INTERSIL EL2157CS

EL2150, EL2157
®
Data Sheet
125MHz Single Supply, Clamping Op
Amps
The EL2150 and EL2157 are the
electronics industry's fastest single
supply op amps available. Prior single
supply op amps have generally been limited to bandwidths
and slew rates ¼ that of the EL2150 and EL2157. The
125MHz bandwidth, 275V/µs slew rate, and 0.05%/0.05°
differential gain/differential phase makes this part ideal for
single or dual supply video speed applications. With its
voltage feedback architecture, these amplifiers can accept
reactive feedback networks, allowing them to be used in
analog filtering applications. The inputs can sense signals
below the bottom supply rail and as high as 1.2V below the
top rail. Connecting the load resistor to ground and operating
from a single supply, the outputs swing completely to ground
without saturating. The outputs can also drive to within 1.2V
of the top rail. The EL2150 and EL2157 will output ±100mA
and will operate with single supply voltages as low as 2.7V,
making them ideal for portable, low power applications.
March 12, 2004
Features
• Specified for 3V, 5V, or ±5V applications
• Power-down to 0µA (EL2157)
• Output voltage clamp (EL2157)
• Large input common mode range
0V < VCM < VS - 1.2V
• Output swings to ground without saturating
• -3dB bandwidth = 125MHz
• ±0.1dB bandwidth = 30MHz
• Low supply current = 5mA
• Slew rate = 275V/µs
• Low offset voltage = 2mV max (SO package)
• Output current = ±100mA
• High open loop gain = 80dB
• Diff gain/phase = 0.05%/0.05°
The EL2157 has a high speed disable feature. Applying a
low logic level to this pin reduces the supply current to 0µA
within 50ns. This is useful for both multiplexing and reducing
power consumption.
Applications
The EL2157 also has an output voltage clamp feature. This
clamp is a fast recovery (<7ns) output clamp that prevents
the output voltage from going above the preset clamp
voltage. This feature is desirable for A/D applications, as A/D
converters can require long times to recover if overdriven.
• A/D drivers
For applications where board space is critical the EL2150 is
available in the tiny 5-pin SOT-23 package, which has a
footprint 28% the size of an 8-pin SO. The EL2150 and
EL2157 are both available in an 8-pin SO package. All parts
operate over the industrial temperature range of -40°C to
+85°C. For dual, triple, or quad applications, contact the
factory.
• RGB applications
1
FN7050.1
• Video amplifiers
• PCMCIA applications
• Line drivers
• Portable computers
• High speed communications
• Broadcast equipment
• Active filtering
Ordering Information
PART NUMBER
PACKAGE
TAPE & REEL PKG. DWG. #
EL2150CS
8-Pin SO
-
MDP0027
EL2150CS-T7
8-Pin SO
7”
MDP0027
EL2150CS-T13
8-Pin SO
13”
MDP0027
EL2150CW-T7
5-Pin SOT-23
7” (3K pcs)
MDP0038
EL2150CW-T7A
5-Pin SOT-23
7” (250 pcs)
MDP0038
EL2157CS
8-Pin SO
-
MDP0027
EL2157CS-T7
8-Pin SO
7”
MDP0027
EL2157CS-T13
8-Pin SO
13”
MDP0027
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 321-724-7143 | Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright © Intersil Americas Inc. 2004. All Rights Reserved. Elantec is a registered trademark of Elantec Semiconductor, Inc.
All other trademarks mentioned are the property of their respective owners.
EL2150, EL2157
Pinouts
EL2150
(8-PIN SO)
TOP VIEW
2
EL2157
(8-PIN SO)
TOP VIEW
EL2150
(5-PIN SOT-23)
TOP VIEW
EL2150, EL2157
Absolute Maximum Ratings (TA = 25°C)
Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Curves
Storage Temperature Range . . . . . . . . . . . . . . . . . .-65°C to +150°C
Ambient Operating Temperature Range . . . . . . . . . .-40°C to +85°C
Operating Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . 150°C
Supply Voltage between VS+ and GND . . . . . . . . . . . . . . . . +12.6V
Input Voltage (IN+, IN-, ENABLE, CLAMP) . . . GND-0.3V, VS+0.3V
Differential Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .±6V
Maximum Output Current. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90mA
Output Short Circuit Duration. . . . . . . . . . . . . . . . . . . . . . . . (Note 1)
CAUTION: Stresses above those listed in “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress only rating and operation of the
device at these or any other conditions above those indicated in the operational sections of this specification is not implied.
IMPORTANT NOTE: All parameters having Min/Max specifications are guaranteed. Typical values are for information purposes only. Unless otherwise noted, all tests
are at the specified temperature and are pulsed tests, therefore: TJ = TC = TA
DC Electrical Specifications
VS = +5V, GND = 0V, TA = 25°C, VCM = 1.5V, VOUT = 1.5V, VCLAMP = +5V, VENABLE = +5V, unless
otherwise specified. (Note 1)
PARAMETER
VOS
DESCRIPTION
Offset Voltage
CONDITIONS
MIN
TYP
MAX
UNIT
SO package
-2
2
mV
SOT-23 package
-3
3
mV
TCVOS
Offset Voltage Temperature
Coefficient
Measured from TMIN to TMAX
IB
Input Bias Current
VIN = 0V
IOS
Input Offset Current
VIN = 0V
TCIOS
Input Bias Current Temperature
Coefficient
Measured from TMIN to TMAX
PSRR
Power Supply Rejection Ratio
VS = VENABLE = 2.7V to 12V, VCLAMP =
OPEN
CMRR
Common Mode Rejection Ratio
10
-750
µV/°C
-5.5
-10
µA
150
750
nA
50
nA/°C
55
70
dB
VCM = 0V to 3.8V
55
65
dB
VCM = 0V to 3.0V
55
70
dB
CMIR
Common Mode Input Range
0
RIN
Input Resistance
Common mode
CIN
Input Capacitance
ROUT
V
2
MΩ
SO package
1
pF
Output Resistance
AV = 1
40
mΩ
IS,ON
Supply Current - Enabled
VS = VCLAMP = 12V, VENABLE = 12V
5
6.5
mA
IS,OFF
Supply Current - Shut Down
VS = VCLAMP = 10V, VENABLE = 0.5V
0
50
µA
VS = VCLAMP = 12V, VENABLE = 0.5V
5
PSOR
Power Supply Operating Range
AVOL
Open Loop Gain
1
VS-1.2
2.7
VS = VCLAMP = 12V, VOUT = 2V
65
µA
12.0
V
80
dB
70
dB
60
dB
10.8
V
10.0
V
4.0
V
9V, RL = 1kΩ to GND
VOUT = 1.5V to 3.5V
RL = 1kΩ to GND
VOUT = 1.5V to 3.5V
RL = 150Ω to GND
VOP
Positive Output Voltage Swing
VS = 12V, AV = 1, RL= 1kΩ to 0V
VS = 12V, AV = 1, RL = 150Ω to 0V
9.6
VS = ±5V, AV = 1, RL = 1kΩ to 0V
3
VS = ±5V, AV = 1, RL = 150Ω to 0V
3.4
3.8
V
VS = 3V, AV = 1, RL = 150Ω to 0V
1.8
1.95
V
EL2150, EL2157
DC Electrical Specifications
VS = +5V, GND = 0V, TA = 25°C, VCM = 1.5V, VOUT = 1.5V, VCLAMP = +5V, VENABLE = +5V, unless
otherwise specified. (Note 1) (Continued)
PARAMETER
VON
IOUT
DESCRIPTION
Negative Output Voltage Swing
Output Current (Note 2)
CONDITIONS
TYP
MAX
UNIT
VS = 12V, AV = 1, RL = 150Ω to 0V
5.5
8
mV
VS = ±5V, AV = 1, RL = 1kΩ to 0V
-4.0
VS = ±5V, AV = 1, RL = 150Ω to 0V
-3.7
VS = ±5V, AV = 1, RL = 10Ω to 0V
MIN
±75
VS = ±5V, AV = 1, RL = 50Ω to 0V
IOUT,OFF
Output Current, Disabled
VENABLE = 0.5V
VIH-EN
ENABLE pin Voltage for Power Up
Relative to GND pin
VIL-EN
ENABLE pin Voltage for Shut Down Relative to GND pin
IIH-EN
ENABLE pin Input Current-High
(Note 3)
VS = VCLAMP = 12V, VENABLE = 12V
IIL-EN
ENABLE pin Input Current-Low
(Note 3)
VS = VCLAMP = 12V, VENABLE = 0.5V
VOR-CL
Voltage Clamp Operating Range
(Note 4)
Relative to GND pin
VACC-CL
CLAMP Accuracy
VIN = 4V, RL = 1kΩ to GND
V
-3.4
±100
mA
±60
mA
0
20
2.0
µA
V
0.5
V
340
410
µA
0
1
µA
VOP
V
100
250
mV
12
25
µA
1.2
-250
V
VCLAMP = 1.5V and 3.5V
IIH-CL
CLAMP pin Input Current - High
VS = VCLAMP = 12V
IIL-CL
CLAMP pin Input Current - Low
VS = 12V, VCLAMP = 1.2V
-20
-15
µA
NOTES:
1. CLAMP pin and ENABLE pin specifications apply only to the EL2157.
2. Internal short circuit protection circuitry has been built into the EL2150/EL2157. See the Applications section.
3. If the disable feature is not desired, tie the ENABLE pin to the VS pin, or apply a logic high level to the ENABLE pin.
4. The maximum output voltage that can be clamped is limited to the maximum positive output Voltage, or VOP. Applying a voltage higher than
VOP inactivates the clamp. If the clamp feature is not desired, either tie the CLAMP pin to the VS pin, or simply let the CLAMP pin float.
4
EL2150, EL2157
Closed Loop AC Electrical Specifications VS = +5V, GND = 0V, TA = 25°C, VCM = +1.5V, VOUT = +1.5V, VCLAMP = +5V,
VENABLE = +5V, AV = +1, RF = 0Ω, RL = 150Ω to GND pin, unless otherwise specified.
(Notes 1 and 2)
PARAMETER
BW
BW
DESCRIPTION
-3dB Bandwidth (VOUT = 400mVP-P)
CONDITIONS
MIN
TYP
MAX
UNIT
VS = 5V, AV = 1, RF = 0Ω
125
MHz
VS = 5V, AV = -1, RF = 500Ω
60
MHz
VS = 5V, AV = 2, RF = 500Ω
60
MHz
VS = 5V, AV = 10, RF = 500Ω
6
MHz
VS = 12V, AV = 1, RF = 0Ω
150
MHz
VS = 3V, AV = 1, RF = 0Ω
100
MHz
25
MHz
VS = 5V, AV = 1, RF = 0Ω
30
MHz
VS = 3V, AV = 1, RF = 0Ω
20
MHz
±0.1dB Bandwidth (VOUT = 400mVP-P) VS = 12V, AV = 1, RF = 0Ω
GBWP
Gain Bandwidth Product
VS = 12V, @ AV = 10
60
MHz
PM
Phase Margin
RL = 1kΩ, CL = 6 pF
55
°
SR
Slew Rate
VS = 10V, RL = 150Ω, VOUT = 0V to 6V
275
V/µs
VS = 5V, RL = 150Ω, VOUT = 0V to 3V
300
V/µs
200
tR,tF
Rise Time, Fall Time
±0.1V step
2.8
ns
OS
Overshoot
±0.1V step
10
%
tPD
Propagation Delay
±0.1V step
3.2
ns
tS
0.1% Settling Time
VS = ±5V, RL = 500Ω, AV = 1, VOUT = ±3V
40
ns
0.01% Settling Time
VS = ±5V, RL = 500Ω, AV = 1, VOUT = ±3V
75
ns
dG
Differential Gain (Note 3)
AV = 2, RF = 1kΩ
0.05
%
dP
Differential Phase (Note 3)
AV = 2, RF = 1kΩ
0.05
°
eN
Input Noise Voltage
f = 10kHz
48
nV/√Hz
iN
Input Noise Current
f = 10kHz
1.25
pA/√Hz
tDIS
Disable Time (Note 4)
50
ns
tEN
Enable Time (Note 4)
25
ns
tCL
Clamp Overload Recovery
7
ns
NOTES:
1. CLAMP pin and ENABLE pin specifications apply only to the EL2157.
2. All AC tests are performed on a “warmed up” part, except slew rate, which is pulse tested.
3. Standard NTSC signal = 286mVP-P, f = 3.58MHz, as VIN is swept from 0.6V to 1.314V.RL is DC coupled.
4. Disable/Enable time is defined as the time from when the logic signal is applied to the ENABLE pin to when the supply current has reached half
its final value.
5
EL2150, EL2157
Typical Performance Curves
Non-Inverting
Frequency Response (Gain)
Non-Inverting
Frequency Response (Phase)
3dB Bandwidth vs
Temperature for
Non-Inverting Gains
Inverting Frequency
Response (Gain)
Inverting Frequency
Response (Phase)
In 3dB Bandwidth vs
Temperature for
Inverting Gains
Frequency Response
for Various RL
Frequency Response
for Various CL
6
Non-Inverting
Frequency Response vs
Common Mode Voltage
EL2150, EL2157
Typical Performance Curves
3dB Bandwidth vs
Supply Voltage for
Non-Inverting Gains
3dB Bandwidth vs Supply
Voltage for Inverting Gains
Open Loop Gain and
Phase vs Frequency
7
(Continued)
Frequency Response for
Various Supply Voltages,
AV = + 1
Frequency Response for
Various Supply Voltages,
AV = + 2
Open Loop Voltage Gain
vs Die Temperature
PSSR and CMRR
vs Frequency
PSRR and CMRR vs
Die Temperature
Closed Loop Output
Impedance vs Frequency
EL2150, EL2157
Typical Performance Curves
Large Signal Step Response,
VS = +3V
(Continued)
Large Signal Step Response,
VS = +5V
Small Signal Step Response
Slew Rate vs Temperature
8
Settling Time vs
Settling Accuracy
Large Signal Step Response,
VS = +12V
Large Signal Step Response,
VS = ±5V
Voltage and Current Noise
vs Frequency
EL2150, EL2157
Typical Performance Curves
(Continued)
Differential Gain for
Single Supply Operation
Differential Phase for
Single Supply Operation
Differential Gain and Phase
for Dual Supply Operation
2nd and 3rd Harmonic
Distortion vs Frequency
2nd and 3rd Harmonic
Distortion vs Frequency
2nd and 3rd Harmonic
Distortion vs Frequency
Output Voltage Swing vs
Frequency for THD < 0.1%
9
Output Voltage Swing vs
Frequency for Unlimited
Distortion
Output Current
vs Die Temperature
EL2150, EL2157
Typical Performance Curves
(Continued)
Supply Current vs
Supply Voltage
Supply Current vs
Die Temperature
Input Resistance vs
Die Temperature
Offset Voltage vs
Die Temperature (4 Samples)
Input Bias Current
vs Input Voltage
Input Offset Current
and Input Bias Current
vs Die Temperature
Positive Output Voltage
Swing vs Die Temperature,
RL = 150Ω to GND
Negative Output Voltage
Swing vs Die Temperature,
RL = 150Ω to GND
Clamp Accuracy
vs Die Temperature
10
EL2150, EL2157
Typical Performance Curves
(Continued)
Clamp Accuracy
RL = 150Ω
Enable Response for a
Family of DC Inputs
Disable/Enable Response for a
Family of Sine Waves
11
Clamp Accuracy
RL = 1kΩ
Clamp Accuracy
RL = 10kΩ
Disable Response for a
Family of DC Inputs
OFF Isolation
EL2150, EL2157
Typical Performance Curves
JEDEC JESD51-7 HIGH EFFECTIVE
THERMAL CONDUCTIVITY TEST BOARD
1.6
1.4
1.2 1.136W
SO8
1
θJA=110°C/W
0.8
0.6
0.4
0.2
0
0
25
50
75 85 100
125
JEDEC JESD51-7 HIGH EFFECTIVE
THERMAL CONDUCTIVITY TEST BOARD
0.6
POWER DISSIPATION (W)
POWER DISSIPATION (W)
1.8
(Continued)
0.5 543mW
0.3
0.2
0.1
0
150
0
AMBIENT TEMPERATURE (°C)
JEDEC JESD51-3 LOW EFFECTIVE
THERMAL CONDUCTIVITY TEST BOARD
0.6
1
0.8
781mW
SO8
θJA=160°C/W
0.6
0.4
0.2
0
0
25
50
75 85 100
125
AMBIENT TEMPERATURE (°C)
Burn-In Circuit
12
25
50
75 85 100
125
150
AMBIENT TEMPERATURE (°C)
POWER DISSIPATION (W)
POWER DISSIPATION (W)
1.2
SOT23-5/6
θJA=230°C/W
0.4
150
JEDEC JESD51-3 LOW EFFECTIVE
THERMAL CONDUCTIVITY TEST BOARD
488mW
0.5
SOT23-5/6
0.4
θJA=256°C/W
0.3
0.2
0.1
0
0
25
50
75 85 100
125
AMBIENT TEMPERATURE (°C)
150
EL2150, EL2157
Simplified Schematic
Applications Information
Product Description
The EL2150 and EL2157 are the industry's fastest single
supply operational amplifiers. Connected in voltage follower
mode, their -3dB bandwidth is 125MHz while maintaining a
275V/µs slew rate. With an input and output common mode
range that includes ground, these amplifiers were optimized
for single supply operation, but will also accept dual
supplies. They operate on a total supply voltage range as
low as +2.7V or up to +12V. This makes them ideal for +3V
applications, especially portable computers.
While many amplifiers claim to operate on a single supply,
and some can sense ground at their inputs, most fail to truly
drive their outputs to ground. If they do succeed in driving to
ground, the amplifier often saturates, causing distortion and
recovery delays. However, special circuitry built into the
EL2150 and EL2157 allows the output to follow the input
signal to ground without recovery delays.
Power Supply Bypassing And Printed Circuit
Board Layout
As with any high-frequency device, good printed circuit
board layout is necessary for optimum performance. Ground
plane construction is highly recommended. Lead lengths
should be as short as possible. The power supply pins must
be well bypassed to reduce the risk of oscillation. The
combination of a 4.7µF tantalum capacitor in parallel with a
0.1µF ceramic capacitor has been shown to work well when
placed at each supply pin. For single supply operation,
where pin 4 (VS-) is connected to the ground plane, a single
4.7µF tantalum capacitor in parallel with a 0.1µF ceramic
capacitor across pins 7 and 4 will suffice.
For good AC performance, parasitic capacitance should be
kept to a minimum. Ground plane construction should be
used. Carbon or Metal-Film resistors are acceptable with the
13
Metal-Film resistors giving slightly less peaking and
bandwidth because of their additional series inductance.
Use of sockets, particularly for the SO package should be
avoided if possible. Sockets add parasitic inductance and
capacitance which will result in some additional peaking and
overshoot.
Supply Voltage Range and Single-Supply
Operation
The EL2150 and EL2157 have been designed to operate
with supply voltages having a span of greater than 2.7V, and
less than 12V. In practical terms, this means that the EL2150
and EL2157 will operate on dual supplies ranging from
±1.35V to ±6V. With a single-supply, the EL2150 and
EL2157 will operate from +2.7V to +12V. Performance has
been optimized for a single +5V supply.
Pins 7 and 4 are the power supply pins. The positive power
supply is connected to pin 7. When used in single supply
mode, pin 4 is connected to ground. When used in dual
supply mode, the negative power supply is connected to
pin 4.
As supply voltages continue to decrease, it becomes
necessary to provide input and output voltage ranges that
can get as close as possible to the supply voltages. The
EL2150 and EL2157 have an input voltage range that
includes the negative supply and extends to within 1.2V of
the positive supply. So, for example, on a single +5V supply,
the EL2150 and EL2157 have an input range which spans
from 0V to 3.8V.
The output range of the EL2150 and EL2157 is also quite
large. It includes the negative rail, and extends to within 1V
of the top supply rail. On a +5V supply, the output is
therefore capable of swinging from 0V to +4V. On split
supplies, the output will swing ±4V. If the load resistor is tied
EL2150, EL2157
to the negative rail and split supplies are used, the output
range is extended to the negative rail.
For other biasing conditions see the Differential Gain and
Differential Phase vs Input Voltage curves.
Choice Of Feedback Resistor, RF
The feedback resistor forms a pole with the input
capacitance. As this pole becomes larger, phase margin is
reduced. This increases ringing in the time domain and
peaking in the frequency domain. Therefore, RF has some
maximum value which should not be exceeded for optimum
performance. If a large value of RF must be used, a small
capacitor in the few picofarad range in parallel with RF can
help to reduce this ringing and peaking at the expense of
reducing the bandwidth.
Output Drive Capability
In spite of their moderately low 5mA of supply current, the
EL2150 and EL2157 are capable of providing ±100mA of
output current into a 10Ω load, or ±60mA into 50Ω. With this
large output current capability, a 50Ω load can be driven to
±3V with VS = ±5V, making it an excellent choice for driving
isolation transformers in telecommunications applications.
Driving Cables and Capacitive Loads
For AV = +1, RF = 0Ω is optimum. For AV = -1 or +2 (noise
gain of 2), optimum response is obtained with RF between
500Ω and 1kΩ. For AV = -4 or +5 (noise gain of 5), keep RF
between 2kΩ and 10kΩ.
When used as a cable driver, double termination is always
recommended for reflection-free performance. For those
applications, the back-termination series resistor will decouple the EL2150 and EL2157 from the cable and allow
extensive capacitive drive. However, other applications may
have high capacitive loads without a back-termination
resistor. In these applications, a small series resistor (usually
between 5Ω and 50Ω) can be placed in series with the
output to eliminate most peaking. The gain resistor (RG) can
then be chosen to make up for any gain loss which may be
created by this additional resistor at the output.
Video Performance
Disable/Power-Down
For good video performance, an amplifier is required to
maintain the same output impedance and the same
frequency response as DC levels are changed at the output.
This can be difficult when driving a standard video load of
150Ω, because of the change in output current with DC
level. Differential Gain and Differential Phase for the EL2150
and EL2157 are specified with the black level of the output
video signal set to +1.2V. This allows ample room for the
sync pulse even in a gain of +2 configuration. This results in
dG and dP specifications of 0.05% and 0.05° while driving
150Ω at a gain of +2. Setting the black level to other values,
although acceptable, will compromise peak performance.
For example, looking at the single supply dG and dP curves
for RL=150Ω, if the output black level clamp is reduced from
1.2V to 0.6V dG/dP will increase from 0.05%/0.05° to
0.08%/0.25° Note that in a gain of +2 configuration, this is
the lowest black level allowed such that the sync tip doesn't
go below 0V.
The EL2157 amplifier can be disabled, placing its output in a
high-impedance state. The disable or enable action takes
only about 40ns. When disabled, the amplifier's supply
current is reduced to 0mA, thereby eliminating all power
consumption by the EL2157. The EL2157 amplifier's power
down can be controlled by standard CMOS signal levels at
the ENABLE pin. The applied CMOS signal is relative to the
GND pin. For example, if a single +5V supply is used, the
logic voltage levels will be +0.5V and +2.0V. If using dual
±5V supplies, the logic levels will be -4.5V and
-3.0V. Letting the ENABLE pin float will disable the EL2157.
If the power-down feature is not desired, connect the
ENABLE pin to the VS+ pin. The guaranteed logic levels of
+0.5V and +2.0V are not standard TTL levels of +0.8V and
+2.0V, so care must be taken if standard TTL will be used to
drive the ENABLE pin.
As far as the output stage of the amplifier is concerned, RF+
RG appear in parallel with RL for gains other than +1. As this
combination gets smaller, the bandwidth falls off.
Consequently, RF has a minimum value that should not be
exceeded for optimum performance.
If your application requires that the output goes to ground,
then the output stage of the EL2150 and EL2157, like all
other single supply op amps, requires an external pull down
resistor tied to ground. As mentioned above, the current
flowing through this resistor becomes the DC bias current for
the output stage NPN transistor. As this current approaches
zero, the NPN turns off, and dG and dP will increase. This
becomes more critical as the load resistor is increased in
value. While driving a light load, such as 1kΩ, if the input
black level is kept above 1.25V, dG and dP are a
respectable 0.03% and 0.03°.
14
Output Voltage Clamp
The EL2157 amplifier has an output voltage clamp. This
clamping action is fast, being activated almost
instantaneously, and being deactivated in <7ns, and
prevents the output voltage from going above the preset
clamp voltage. This can be very helpful when the EL2157 is
used to drive an A/D converter, as some converters can
require long times to recover if overdriven. The output
voltage remains at the clamp voltage level as long as the
product of the input voltage and the gain setting exceeds the
clamp voltage. If the EL2157 is connected in a gain of 2, for
example, and +3V DC is applied to the CLAMP pin, any
voltage higher than +1.5V at the inputs will be clamped and
+3V will be seen at the output.
EL2150, EL2157
Figure 1 below is a unity gain connected EL2157 being
driven by a 3VP-P sinewave, with 2.25V applied to the
CLAMP pin. The resulting output waveform, with its output
being clamped to 2.25V, is shown in Figure 2.
FIGURE 1.
clamp voltage. Curves of Clamp Accuracy vs VCLAMP, and
VIN for 3 values of RL are included in the Typical
Performance Curves Section.
Unlike amplifiers that clamp at the input and are therefore
limited to non-inverting applications only, the EL2157 output
clamp architecture works for both inverting and non-inverting
gain applications. There is also no maximum voltage
difference limitation between VIN and VCLAMP which is
common on input clamped architectures.
The voltage clamp operates for any voltage between +1.2V
above the GND pin, and the minimum output voltage swing,
VOP. Forcing the CLAMP pin much below +1.2V can
saturate transistors and should therefore be avoided.
Forcing the CLAMP pin above VOP simply de-activates the
CLAMP feature. In other words, one cannot expect to clamp
any voltage higher than what the EL2157 can drive to in the
first place. If the clamp feature is not desired, either let the
CLAMP pin float or connect it to the VS+ pin.
EL2157 Comparator Application
FIGURE 2.
Figure 3 shows the output of the same circuit being driven by
a 0.5V to 2.75V square wave, as the clamp voltage is varied
from 1.0V to 2.5V, as well as the unclamped output signal.
The rising edge of the signal is clamped to the voltage
applied to the CLAMP pin almost instantaneously. The
output recovers from the clamped mode within 5ns - 7ns,
depending on the clamp voltage. Even when the CLAMP pin
is taken 0.2V below the minimum 1.2V specified, the output
is still clamped and recovers in about 11ns.
The EL2157 can be used as a very fast, single supply
comparator by utilizing the clamp feature. Most op amps
used as comparators allow only slow speed operation
because of output saturation issues. However, by applying a
DC voltage to the CLAMP pin of the EL2157, the maximum
output voltage can be clamped, thus preventing saturation.
Figure 4 below is the EL2157 implemented as a comparator.
2.5V DC is applied to the CLAMP pin, as well as the IN- pin.
A differential signal is then applied between the inputs.
Figure 5 shows the output square wave that results when a
±1V, 10MHz triangular wave is applied, while Figure 6 is a
graph of propagation delay vs. overdrive as a square wave is
presented at the input.
FIGURE 4.
FIGURE 3.
The clamp accuracy is affected by 1) the CLAMP pin
voltage, 2) the input voltage, and 3) the load resistor.
Depending upon the application, the accuracy may be as
little as a few tens of millivolts to a few hundred millivolts. Be
sure to allow for these inaccuracies when choosing the
15
FIGURE 5.
EL2150, EL2157
Propagation Delay vs Overdrive
EL2157 as a Comparator
outputs are tied directly together. Decoupling resistors at
each output are not necessary. In fact, adding them
approximately doubles the switching time to 100ns.
FIGURE 6.
Video Sync Pulse Remover Application
All CMOS Analog to Digital Converters (A/Ds) have a
parasitic latch-up problem when subjected to negative input
voltage levels. Since the sync tip contains no useful video
information and it is a negative going pulse, we can chop it
off. Figure 7 shows a unity gain connected EL2150 and
EL2157. Figure 8 shows the complete input video signal
applied at the input, as well as the output signal with the
negative going sync pulse removed.
FIGURE 9.
FIGURE 10.
FIGURE 7.
Short Circuit Current Limit
FIGURE 8.
Multiplexing with the EL2157
The ENABLE pin on the EL2157 allows for multiplexing
applications. Figure 9 shows two EL2157s with their outputs
tied together, driving a back terminated 75Ω video load. A
2VP-P 10MHz sinewave is applied at one input, and a 1VP-P
5MHz sinewave to the other. Figure 10 shows the CLOCK
signal which is applied, and the resulting output waveform at
VOUT. Switching is complete in about 50ns. Notice the
16
The EL2150 and EL2157 have internal short circuit
protection circuitry that protect it in the event of its output
being shorted to either supply rail. This limit is set to around
100mA nominally and reduces with increasing junction
temperature. It is intended to handle temporary shorts. If an
output is shorted indefinitely, the power dissipation could
easily increase such that the part will be destroyed.
Maximum reliability is maintained if the output current never
exceeds ±90mA. A heat sink may be required to keep the
junction temperature below absolute maximum when an
output is shorted indefinitely.
Power Dissipation
With the high output drive capability of the EL2150 and
EL2157, it is possible to exceed the 150°C Absolute
Maximum junction temperature under certain load current
conditions. Therefore, it is important to calculate the
maximum junction temperature for the application to
determine if power-supply voltages, load conditions, or
EL2150, EL2157
package type need to be modified for the EL2150 and
EL2157 to remain in the safe operating area.
Single Supply Voltage
vs RLOAD for Various
VOUT (SO Package)
The maximum power dissipation allowed in a package is
determined according to [1]:
T JMAX - T AMAX
PD MAX = -------------------------------------------θ JA
where:
TJMAX = Maximum junction temperature
TAMAX = Maximum ambient temperature
θJA = Thermal resistance of the package
PDMAX = Maximum power dissipation in the package
The maximum power dissipation actually produced by an IC
is the total quiescent supply current times the total power
supply voltage, plus the power in the IC due to the load, or
[2]
FIGURE 11.
Single Supply Voltage
vs RLOAD for Various
VOUT (SOT-23 Package)
V OUT
PD MAX = V S × I SMAX + ( V s - V OUT ) × ---------------RL
where:
VS = Total supply voltage
ISMAX = Maximum supply current
VOUT = Maximum output voltage of the application
RL = Load resistance tied to ground
If we set the two PDMAX equations, [1] & [2], equal to each
other, and solve for VS, we can get a family of curves for
various loads and output voltages according to [3]:
R L × ( T AMAX - T AMAX )
2
---------------------------------------------------------------- + ( V OUT )
θ JA
V S = ----------------------------------------------------------------------------------------------( I s × R L ) + V OUT
Figures 11 and 12 show total single supply voltage VS vs RL
for various output voltage swings for the SO package. The
curves assume WORST CASE conditions of TA = +85°C
and IS = 6.5mA.
17
FIGURE 12.
EL2150, EL2157
EL2157 Macromodel
* Revision A, July 1995
* When not being used, the clamp pin, pin 1,
* should be connected to +Vsupply, pin 7
* Connections:
+input
*
|
-input
*
|
|
+Vsupply
*
|
|
|
-Vsupply
*
|
|
|
|
output
*
|
|
|
|
|
clamp
*
|
|
|
|
|
|
.subckt EL2157/el 3 2 7 4 6 1
*
* Input Stage
*
i1 7 10 250uA
i2 7 11 250uA
r1 10 11 4k
q1 12 2 10 qp
q2 13 3 11 qpa
r2 12 4 100
r3 13 4 100
*
* Second Stage & Compensation
*
gm 15 4 13 12 4.6m
r4 15 4 15Meg
c1 15 4 0.36pF
*
* Poles
*
e1 17 4 15 4 1.0
r6 17 25 400
c3 25 4 1pF
r7 25 18 500
c4 18 4 1pF
*
* Output Stage & Clamp
*
i3 20 4 1.0mA
q3 7 23 20 qn
q4 7 18 19 qn
q5 7 18 21 qn
q6 4 20 22 qp
q7 7 23 18 qn
d1 19 20 da
d2 18 1 da
r8 21 6 2
r9 22 6 2
r10 18 21 10k
r11 7 23 100k
d3 23 24 da
d4 24 4 da
d5 23 18 da
*
* Power Supply Current
*
ips 7 4 3.2mA
*
* Models
18
EL2150, EL2157
*
.model qn npn(is=800e-18 bf=150 tf=0.02nS)
.model qpa pnp(is=810e-18 bf=50 tf=0.02nS)
.model qp pnp(is=800e-18 bf=54 tf=0.02nS)
.model da d(tt=0nS)
.ends
EL2157 Macromodel
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Intersil products are sold by description only. Intersil Corporation reserves the right to make changes in circuit design, software and/or specifications at any time without
notice. Accordingly, the reader is cautioned to verify that data sheets are current before placing orders. Information furnished by Intersil is believed to be accurate and
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19