This is the voltage that would be reflected from any line
termination. As ZL becomes equal to Z0, this quantity
becomes zero. Often this is expressed in dB and is
called return loss. Reflection coefficient values less
than 0.1 corresponding to a return loss of -20dB are
generally seen as adequate. The MAX3406/MAX3407/
MAX3408 will typically provide reflection coefficients
below 0.01 or -40dB return loss.
In most cases, Z0 and ZL are considered real resistive
quantities and the result is a dimensionless scalar
quantity, but the equation is valid in the complex case
as well.
Resistance vs. Temperature
The MAX3406/MAX3407/MAX3408 resistance is con-
stant over temperature. The typical temperature coeffi-
cient of resistance is 150ppm/°C. Over a -40°C to
+85°C range centered at +25°C, this would be a ±1%
change in resistance. The initial accuracy at room tem-
perature is ±1.5%. This provides improved perfor-
mance over discrete 5% resistors with a 100ppm temp-
co, which are typically used for termination, ±5.6%
worst case. The reflections from such a mistermination
are minimal and correspond to a worst-case reflection
coefficient for the MAX3406/MAX3407/MAX3408 of
±0.015 or a -36dB return loss.
Resistance vs. Input Voltage Range
The MAX3406/MAX3407/MAX3408 accept input volt-
ages (V
AB
) from -3.6V to +3.6V. There is virtually no
resistance variation over this range (0.02% typically).
The initial accuracy specifications in the data sheet
already account for resistance variations of the signal
voltage range.
Impedance vs. Frequency
As seen in the Typical Operating Characteristics, there
is a slight impedance variation in the MAX3406/
MAX3407/MAX3408 with frequency. The reactive com-
ponents are parasitic inductance and capacitance
associated with packaging, lead frame, and bond
wires. These impedance components are very small up
to frequencies above 20MHz. These parasitics are also
similar to those that would be present with a discrete
resistor terminator, and they can generally be ignored.
These effects should be evaluated for applications with
significant frequency content above 20MHz. This
applies to sine wave sources above 20MHz and square
and video sources above 8MHz. For all intended appli-
cations, E1/T1, Standard Video, etc. they can be
ignored.
Decoupling V
CC
The V
CC
pin for the MAX3406/MAX3407/MAX3408 must
be decoupled with a 0.1µF ceramic capacitor to GND
placed as close to the device as possible. This is
required for proper operation of the part.
Chip Information
TRANSISTOR COUNT: 102
PROCESS: BiCMOS
MAX3406/MAX3407/MAX3408
75Ω/100Ω/120Ω Switchable Termination
Networks
_______________________________________________________________________________________ 5
