19-1902; Rev 1; 8/94
High-Voltage, Fault-Protected
Analog Multiplexers
____________________________Features
The MAX378 8-channel single-ended (1-of-8) multiplexer
and the MAX379 4-channel differential (2-of-8) multiplexer
use a series N-channel/P-channel/N-channel structure to
provide significant fault protection. If the power supplies to
the MAX378/MAX379 are inadvertently turned off while
input voltages are still applied, all channels in the muxes
are turned off, and only a few nanoamperes of leakage current will flow into the inputs. This protects not only the
MAX378/MAX379 and the circuitry they drive, but also the
sensors or signal sources that drive the muxes.
♦
♦
♦
♦
The series N-channel/P-channel/N-channel protection
structure has two significant advantages over the simple
current-limiting protection scheme of the industry’s firstgeneration fault-protected muxes. First, the Maxim protection scheme limits fault currents to nanoamp leakage
values rather than many milliamperes. This prevents damage to sensors or other sensitive signal sources. Second,
the MAX378/MAX379 fault-protected muxes can withstand
a continuous ±60V input, unlike the first generation, which
had a continuous ±35V input limitation imposed by power
dissipation considerations.
♦
♦
♦
♦
All digital inputs have logic thresholds of 0.8V and 2.4V,
ensuring both TTL and CMOS compatibility without requiring pull-up resistors. Break-before-make operation is
guaranteed. Power dissipation is less than 2mW.
________________________Applications
Data Acquisition Systems
Industrial and Process Control Systems
Avionics Test Equipment
Signal Routing Between Systems
♦
♦
Fault Input Voltage ±75V with Power Supplies Off
Fault Input Voltage ±60V with ±15V Power Supplies
All Switches Off with Power Supplies Off
On Channel Turns OFF if Overvoltage Occurs on
Input or Output
Only Nanoamperes of Input Current Under All
Fault Conditions
No Increase in Supply Currents Due to Fault
Conditions
Latchup-Proof Construction
Operates from ±4.5V to ±18V Supplies
All Digital Inputs are TTL and CMOS Compatible
Low-Power Monolithic CMOS Design
______________Ordering Information
TEMP. RANGE
PART
PIN-PACKAGE
0°C to +70°C
MAX378CPE
16 Plastic DIP
MAX378CWG
0°C to +70°C
24 Wide SO
MAX378CJE
0°C to +70°C
16 CERDIP
MAX378C/D
0°C to +70°C
Dice**
MAX378EPE
-40°C to +85°C
16 Plastic DIP
MAX378EWG
-40°C to +85°C
24 Wide SO
MAX378EJE
-40°C to +85°C
16 CERDIP
MAX378MJE
-55°C to +125°C
16 CERDIP
MAX378MLP
-55°C to +125°C
20 LCC*
Ordering Information continued at end of data sheet.
* Contact factory for availability.
**The substrate may be allowed to float or be tied to V+ (JI CMOS).
__________________________________________________________Pin Configurations
TOP VIEW
A0 1
16 A1
A0 1
16 A1
EN 2
15 A2
EN 2
15 GND
V- 3
14 GND
V- 3
IN1 4
MAX378
14 V+
MAX379
13 V+
IN1A 4
IN2 5
12 IN5
IN2A 5
12 IN2B
IN3 6
11 IN6
IN3A 6
11 IN3B
IN4 7
10 IN7
IN4A 7
10 IN4B
OUT 8
9
IN8
DIP
Pin Configurations continued at end of data sheet.
OUTA 8
13 IN1B
9
OUTB
DIP
________________________________________________________________ Maxim Integrated Products
Call toll free 1-800-998-8800 for free samples or literature.
1
MAX378/MAX379
_______________General Description
MAX378/MAX379
High-Voltage, Fault-Protected
Analog Multiplexers
ABSOLUTE MAXIMUM RATINGS
Voltage between Supply Pins ..............................................+44V
V+ to Ground ...................................................................+22V
V- to Ground......................................................................-22V
Digital Input Overvoltage:
V+......................................................................+4V
VEN, VA
V- ........................................................................-4V
Analog Input with Multiplexer Power On..............................±65V
Recommended
V+ .....................................+15V
Power Supplies
V- .......................................-15V
Analog Input with Multiplexer Power Off..............................±80V
{
{
}
Continuous Current, IN or OUT...........................................20mA
Peak Current, IN or OUT
(Pulsed at 1ms, 10% duty cycle max) ............................40mA
Power Dissipation (Note 1) (CERDIP) ................................1.28W
Operating Temperature Range:
MAX378/379C .....................................................0°C to +70°C
MAX378/379E ..................................................-40°C to +85°C
MAX378/379M ...............................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Note 1: Derate 12.8mW/°C above TA = +75°C
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.
ELECTRICAL CHARACTERISTICS
(V+ = +15V, V- = -15V; VAH (Logic Level High) = +2.4V, VAL (Logic Level Low) = +0.8V, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
TEMP
-55°C to +125°C
0°C to +70°C
and
-40°C to +85°C
MIN TYP MAX
MIN TYP MAX
UNITS
STATIC
ON Resistance
rDS(ON)
OFF Input Leakage Current
IIN(OFF)
OFF Output Leakage Current
ON Channel Leakage Current
Analog Signal Range
Differential OFF Output
Leakage Current
IOUT(OFF)
IOUT(ON)
VOUT = ±10V, IIN = 100µA
VAL = 0.8V, VAH = 2.4V
±
VIN = ±10V, VOUT = 10V
VEN = 0.8V (Note 6)
+25°C
2.0
3.0
2.0
3.5
Full
3.0
4.0
3.0
4.0
-0.5 0.03
0.5
-1.0 0.03
1.0
-50
50
-50
50
VOUT = ±10V, VIN = ± 10V
VEN = 0.8V
MAX378
(Note 6)
MAX379
+25°C
-1.0
1.0
-2.0
Full
-200
200
-200
200
Full
-100
100
-100
100
VIN(ALL) = VOUT = ±10V
VAH = VEN = 2.4V
MAX378
VAL = 0.8V (Note 5)
MAX379
+25°C
-10
10
-20
Full
-600
600
-600
600
Full
-300
300
-300
300
+25°C
Full
0.1
0.1
0.1
0.1
kΩ
nA
2.0
nA
20
nA
VAN
(Note 2)
Full
-15
+15
-15
+15
V
IDIFF
MAX379 only
(Note 6)
Full
-50
50
-50
50
nA
FAULT
Output Leakage Current
(with Input Overvoltage)
IOUT(OFF)
VOUT = 0V, VIN = ±60V
(Notes 3, 4)
Input Leakage Current
(with Overvoltage)
IIN(OFF)
VIN = ±60V, VOUT = ±10V
(Notes 3, 4)
Input Leakage Current
(with Power Supplies Off)
IIN(OFF)
VIN = ±75V, VEN = VOUT = 0V
A0 = A1 = A2 = 0V or 5V
+25°C
20
20
nA
Full
10
20
µA
+25°C
25
40
µA
+25°C
10
20
µA
0.8
V
CONTROL
Input Low Threshold
VAL
(Note 4)
Full
Input High Threshold
VAH
(Note 4)
Full
2.4
VA = 5V or 0V (Note 5)
Full
-1.0
Input Leakage Current
(High or Low)
2
IA
0.8
2.4
1.0
-1.0
_______________________________________________________________________________________
V
1.0
µA
High-Voltage, Fault-Protected
Analog Multiplexers
(V+ = +15V, V- = -15V; VAH (Logic Level High) = +2.4V, VAL (Logic Level Low) = +0.8V, unless otherwise noted.)
PARAMETER
SYMBOL
CONDITIONS
TEMP
-55°C to +125°C
0°C to +70°C
and
-40°C to +85°C
MIN TYP MAX
MIN TYP MAX
0.5
0.5
UNITS
DYNAMIC
Access Time
tA
Figure 1
+25°C
tON-tOFF
VEN = +5V, VIN = ±10V
A0, A1, A2 strobed
+25°C
Enable Delay (ON)
tON(EN)
Figure 3
Enable Delay (OFF)
tOFF(EN)
Figure 3
Settling Time (0.1%)
(0.01%)
tSETT
Break-Before-Make Delay
(Figure 2)
“OFF Isolation”
OFF(ISO)
Channel Input Capacitance
CIN(OFF)
Channel Output Capacitance
Digital Input Capacitance
Input to Output Capacitance
25
+25°C
200
400
Full
+25°C
300
Full
25
50
1.0
200
750
400 1000
1500
500
300
1000
1.2
1.2
3.5
3.5
68
50
µs
ns
1000
1000
+25°C
VEN = 0.8V, RL = 1kΩ, CL = 15pF
+25°C
V = 7VRMS, f = 100kHz
1.0
ns
ns
µs
68
dB
pF
+25°C
5
5
MAX378
+25°C
MAX379
25
25
12
12
CA
+25°C
5
5
pF
CDS(OFF)
+25°C
0.1
0.1
pF
COUT(OFF)
pF
SUPPLY
Positive Supply Current
I+
VEN = 0.8V or 2.4V
All VA = 0V or 5V
+25°C
0.1
0.6
0.2
1.0
Full
0.3
0.7
0.5
1.0
Negative Supply Current
I-
VEN = 0.8V or 2.4V
All VA = 0V or 5V
+25°C
0.01
0.1
0.01
0.1
Full
0.02
0.2
0.02
0.1
Power-Supply Range for
Continuous Operation
VOP
(Note 7)
+25°C
±4.5
±18
±4.5
mA
mA
±18
V
Note 2: When the analog signal exceeds +13.5V or -12V, the blocking action of Maxim’s gate structure goes into operation. Only
leakage currents flow and the channel ON resistance rises to infinity.
Note 3: The value shown is the steady-state value. The transient leakage is typically 50µA. See Detailed Description.
Note 4: Guaranteed by other static parameters.
Note 5: Digital input leakage is primarily due to the clamp diodes. Typical leakage is less than 1nA at +25°C.
Note 6: Leakage currents not tested at TA = cold temp.
Note 7: Electrical characteristics, such as ON Resistance, will change when power supplies other than ±15V are used.
_______________________________________________________________________________________
3
MAX378/MAX379
ELECTRICAL CHARACTERISTICS (continued)
__________________________________________Typical Operating Characteristics
OFF CHANNEL LEAKAGE CURRENT vs.
INPUT VOLTAGE WITH ±15V SUPPLIES
10n
1n
1n
OPERATING
RANGE
+80V
100p
-80V
100p
10n
-60V
OPERATING
RANGE
100n
10p
-100
0
-50
50
MAX378-3
1n
100p
OPERATING
RANGE
+60V
100n
IOUT(OFF) (A)
1µ
1µ
+60V
10µ
10n
MAX378-2
10µ
IIN(OFF) (A)
INPUT CURRENT (A)
100µ
MAX378-1
1m
100µ
OUTPUT LEAKAGE CURRENT vs. OFF CHANNEL
OVERVOLTAGE WITH ±15V SUPPLIES
-60V
INPUT LEAKAGE vs.
INPUT VOLTAGE WITH V+ = V- = 0V
10p
10p
1p
-120
100
0
-60
VIN (V)
60
1p
-120
120
0
-60
VIN (V)
60
VIN(OFF) (V)
DRAIN-SOURCE ON-RESISTANCE vs.
ANALOG INPUT VOLTAGE
+3.5V
MAX3784
7
+4V
6
+13V
±5V
SUPPLIES
RDS(ON) (kΩ)
5
4
+13V
3
±15V
SUPPLIES
2
NOTE: Typical RDS(ON) match @ +10V
Analog in (±15V supplies) = 2%
for lowest to highest R DS(ON)
channel; @ -10V Analog in,
match = 3%.
MAX378: VAH = 3.0V
1
0
-15
-10
-5
0
5
10
15
20
ANALOG INPUT (V)
A2
ADDRESS
DRIVE (VA)
IN1
IN2
50%
A1
0V
VA
+10V
OUTPUT A
+VAH
50Ω
±10V
MAX378 IN2-IN7
A0
IN8
EN
OUT
±
MAX378/MAX379
High-Voltage, Fault-Protected
Analog Multiplexers
GND
90%
PROBE
10V
-10V
10M
14pF
tA
Figure 1. Access Time vs. Logic Level (High)
4
_______________________________________________________________________________________
120
High-Voltage, Fault-Protected
Analog Multiplexers
A1
VA
2.4V
50%
50%
+5V
IN1
IN2
ADDRESS
DRIVE (VA)
0V
MAX378/MAX379
A2
MAX358: VAH = 3.0V
50Ω
OUTPUT
MAX378* IN2-IN7
A0
IN8
EN
OUT
VOUT
GND
12.5pF
1k
tOPEN
*SIMILAR CONNECTION FOR MAX379
Figure 2. Break-Before-Make Delay (tOPEN)
MAX378: VAH = 3.0V
A2
IN1
A1
MAX378* IN2-IN7
+10V
ENABLE DRIVE
50%
0V
A0
90%
OUT
EN
VA
OUTPUT
GND
12.5pF
1k
50Ω
90%
tON(EN)
tOFF(EN)
*SIMILAR CONNECTION FOR MAX379
Figure 3. Enable Delay (tON(EN), tOFF(EN))
+5V
+15V
A0
0V
V-
A0
+5V
or
0V
A1
A2
EN
I
MAX378
A1
A2
EN
I
OUT
IN1
V-
MAX378
OUT
IN1
IN8
±60V
V-
V
±10V
ANALOG
SIGNAL
GND
-15V
Figure 4. Input Leakage Current (Overvoltage)
10k
±75V
V-
GND
10k
0V
Figure 5. Input Leakage Current (with Power Supplies OFF)
_______________________________________________________________________________________
5
MAX378/MAX379
High-Voltage, Fault-Protected
Analog Multiplexers
Truth Table—MAX378
Truth Table—MAX379
A2
A1
A0
EN
ON
SWITCH
X
0
0
0
0
1
1
1
1
X
0
0
1
1
0
0
1
1
X
0
1
0
1
0
1
0
1
0
1
1
1
1
1
1
1
1
NONE
1
2
3
4
5
6
7
8
A1
A0
EN
ON
SWITCH
X
0
0
1
1
X
0
1
0
1
0
1
1
1
1
NONE
1
2
3
4
Note: Logic “0” = VAL ≤ 0.8V, Logic “1” = VAH ≥ 2.4V
+15V
THERMOCOUPLE
IN1
STRAIN GUAGE
IN2
4-20mA LOOP
TRANSMITTER
IN3
V+
+15V
OUT
MAX420
-15V
+15V
IN4
V+
IN5
IN1
IN6
+10V
GAIN REFERENCE
IN7
ZERO REFERENCE
IN8
1M
MAX378
100k
IN2
OUT
V-
GND
-15V
DG508A
MAX358
OR
MAX378
10k
IN3
IN4
1k
IN5
V-
GND
111Ω
-15V
Figure 6. Typical Data Acquisition Front End
_______________Typical Applications
Figure 6 shows a typical data acquisition system
using the MAX378 multiplexer. Since the multiplexer
is driving a high-impedance input, its error is a function of its own resistance (RDS(ON)) times the multiplexer leakage current (IOUT(ON)) and the amplifier
bias current (IBIAS):
VERR = RDS(ON) x (IOUT(ON) + IBIAS (MAX420))
= 2.0kΩ x (2nA + 30pA)
= 18.0µV maximum error
In most cases, this error is low enough that preamplification of input signals is not needed, even with very
low-level signals such as 40µV/°C from type J thermocouples.
6
In systems with fewer than eight inputs, an unused channel can be connected to the system ground reference
point for software zero correction. A second channel
connected to the system voltage reference allows gain
correction of the entire data acquisition system as well.
A MAX420 precision op amp is connected as a programmable-gain amplifier, with gains ranging from 1 to
10,000. The guaranteed 5µV unadjusted offset of the
MAX420 maintains high signal accuracy, while programmable gain allows the output signal level to be scaled to
the optimum range for the remainder of the data acquisition system, normally a Sample/Hold and A/D. Since
the gain-changing multiplexer is not connected to the
external sensors, it can be either a DG508A multiplexer
or the fault-protected MAX358 or MAX378.
_______________________________________________________________________________________
High-Voltage, Fault-Protected
Analog Multiplexers
+60V
OVERVOLTAGE
N-CHANNEL MOSFET
IS TURNED OFF
BECAUSE VGS = -60V
Q2
Q1
S
Q3
D
S
D
Fault Protection Circuitry
-15V
+15V
-60V
OVERVOLTAGE
-60V Q2
Q1
N-CHANNEL MOSFET
IS TURNED OFF
BECAUSE VGS = +45V
Q1
S
N-CHANNEL MOSFET
IS TURNED ON
BECAUSE VGS = +60V
D
G
-60V Q2
D
S
G
Q3
D
S
G
P-CHANNEL
MOSFET IS OFF
Figure 7. -60V Overvoltage with Multiplexer Power OFF
+15V FROM
DRIVERS
-15V FROM
DRIVERS
-15V +60V FORCED
ON COMMON
OUTPUT
LINE BY
EXTERNAL
CIRCUITRY
Q3
N-CHANNEL
MOSFET IS OFF
P-CHANNEL
MOSFET IS OFF
Figure 9. -60V Overvoltage on an OFF Channel with
Multiplexer Power Supply ON
-15V
-60V
OVERVOLTAGE
G
Figure 8. +60V Overvoltage with Multiplexer Power OFF
_______________Detailed Description
The MAX378/MAX379 are fully fault protected for continuous input voltages up to ±60V, whether or not the V+
and V- power supplies are present. These devices use
a “series FET” switching scheme which not only protects the multiplexer output from overvoltage, but also
limits the input current to sub-microamp levels.
Figures 7 and 8 show how the series FET circuit protects against overvoltage conditions. When power is
off, the gates of all three FETs are at ground. With a -60V
input, N-channel FET Q1 is turned on by the +60V gate-
D
S
G
G
MAX378/MAX379
Input switching, however, must be done with a faultprotected MAX378 multiplexer, to provide the level of
protection and isolation required with most data acquisition inputs. Since external signal sources may continue to supply voltage when the multiplexer and system
power are turned off, non-fault-protected multiplexers,
or even first-generation fault-protected devices, will
allow many milliamps of fault current to flow from outside sources into the multiplexer. This could result in
damage to either the sensors or the multiplexer. A nonfault-protected multiplexer will also allow input overvoltages to appear at its output, perhaps damaging
Sample/Holds or A/Ds. Such input overdrives may also
cause input-to-input shorts, allowing the high current
output of one sensor to possibly damage another.
The MAX378 eliminates all of the above problems. It
not only limits its output voltage to safe levels, with or
without power applied (V+ and V-), but also turns all
channels off when power is removed. This allows it to
draw only sub-microamp fault currents from the inputs,
and maintain isolation between inputs for continuous
input levels up to ±75V with power supplies off.
+60V
OVERVOLTAGE
N-CHANNEL MOSFET
IS TURNED ON
BECAUSE VGS = -45V
Q1
+15V
+13.5V Q2
-15V
Q3
+13.5V
OUTPUT
VTN = +1.5V
+15V FROM
DRIVERS
-15V FROM
DRIVERS
N-CHANNEL
MOSFET IS ON
Figure 10. +60V Overvoltage Input to the ON Channel
_______________________________________________________________________________________
7
MAX378/MAX379
High-Voltage, Fault-Protected
Analog Multiplexers
to-source voltage. The P-channel device (Q2), however, has +60V VGS and is turned off, thereby preventing
the input signal from reaching the output. If the input
voltage is +60V, Q1 has a negative VGS, which turns it
off. Similarly, only sub-microamp leakage currents can
flow from the output back to the input, since any voltage will turn off either Q1 or Q2.
Figure 9 shows the condition of an OFF channel with
V+ and V- present. As with Figures 7 and 8, either an
N-channel or a P-channel device will be off for any
input voltage from -60V to +60V. The leakage current
with negative overvoltages will immediately drop to a
few nanoamps at +25°C. For positive overvoltages,
that fault current will initially be 40µA or 50µA, decaying
over a few seconds to the nanoamp level. The time
constant of this decay is caused by the discharge of
stored charge from internal nodes, and does not compromise the fault-protection scheme.
Figure 10 shows the condition of the ON channel with
V+ and V- present. With input voltages less than ±10V,
all three FETs are on and the input signal appears at the
output. If the input voltage exceeds V+ minus the Nchannel threshold voltage (VTN), then the N-channel
FET will turn off. For voltages more negative than Vminus the P-channel threshold (VTP), the P-channel
device will turn off. Since VTN is typically 1.5V and VTP
is typically 3V, the multiplexer’s output swing is limited
to about -12V to +13.5V with ±15V supplies.
The Typical Operating Characteristics graphs show typical leakage vs. input voltage curves. Although the maximum rated input of these devices is ±65V, the
MAX378/MAX379 typically have excellent performance
up to ±75V, providing additional margin for the unknown
transients that exist in the real world. In summary, the
MAX378/MAX379 provide superior protection from all
fault conditions while using a standard, readily produced junction-isolated CMOS process.
Switching Characteristics
and Charge Injection
Table 1 shows typical charge-injection levels vs.
power-supply voltages and analog input voltage. Note
that since the channels are well matched, the differential charge injection for the MAX379 is typically less
than 5pC. The charge injection that occurs during
switching creates a voltage transient whose magnitude
is inversely proportional to the capacitance on the multiplexer output.
The channel-to-channel switching time is typically 600ns,
with about 200ns of break-before-make delay. This 200ns
break-before-make delay prevents the input-to-input short
that would occur if two input channels were simultaneous8
ly connected to the output. In a typical data acquisition
system, such as in Figure 6, the dominant delay is not the
switching time of the MAX378 multiplexer, but is the settling time of the following amplifiers and S/H. Another limiting factor is the RC time constant of the multiplexer
RDS(ON) plus the signal source impedance multiplied by
the load capacitance on the output of the multiplexer.
Even with low signal source impedances, 100pF of capacitance on the multiplexer output will approximately double
the settling time to 0.01% accuracy.
Operation with Supply Voltage
Other than ±15V
The main effect of supply voltages other than ±15V is
the reduction in output signal range. The MAX378 limits
the output voltage to about 1.5V below V+ and about 3V
above V-. In other words, the output swing is limited to
+3.5V to -2V when operating from ±5V. The Typical
Operating Characteristics graphs show typical RDS(ON),
for ±15V, ±10V, and ±5V power supplies. Maxim tests
and guarantees the MAX378/MAX379 for operation from
±4.5V to ±18V supplies. The switching delays are
increased by about a factor of 2 at ±5V, but breakbefore-make action is preserved.
The MAX378/MAX379 can be operated with a single +9V
to +22V supply, as well as asymmetrical power supplies
such as +15V and -5V. The digital threshold will remain
approximately 1.6V above GND and the analog characteristics such as RDS(ON) are determined by the total voltage
difference between V+ and V-. Connect V- to 0V when
operating with a +9V to +22V single supply.
This means that the MAX378/MAX379 will operate with
standard TTL-logic levels, even with ±5V power supplies. In all cases, the threshold of the EN pin is the
same as the other logic inputs.
Table 1a. MAX378 Charge Injection
Supply Voltage
Analog Input Level
Injected Charge
±5V
+1.7V
0V
-1.7V
+100pC
+70pC
+45pC
±10V
+5V
0V
-5V
+200pC
+130pC
+60pC
±15V
+10V
0V
-10V
+500pC
+180pC
+50pC
Test Conditions: CL = 1000pF on multiplexer output; the tabulated analog input level is applied to channel 1; channels 2
through 8 are open circuited. EN = +5V, A1 = A2 = 0V, A0 is
toggled at 2kHz rate between 0V and 3V. +100pC of charge
creates a +100mV step when injected into a 1000pF load
capacitance.
_______________________________________________________________________________________
High-Voltage, Fault-Protected
Analog Multiplexers
Injected Charge
Supply
Voltage
Analog
Input Level
Out A
Out B
Differential
A-B
±5V
+1.7V
0V
-1.7V
+105pC
+73pC
+48pC
+107pC
+74pC
+50pC
-2pC
-1pC
-2pC
±10V
+5V
0V
-5V
+215pC
+135pC
+62pC
+220pC
+139pC
+63pC
-5pC
-4pC
-1pC
±15V
+10V
0V
-10V
+525pC
+180pC
+55pC
+530pC
+185pC
+55pC
-5pC
-5pC
0pC
Test Conditions: CL = 1000pF on Out A and Out B; the tabulated analog input level is applied to inputs 1A and 1B; channels
2 through 4 are open circuited. EN = +5V, A1 = 0V, A0 is toggled from 0V to 3V at a 2kHz rate.
rents as the off-channel input voltages are varied. The
MAX378 output leakage varies only a few picoamps as
all seven off inputs are toggled from -10V to +10V. The
output voltage change depends on the impedance level
at the MAX378 output, which is RDS(ON) plus the input
signal source resistance in most cases, since the load
driven by the MAX378 is usually a high impedance. For
a signal source impedance of 10kΩ or lower, the DC
crosstalk exceeds 120dB.
Table 2 shows typical AC crosstalk and off-isolation performance. Digital feedthrough is masked by the analog
charge injection when the output is enabled. When the
output is disabled, the digital feedthrough is virtually
unmeasurable, since the digital pins are physically isolated from the analog section by the GND and V- pins.
The ground plane formed by these lines is continued
onto the MAX378/MAX379 die to provide over 100dB
isolation between the digital and analog sections.
Digital Interface Levels
The typical digital threshold of both the address lines
and the EN pin is 1.6V, with a temperature coefficient of
about -3mV/°C. This ensures compatibility with 0.8V to
2.4V TTL-logic swings over the entire temperature
range. The digital threshold is relatively independent of
the supply voltages, moving from 1.6V typical to 1.5V
typical as the power supplies are reduced from ±15V to
±5V. In all cases, the digital threshold is referenced to
GND.
The digital inputs can also be driven with CMOS-logic
levels swinging from either V+ to V- or from V+ to GND.
The digital input current is just a few nanoamps of leakage at all input voltage levels, with a guaranteed maximum of 1µA. The digital inputs are protected from ESD
by a 30V zener diode between the input and V+, and
can be driven ±4V beyond the supplies without drawing
excessive current.
Operation as a Demultiplexer
The MAX378/MAX379 will function as a demultiplexer,
where the input is applied to the OUT pin, and the input
pins are used as outputs. The MAX378/MAX379 provide both break-before-make action and full fault protection when operated as a demultiplexer, unlike earlier
generations of fault-protected multiplexers.
Channel-to-Channel Crosstalk,
Off Isolation, and Digital Feedthrough
At DC and low frequencies, channel-to-channel
crosstalk is caused by variations in output leakage cur-
Table 2a. Typical Off-Isolation
Rejection Ratio
Frequency
100kHz
500kHz
1MHz
One Channel Driven
74dB
72dB
66dB
All Channels Driven
64dB
48dB
44dB
Test Conditions: V IN = 20VP-P at the tabulated frequency,
RL = 1.5kΩ between OUT and GND, EN = 0V.
20VP-P
OIRR = 20 Log ____________
VOUT (P-P)
Table 2b. Typical Crosstalk
Rejection Ratio
Frequency
100kHz
500kHz
1MHz
FL = 1.5k
70dB
68dB
64dB
RL = 10k
62dB
46dB
42dB
Test Conditions: Specified RL connected from OUT to GND,
EN = +5V, A0 = A1 = A2 = +5V (Channel 1 selected). 20VP-P
at the tabulated frequency is applied to Channel 2. All other
channels are open circuited. Similar crosstalk rejection can be
observed between any two channels.
_______________________________________________________________________________________
9
MAX378/MAX379
Table 1b. MAX379 Charge Injection
_____________________________________________Pin Configurations (continued)
TOP VIEW
A0 1
24 A1
A0 1
24 A1
EN 2
23 A2
EN 2
23 N.C.
N.C. 3
22 GND
N.C. 3
22 GND
N.C. 4
21 N.C.
N.C. 4
21 N.C.
MAX378
V- 5
MAX379
20 V+
V- 5
IN1 6
19 IN5
IN1A 6
19 IN1B
IN2 7
18 IN6
IN2A 7
18 IN2B
IN3 8
17 N.C.
IN3A
8
17 IN3B
16 IN7
IN4A 9
16 IN4B
N.C. 10
15 N.C.
N.C. 10
15 N.C.
N.C. 11
14 N.C.
N.C. 11
14 N.C.
OUT 12
13 IN8
OUTA 12
13 OUTB
V- 4
18 GND
19 GND
20 A1
1 N.C.
V- 4
18 V+
17 V+
IN1A 5
16 N.C.
N.C. 6
IN2 7
15 IN5
IN2A 7
15 IN2B
IN3 8
14 IN6
IN3A 8
14 IN3B
LCC
16 N.C.
IN4B 13
OUTB 12
N.C. 11
MAX379
9
IN7 13
IN8 12
N.C. 11
IN4
9
MAX378
17 IN1B
IN4A
N.C. 6
OUTA 10
IN1 5
2 A0
3 EN
19 A2
SO
20 A1
1 N.C.
2 A0
3 EN
SO
10
20 V+
IN4 9
OUT 10
MAX378/MAX379
High-Voltage, Fault-Protected
Analog Multiplexers
LCC
______________________________________________________________________________________
High-Voltage, Fault-Protected
Analog Multiplexers
PART
TEMP. RANGE
_________________Chip Topographies
PIN-PACKAGE
MAX379CPE
0°C to +70°C
16 Plastic DIP
MAX379CWG
MAX379CJE
MAX379C/D
MAX379EPE
MAX379EWG
MAX379EJE
MAX379MJE
MAX379MLP
0°C to +70°C
0°C to +70°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
-55°C to +125°C
24 Wide SO
16 CERDIP
Dice**
16 Plastic DIP
24 Wide SO
16 CERDIP
16 CERDIP
20 LCC*
* Contact factory for availability.
**The substrate may be allowed to float or be tied to V+ (JI CMOS).
MAX378
IN8 OUT
IN4
IN7
IN7
IN3
0.229"
(5.816mm)
IN6
IN2
IN5
V+
IN1
V-
GND
A2
A1
A0
EN
0.151"
(3.835mm)
NOTE: Connect substrate to V+ or leave it floating.
MAX379
OUTB OUTA
IN4A
IN4B
IN3B
IN3A
0.229"
(5.816mm)
IN2B
IN2A
IN1B
V+
IN1A
V-
GND
A1
A0
EN
0.151"
(3.835mm)
NOTE: Connect substrate to V+ or leave it floating.
______________________________________________________________________________________
11
MAX378/MAX379
_Ordering Information (continued)
MAX378/MAX379
High-Voltage, Fault-Protected
Analog Multiplexers
________________________________________________________Package Information
DIM
D
0°- 8°
A
e
B
0.101mm
0.004in.
A1
C
L
A
A1
B
C
E
e
H
L
INCHES
MAX
MIN
0.104
0.093
0.012
0.004
0.019
0.014
0.013
0.009
0.299
0.291
0.050
0.419
0.394
0.050
0.016
DIM PINS
E
Wide SO
SMALL-OUTLINE
PACKAGE
(0.300 in.)
H
D
D
D
D
D
16
18
20
24
28
INCHES
MIN MAX
0.398 0.413
0.447 0.463
0.496 0.512
0.598 0.614
0.697 0.713
MILLIMETERS
MIN
MAX
2.35
2.65
0.10
0.30
0.35
0.49
0.23
0.32
7.40
7.60
1.27
10.00
10.65
0.40
1.27
MILLIMETERS
MIN
MAX
10.10 10.50
11.35 11.75
12.60 13.00
15.20 15.60
17.70 18.10
21-0042A
DIM
D1
A
A1
A2
A3
B
B1
C
D
D1
E
E1
e
eA
eB
L
α
E
E1
D
A3
A A2
L A1
INCHES
MAX
MIN
0.200
–
–
0.015
0.150
0.125
0.080
0.055
0.022
0.016
0.065
0.050
0.012
0.008
0.765
0.745
0.030
0.005
0.325
0.300
0.280
0.240
0.100 BSC
0.300 BSC
0.400
–
0.150
0.115
15˚
0˚
MILLIMETERS
MIN
MAX
–
5.08
0.38
–
3.18
3.81
1.40
2.03
0.41
0.56
1.27
1.65
0.20
0.30
18.92
19.43
0.13
0.76
7.62
8.26
6.10
7.11
2.54 BSC
7.62 BSC
–
10.16
2.92
3.81
0˚
15˚
21-587A
α
C
e
B1
B
eA
16-PIN PLASTIC
DUAL-IN-LINE
PACKAGE
eB
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.
12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600
© 1994 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.