The EL1507 is a very low power dual operational amplifier
designed for central office and customer premise line driving
for DMT ADSL solutions. This device features a high drive
capability of 400mA while consuming only 7.5mA of supply
current per amplifier from ±12V supplies. This driver
achieves a typical distortion of less than -75dBc, at 1MHz
into a 50Ω load. The EL1507 is available in the thermallyenhanced 16 Ld SO package, as well as a 16 Ld QFN
package. Both are specified for operation over the full
-40°C to +85°C temperature range.
The EL1507 has two control pins, C
selection of C
power, ¾-I
and C1, the device can be set into full-IS
0
power, ½-IS power, and power down disable
S
and C1. With the
0
modes. The EL1507 maintains excellent distortion and load
driving capabilities even in the lowest power settings.
NOTE: Intersil Pb-free plus anneal products employ special Pb-free
material sets; molding compounds/die attach materials and 100%
matte tin plate termination finish, which are RoHS compliant and
compatible with both SnPb and Pb-free soldering operations. Intersil
Pb-free products are MSL classified at Pb-free peak reflow
temperatures that meet or exceed the Pb-free requirements of
IPC/JEDEC J STD-020.
MARKING
EL1507CSZ-16 Ld SOIC
EL1507CSZ7”16 Ld SOIC
EL1507CSZ13”16 Ld SOIC
1507CLZ-16 Ld QFN
1507CLZ7”16 Ld QFN
1507CLZ13”16 Ld QFN
TAPE &
REELPACKAGE
(Pb-Free)
(Pb-Free)
(Pb-Free)
(Pb-Free)
(Pb-Free)
(Pb-Free)
PKG.
DWG. #
MDP0027
MDP0027
MDP0027
MDP0046
MDP0046
MDP0046
FN7013.3
Features
• Drives 360mA at 16V
•40V
differential output drive into 100Ω
P-P
• -75dBc typical driver output distortion driving 50Ω at 1MHz
and 1/2-I
bias current
S
• Low quiescent current of 3.5mA per amplifier in 1/2-I
mode
• Power down disable mode
• Pb-free plus anneal available (RoHS compliant)
on ±12V supplies
P-P
S
Applications
• ADSL G.DMT and G.lite CO line driving
• G.SHDSL, HDSL2 line driver
• ADSL CPE line driving
• Video distribution amplifier
• Video twisted-pair line driver
1
CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774
| Intersil (and design) is a registered trademark of Intersil Americas Inc.
Copyright Intersil Americas Inc. 2001, 2005-2007. All Rights Reserved
All other trademarks mentioned are the property of their respective owners.
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 = T
Negative Supply Current per Amplifier All outputs at 0V, C0 = C1 = 0V-7-8.5mA
Positive Supply Current per AmplifierAll outputs at 0V, C0 = 5V, C1 = 0V67.5mA
Negative Supply Current per Amplifier All outputs at 0V, C0 = 5V, C1 = 0V-5.5-7mA
Positive Supply Current per AmplifierAll outputs at 0V, C0 = 0V, C1 = 5V3.95.1mA
Negative Supply Current per Amplifier All outputs at 0V, C0 = 0V, C1 = 5V-3.3-4.6mA
Positive Supply Current per AmplifierAll outputs at 0V, C0 = C1 = 5V0.61mA
Negative Supply Current per Amplifier All outputs at 0V, C0 = C1 = 5V00.75mA
GND Supply Current per AmplifierAll outputs at 0V0.61mA
Typical Performance Curves
28
VS=±12V
A
=10
V
=100Ω
R
24
L
20
16
GAIN (dB)
12
1kΩ
1.5kΩ
2kΩ
22
VS=±12V
=5
A
V
18
=100Ω
R
L
14
10
GAIN (dB)
6
1.5kΩ
1kΩ
2kΩ
8
100K1M10M100M
FREQUENCY (Hz)
FIGURE 1. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CS - FULL POWER MODE)
28
VS=±12V
=10
A
V
R
=100Ω
24
L
20
16
GAIN (dB)
12
8
100K1M10M100M
FREQUENCY (Hz)
1kΩ
1.5kΩ
2kΩ
FIGURE 3. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CS - 3/4 POWER MODE)
2
100K1M10M100M
FREQUENCY (Hz)
F
FIGURE 2. DIFFERENTIAL FREQUENCY RESPONSE vs R
F
(EL1507CS - FULL POWER MODE)
22
VS=±12V
=5
A
V
R
=100Ω
18
L
14
10
GAIN (dB)
6
2
100K1M10M100M
F
FIGURE 4. DIFFERENTIAL FREQUENCY RESPONSE vs R
1.5kΩ
FREQUENCY (Hz)
1kΩ
2kΩ
F
(EL1507CS - 3/4 POWER MODE)
4
FN7013.3
March 26, 2007
www.BDTIC.com/Intersil
Typical Performance Curves
EL1507
28
VS=±12V
=10
A
V
=100Ω
R
24
L
20
16
GAIN (dB)
12
8
100K1M10M100M
FREQUENCY (Hz)
1kΩ
1.5kΩ
2kΩ
FIGURE 5. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CS - 1/2 POWER MODE)
28
VS=±12V
=10
A
V
R
=100Ω
24
L
20
16
GAIN (dB)
12
1kΩ
1.5kΩ
2kΩ
22
VS=±12V
=5
A
V
R
=100Ω
18
L
14
10
GAIN (dB)
6
2
100K1M10M100M
FREQUENCY (Hz)
F
FIGURE 6. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CS - 1/2 POWER MODE)
22
VS=±12V
A
=5
V
=100Ω
R
18
L
14
10
GAIN (dB)
6
1.5kΩ
1.5kΩ
1kΩ
2kΩ
F
1kΩ
2kΩ
8
100K1M10M100M
FREQUENCY (Hz)
FIGURE 7. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CL - FULL POWER MODE)
28
VS=±12V
=10
A
V
24
=100Ω
R
L
20
16
GAIN (dB)
12
8
100K1M10M100M
FREQUENCY (Hz)
1kΩ
1.5kΩ
2kΩ
FIGURE 9. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CL - 3/4 POWER MODE)
2
100K1M10M100M
FREQUENCY (Hz)
F
F
FIGURE 8. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CL - FULL POWER MODE)
22
VS=±12V
=5
A
V
18
R
=100Ω
L
14
10
GAIN (dB)
6
2
100K1M10M100M
FREQUENCY (Hz)
1.5kΩ
1kΩ
2kΩ
FIGURE 10. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CL - 3/4 POWER MODE)
F
F
5
FN7013.3
March 26, 2007
www.BDTIC.com/Intersil
Typical Performance Curves
EL1507
28
VS=±12V
=10
A
V
24
=100Ω
R
L
20
16
GAIN (dB)
12
8
100K1M10M100M
1.5kΩ
FREQUENCY (Hz)
1kΩ
2kΩ
FIGURE 11. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CL - 1/2 POWER MODE)
30
VS=±12V
=5
A
V
R
=100Ω
22
L
=1.5kΩ
R
F
14
6
GAIN (dB)
22pF
10pF
0pF
22
VS=±12V
A
=5
V
18
=100Ω
R
L
14
10
GAIN (dB)
6
2
100K1M10M100M
F
FIGURE 12. DIFFERENTIAL FREQUENCY RESPONSE vs R
(EL1507CL - 1/2 POWER MODE)
30
VS=±12V
A
=5
V
=100Ω
R
22
L
=1.5kΩ
R
F
14
6
GAIN (dB)
1.5kΩ
FREQUENCY (Hz)
1kΩ
2kΩ
F
22pF
10pF
0pF
-2
-10
100K1M10M100M
FREQUENCY (Hz)
FIGURE 13. FREQUENCY RESPONSE vs C
(EL1507CS - FULL POWER MODE)
30
VS=±12V
=5
A
V
=100Ω
R
22
L
R
=1.5kΩ
F
14
6
GAIN (dB)
-2
-10
100K1M10M100M
FREQUENCY (Hz)
10pF
FIGURE 15. FREQUENCY RESPONSE vs C
(EL1507CS - 3/4 POWER MODE)
LOAD
0pF
LOAD
22pF
-2
-10
100K1M10M100M
FREQUENCY (Hz)
FIGURE 14. FREQUENCY RESPONSE vs C
(EL1507CL - FULL POWER MODE)
30
VS=±12V
=5
A
V
=100Ω
R
22
L
R
=1.5kΩ
F
14
6
GAIN (dB)
-2
-10
100K1M10M100M
FREQUENCY (Hz)
10pF
FIGURE 16. FREQUENCY RESPONSE vs C
(EL1507CL - 3/4 POWER MODE)
LOAD
22pF
0pF
LOAD
6
FN7013.3
March 26, 2007
www.BDTIC.com/Intersil
Typical Performance Curves
EL1507
30
VS=±12V
A
=5
V
=100Ω
R
22
L
=1.5kΩ
R
F
14
6
GAIN (dB)
-2
-10
100K1M10M100M
FREQUENCY (Hz)
10pF0pF
FIGURE 17. FREQUENCY RESPONSE vs C
(EL1507CS - 1/2 POWER MODE)
55
AV=5, RF=1.5kΩ,
50
U
F
45
40
BANDWIDTH (MHz)
35
1
30
5 6 7 8 9 101112
ER
W
PO
L
L
F
U
L
L
P
O
W
R
E
W
O
P
2
/
P
4
/
3
E
R
(V)
±V
S
W
O
3
R
E
EL1507CL
EL1507CS
22pF
LOAD
4
/
/
1
30
VS=±12V
=5
A
V
=100Ω
R
22
L
R
=1.5kΩ
F
14
6
GAIN (dB)
-2
-10
100K1M10M100M
FREQUENCY (Hz)
FIGURE 18. FREQUENCY RESPONSE vs C
(EL1507CL - 1/2 POWER MODE)
R
E
W
O
P
R
E
W
O
P
2
-50
VS=±12V
-55
=5
A
V
=100Ω
R
L
-60
R
=1.5kΩ
F
f=1MHz
-65
-70
HD (dB)
-75
-80
-85
-90
HD2
HD3
2 1018263442
(V)
V
OP-P
22pF
10pF
0pF
LOAD
EL1507CL
EL1507CS
HD3
HD2
FIGURE 19. DIFFERENTIAL BANDWIDTH vs SUPPL Y
VOLTAGE
FIGURE 20. DIFFERENTIAL HARMONIC DISTORTION vs
DIFFERENTIAL OUTPUT AMPLITUDE
(FULL POWER MODE)
18
IS- (FULL POWER)
16
IS+ (3/4 POWER)
14
12
10
(mA)
S
8
I
6
4
2
0
024681012
IS- (1/2 POWER)
IS+ (FULL POWER)
IS- (3/4 POWER)
IS+ (1/2 POWER)
(V)
±V
S
-50
VS=±12V
-55
=10
A
V
R
=100Ω
L
-60
=1.5kΩ
R
F
f=1MHz
-65
-70
HD (dB)
HD2
-75
-80
HD3
-85
-90
2 1018263442
V
OP-P
EL1507CL
EL1507CS
HD3
HD2
(V)
FIGURE 21. SUPPLY CURRENT vs SUPPLY VOLTAGEFIGURE 22. DIFFERENTIAL HARMONIC DISTORTION vs
DIFFERENTIAL OUTPUT AMPLITUDE
(3/4 POWER MODE)
7
FN7013.3
March 26, 2007
www.BDTIC.com/Intersil
Typical Performance Curves
EL1507
-40
RF=1.5kΩ
=5
A
V
R
=100Ω
-50
L
f=150kHz
ALL POWER
LEVELS
-60
CS & CL
THD (dB)
-70
-80
-90
2 1018263442
VS=±6V
V
OP-P
VS=±12V
(V)
FIGURE 23. DIFFERENTIAL TOTAL HARMONIC DISTORTION
vs DIFFERENTIAL OUTPUT AMPLITUDE
-50
VS=±12V
=5
A
V
-55
=100Ω
R
L
R
=1.5kΩ
F
f=1MHz
-60
-65
THD (dB)
-70
-75
-80
23442
3/4 POWER
101826
V
OP-P
1/2 POWER
FULL POWER
(V)
-50
VS=±12V
-55
=10
A
V
=100Ω
R
L
-60
R
=1.5kΩ
F
f=1MHz
-65
-70
HD (dB)
-75
-80
-85
-90
2 1018263442
HD3
HD3
V
OP-P
EL1507CL
EL1507CS
HD2
HD2
(V)
FIGURE 24. DIFFERENTIAL HARMONIC DISTORTION vs
DIFFERENTIAL OUTPUT AMPLITUDE
(1/2 POWER MODE)
-45
VS=±6V
-50
=5
A
V
=100Ω
R
L
-55
R
=1.5kΩ
F
f=1MHz
-60
-65
-70
HD (dB)
HD2
-75
-80
-85
-90
26101418 20
481216
V
OP-P
HD2
(V)
EL1507CL
EL1507CS
HD3
HD3
FIGURE 25. DIFFERENTIAL TOTAL HARMONIC DISTORTION
vs DIFFERENTIAL OUTPUT AMPLITUDE
(EL1507CS)
-50
VS=±12V
=5
A
V
-55
=100Ω
R
L
R
=1.5kΩ
F
f=1MHz
-60
-65
THD (dB)
3/4 POWER
-70
-75
-80
212223242
1/2 POWER
FULL POWER
(V)
V
OP-P
FIGURE 27. DIFFERENTIAL TOTAL HARMONIC DISTORTION
vs DIFFERENTIAL OUTPUT AMPLITUDE
(EL1507CL)
8
FIGURE 26. DIFFERENTIAL HARMONIC DISTORTION vs
DIFFERENTIAL OUTPUT AMPLITUDE
(3/4 POWER MODE)
-45
VS=±6V
-50
=5
A
V
R
=100Ω
L
-55
=1.5kΩ
R
F
-60
f=1MHz
-65
-70
HD (dB)
-75
-80
-85
-90
26101418 20
481216
V
OP-P
HD2
HD2
(V)
EL1507CL
EL1507CS
HD3
HD3
FIGURE 28. DIFFERENTIAL HARMONIC DISTORTION vs
DIFFERENTIAL OUTPUT AMPLITUDE
(1/2 POWER MODE)
FN7013.3
March 26, 2007
www.BDTIC.com/Intersil
Typical Performance Curves
EL1507
-45
VS=±6V
-50
=5
A
V
=100Ω
R
L
-55
R
=1.5kΩ
F
-60
f=1MHz
-65
-70
HD (dB)
-75
-80
-85
-90
248 121620
HD2
HD2
6 101418
V
OP-P
HD3
(V)
EL1507CL
EL1507CS
HD3
FIGURE 29. DIFFERENTIAL HARMONIC DISTORTION vs
DIFFERENTIAL OUTPUT AMPLITUDE
(FULL POWER MODE)
-45
VS=±6V
=5
A
-50
V
R
=100Ω
L
=1.5kΩ
R
F
-55
f=1MHz
-60
-65
THD (dB)
3/4 POWER
-70
-75
-80
21820
61014481216
1/2 POWER
(V)
V
OP-P
FULL POWER
-45
VS=±6V
A
=5
-50
V
=100Ω
R
L
=1.5kΩ
R
F
-55
f=1MHz
-60
-65
THD (dB)
1/2 POWER
-70
-75
-80
248 121620
3/4 POWER
FULL POWER
6 101418
(V)
V
OP-P
FIGURE 30. DIFFERENTIAL TOTAL HARMONIC DISTORTION
vs DIFFERENTIAL OUTPUT AMPLITUDE
(EL1507CS)
100
VS=±12V
=1
A
V
=1.5kΩ
R
10
F
1
0.1
0.01
OUTPUT IMPEDANCE (Ω)
0.001
10K100K1M100M
FREQUENCY (Hz)
10M
FIGURE 31. DIFFERENTIAL TOTAL HARMONIC DISTORTION
vs DIFFERENTIAL OUTPUT AMPLITUDE
(EL1507CL)
-10
-30
-50
-70
B → AA → B
-90
CHANNEL SEPARATION (dB)
-110
10K100K1M10M100M
FREQUENCY (Hz)
FIGURE 33. CHANNEL SEPARATION vs FREQUENCY
(ALL POWER LEVELS)
9
FIGURE 32. OUTPUT IMPEDANCE vs FREQUENCY
(ALL POWER LEVELS)
20
0
-20
-40
PSRR (dB)
-60
-80
10K100M
PSRR-PSRR+
100K1M
FREQUENCY (Hz)
10M
FIGURE 34. PSRR vs FREQUENCY
FN7013.3
March 26, 2007
www.BDTIC.com/Intersil
Typical Performance Curves
EL1507
10M
1M
PHASE
100k
10K
MAGNITUDE (Ω)
1K
100
1K100K1M100M
10K10M
FREQUENCY (Hz)
GAIN
40
0
-40
-80
-120
-160
-200
-240
-280
-320
PHASE (°)
100
IB-
10
E
N
CURRENT NOISE (pA/√Hz)
VOLTAGE NOISE (nV/√Hz),
1
1010010K100K1M10M
1K
FREQUENCY (Hz)
IB+
FIGURE 35. TRANSIMPEDANCE (ROL) vs FREQUENCYFIGURE 36. VOLTAGE AND CURRENT NOISE vs FREQUENCY
FIGURE 43. POSITIVE SUPPLY CURRENT vs TEMPERATUREFIGURE 44. SLEW RATE vs TEMPERATURE
18
16
14
12
10
8
6
4
2
INPUT BIAS CURRENT (µA)
0
-2
-50100150-250501252575
TEMPERATURE (°C)
IB-
IB+
11.8
10.8
9.8
8.8
7.8
6.8
OUTPUT VOLTAGE (±V)
5.8
RL=100Ω
4.8
-50100150-250501252575
TEMPERATURE (°C)
FIGURE 45. INPUT BIAS CURRENT vs TEMPERATUREFIGURE 46. OUTPUT VOLTAGE vs TEMPERATURE
11
FN7013.3
March 26, 2007
www.BDTIC.com/Intersil
Typical Performance Curves
EL1507
10
8
6
4
2
OFFSET VOLTAGE (mV)
0
-2
-50100150-250501252575
TEMPERATURE (°C)
3.5
3
2.5
2
1.5
1
TRANSIMPEDANCE (MΩ)
0.5
0
-50100150-250501252575
TEMPERATURE (°C)
FIGURE 47. OFFSET VOLTAGE vs TEMPERATUREFIGURE 48. TRANSIMPEDANCE vs TEMPERATURE
JEDEC JESD51-3 LOW EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD
1.2
1.136W
1
0.8
833mW
0.6
0.4
0.2
POWER DISSIPATION (W)
0
0 255075100150
QFN16
θJA=150°C/W
AMBIENT TEMPERATURE (°C)
SO16
θJA=110°C/W
12585
JEDEC JESD51-7 HIGH EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD - QFN EXPOSED
DIEPAD SOLDERED TO PCB PER JESD51-5
4.5
4
3.5
3.125W
3
2.5
2
1.563W
1.5
1
POWER DISSIPATION (W)
0.5
θJA=80°C/W
0
0 255075100150
QFN16
θJA=40°C/W
SO16
12585
AMBIENT TEMPERATURE (°C)
FIGURE 49. PACKAGE POWER DISSIPA TION vs AMBIENT
TEMPERATURE
12
FIGURE 50. PACKAGE POWER DISSIPA TION vs AMBIENT
TEMPERATURE
FN7013.3
March 26, 2007
www.BDTIC.com/Intersil
Applications Information
V
The EL1507 consists of two high-power line driver amplifiers
that can be connected for full duplex differential line
transmission. The amplifiers are designed to be used with
signals up to 4MHz and produce low distortion levels. A
typical interface circuit is shown in Figure 51 below.
R
DRIVER
INPUT
RECEIVE
OUT +
RECEIVE
OUT -
FIGURE 51. TYPICAL LINE INTERFACE CONNECTION
RECEIVE
AMPLIFIERS
+
R
F
R
G
R
F
-
+
R
R
F
R
IN
-
+
+
R
-
R
R
IN
F
OUT
R
The amplifiers are wired with one in positive gain and the
other in a negative gain configuration to generate a
differential output for a single-ended input. They will exhibit
very similar frequency responses for gains of three or
greater and thus generate very small common-mode outputs
over frequency, but for low gains the two drivers R
to be adjusted to give similar frequency responses. The
positive-gain driver will generally exhibit more bandwidth and
peaking than the negative-gain driver.
If a differential signal is available to the drive amplifiers, they
may be wired so:
+
R
F
2R
G
R
F
-
+
FIGURE 52. DRIVERS WIRED FOR DIFFERENTIAL INPUT
OUT
LINE +
LINE -
F
Z
LINE
's need
EL1507
Input Connections
The EL1507 amplifiers are somewhat sensitive to source
impedance. In particular, they do not like being driven by
inductive sources. More than 100nH of source impedance
can cause ringing or even oscillations. This inductance is
equivalent to about 4” of unshielded wiring, or 6” of
unterminated transmission line. Normal high-frequency
construction obviates any such problem.
Power Supplies & Dissipation
Due to the high power drive capability of the EL1507, much
attention needs to be paid to power dissipation. The power
that needs to be dissipated in the EL1507 has two main
contributors. The first is the quiescent current dissipation.
The second is the dissipation of the output stage.
The quiescent power in the EL1507 is not constant with
varying outputs. In reality, 7mA of the 15mA needed to
power the drivers is converted in to output current.
Therefore, in the equation below we should subtract the
average output current, I
We’ll call this term I
Therefore, we can determine a quiescent current with the
equation:
P
DquiescentVSIS2IX
where:
V
is the supply voltage (VS+ to VS-)
S
IS is the maximum quiescent supply current (IS+ + IS-)
IX is the lesser of IO or 7mA (generally IX = 7mA)
The dissipation in the output stage has two main
contributors. Firstly, we have the average voltage drop
across the output transistor and secondly, the average
output current. For minimal power dissipation, the user
should select the supply voltage and the line transformer
ratio accordingly. The supply voltage should be kept as low
as possible, while the transformer ratio should be selected
so that the peak voltage required from the EL1507 is close to
the maximum available output swing. There is a trade off,
however, with the selection of transformer ratio. As the ratio
is increased, the receive signal available to the receivers is
reduced.
Once the user has selected the transformer ratio, the
dissipation in the output stages can be selected with the
following equation:
P
Dtransistors
, or 7mA, whichever is the lowest.
O
.
X
–()×=
S
⎛
-------
××V
=
2I
O
–
O
⎝
2
⎞
⎠
Each amplifier has identical positive gain connections, and
optimum common-mode rejection occurs. Further, DC input
errors are duplicated and create common-mode rather than
differential line errors.
where:
V
is the supply voltage (VS+ to VS-)
S
VO is the average output voltage per channel
IO is the average output current per channel
13
FN7013.3
March 26, 2007
www.BDTIC.com/Intersil
EL1507
The overall power dissipation (P
P
Dquiescent
and P
Dtransistor
.
) is obtained by adding
DISS
Then, the θJA requirement needs to be calculated. This is
done using the equation:
T
-------------------------------------------------
θ
=
JA
–()
JUNCTTAMB
P
DISS
where:
T
T
P
is the maximum die temperature (150°C)
JUNCT
is the maximum ambient temperature
AMB
is the dissipation calculated above
DISS
θJA is the junction to ambient thermal resistance for the
package when mounted on the PCB
This θ
value is then used to calculate the area of copper
JA
needed on the board to dissipate the power.
The SO power packages are designed so that heat may be
conducted away from the device in an efficient manner. To
disperse this heat, the center leads are internally connected
to the mounting platform of the die. Heat flows through the
leads into the circuit board copper, then spreads and
convects to air. Thus, the ground plane on the component
side of the board becomes the heatsink. This has proven to
be a very effective technique. A separate application note
details the 16 Ld QFN PCB design considerations.
Single Supply Operation
The EL1507 can also be powered from a single supply
voltage. When operating in this mode, the GND pins can still
be connected directly to GND. To calculate power
dissipation, the equations in the previous section should be
used, with V
equal to half the supply rail.
S
Output Loading
While the drive amplifiers can output in excess of 400mA
transiently, the internal metallization is not designed to carry
more than 75mA of steady DC current and there is no
current-limit mechanism. This allows safely driving rms
sinusoidal currents of 2 x 75mA, or 150mA. This current is
more than that required to drive line impedances to large
output levels, but output short circuits cannot be tolerated.
The series output resistor will usually limit currents to safe
values in the event of line shorts. Driving lines with no series
resistor is a serious hazard.
The amplifiers are sensitive to capacitive loading. More than
25pF will cause peaking of the frequency response. The same
is true of badly terminated lines connected without a series
matching resistor.
Power Supplies
The power supplies should be well bypassed close to the
EL1507. A 3.3µF tantalum capacitor for each supply works well.
Since the load currents are differential, they should not travel
through the board copper and set up ground loops that can
return to amplifier inputs. Due to the class AB output stage
design, these currents have heavy harmonic content. If the
ground terminal of the positive and negative bypass capacitors
are connected to each other directly and then returned to circuit
ground, no such ground loops will occur. This scheme is
employed in the layout of the EL1507 demonstration board,
and documentation can be obtained from the factory .
Feedback Resistor Value
The bandwidth and peaking of the amplifiers varies with supply
voltage somewhat and with gain settings. The feedback resistor
values can be adjusted to produce an optimal frequency
response. Here is a series of resistor values that produce an
optimal driver frequency response (<1dB peaking) for different
supply voltages and gains:
TABLE 1. OPTIMUM DRIVER FEEDBACK RESISTOR FOR
VARIOUS GAINS AND SUPPLY VOLTAGES
Supply
Voltage
±5V2k1.8k1.5k
±12V2k1.8k1.5k
Driver Voltage Gain
2.5510
Power Control Function
The EL1507 contains two forms of power control operation.
Two digital inputs, C
current of the EL1507 drive amplifiers. As the supply current is
reduced, the EL1507 will start to exhibit slightly higher levels of
distortion and the frequency response will be limited. The 4
power modes of the EL1507 are set up as shown in the table
below:
TABLE 2. POWER MODES OF THE EL1507
C
1
00I
01¾-I
10½-I
11Power Down
and C1, can be used to control the supply
0
C
0
Full Power Mode
S
Power Mode
S
Power Mode
S
Operation
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