MAX4553 Maxim, MAX4553 Datasheet - Page 9

• Manufacturer Part Number: MAX4553
• Description: The MAX4551/MAX4552/MAX4553 are quad, low-voltage, single-pole/single-throw (SPST) analog switches
• Manufacturer: Maxim

The MAX4551/MAX4552/MAX4553 construction is typi-
cal of most CMOS analog switches. They have three
supply pins: V+, V-, and GND. V+ and V- are used to
drive the internal CMOS switches, and they set the lim-
its of the analog voltage on any switch. Reverse ESD-
protection diodes are internally connected between
each analog-signal pin and both V+ and V-. If any ana-
log signal exceeds V+ or V-, one of these diodes con-
ducts. During normal operation these reverse-biased
ESD diodes leak, forming the only current drawn from
V+ or V-.
Virtually all the analog leakage current is through the
ESD diodes. Although the ESD diodes on a given sig-
nal pin are identical and therefore fairly well balanced,
they are reverse biased differently. Each is biased by
either V+ or V- and the analog signal. This means their
leakages vary as the signal varies. The difference in the
two diode leakages from the signal path to the V+ and
V- pins constitutes the analog-signal-path leakage cur-
rent. All analog leakage current flows to the supply ter-
minals, not to the other switch terminal. This explains
how both sides of a given switch can show leakage
currents of the same or opposite polarity.
The analog signal paths consist of an N-channel and P-
channel MOSFET with their sources and drains paral-
leled, and their gates driven out of phase to V+ and V-
by the logic-level translators.
V+ and GND power the internal logic and logic-level
translators, and set the input logic thresholds. The
logic-level translators convert the logic levels to
switched V+ and V- signals, to drive the gates of the
analog switches. This drive signal is the only connec-
tion between the logic supplies and the analog sup-
plies. V+ and V- have ESD-protection diodes to GND.
The logic-level inputs and output have ESD protection
to V+ and to GND.
Increasing V- has no effect on the logic-level thresh-
olds, but it does increase the drive to the P-channel
switches, reducing their on-resistance. V- also sets the
negative limit of the analog signal voltage.
The logic-level thresholds are CMOS/TTL compatible
when V+ = +5V. The threshold increases slightly as V+
is raised, and when V+ reaches +12V, the level thresh-
old is about 3.1V. This is above the TTL output high-
level minimum of 2.8V, but still compatible with CMOS
outputs.
Power-Supply Considerations
_______________________________________________________________________________________
Low-Voltage, SPST Analog Switches
Overview
±15kV ESD-Protected, Quad,
The MAX4551/MAX4552/MAX4553 operate with bipolar
supplies between ±2V and ±6V. The V+ and V- sup-
plies need not be symmetrical, but their sum cannot
exceed the absolute maximum rating of 13.0V. Do not
connect the MAX4551/MAX4552/MAX4553 V+ to +3V,
and then connect the logic-level-input pins to TTL
logic-level signals. TTL logic-level outputs in excess
of the absolute maximum ratings can damage the
part and/or external circuits.
Caution: The absolute maximum V+ to V- differential
voltage is 13.0V. Typical ±6V or 12V supplies with
±10% tolerances can be as high as 13.2V. This voltage
can damage the MAX4551/MAX4552/MAX4553. Even
±5% tolerance supplies may have overshoot or noise
spikes that exceed 13.0V.
The MAX4551/MAX4552/MAX4553 operate from a
single supply between +2V and +12V when V- is con-
nected to GND. All of the bipolar precautions must be
observed.
In 50Ω systems, signal response is reasonably flat up
to 50MHz (see Typical Operating Characteristics ).
Above 20MHz, the on-response has several minor
peaks that are highly layout-dependent. The problem
with high-frequency operation is not turning the switch
on, but turning it off. The off-state switch acts like a
capacitor and passes higher frequencies with less
attenuation. At 10MHz, off-isolation is about -52dB in
50Ω systems, becoming worse (approximately 20dB
per decade) as frequency increases. Higher circuit
impedances also make off-isolation worse. Adjacent
channel attenuation is about 3dB above that of a bare
IC socket, and is due entirely to capacitive coupling.
High-Frequency Performance
Bipolar Supplies
Single Supply
9