MAX4631 Datasheet, PDF (10/16 Pages) Maxim Integrated Products – Fault-Protected, High-Voltage, Dual Analog Switches

Fault-Protected, High-Voltage,
Dual Analog Switches
Table 1. Switch States in Normal and Fault Conditions
POWER
SUPPLIES
(V+, V-)
On
On
On
On
On
On
INPUT
RANGE
Between Rails
Between Rails
Between V+ and (+40V - V+)
Between V+ and (+40V - V+)
Between V- and (-40V - V-)
Between V+ and (-40V - V-)
NC_
On
Off
On
Off
On
Off
NO_
Off
On
Off
On
Off
On
Off
Between Rails
Off
Off
OUTPUT
NC_
NO_
V+
V+
V-
V-
Follows the load
terminal voltage
Transient Fault Response and Recovery
When a fast rising and falling transient on NO_ (or NC_)
exceeds V+ or V-, the output (COM_) follows the input
(IN_) to the supply rail with only a few nanoseconds of
delay. This delay is due to the switch on-resistance and
circuit capacitance to ground. However, when the input
transient returns to within the supply rails, there is a
longer output recovery time delay. For positive and
negative faults, the recovery time is typically 2.5µs.
These values depend on the COM_ output resistance
and capacitance, and are not production tested or
guaranteed. The delays are not dependent on the fault
amplitude. Higher COM_ output resistance and capaci-
tance increase recovery times.
Fault-Protection Voltage and Power Off
The maximum fault voltage on the NO_ (or NC_) pins is
±40V when the power is off. For the MAX4631/
MAX4633, with ±15V supplies, the highest voltage on
NO_ (or NC_) can be +36V, and the lowest voltage on
NO (or NC_) can be -36V. For the MAX4632, with ±15V
supplies, the highest voltage on NO_ (or NC_) can be
+25V, and the lowest voltage on NO_ (or NC_) can be
-25V. Exceeding these limits can damage the device.
IN_ Logic-Level Thresholds
The logic-level thresholds are TTL/CMOS compatible
when V+ is +15V. Raising V+ increases the threshold
slightly; when V+ reaches +25V, the level threshold is
about 2.8V—higher than the TTL output high-level mini-
mum of 2.4V, but still compatible with CMOS outputs
(see Typical Operating Characteristics).
Increasing V- has no effect on the logic-level thresh-
olds, but it does increase the gate-drive voltage to the
signal FETs, reducing their on-resistance.
Failure Modes
The MAX4631/MAX4632/MAX4633 are not lightning
arrestors or surge protectors. Exceeding the fault-pro-
tection voltage limits on NO_ or NC_, even for very short
periods, can cause the device to fail. The failure modes
may not be obvious, and failure in one switch may or
may not affect other switches in the same package.
__________Applications Information
Ground
There is no connection between the analog signal
paths and GND. The analog signal paths consist of an
N-channel and a P-channel MOSFET with their sources
and drains paralleled 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 analog switch gates. This
drive signal is the only connection between the power
supplies and the analog signals. GND, IN_, and COM_
have ESD-protection diodes to V+ and V-.
Supply-Current Reduction
When the logic signals are driven rail-to-rail from 0 to
+12V or -15V to +15V, the supply current reduces to
approximately half of the supply current when the logic
input levels are at 0 to +5V.
Power Supplies
The MAX4631/MAX4632/MAX4633 operate with bipolar
supplies between ±4.5V and ±18V. The V+ and V- sup-
plies need not be symmetrical, but their difference can
not exceed the absolute maximum rating of +44V.
These devices operate from a single supply between
+9V and +36V when V- is connected to GND.
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