Detailed Description
The MAX14508E–MAX14511E/MAX14509AE are high-
ESD-protected single DPDT switches that operate from
a +2.7V to +5.0V supply and are designed to multiplex
USB 2.0 Hi-Speed signals and AC-coupled analog sig-
nals. These switches combine the low on-capacitance
(C
ON
) and low on-resistance (R
ON
) necessary for high-
performance switching applications. These devices
meet the requirements for USB low-speed and full-
speed signaling. The negative signal capability of the
analog channel allows signals below ground to pass
through without distortion.
Analog Signal Levels
The MAX14508E–MAX14511E/MAX14509AE are bidi-
rectional, allowing ANO_, UNC_, and COM_ to be con-
figured as either inputs or outputs. Note that UNC_ and
ANO_ are only protected against ESD up to ±2kV
(Human Body Model) and may require additional ESD
protection if used as outputs. These devices feature a
charge pump that generates a negative supply to allow
analog signals as low as V
CC
- 5.0V to pass through
ANO_. This allows AC-coupled signals that drop below
ground to pass when operating from a single power
supply. The negative charge pump is controlled by the
enable line and the output of the COM_ fault protection
circuit. The negative charge pump is active when EN is
high and V
COM_
< V
FP
. Note that if the fault protection
is activated by a COM_ voltage greater than V
FP
, there
must not be a negative voltage attached to the ANO_
inputs. For the MAX14508E/MAX14509E/MAX14509AE
connect negative signals to ANO_ or COM_ only when
EN is driven high.
Overvoltage Fault Protection
The MAX14508E–MAX14511E feature overvoltage fault
protection on COM_, allowing compliance with USB
requirements for voltage levels. Fault protection is trig-
gered if the voltage applied to COM_ rises above V
FP
,
protecting the switch and USB transceiver from damag-
ing voltage levels.
VBUS Detection Input
The MAX14510E/MAX14511E feature a VBUS detection
input (VB) that connects COM_ to UNC_ when V
VB
exceeds the VBUS detection threshold (V
VBDET
). For
applications where VBUS is always present, drive the
Audio Override Input (AOR) high to connect ANO_ to
COM_ (see the
MAX14510E/MAX14511E Functional
Diagrams/Truth Table
). Drive AOR low to have VB con-
trol the switch position. Drive AOR rail-to-rail to mini-
mize power consumption.
Digital Control Input (CB)
The MAX14508E/MAX14509E/MAX14509AE provide a
single-bit control logic input, CB. CB controls the switch
position as shown in the
MAX14508E/MAX14509E/
MAX14509AE Functional Diagrams/Truth Table
. Drive
CB rail-to-rail to minimize power consumption.
Enable Input (EN)
The MAX14508E/MAX14509E/MAX14509AE feature a
shutdown mode that reduces the supply current to less
than 10nA and places the switches in high impedance.
Drive EN low to place the devices in shutdown mode.
Drive EN high for normal operation.
Click-and-Pop Suppression
The switched 100Ω shunt resistors on the MAX14508E/
MAX14510E automatically discharge any capacitance
at the ANO_ terminals when they are unconnected from
COM_. This reduces audio click-and-pop sounds that
may occur when switching between USB and audio
sources.
Applications Information
Extended ESD Protection
ESD-protection structures are incorporated on all pins
to protect against electrostatic discharges up to ±2kV
(Human Body Model) encountered during handling and
assembly. COM1 and COM2 are further protected
against ESD up to ±15kV (Human Body Model) without
damage. The ESD structures withstand high ESD
both in normal operation and when the device is
powered down. After an ESD event, the MAX14508E–
MAX14511E/MAX14509AE continue to function without
latchup.
ESD Test Conditions
ESD performance depends on a variety of conditions.
Contact Maxim for a reliability report that documents
test setup, test methodology, and test results.
Human Body Model
Figure 5 shows the Human Body Model. Figure 6 shows
the current waveform it generates when discharged into
a low impedance. This model consists of a 100pF
capacitor charged to the ESD voltage of interest that is
then discharged into the device through a 1.5kΩ resistor.
Layout
USB Hi-Speed requires careful PCB layout with 45Ω
single-ended/90Ω differential controlled-impedance
matched traces of equal lengths. Ensure that bypass
capacitors are as close to the device as possible. Use
large ground planes where possible.
MAX14508E–MAX14511E/MAX14509AE
USB 2.0 Hi-Speed and Audio Switches
with Negative Signal Capability
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