MAX4526 Datasheet, PDF (8/12 Pages) Maxim Integrated Products – Phase-Reversal Analog Switches

Phase-Reversal Analog Switches
Single Supply
The MAX4526/MAX4527 operate from a single supply
between +4.5V and +36V when V- is connected to
GND. Observe all of the bipolar precautions when
operating from a single supply.
__________Applications Information
The MAX4526/MAX4527 are designed for DC and
low-frequency-signal phase-reversal applications. Both
DC and AC symmetry are optimized for use with ±15V
supplies.
Signal Phase/Polarity Reversal
The MAX4526/MAX4527 can reverse the phase or
polarity of a pair of signals that are out-of-phase and
balanced to ground. This is done by routing signals
through the MAX4526/MAX4527 and under control of
the IN pin, reversing the two signals paths inside the
switch before sending out to a balanced output. Figure
1 shows a typical example. The MAX4526/MAX4527
cannot reverse the phase or polarity of a single-
grounded signal, as can be done with an inverting
op amp or transformer.
Balanced Modulators/Demodulators
The MAX4526/MAX4527 can be used as a balanced
modulator/demodulator at carrier frequencies up to
100kHz (Figure 2). Higher frequencies are possible, but
as frequency increases, small imbalances in the
MAX4526/MAX4527’s internal capacitance and resis-
tance gradually impair performance. Similarly, imbal-
ances in external circuit capacitance and resistance to
GND reduce overall carrier suppression.
The carrier is applied as a logic-level square wave to
IN. (Note that this voltage can go as negative as V-.)
For best carrier suppression, the power-supply volt-
ages should be equal, the square wave should have a
precise 50% duty cycle, and both the input and output
signals should be symmetrical about ground. Bypass
V+ and V- to GND with 0.1µF ceramic capacitors, as
close to the IC pins as possible. Since the logic-level
translator/driver in the MAX4526 is faster than the one
in the MAX4527, it gives better results at higher
frequencies. In critical applications, carrier suppression
can be optimized by trimming duty cycle, DC bias
around GND, or external source and load capacitance.
In signal lines, balancing both capacitance and resis-
tance to GND produces the best carrier suppression.
Transformer coupling of input and output signals
provides the best isolation and carrier suppression.
Transformers can also provide signal filtering, imped-
ance matching, or low-noise voltage gain. Use a
center-tapped transformer or high-resistance voltage
divider to provide a DC path to GND on either the input
signal or output signal. This ensures a DC path to GND
and symmetrical operation of the internal switches.
______________________________________________Test Circuits/Timing Diagrams
V+
V_IN
IN
V+
A
50Ω
MAX4526
B
MAX4527
X
GND V-
V-
-10V
+10V
300Ω
V_OUT
35pF
V- IS CONNECTED TO GND (0V) FOR SINGLE-SUPPLY OPERATION.
V+
V_IN
0V
V_B
V_OUT ^0V
V_A
t_TRANS
50%
90%
90%
t_TRANS
Figure 3. Address Transition Time
8 _______________________________________________________________________________________