The MAX14778 dual 4:1 analog multiplexer supports
analog signals up to Q25V with a single 3.0 to 5.5V
supply. Each multiplexer has separate control inputs to
allow independent switching, making the device ideal for
multiplexing different communications signals with the
same connector pins. Extended ESD protection of Q6kV
(Human Body Model) enable direct interfacing to cables
and connectors.
The MAX14778 features a low 1.5I (max) on-resistance
and 3mI (typ) flatness to maximize signal integrity over
the entire common-mode voltage range. Each multiplexer can carry up to 300mA of continuous current through
the multiplexer in either direction.
The MAX14778 supports switching of full-speed USB 1.1
signals (12Mbps) and RS-485 data rates of up to 20Mbps.
The MAX14778 is available in a 20-pin (5mm x 5mm)
TQFN package and is specified over the -40NC to +85NC
extended temperature range.
Applications
RS-485/RS-232/USB 1.1 Multiplexing
POS Peripherals
Handheld Industrial Devices
Communication Systems
Audio/Data Multiplexing
Connector Sharing
Gaming Machines
Features
S±25V Signal Range
SSingle 3.0V to 5.5V Supply
STwo Independent Multiplexers
S1.5I RON (max)
S3mI RON Flatness (typ)
S300mA Maximum Current Through Multiplexer
S78pF Input Capacitance
S75MHz Large-Signal Bandwidth
SBreak-Before-Make Operation
SExtended ESD Protection on A� and B� Pins
Q6kV Human Body Model (HBM)
Ordering Information appears at end of data sheet.
For related parts and recommended products to use with this part,
refer to www.maxim-ic.com/MAX14778.related.
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX14778
Dual ±25V Above- and Below-the-Rails
4:1 Analog Multiplexer
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND.)
VDD .......................................................................... -0.3V to +6V
VP ........................... -0.3V to the lesser of +52V and (VN + 70V)
VN ................ The lesser of (VDD - 40V) and (VP - 70V) to +0.3V
VP to VN ................................................................. -0.3V to +70V
ENA, ENB, SA_, SB_ ................................ -0.3V to (VDD + 0.3V)
A_, ACOM, B_,
BCOM .. (VN - 0.3V) to the lesser of (VP + 0.3V) and (VN + 52V)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute
maximum rating conditions for extended periods may affect device reliability.
= -40NC to +85NC, unless otherwise noted. Typical values are at VDD = 5V, T
A
VDD = 5.5V0.8
VDD = 4.5V0.8
VDD = 3.6V0.7
VDD = 3.0V0.7
VDD = 5.5V2.1
VDD = 4.5V2.0
VDD = 3.6V1.9
VDD = 3.0V1.7
Figure 3, VIN = Q10V, RL = 10kI,
CL = 15pF
Figure 3, VIN = Q10V, RL = 10kI,
CL = 15pF
Figure 4, VIN = Q10V, RL = 10kI,
CL = 15pF
Figure 6, VA_ = 1V
RL = 50I, CL = 15pF
Figure 6, f = 100kHz, RS = RL = 50I
, f = 100kHz,
RMS
POR
ON
OFF
t
BBM
ISO
IL
IH
CT
= +25NC.) (Note 2)
A
404ms
2ms
1.5ms
840
-80dB
-103dB
V
V
Fs
-3dB BandwidthBW
Total Harmonic Distortion
Plus Noise
Input CapacitanceC
THERMAL PROTECTION
Thermal-Shutdown
Threshold
Thermal-Shutdown
Hysteresis
ESD PROTECTION
A_, B_ Pins (Note 4)Human Body Model
All Other PinsHuman Body Model
Note 2: All units are production tested at TA = +25NC. Specifications over temperature are guaranteed by design.
Note 3: When VDD is higher than the charge-pump threshold, the internal 5V regulated charge pump is turned off and the input to
the high-voltage charge pumps is provided by VDD.
Note 4: The MAX14778 requires a 100nF capacitor on both VP and VN to GND to guarantee full ESD protection. See the
Applications Information section for details on ESD test conditions.
MEASUREMENTS ARE STANDARDIZED AGAINST SHORTS AT IC TERMINALS.
OFF-ISOLATION IS MEASURED BETWEEN ACOM AND "OFF" A_ TERMINAL ON EACH MULTIPLEXER.
-3dBW IS MEASURED BETWEEN ACOM AND "ON" A_ TERMINAL ON EACH MULTIPLEXER.
CROSSTALK IS MEASURED FROM ONE CHANNEL TO ALL OTHER CHANNELS.
SIGNAL DIRECTION THROUGH MULTIPLEXER IS REVERSED; WORST VALUES ARE RECORDED.
V
DD
MAX14778
ACOM
Q = CL x DV
NETWORK
ANALYZER
50
V
A0
IN
V
OUT
I
MEASREF
50I
I
50
50I
OFF-ISOLATION = 20log
ON-LOSS = 20log
CROSSTALK = 20log
OUT
V
OUT
V
IN
V
OUT
V
IN
V
OUT
V
IN
Figure 6. Off-Isolation, -3dB Bandwidth, and Crosstalk
5ACOMMUX A Common Terminal
6A0MUX A Bidirectional Analog Input/Output 0
7A1MUX A Bidirectional Analog Input/Output 1
8A2MUX A Bidirectional Analog Input/Output 2
9A3MUX A Bidirectional Analog Input/Output 3
10ENAMUX A Enable Input
11SA0MUX A Channel Select Input 0
12SA1MUX A Channel Select Input 1
13V
DD
14SB1MUX B Channel Select Input 1
15SB0MUX B Channel Select Input 0
16ENBMUX B Enable Input
17B3MUX B Bidirectional Analog Input/Output 3
18B2MUX B Bidirectional Analog Input/Output 2
19B1MUX B Bidirectional Analog Input/Output 1
20B0MUX B Bidirectional Analog Input/Output 0
—EPExposed Pad. Connect EP to VN. EP is not intended as an electrical connection point.
Positive Charge-Pump Output. Bypass VP to GND with a 100nF 50V ceramic capacitor.
Negative Charge-Pump Output. Bypass VN to GND with a 100nF 50V ceramic capacitor.
Power-Supply Input. Bypass VDD to GND with a 1FF ceramic capacitor.
Table 1. MUX A Channel SelectionTable 2. MUX B Channel Selection
ENASA1SA0
0XXOpen
100A0
101A1
110A2
111A3
X = Don’t care
ACOM
CONNECTED TO
Detailed Description
The MAX14778 dual 4:1 analog multiplexer integrates
bias circuitry to provide a Q25V analog voltage range
with a single 3.0 to 5.5V supply. This extended input
range allows multiplexing different communications
signals such as RS-232, RS-485, audio and USB 1.1 onto
the same connector.
Integrated Bias Generation
The MAX14778 contains a total of three charge pumps to
generate bias voltages for the internal switches: a 5V regulated charge pump, a positive high-voltage (+35V) charge
pump, and a negative high-voltage (-27V) charge pump.
When VDD is above 4.7V (typ), the 5V regulated charge
pump is bypassed and VDD provides the input for the highvoltage charge pumps, reducing overall supply current.
An external 100nF capacitor is required for each highvoltage charge pump between VP/VN and GND.
Analog Signal Levels
The MAX14778 transmits signals of up to Q25V with a
single 3.0 to 5.5V supply due to integrated bias circuitry.
The device features 1.5Ω (max) on-resistance and 3mI
(typ) flatness for analog signals between -25V and +25V
(see the Typical Operating Characteristics). The current
flow through the multiplexers can be bidirectional, allowing operation either as a multiplexer or demultiplexer.
ENBSB1SB0
0XXOpen
100B0
101B1
110B2
111B3
X = Don’t care
BCOM
CONNECTED TO
Digital Interface
The MAX14778 has two digital select inputs for each
MUX: SA1 and SA0 control MUX A; SB1 and SB0 control
MUX B. Drive the digital select inputs high or low to select
which input (A_, B_) is connected to the common terminal (ACOM, BCOM) for each MUX. See the Truth Tables
for more information.
Each MUX features an independent enable input (ENA
and ENB). Drive ENA or ENB low to disconnect all inputs
from the common terminal for that MUX, regardless of the
status of the select inputs or the other enable input.
Applications Information
Connector Sharing
The MAX14778 supports a Q25V analog signal range
independently for each input/output, allowing physical
connector sharing between interface types that have
differing signal ranges.
The multiprotocol connector-sharing application in the
Typical Operating Circuits shows an application with
RS-232, half-duplex RS-485, full-speed USB 1.1, and
audio signals sharing the same connector. The device
allows signals to pass over the entire signal range specified by each standard while safely isolating the unused
transceivers.
The MAX14778 can tolerate input voltages on the A_, B_,
ACOM, and BCOM pins in the ±25V range when it is not
powered.
When VDD = 0V, the DC input leakage current into the
A_, B_, ACOM or BCOM pins will typically be below 1µA.
Some devices can have a larger leakage current up to
mA range due to technology spread.
With VDD not powered, internal diodes between the analog pins and the VP and VN will charge up the external
capacitors on VP and VN when positive and/or negative
voltages are applied to these pins. This causes transient
input current flow.
Large dv/dt on the inputs causes large capacitive charging currents, which have to be limited to the 300mA
Absolute Maximum Ratings in order to not destroy the
internal diodes. With 100nF capacitors on VP and VN, the
dv/dt must be limited to 3V/µs once the capacitors reach
their final voltage; the input current decays to the leakage
current levels mentioned above.
High-ESD Protection
Electrostatic discharge (ESD)-protection structures are
incorporated on all pins to protect against electrostatic
discharges up to Q2kV Human Body Model (HBM)
encountered during handling and assembly. A_ and B_
are further protected against ESD up to Q6kV (HBM)
without damage. The ESD structures withstand high ESD
both in normal operation and when the device is powered
down. After an ESD event, the MAX14778 continues 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.
The MAX14778 requires a 100nF capacitor on both V
P
and VN to GND to guarantee full ESD protection.
Human Body Model
Figure 7 shows the Human Body Model. Figure 8 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 1.5kI resistor.
R
C
1MI
CHARGE CURRENT-
LIMIT RESISTOR
HIGH-
VOLTAGE
DC
SOURCE
Figure 7. Human Body ESD Test ModelFigure 8. Human Body Current Waveform
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
-40NC to +85NC
20 TQFN-EP*
Chip Information
PROCESS: BiCMOS
Package Information
For the latest package outline information and land patterns
(footprints), go to www.maxim-ic.com/packages. Note that a
“+”, “#”, or “-” in the package code indicates RoHS status only.
Package drawings may show a different suffix character, but
the drawing pertains to the package regardless of RoHS status.
Added new TOCs 14 and 15, updated Non-Powered Condition section, updated
Note 4, Pin Description, ESD Test Conditions, Typical Operating Circuits, updated
capacitor values
PAGES
CHANGED
3, 8, 9, 10, 11,
12, 13
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied.
Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in the Electrical
Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 15