MAX14777 Datasheet, PDF (13/16 Pages) Maxim Integrated Products – Quad Beyond-the-Rails -15V to +35V Analog Switch

MAX14777
Quad Beyond-the-Rails -15V to +35V
Analog Switch
V_L Supply Logic Input
The MAX14777 features a separate logic supply input
(V_L) that sets the high and low thresholds for the logic
inputs (EN_ and SEL35). This feature allows flexibility in
interfacing to controllers that have a different logic level
than V_CC. Connect V_L to a voltage between 1.62V and
5.5V for normal operation.
Applications Information
Non-Powered Condition
To understand the behavior of the MAX14777 when not
powered (i.e. V_CC = 0V), both the transient and DC signal
conditions should be considered. Every A_ and B_ pin
has internal diodes to V_P and V_N, as shown in Figure 8.
Applying a positive voltage on A_ or B_ charges the V_P
capacitor through the diode to V_P. Applying a negative
voltage on A_ or B_ charges the V_N capacitor negative
through the diode to V_N. Switch terminals A_, B_ are tol-
erant to high-voltage signals ranging from -15V to +35V
when device is unpowered; i.e, V_CC = 0 or V_CC floating.
Once the capacitor is charged to a DC voltage, the
I_{L_IO_OFF} current flows. Thus, under transient conditions,
applying a changing voltage to an A_ or B_ pin results in
flow into or out of the pin due to a charge movement at
the external capacitors on V_P and V_N.
Under DC conditions, when a voltage is applied to an A_
or B_ pin, with V_CC unpowered, the switch is open when
the voltage difference between the A_and B_ pin is larger
than 3V. Under these conditions, DC leakage current
flows into the pin. When |V_A - V_B| < 3V DC, the switch
is not fully open, and currents up to a few mA can flow
between A_ and B_.
If SEL35 is connected low, the V_P capacitor charges to
about 25V. Applying a positive voltage above about 25V
on A_ or B_ charges the V_P capacitor through the diode
to V_P. Once the V_P capacitor is charged to this increased
voltage, current flow from A_ or B_ ceases. Thus, even
when SEL35 is low, any of A_ or B_ tolerate voltages up
to 35V.
SEL35
A1
A2
A3
A4
VL
CONFIG
VP
MAX14777
V_CC
BIAS
GENERATION
VP
VP
VN
10nF
50V/100V
10nF
50V/100V
B1
B2
B3
B4
VN
EN1 EN2 EN3 EN4
VN
Figure 8. Typical Application Circuit
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