INTERSIL EL5157IW-T7

EL5156, EL5157, EL5256, EL5257
®
Data Sheet
PRELIMINARY
July 2, 2004
FN7386.2
<1mV Voltage Offset, 600MHz Amplifiers
Features
The EL5156, EL5157, EL5256, and
EL5257 are 600MHz bandwidth -3dB
voltage mode feedback amplifiers with
DC accuracy of <0.01%, 1mV offsets and 40kV/V open loop
gains. These amplifiers are ideally suited for applications
ranging from precision measurement instrumentation to high
speed video and monitor applications demanding the very
highest linearity at very high frequency. Capable of operating
with as little as 6.0mA of current from a single supply ranging
from 5V to 12V and dual supplies ranging from ±2.5V to
±5.0V these amplifiers are also well suited for handheld,
portable and battery-powered equipment. With their
capability to output as much as 140mA, member of this
family is comfortable with demanding load conditions.
• 600MHz -3dB bandwidth, 240MHz 0.1dB bandwidth
Single amplifiers are available in SOT-23 packages and
duals in a 10-pin MSOP package for applications where
board space is critical. Additionally, singles and duals are
available in the industry-standard 8-pin SO package. All
parts operate over the industrial temperature range of -40°C
to +85°C.
Applications
• <1mV input offset
• Very high open loop gains 92dB
• Low supply current = 6mA
• 140mA output current
• Single supplies from 5V to 12V
• Dual supplies from ±2.5V to ±5V
• Fast disable on the EL5156 and EL5256
• Low cost
• Imaging
• Instrumentation
• Video
• Communications devices
Ordering Information
PART
NUMBER
• 700V/µs slew rate
PACKAGE
TAPE & REEL
PKG. DWG. #
EL5156IS
8-Pin SO
-
MDP0027
EL5156IS-T7
8-Pin SO
7”
MDP0027
EL5156IS-T13
8-Pin SO
13”
MDP0027
EL5157IW-T7
5-Pin SOT-23
7” (3K pcs)
MDP0038
EL5157IW-T7A
5-Pin SOT-23
7” (250 pcs)
MDP0038
EL5256IY
10-Pin MSOP
-
MDP0043
EL5256IY-T7
10-Pin MSOP
7”
MDP0043
EL5256IY-T13
10-Pin MSOP
13”
MDP0043
EL5257IS
8-Pin SO
-
MDP0027
EL5257IS-T7
8-Pin SO
7”
MDP0027
EL5257IS-T13
8-Pin SO
13”
MDP0027
EL5257IY
8-Pin MSOP
-
MDP0043
EL5257IY-T7
8-Pin MSOP
7”
MDP0043
EL5257IY-T13
8-Pin MSOP
13”
MDP0043
1
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.
EL5156, EL5157, EL5256, EL5257
Pinouts
EL5157
(5-PIN SOT-23)
TOP VIEW
EL5156
(8-PIN SO)
TOP VIEW
NC 1
IN- 2
IN+ 3
+
VS- 4
8 CE
OUT 1
7 VS+
VS- 2
6 OUT
IN+ 3
INA+ 1
4 IN-
EL5257
(8-PIN SO)
TOP VIEW
10 INA+
VS- 3
CEB 4
+ -
5 NC
EL5256
(10-PIN MSOP)
TOP VIEW
CEA 2
5 VS+
+
-
9 OUTA
INA- 2
8 VS+
INA+ 3
7 OUTB
6 INB-
INB+ 5
2
OUTA 1
VS- 4
8 VS+
7 OUTB
+
6 INB+
5 INB+
EL5156, EL5157, EL5256, EL5257
Absolute Maximum Ratings (TA = 25°C)
Supply Voltage between VS and GND. . . . . . . . . . . . . . . . . . . 13.2V
Maximum Continuous Output Current . . . . . . . . . . . . . . . . . . . 50mA
Pin Voltages . . . . . . . . . . . . . . . . . . . . . . . . . GND -0.5V to VS +0.5V
Power Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See Curves
Junction Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +125°C
Storage Temperature . . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Ambient Operating Temperature . . . . . . . . . . . . . . . .-40°C to +85°C
Current into IN+, IN-, CE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5mA
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
Electrical Specifications
PARAMETER
VS+ = +5V, VS- = -5V, CE = +5V, RF = RG = 562Ω, RL = 150Ω, TA = 25°C, unless otherwise specified.
DESCRIPTION
CONDITIONS
MIN
TYP
MAX
UNIT
AC PERFORMANCE
BW
-3dB Bandwidth
AV = +1, RL = 500Ω, CL = 4.7pF
600
MHz
AV = +2, RL = 150Ω
180
MHz
GBWP
Gain Bandwidth Product
RL = 150Ω
210
MHz
BW1
0.1dB Bandwidth
AV = +2
70
MHz
SR
Slew Rate
VO = -3.2V to +3.2V, AV = +2, RL = 150Ω
640
V/µs
VO = -3.2V to +3.2V, AV = +1, RL = 500Ω
700
V/µs
15
ns
500
tS
0.1% Settling Time
AV = +1
dG
Differential Gain Error
AV = +2, RL = 150Ω
0.005
%
dP
Differential Phase Error
AV = +2, RL = 150Ω
0.04
°
VN
Input Referred Voltage Noise
12
nV/√Hz
IN
Input Referred Current Noise
5.5
pA/√Hz
DC PERFORMANCE
VOS
Offset Voltage
TCVOS
Input Offset Voltage Temperature
Coefficient
Measured from TMIN to TMAX
AVOL
Open Loop Gain
VO is from -2.5V to 2.5V
-1
10
0.5
1
mV
-3
µV/°C
40
kV/V
INPUT CHARACTERISTICS
CMIR
Common Mode Input Range
Guaranteed by CMRR test
CMRR
Common Mode Rejection Ratio
VCM = 2.5V to -2.5V
80
108
IB
Input Bias Current
EL5156 & EL5157
-1
-0.4
+1
µA
EL5256 & EL5257
-600
-200
+600
nA
-250
100
+250
nA
10
25
MΩ
1
pF
IOS
Input Offset Current
RIN
Input Resistance
CIN
Input Capacitance
-2.5
+2.5
V
dB
OUTPUT CHARACTERISTICS
VOUT
IOUT
Output Voltage Swing
Peak Output Current
RL = 150Ω to GND
±3.4
±3.6
V
RL = 500Ω to GND
±3.6
±3.8
V
RL = 10Ω to GND
±80
±140
mA
ENABLE (EL5156 and EL5256 ONLY)
tEN
Enable Time
200
ns
tDIS
Disable Time
300
ns
3
EL5156, EL5157, EL5256, EL5257
Electrical Specifications
PARAMETER
VS+ = +5V, VS- = -5V, CE = +5V, RF = RG = 562Ω, RL = 150Ω, TA = 25°C, unless otherwise specified.
DESCRIPTION
CONDITIONS
IIHCE
CE Pin Input High Current
CE = VS+
IILCE
CE Pin Input Low Current
CE = VS-
VIHCE
CE Input High Voltage for Power-down
VILCE
CE Input Low Voltage for Power-up
MIN
5
TYP
MAX
UNIT
0
-1
µA
13
25
µA
VS+ -1
V
VS+ -3
V
SUPPLY
ISON
Supply Current - Enabled (per amplifier)
ISOFF
PSRR
No load, VIN = 0V, CE = +5V
5.1
6.0
6.9
mA
Supply Current - Disabled (per amplifier) No load, VIN = 0V, CE = 5V
5
13
25
µA
Power Supply Rejection Ratio
75
90
DC, VS = ±3.0V to ±6.0V
dB
Typical Performance Curves
4
2
135
RL=150Ω
CL=4.7pF
90
1
AV=+2
0
-1
-2
AV=+10
-3
45
AV=+1
AV=+2
-45
AV=+5
-90
AV=+10
-135
-180
AV=+5
-4
RL=150Ω
CL=4.7pF
0
PHASE (°)
NORMALIZED GAIN (dB)
3
-225
-5
-270
-6
100K
1M
10M
100M
-315
100K
1G
1M
FREQUENCY (Hz)
FIGURE 1. SMALL SIGNAL FREQUENCY RESPONSE - GAIN
5
1
4
3
RL=500Ω
0
-1
RL=150Ω
-2
RL=750Ω
-3
CL=10pF
CL=4.7pF
1
0
-1
CL=1pF
-3
-4
-5
-6
100K
1G
CL=27pF
-2
RL=50Ω
-4
AV=+1
RL=500Ω
2
GAIN (dB)
NORMALIZED GAIN (dB)
2
VS=±5V
AV=+2
RF=RG=562Ω
100M
FIGURE 2. SMALL SIGNAL FREQUENCY RESPONSE PHASE FOR VARIOUS GAINS
4
3
10M
FREQUENCY (Hz)
1M
10M
100M
1G
FREQUENCY (Hz)
FIGURE 3. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS RL
4
-5
100K
1M
10M
100M
1G
FREQUENCY (Hz)
FIGURE 4. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS CL
EL5156, EL5157, EL5256, EL5257
Typical Performance Curves (Continued)
5
3
16
AV=+2
RL=500Ω
RF=RG=500Ω
14
22pF
12
2
8.2pF
0
4.7pF
-1
0pF
-2
4
10pF
2
0pF
-4
-2
10M
100M
33pF
6
0
1M
-4
100K
1G
1M
FREQUENCY (Hz)
3
1G
5
AV=+5
RL=500Ω
100pF
2
82pF
68pF
1
0
22pF
-1
-2
-3
-5
100K
4
3
RL=500Ω
CL=4.7pF
AV=+1
2
±2.0V
1
0
±3.0V
-1
±4.0V
-2
±5.0V
-3
-4
-4
1M
10M
100M
100K
1G
1M
FIGURE 7. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS CL
4
4
3
NORMALIZED GAIN (dB)
AV=+1
2
1
0
-1
-2
-3
-4
-5
100K
AV=+2
AV=+1
RL=500Ω
CL=4.7pF
1M
AV=+5
10M
2
VS=±5V
RF=620Ω
RL=150Ω
AV=-1
1
0
-1
-2
AV=-2
-3
-4
-5
100M
1G
FREQUENCY (Hz)
FIGURE 9. EL5256 SMALL SIGNAL FREQUENCY
RESPONSE FOR VARIOUS GAINS
5
500M
FIGURE 8. FREQUENCY RESPONSE vs POWER SUPPLY
5
3
100M
10M
FREQUENCY (Hz)
FREQUENCY (Hz)
NORMALIZED GAIN (dB)
100M
FIGURE 6. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS CL
NORMALIZED GAIN (dB)
NORMALIZED GAIN (dB)
4
10M
FREQUENCY (Hz)
FIGURE 5. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS CL
5
180pF
100pF
8
-3
-5
100K
AV=+2
RF=RG=562Ω
RL=150Ω
10
10pF
1
GAIN (dB)
NORMALIZED GAIN (dB)
4
-6
100K
1M
10M
100M
1G
FREQUENCY (Hz)
FIGURE 10. SMALL SIGNAL INVERTING FREQUENCY
RESPONSE FOR VARIOUS GAINS
EL5156, EL5157, EL5256, EL5257
Typical Performance Curves (Continued)
NORMALIZED GAIN (dB)
5
AV=+1
CL=0.2pF
4
RL=500Ω
2
1
NORMALIZED GAIN (dB)
4
3
RL=300Ω
0
-1
RL=150Ω
-2
-3
-4
-5
3
AV=+1
CL=4.7pF
500Ω
2
1
0
-1
200Ω
-2
100Ω
-3
50Ω
-4
-6
100K
1M
10M
100M
-5
100K
1G
1M
FIGURE 11. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS RL
2
4
12pF
NORMALIZED GAIN (dB)
NORMALIZED GAIN (dB)
3
8.2pF
4.7pF
1
0
-1
0.2pF
-2
0pF
-3
-4
3
2
1
AV=+5
CL=4.7pF
RL=500Ω
RF=102Ω
68pF
47pF
0
-1
22pF
4.7pF
0pF
-2
-3
-4
-5
-5
100K
1M
10M
100M 200M
100K
1M
FREQUENCY (Hz)
6
5
RF=RG=1kΩ
NORMALIZED GAIN
NORMALIZED GAIN (dB)
1
VS=±5V
AV=+2
RL=150Ω
CL=4.7pF
0
-1
350Ω
562Ω
500Ω
250Ω
-2
-3
4
1G
FREQUENCY (Hz)
FIGURE 15. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS RF AND RG
6
500Ω
0
200Ω
-1
-3
100M
1kΩ
1
-5
10M
2kΩ
2
-2
1M
RF=RG=3kΩ
AV=+2
CL=4.7pF
RL=500Ω
3
-4
-6
100K
100M 200M
FIGURE 14. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS CIN
4
2
10M
FREQUENCY (Hz)
FIGURE 13. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS CIN
3
1G
FIGURE 12. EL5256 SMALL SIGNAL FREQUENCY
RESPONSE FOR VARIOUS RL
5
AV=+2
RL=500Ω
CL=4.7pF
RF=500Ω
100M
FREQUENCY (Hz)
FREQUENCY (Hz)
4
10M
-4
100K
1M
10M
100M
FREQUENCY (Hz)
FIGURE 16. EL5256 SMALL SIGNAL FREQUENCY
RESPONSE FOR VARIOUS RF/RG
1G
EL5156, EL5157, EL5256, EL5257
Typical Performance Curves (Continued)
4
3
5
AV=+2
RL=200Ω
CL=4.7pF
2
1
-20dBm
0
10dBm
-1
15dBm
-2
17dBm
-3
20dBm
-4
-5
100K
1M
CHANNEL #1
4
NORMALIZED GAIN (dB)
NORMALIZED GAIN (dB)
5
3
CHANNEL #2
2
1
0
-1
-2
AV=+1
RL=500Ω
CL=4.7pF
-3
-4
100M
10M
-5
100K
600M
1M
FREQUENCY (Hz)
700
AV=+1,RL=500Ω, CL=5pF
600
500
BW (MHz)
CROSS TALK (10dB)
AV=+5
RL=500Ω
CL=4.7pF
-30
-40
-50
-60
-70
AV=+1, RL=150Ω
400
300
200
-80
AV=+2,RL=150Ω
100
-90
-100
100K
1M
10M
100M
0
4.5
1G
5.5
6.5
7.5
8.5
VS (V)
FREQUENCY (Hz)
FIGURE 19. EL5256 CROSS TALK vs FREQUENCY CHANNEL
A TO B & B TO A
NORMALIZED GAIN (dB)
3
2
1
500Ω
1000Ω
0
-1
-2
-3
100Ω
-4
50Ω
-5
1M
10.5
11.5
1K
AV=+5
CL=4.7pF
-6
100K
9.5
FIGURE 20. BANDWIDTH vs SUPPLY VOLTAGE
VOLTAGE NOISE (nV/√Hz),
CURRENT NOISE (pA/√Hz)
4
1G
FIGURE 18. CHANNEL TO CHANNEL FREQUENCY
RESPONSE
0
-20
100M
FREQUENCY (Hz)
FIGURE 17. LARGE SIGNAL FREQUENCY RESPONSE FOR
VARIOUS INPUT AMPLITUDES
-10
10M
10M
100M
1G
FREQUENCY (Hz)
FIGURE 21. SMALL SIGNAL FREQUENCY RESPONSE FOR
VARIOUS RL
7
100
VN
10
IN
1
10
100
1K
10K
100K
1M
10M
FREQUENCY (Hz)
FIGURE 22. VOLTAGE AND CURRENT NOISE vs FREQUENCY
EL5156, EL5157, EL5256, EL5257
Typical Performance Curves (Continued)
-20
1000
-30
IMPEDANCE (Ω)
CMRR (dB)
-40
-50
-60
-70
-80
-90
AV=+2
RL=0Ω
RG=RF=400Ω
100
10
1
0.01
-100
-110
0.001
100
1K
10K
100K
1M
10M
100M
1K
10K
FREQUENCY (Hz)
FIGURE 23. CMRR
-30
100M
10M
6.1
VS=±5V
AV=+2
RL=150Ω
6
-40
5.9
-50
5.8
-60
-70
-80
-90
5.5
-100
5.4
1M
10M
100M
IS-
5.7
5.6
-110
100K
1M
FIGURE 24. OUTPUT IMPEDANCE
IS (mA)
DISABLED ISOLATION (dB)
-10
-20
100K
FREQUENCY (Hz)
IS+
5.3
4.5 5 5.5 6 6.5 7 7.5 8 8.5 9 9.5 10 10.51111.5 12
1G
FREQUENCY (Hz)
VS (V)
FIGURE 25. INPUT TO OUTPUT ISOLATION vs FREQUENCY DISABLE
FIGURE 26. SUPPLY CURRENT vs SUPPLY VOLTAGE
0.8
AV=+2
RL=500Ω
SUPPLY=±5.0V
±12.3mA
PEAKING (dB)
ENABLE
192ns
0.7
DISABLE
322ns
0.6
AV=+1
RL=500Ω
CL=5pF
0.5
0.4
0.3
0.2
0.1
TIME (400ns/DIV)
FIGURE 27. ENABLE/DISABLE RESPONSE
8
0
4.5
5.5
6.5
7.5
8.5
VS (V)
9.5
10.5
11.5
FIGURE 28. PEAKING vs SUPPLY VOLTAGE
EL5156, EL5157, EL5256, EL5257
AV=+2
RL=500Ω
SUPPLY=±5.0V ±12.3mA
OUTPUT=200mVP-P
VOUT (40mV/DIV)
VOUT (40mV/DIV)
Typical Performance Curves (Continued)
0
RISE
20%-80%
∆T=2.025ns
0
FALL
80%-20%
∆T=1.91ns
AV=+2
RL=500Ω
SUPPLY=±5.0V ±12.3mA
OUTPUT=200mVP-P
TIME (4ns/DIV)
TIME (4ns/DIV)
FIGURE 30. SMALL SIGNAL FALL TIME
AV=+2
RL=500Ω
SUPPLY=±5.0V ±12.3mA
OUTPUT=2.0VP-P
VOUT (400mV/DIV)
VOUT (400mV/DIV)
FIGURE 29. SMALL SIGNAL RISE TIME
0
RISE
20%-80%
∆T=1.657ns
AV=+2
RL=500Ω
SUPPLY=±5.0V ±12.3mA
OUTPUT=2.0VP-P
0
FALL
80%-20%
∆T=1.7ns
TIME (2ns/DIV)
TIME (2ns/DIV)
FIGURE 32. LARGE SIGNAL FALL TIME
FIGURE 31. LARGE SIGNAL RISE TIME
1.2
1.6
POWER DISSIPATION (W)
POWER DISSIPATION (W)
1.8
JEDEC JESD51-7 HIGH EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD
1.4
1.2 1.136W
SO8
θJA=110°C/W
1
0.8
0.6 543mW
0.4
SOT23-5
θJA=230°C/W
0.2
0
0
25
50
75 85 100
125
150
AMBIENT TEMPERATURE (°C)
FIGURE 33. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
9
JEDEC JESD51-3 LOW EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD
1
781mW
0.8
SO8
θJA=160°C/W
0.6
0.4 488mW
SOT23-5
θJA=256°C/W
0.2
0
0
25
50
75 85 100
125
150
AMBIENT TEMPERATURE (°C)
FIGURE 34. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
EL5156, EL5157, EL5256, EL5257
Typical Performance Curves (Continued)
1
JEDEC JESD51-7 HIGH EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD
POWER DISSIPATION (W)
POWER DISSIPATION (W)
0.9
870mW
0.8
0.7
MSOP8/10
0.6
θJA=115°C/W
0.6
0.5
0.4
0.3
0.2
JEDEC JESD51-3 LOW EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD
0.5
486mW
MSOP8/10
0.4
θJA=206°C/W
0.3
0.2
0.1
0.1
0
0
0
25
50
75 85
100
125
AMBIENT TEMPERATURE (°C)
FIGURE 35. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
10
0
25
50
75 85
100
125
AMBIENT TEMPERATURE (°C)
FIGURE 36. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
EL5156, EL5157, EL5256, EL5257
Product Description
The EL5156, EL5157, EL5256, and EL5257 are wide
bandwidth, single or dual supply, low power and low offset
voltage feedback operational amplifiers. Both amplifiers are
internally compensated for closed loop gain of +1 or greater.
Connected in voltage follower mode and driving a 500Ω
load, the -3dB bandwidth is about 610MHz. Driving a 150Ω
load and a gain of 2, the bandwidth is about 180MHz while
maintaining a 600V/µs slew rate. The EL5156 and EL5256
are available with a power down pin to reduce power to
17µA typically while the amplifier is disabled.
Input, Output and Supply Voltage Range
The EL5156 and EL5157 families have been designed to
operate with supply voltage from 5V to 12V. That means for
single supply application, the supply voltage is from 5V to
12V. For split supplies application, the supply voltage is from
±2.5V to ±5V. The amplifiers have an input common mode
voltage range from 1.5V above the negative supply (VS- pin)
to 1.5V below the positive supply (VS+ pin). If the input
signal is outside the above specified range, it will cause the
output signal distorted.
The outputs of the EL5156 and EL5157 families can swing
from -4V to 4V for VS = ±5V. As the load resistance becomes
lower, the output swing is lower. If the load resistor is 500Ω,
the output swing is about -4V at a 4V supply. If the load
resistor is 150Ω, the output swing is from -3.5V to 3.5V.
Choice of Feedback Resistor and Gain Bandwidth
Product
For applications that require a gain of +1, no feedback
resistor is required. Just short the output pin to the inverting
input pin. For gains greater than +1, the feedback resistor
forms a pole with the parasitic capacitance at the inverting
input. As this pole becomes smaller, the amplifier's phase
margin is reduced. This causes ringing in the time domain
and peaking in the frequency domain. Therefore, RF can't be
very big for optimum performance. If a large value of RF
must be used, a small capacitor in the few Pico farad range
in parallel with RF can help to reduce the ringing and
peaking at the expense of reducing the bandwidth.
For gain of +1, RF = 0 is optimum. For the gains other than
+1, optimum response is obtained with RF between 500Ω to
750Ω.
The EL5156 and EL5157 families have a gain bandwidth
product of 210MHz. For gains > = 5, its bandwidth can be
predicted by the following equation: (Gain)X(BW) = 210MHz.
Video Performance
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 is especially difficult when driving a standard video load
of 150Ω, because of the change in output current with DC
level. The dG and dP for these families are about 0.006%
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and 0.04%, while driving 150Ω at a gain of 2. Driving high
impedance loads would give a similar or better dG and dP
performance.
Driving Capacitive Loads and Cables
The EL5156 and EL5157 families can drive 27pF loads in
parallel with 500Ω with less than 5dB of peaking at gain of
+1. If less peaking is desired in applications, a small series
resistor (usually between 5Ω to 50Ω) can be placed in series
with the output to eliminate most peaking. However, this will
reduce the gain slightly. If the gain setting is greater than 1,
the gain resistor RG can then be chosen to make up for any
gain loss which may be created by the additional series
resistor at the output.
When used as a cable driver, double termination is always
recommended for reflection-free performance. For those
applications, a back-termination series resistor at the
amplifier's output will isolate the amplifier from the cable and
allow extensive capacitive drive. However, other applications
may have high capacitive loads without a back-termination
resistor. Again, a small series resistor at the output can help
to reduce peaking.
Disable/Power-Down
The EL5156 and EL5256 can be disabled and their output
placed in a high impedance state. The turn off time is about
330ns and the turn on time is about 130ns. When disabled,
the amplifier's supply current is reduced to 17µA typically,
thereby effectively eliminating the power consumption. The
amplifier's power down can be controlled by standard TTL or
CMOS signal levels at the ENABLE pin. The applied logic
signal is relative to VS- pin. Letting the ENABLE pin float or
applying a signal that is less than 0.8V above VS- will enable
the amplifier. The amplifier will be disabled when the signal
at ENABLE pin is above VS+ -1.5V.
Output Drive Capability
The EL5156 and EL5157 families do not have internal short
circuit protection circuitry. They have a typical short circuit
current of 95mA and 70mA. If the output is shorted
indefinitely, the power dissipation could easily overheat the
die or the current could eventually compromise metal
integrity. Maximum reliability is maintained if the output
current never exceeds ±40mA. This limit is set by the design
of the internal metal interconnect. Note that in transient
applications, the part is robust.
Power Dissipation
With the high output drive capability of the EL5156 and
EL5157 families, it is possible to exceed the 125°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 the load conditions or package types need to be
modified for the amplifier to remain in the safe operating
area.
EL5156, EL5157, EL5256, EL5257
The maximum power dissipation allowed in a package is
determined according to:
Power Supply Bypassing and Printed Circuit
Board Layout
T JMAX – T AMAX
PD MAX = -------------------------------------------Θ JA
As with any high frequency device, a good printed circuit
board layout is necessary for optimum performance. Lead
lengths should be as sort as possible. The power supply pin
must be well bypassed to reduce the risk of oscillation. For
normal single supply operation, where the VS- pin is
connected to the ground plane, a single 4.7µF tantalum
capacitor in parallel with a 0.1µF ceramic capacitor from VS+
to GND will suffice. This same capacitor combination should
be placed at each supply pin to ground if split supplies are to
be used. In this case, the VS- pin becomes the negative
supply rail.
Where:
TJMAX = Maximum junction temperature
TAMAX = Maximum ambient temperature
θJA = Thermal resistance of 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:
For sourcing:
n
V OUTi
∑ ( VS – VOUTi ) × ---------------R Li
PD MAX = V S × I SMAX +
i=1
For sinking:
n
∑ ( VOUTi – VS ) × ILOADi
PD MAX = V S × I SMAX +
i=1
Where:
For good AC performance, parasitic capacitance should be
kept to minimum. Use of wire wound resistors should be
avoided because of their additional series inductance. Use
of sockets should also be avoided if possible. Sockets add
parasitic inductance and capacitance that can result in
compromised performance. Minimizing parasitic capacitance
at the amplifier's inverting input pin is very important. The
feedback resistor should be placed very close to the
inverting input pin. Strip line design techniques are
recommended for the signal traces.
VS = Supply voltage
ISMAX = Maximum quiescent supply current
VOUT = Maximum output voltage of the application
RLOAD = Load resistance tied to ground
ILOAD = Load current
N = number of amplifiers (Max = 2)
By setting the two PDMAX equations equal to each other, we
can solve the output current and RLOAD to avoid the device
overheat.
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