latch Pin Dynamics
The EL5285C contains a “transparent” latch for each
channel. The latch pin is designed to be driven with
either a TTL or CMOS output. When the latch is connected to a logic high level or left floating, the
comparator is transparent and immediately responds to
the changes at the input terminals. When the latch is
switched to a logic low level, the comparator output
remains latched to its value just before the latch’s highto-low transition. To guarantee data retention, the input
signal must remain the same state at least 1ns (hold time)
after the latch goes low and at least 2ns (setup time)
before the latch goes low. When the latch goes high, the
new data will appear at the output in approximately 6ns
(latch propagation delay).
Hysteresis
Hysteresis can be added externally. The following two
methods can be used to add hysteresis.
Inverting comparator with hysteresis:
V
REF
R
2
R
1
R
3
+
-
V
IN
Input Slew Rate
Most high speed comparators oscillate when the voltage
of one of the inputs is close to or equal to the voltage on
the other input due to noise or undesirable feedback. For
clean output waveform, the input must meet certain min-
R3 adds a portion of the output to the threshold set by R
and R2. The calculation of the resistor values are as
follows:
8
1
Page 9
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
EL5285C - Preliminary
Select the threshold voltage VTH and calculate R1 and
R2. The current through R1/R2 bias string must be many
times greater than the input bias current of the
comparator:
R
REF
-------------------×=
R1R2+
1
VTHV
Let the hysteresis be VH, and calculate R3:
V
O
-------V
×=
H
||
R
( R2)
1
R
3
where:
VO=VSD-0.8V (swing of the output)
Recalculate R2 to maintain the same value of VTH:
R21V
( VTH)
REF
÷–
----------R
TH
-------------------------------------
+=
1
R
3
V
VTH0.5VSD–
Non inverting comparator with hysteresis:
R
3
R
1
V
IN
+
-
V
REF
R3 adds a portion of the output to the positive input.
Note that the current through R3 should be much greater
than the input bias current in order to minimize errors.
The calculation of the resistor values as follows:
Pick the value of R1. R
should be small (less than 1kΩ)
1
in order to minimize the propagation delay time.
Choose the hysteresis VH and calculate R3:
R
R
3V(SD
0.8)
1
--------×–=
V
H
Check the current through R3 and make sure that it is
much greater than the input bias current as follows:
0.5VSDV
–
----------------------------------------
I
=
REF
R
3
The above two methods will generate hysteresis of up to
a few hundred millivolts. Beyond that, the impedance of
R3 is low enough to affect the bias string and adjustment
of R1 may be required.
Power Dissipation
When switching at high speeds, the comparator's drive
capability is limited by the rise in junction temperature
caused by the internal power dissipation. For reliable
operation, the junction temperature must be kept below
T
(125°C).
JMAX
An approximate equation for the device power dissipation is as follows. Assume the power dissipation in the
load is very small:
P
DISSVSISVSDISD
)×+×(=
where:
VS is the analog supply voltage from VS+ to VS-
IS is the analog quiescent supply current per comparator
VSD is the digital supply voltage from VSD to ground
I
is the digital supply current per comparator
SD
ISD strongly depends on the input switching frequency.
Please refer to the performance curve to choose the input
driving frequency. Having obtained the power dissipation, the maximum junction temperature can be
determined as follows:
T
JMAXTMAXΘJAPDISS
×+=
where:
T
is the maximum ambient temperature
MAX
θ
is the thermal resistance of the package
JA
Threshold Detector
The inverting input is connected to a reference voltage
and the non-inverting input is connected to the input. As
the input passes the V
threshold, the comparator's
REF
9
Page 10
EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
output changes state. The non-inverting and inverting
inputs may be reversed.
EL5285C - Preliminary
V
V
REF
+
IN
-
V
OUT
Crystal Oscillator
A simple crystal oscillator using one comparator of an
EL5285C is shown below. The resistors R1 and R2 set
the bias point at the comparator's non-inverting input.
Resistors R3, R4, and C1 set the inverting input node at
an appropriate DC average voltage based on the output.
The crystal's path provides resonant positive feedback
and stable oscillation occurs. Although the EL5285C
will give the correct logic output when an input is outside the common mode range, additional delays may
occur when it is so operated. Therefore, the DC bias
voltages at the inputs are set about 500mV below the
center of the common mode range and the 200Ω resistor
attenuates the feedback to the non-inverting input. The
circuit will operate with most AT-cut crystal from 1MHz
to 8MHz over a 2V to 7V supply range. The output duty
cycle for this circuit is roughly 50% at 5V VCC, but it is
affected by the tolerances of the resistors. The duty cycle
can be adjusted by changing VCC value.
5V
5kΩ
R
1
1.5kΩ
R
2
C
1
0.01µF
200Ω
+
-
2kΩ
1MHz to
8MHz
V
OUT
R
3
R
4
2kΩ
10
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EL5285C - Preliminary
Dual and Window 4ns High-Speed Comparators
EL5285C - Preliminary
General Disclaimer
Specifications contained in this data sheet are in effect as of the publication date shown. Elantec, Inc. reserves the right to make changes in the circuitry or specifications contained herein at any time without notice. Elantec, Inc. assumes no responsibility for the use of any circuits described
herein and makes no representations that they are free from patent infringement.
WARNING - Life Support Policy
Elantec, Inc. products are not authorized for and should not be used
within Life Support Systems without the specific written consent of
Elantec, Inc. Life Support systems are equipment intended to sup-
Elantec Semiconductor, Inc.
675 Trade Zone Blvd.
Milpitas, CA 95035
Telephone: (408) 945-1323
(888) ELANTEC
Fax: (408) 945-9305
European Office: +44-118-977-6020
Japan Technical Center: +81-45-682-5820
port or sustain life and whose failure to perform when properly used
in accordance with instructions provided can be reasonably
expected to result in significant personal injury or death. Users contemplating application of Elantec, Inc. Products in Life Support
Systems are requested to contact Elantec, Inc. factory headquarters
to establish suitable terms & conditions for these applications. Elantec, Inc.’s warranty is limited to replacement of defective
components and does not cover injury to persons or property or
other consequential damages.
September 7, 2001
11
Printed in U.S.A.
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