EL5173, EL5373
Maximum reliability is maintained if the output current never
exceeds ±60mA. This limit is set by the design of the internal
metal interconnect.
Where:
• V
S
= Total supply voltage
• I
SMAX
= Maximum quiescent supply current per channel
•
∆V
O
= Maximum differential output voltage of the
application
• R
LD
= Differential load resistance
• I
LOAD
= Load current
• i = Number of channels
By setting the two PD
MAX
equations equal to each other, we
can solve the output current and R
LOAD
to avoid the device
overheat.
Power Dissipation
With the high output drive capability of the EL5173 and
EL5373 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.
The maximum power dissipation allowed in a package is
determined according to:
T
JMAX
–
T
AMAX
PD
MAX
=
--------------------------------------------
-
Θ
JA
Power Supply Bypassing and Printed Circuit
Board Layout
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 V
S
- pin is
connected to the ground plane, a single 4.7µF tantalum
capacitor in parallel with a 0.1µF ceramic capacitor from V
S
+
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 V
S
- pin becomes the negative
supply rail.
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.
Where:
• T
JMAX
= Maximum junction temperature
• T
AMAX
= Maximum ambient temperature
•
θ
JA
= 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:
∆V
O
-
PD
=
i
×
V
S
×
I
SMAX
+
V
S
×
-----------
R
LD
Typical Applications
Twisted pair cable driver
0Ω
50
50Ω
EL5173/
EL5373
V
FB
V
IN
V
INB
V
REF
EL5175/
EL5375
50
Z
O
= 100Ω
50Ω
V
OUT
FIGURE 22. TWISTED PAIR CABLE DRIVER
10
FN7312.4
February 16, 2005
INTERSIL [ INTERSIL CORPORATION ]
