MAX4530 Maxim, MAX4530 Datasheet - Page 9

• Manufacturer Part Number: MAX4530
• Description: The MAX4530/MAX4531/MAX4532 are low-voltage, CMOS analog ICs configured as an 8-channel multiplexer (mux) (MAX4530), two 4-channel muxes (MAX4531), and three single-pole/double-throw switches (MAX4532)
• Manufacturer: Maxim

Low-Voltage, CMOS Analog Multiplexers/Switches
The MAX4530/MAX4531/MAX4532 construction is typi-
cal of most CMOS analog switches. They have three
supply pins: V+, V-, and GND. V+ and V- drive the
internal CMOS switches and set the limits of the analog
voltage on any switch. Reverse ESD-protection diodes
are internally connected between each analog-signal
pin and both V+ and V-. One of these diodes conducts
if any analog signal exceeds V+ or V-. During normal
operation, these and other reverse-biased ESD diodes
leak, forming the only current drawn from V+ or V-.
Virtually all of the analog leakage current comes from
the ESD diodes. Although the ESD diodes on a given
signal pin are identical and therefore fairly well bal-
anced, 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 to the V+ and V-
pins constitutes the analog-signal-path leakage current.
All analog leakage current flows between each pin and
one of the supply terminals, not to the other switch ter-
minal. For this reason, both sides of a given switch can
show leakage currents of either the same or opposite
polarity.
The analog-signal paths and GND are not connected.
V+ and GND power the internal logic and logic-level
translators, and set both the input and output logic lim-
its. The logic-level translators convert the logic levels
into switched V+ and V- signals to drive the analog sig-
nals’ gates. This drive signal is the only connection
between the logic supplies and signals and the analog
supplies. V+ and V- have ESD-protection diodes to
GND.
__________Applications Information
Power-Supply Considerations
_______________________________________________________________________________________
with Enable Inputs and Address Latching
Overview
The logic-level thresholds are TTL/CMOS compatible
when V+ = +5V. As V+ rises, the threshold increases
slightly, so when V+ reaches +12V, the threshold is
about 3.1V—above the TTL guaranteed, high-level min-
imum of 2.8V, but still compatible with CMOS outputs.
The MAX4530/MAX4531/MAX4532 operate with bipolar
supplies between ±2.0V and ±6V. The V+ and V- sup-
plies need not be symmetrical, but their sum cannot
exceed the +13V absolute maximum rating.
The MAX4530/MAX4531/MAX4532 operate from a sin-
gle supply between +2V and +12V when V- is connect-
ed to GND. All of the bipolar precautions must be
observed. At room temperature, they actually work with
a single supply at, near, or below +1.7V, although as
supply voltage decreases, switch on-resistance and
switching times become very high.
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 is
not in turning the switch on, but in turning it off. The off-
state switch acts like a capacitor and passes higher
frequencies with less attenuation. At 10MHz, off isola-
tion is about -65dB in 50Ω systems, becoming worse
(approximately 20dB per decade) as frequency
increases. Higher circuit impedances also make off iso-
lation 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