MAXIM MAX378, MAX379 User Manual

19-1902; Rev 1; 8/94

High-Voltage, Fault-Protected

Analog Multiplexers

_______________General Description

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

____________________________Features

♦ 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

PART

MAX378CPE

MAX378CWG
MAX378CJE 0°C to +70°C
MAX378C/D 0°C to +70°C Dice**
MAX378EPE
MAX378EWG -40°C to +85°C
MAX378EJE
MAX378MJE -55°C to +125°C
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).

TEMP. RANGE PIN-PACKAGE

0°C to +70°C
0°C to +70°C

-40°C to +85°C 16 Plastic DIP

-40°C to +85°C 16 CERDIP

16 Plastic DIP
24 Wide SO
16 CERDIP

24 Wide SO

16 CERDIP

MAX378/MAX379

__________________________________________________________Pin Configurations

A0

1
2

EN

V-

3

IN1
IN2
IN3

IN4

OUT

Pin Configurations continued at end of data sheet.

MAX378

4
5
6
7
8

DIP

________________________________________________________________

A1

16

A2

15

GND

14
13

V+

12

IN5

11

IN6

10

IN7

9

IN8

TOP VIEW

IN1A
IN2A
IN3A

IN4A

OUTA

A0

1
2

EN

V-

3

MAX379

4
5
6
7
8

DIP

A1

16

GND

15

V+

14
13

IN1B

12

IN2B

11

IN3B

10

IN4B

9

OUTB

Maxim Integrated Products

Call toll free 1-800-998-8800 for free samples or literature.

1

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:

VEN, V

Analog Input with Multiplexer Power On..............................±65V

Analog Input with Multiplexer Power Off..............................±80V

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.

V+......................................................................+4V

A

{

V-........................................................................-4V

Recommended V+.....................................+15V

{}

Power Supplies V-.......................................-15V

ELECTRICAL CHARACTERISTICS

(V+ = +15V, V- = -15V; VAH(Logic Level High) = +2.4V, VAL(Logic Level Low) = +0.8V, unless otherwise noted.)

MAX378/MAX379

CONDITIONS UNITS

V

= ±10V, IIN= 100µA

OUT

VAL= 0.8V, VAH= 2.4V
VIN= ±10V, V

= 0.8V (Note 6)

V

EN

V

OUT

VEN= 0.8V MAX378
(Note 6) MAX379

V

IN(ALL)

VAH= VEN= 2.4V MAX378
VAL= 0.8V (Note 5) MAX379

(Note 2)
MAX379 only

(Note 6)

V

OUT

(Notes 3, 4)
VIN= ±60V, V

(Notes 3, 4)
VIN= ±75V, VEN= V

A0= A1= A2= 0V or 5V

(Note 4)
(Note 4)

VA= 5V or 0V (Note 5)

OUT

= ±10V, VIN= 10V

= V

OUT

= 0V, VIN= ±60V

OUT

STATIC

ON Resistance

OFF Input Leakage Current

OFF Output Leakage Current

ON Channel Leakage Current

Analog Signal Range
Differential OFF Output

Leakage Current

FAULT

Output Leakage Current
(with Input Overvoltage)

Input Leakage Current
(with Overvoltage)

Input Leakage Current
(with Power Supplies Off)

CONTROL

Input Low Threshold
Input High Threshold
Input Leakage Current

(High or Low)

SYMBOLPARAMETER TEMP

r

DS(ON)

I

IN(OFF)

I

OUT(OFF)

I

OUT(ON)

AN

DIFF

I

OUT(OFF)

IN(OFF)

IN(OFF)

AL
AH

A

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

0°C to +70°C

and

-40°C to +85°C

2.0 3.5

3.0 4.0

-1.0 0.03 1.0

-50 50

-2.0 0.1 2.0

-200 200

-100 100

-20 0.1 20

-600 600

-15 +15

-50 50

20

2.4

-1.0 1.0

±

= 10V

±

= ±10V

= ±10V

OUT

-55°C to +125°C

MIN TYP MAX MIN TYP MAX

+25°C

Full

+25°C

Full

+25°C

Full
Full

+25°C

Full
Full
Full

Full

+25°C

Full

+25°C

= 0V

+25°C 20

Full
Full

Full

2.0 3.0

3.0 4.0

-0.5 0.03 0.5

-50 50

-1.0 0.1 1.0

-100 100

-10 0.1 10

-300 300 -300 300

20
40

0.8

kΩ

nA

nA-200 200

nA-600 600

V-15 +15V

nA-50 50I

nA20
µA10

µA25I

µA10I

V0.8V
V2.4V

µA-1.0 1.0I

2 _______________________________________________________________________________________

High-Voltage, Fault-Protected

Analog Multiplexers

ELECTRICAL CHARACTERISTICS (continued)

(V+ = +15V, V- = -15V; VAH(Logic Level High) = +2.4V, VAL(Logic Level Low) = +0.8V, unless otherwise noted.)

1000

1000

0°C to +70°C

and

-40°C to +85°C

400 1000

1500

300

1000

1.2

3.5

50 68

5
25
12

5

0.1

0.2 1.0

0.5 1.0

0.01 0.1

0.02 0.1

±4.5 ±18

.

SYMBOLPARAMETER

DYNAMIC

Access Time +25°C 0.5 1.0
Break-Before-Make Delay

(Figure 2)

Enable Delay (ON)

Enable Delay (OFF)

Settling Time (0.1%)

(0.01%)

“OFF Isolation”

Channel Input Capacitance
Channel Output Capacitance

Digital Input Capacitance

Input to Output Capacitance

SUPPLY

Power-Supply Range for
Continuous Operation

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
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 T
Note 7: Electrical characteristics, such as ON Resistance, will change when power supplies other than ±15V are used.

t

ON(EN)

t

OFF(EN)

t

SETT

IN(OFF)

C

OUT(OFF)

DS(OFF)

I+Positive Supply Current

I-Negative Supply Current

OP

A

OFF

(ISO)

A

A

= cold temp.

CONDITIONS

Figure 1 µs0.5 1.0t
VEN= +5V, VIN= ±10V

A0, A1, A2strobed

Figure 3

Figure 3

VEN= 0.8V, RL= 1kΩ, CL= 15pF
V = 7V

VEN= 0.8V or 2.4V
All VA= 0V or 5V

VEN= 0.8V or 2.4V
All VA= 0V or 5V

(Note 7)

, f = 100kHz

RMS

MAX378
MAX379

-55°C to +125°C

TEMP

MIN TYP MAX MIN TYP MAX

+25°C 25 200
+25°C

Full

+25°C

Full

+25°C

+25°C
+25°C
+25°C

+25°C

+25°C

+25°C

Full

+25°C

Full

+25°C

400 750

300 500

1.2

3.5

25
12

0.1 0.6

0.3 0.7

0.01 0.1

0.02 0.2

Detailed Description

MAX378/MAX379

UNITS

ns25 200tON-t

ns

ns

µs

dB50 68OFF
pF5C
pF

pF5C

pF0.1C

mA

mA

V±4.5 ±18V

_______________________________________________________________________________________ 3

High-Voltage, Fault-Protected
Analog Multiplexers

__________________________________________Typical Operating Characteristics

INPUT LEAKAGE vs.

INPUT VOLTAGE WITH V+ = V- = 0V

1m

100µ

10µ

1µ

100n

10n

INPUT CURRENT (A)

1n

100p

10p

MAX378/MAX379

-100 -50 50 100

NOTE: Typical R

Analog in (±15V supplies) = 2%
for lowest to highest R
channel; @ -10V Analog in,

-80V

OPERATING

RANGE

V

DS(ON)

IN

+80V

0

(V)

match @ +10V

DS(ON)

match = 3%.

MAX378-1

OFF CHANNEL LEAKAGE CURRENT vs.
INPUT VOLTAGE WITH ±15V SUPPLIES

100µ

10µ

1µ

100n

(A)

10n

IN(OFF)

I

1n

100p

10p

1p

-120 -60 60 120

OPERATING

RANGE

-60V

V

IN

0

(V)

DRAIN-SOURCE ON-RESISTANCE vs.

ANALOG INPUT VOLTAGE

(kΩ)

DS(ON)

R

7

6

5

4

3

2

1
0

+3.5V +4V

+13V

-10 -5 5 15-15 0 20

±5V

SUPPLIES

SUPPLIES

ANALOG INPUT (V)

±15V

OUTPUT LEAKAGE CURRENT vs. OFF CHANNEL

OVERVOLTAGE WITH ±15V SUPPLIES

10n

MAX378-2

1n

(A)

100p

OUT(OFF)

+60V

+13V

10

I

10p

1p

-120 -60 60 120

MAX3784

-60V

OPERATING

RANGE

0

V

IN(OFF)

(V)

MAX378-3

+60V

A2

MAX378

A1
A0

+V

AH

EN

GND

IN2-IN7

OUT

IN1

±10V

IN2

±

IN8

10V

+10V

50%

MAX378: VAH = 3.0V

90%

t

A

ADDRESS

DRIVE (V

OUTPUT A

-10V

)

A

0V

V

A

50Ω

Figure 1. Access Time vs. Logic Level (High)

4 _______________________________________________________________________________________

PROBE

10M

14pF

High-Voltage, Fault-Protected

Analog Multiplexers

MAX378/MAX379

MAX358: VAH = 3.0V

ADDRESS

0V

t

OPEN

DRIVE (V

OUTPUT

50%50%

Figure 2. Break-Before-Make Delay (t

90%

t

ON(EN)

= 3.0V

AH

ON(EN)

ENABLE DRIVE

t

OFF(EN)

, t

OFF(EN)

MAX378: V

50%

Figure 3. Enable Delay (t

A

OPEN

OUTPUT

)

90%

A2

MAX378*

A1

V

A

50Ω

A0

2.4V
EN

*SIMILAR CONNECTION FOR MAX379

GND

IN2-IN7

OUT

IN1
IN2

IN8

1k

+5V

V

OUT

12.5pF

)

A2

MAX378*

0V

V

A

50Ω

A1
A0
EN

*SIMILAR CONNECTION FOR MAX379

IN1

IN2-IN7

OUT

GND

+10V

1k

12.5pF

)

+15V+5V

V-

A0
A1
A2

MAX378

EN

±60V

I

IN1
IN8

V

±10V

ANALOG

SIGNAL

-15V

OUT

V-

GND

Figure 4. Input Leakage Current (Overvoltage)

_______________________________________________________________________________________ 5

0V

V-

+5V

or

0V

10k

±75V

A0
A1
A2

MAX378

EN

I

IN1

OUT

V-

GND

0V

10k

Figure 5. Input Leakage Current (with Power Supplies OFF)

High-Voltage, Fault-Protected
Analog Multiplexers

Truth Table—MAX378

A2 A1 A0 EN

X
0
0
0
0
1
1
1
1

MAX378/MAX379

X
0
0
1
1
0
0
1
1

THERMOCOUPLE

STRAIN GUAGE

4-20mA LOOP
TRANSMITTER

+10V

GAIN REFERENCE
ZERO REFERENCE

X
0
1
0
1
0
1
0
1

0
1
1
1
1
1
1
1
1

IN1
IN2
IN3

IN4
IN5
IN6
IN7
IN8

V- GND

-15V

MAX378

+15V

V+

ON

SWITCH

NONE

1
2
3
4
5
6
7
8

OUT

Truth Table—MAX379

A1 A0 EN

X

0
0
1
1

Note: Logic “0” = VAL≤ 0.8V, Logic “1” = VAH≥ 2.4V

+15V

V+

OUT

DG508A

MAX358

OR

MAX378

V- GND

-15V

IN1

IN2

IN3

IN4

IN5

MAX420

X
0
1
0
1

+15V

-15V

0
1
1
1
1

ON

SWITCH

NONE

1
2
3
4

1M

100k

10k

1k

111Ω

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 (R
plexer leakage current (I
bias current (I

V

ERR

= R

BIAS

DS(ON)

):

x (I

OUT(ON)

OUT(ON)

= 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 _______________________________________________________________________________________

) times the multi-

DS(ON)

) and the amplifier

+ I

(MAX420))

BIAS

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

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.

_______________Detailed Description

Fault Protection Circuitry

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-

+60V

OVERVOLTAGE

N-CHANNEL MOSFET

IS TURNED OFF

GS

= -60V

BECAUSE V

Q

1

S

D

G

Q

2

D

S

G

Q

3

D

S

G

Figure 8. +60V Overvoltage with Multiplexer Power OFF

-60V

OVERVOLTAGE

N-CHANNEL MOSFET

IS TURNED OFF

GS

= +45V

BECAUSE V

-15V +15V -15V

-60V

Q

2

+15V FROM

DRIVERS

Q

1

-15V FROM
DRIVERS

P-CHANNEL

MOSFET IS OFF

+60V FORCED

ON COMMON

OUTPUT

LINE BY
EXTERNAL
CIRCUITRY

Q

3

N-CHANNEL

MOSFET IS OFF

Figure 9. -60V Overvoltage on an OFF Channel with
Multiplexer Power Supply ON

MAX378/MAX379

-60V

OVERVOLTAGE

N-CHANNEL MOSFET

IS TURNED ON

GS

= +60V

BECAUSE V

Q

1

S

G

P-CHANNEL

MOSFET IS OFF

Q

-60V

2

D

S

D

G

Q

3

D

S

G

Figure 7. -60V Overvoltage with Multiplexer Power OFF

_______________________________________________________________________________________ 7

-15V +15V -15V

+60V

OVERVOLTAGE

N-CHANNEL MOSFET

IS TURNED ON

GS

= -45V

BECAUSE V

Q

1

V

TN = +1.5V

+15V FROM

DRIVERS

+13.5V

Q

2

-15V FROM
DRIVERS

Q

3

N-CHANNEL

MOSFET IS ON

Figure 10. +60V Overvoltage Input to the ON Channel

+13.5V

OUTPUT

High-Voltage, Fault-Protected
Analog Multiplexers

to-source voltage. The P-channel device (Q2), howev­er, has +60V VGSand 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

MAX378/MAX379

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 VTNis typically 1.5V and V
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 simultaneous-

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
R

plus the signal source impedance multiplied by

DS(ON)

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

Operating Characteristics

graphs show typical R
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

TP

such as +15V and -5V. The digital threshold will remain
approximately 1.6V above GND and the analog character­istics such as R

are determined by the total voltage

DS(ON)

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

±10V

±15V

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.

+1.7V

0V

-1.7V
+5V

0V

-5V

+10V

0V

-10V

+100pC

+70pC
+45pC

+200pC
+130pC

+60pC

+500pC
+180pC

+50pC

Typical

DS(ON)

,

8 _______________________________________________________________________________________

High-Voltage, Fault-Protected

Analog Multiplexers

Table 1b. MAX379 Charge Injection

Supply
Voltage

±5V

±10V

±15V

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.

Analog

Input Level

+1.7V

0V

-1.7V
+5V

0V

-5V

+10V

0V

-10V

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-

Injected Charge

Out A Out B

+105pC

+73pC
+48pC

+215pC
+135pC

+62pC

+525pC
+180pC

+55pC

+107pC

+74pC
+50pC

+220pC
+139pC

+63pC

+530pC
+185pC

+55pC

Differential

A-B

-2pC

-1pC

-2pC

-5pC

-4pC

-1pC

-5pC

-5pC
0pC

Digital Interface Levels

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 R

DS(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.

Table 2a. Typical Off-Isolation
Rejection Ratio

Frequency 100kHz 500kHz 1MHz

One Channel Driven
All Channels Driven

Test Conditions: VIN= 20V

= 1.5kΩ between OUT and GND, EN = 0V.

R

L

OIRR = 20 Log ____________

74dB 72dB 66dB
64dB 48dB 44dB

at the tabulated frequency,

P-P

20V

P-P

V

OUT (P-P)

Table 2b. Typical Crosstalk
Rejection Ratio

Frequency

FL= 1.5k
RL= 10k

Test Conditions: Specified RLconnected from OUT to GND,
EN = +5V, A0 = A1 = A2 = +5V (Channel 1 selected). 20V
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.

100kHz 500kHz 1MHz

70dB 68dB 64dB
62dB 46dB 42dB

P-P

MAX378/MAX379

_______________________________________________________________________________________ 9

High-Voltage, Fault-Protected
Analog Multiplexers

_____________________________________________Pin Configurations (continued)

TOP VIEW

A0

1

EN

2

N.C.

3

N.C.

4

MAX378

V-

5

MAX378/MAX379

IN1
IN2
IN3

IN4
N.C.
N.C.
OUT

6
7
8

9
10
11
12

24
23
22
21
20
19
18
17
16
15
14
13

SO

A0

N.C.

A1

2

1

20

IN1

N.C.

IN2
IN3

EN

3

V-

5
6
7
8

MAX378

N.C.
N.C.

IN1A
IN2A
IN3A

IN4A

N.C.
N.C.

OUTA

A0

1

EN

2
3
4

V-

MAX379

5
6
7
8

9
10
11
12

A1

24

N.C.

23

GND

22

N.C.

21

V+

20

IN1B

19

IN2B

18

IN3B

17

IN4B

16

N.C.

15

N.C.

14

OUTB

13

A1
A2
GND
N.C.
V+
IN5
IN6
N.C.
IN7
N.C.
N.C.
IN8

SO

A0

A2

19

IN1A

N.C.
IN2A
IN3A

V-

5
6
7
8

184

GND

17

V+

16

N.C.

15

IN5

14

IN6

EN

3

2

MAX379

N.C.

1

A1

GND

20

19

184

V+

17

IN1B

16

N.C.

15

IN2B

14

IN3B

9

IN4

101112

OUT

N.C.

LCC

IN8

13

IN7

9

IN4A

101112

N.C.

OUTA

LCC

OUTB

13

IN4B

10 ______________________________________________________________________________________

High-Voltage, Fault-Protected

Analog Multiplexers

_Ordering Information (continued)

PART

MAX379CPE

MAX379CWG
MAX379CJE 0°C to +70°C
MAX379C/D 0°C to +70°C Dice**
MAX379EPE
MAX379EWG -40°C to +85°C
MAX379EJE
MAX379MJE -55°C to +125°C
MAX379MLP -55°C to +125°C 20 LCC*

* Contact factory for availability.
**The substrate may be allowed to float or be tied to V+ (JI CMOS).

TEMP. RANGE PIN-PACKAGE

0°C to +70°C
0°C to +70°C

-40°C to +85°C 16 Plastic DIP

-40°C to +85°C 16 CERDIP

16 Plastic DIP
24 Wide SO
16 CERDIP

24 Wide SO

16 CERDIP

_________________Chip Topographies

MAX378

IN8 OUT

IN7

IN7

IN6

IN5

V+

GND

A2 A1 EN

0.151"

(3.835mm)

NOTE: Connect substrate to V+ or leave it floating.

MAX379

OUTB OUTA

IN4B

IN4

IN3

0.229"

(5.816mm)

IN2

IN1
V-

A0

IN4A

MAX378/MAX379

IN3B

IN2B

IN1B

V+

GND

A0

A1 EN

0.151"

(3.835mm)

NOTE: Connect substrate to V+ or leave it floating.

______________________________________________________________________________________ 11

IN3A

(5.816mm)

IN2A

IN1A
V-

0.229"

High-Voltage, Fault-Protected
Analog Multiplexers

________________________________________________________Package Information

INCHES MILLIMETERS

DIM

D

A

0.101mm

e

B

A1

0.004in.

C

0°- 8°

L



A

A1

B
C
E
e
H
L

MIN

0.093

0.004

0.014

0.009

0.291

0.394

0.016



0.050

MAX

0.104

0.012

0.019

0.013

0.299


0.419

0.050

MIN

2.35

0.10

0.35

0.23

7.40


10.00

0.40

1.27

MAX

2.65

0.30

0.49

0.32

7.60


10.65

1.27

MAX378/MAX379

HE

D1

D

A2

A

L

A1

Wide SO

SMALL-OUTLINE

PACKAGE

(0.300 in.)

E

E1

A3

α

DIM

D
D
D
D
D

DIM

A
A1
A2
A3

B
B1

C

D
D1

E
E1

e

e
e

L

α







A



B

INCHES MILLIMETERS

PINS

MIN

MAX

–




0.413

0.463

0.512

0.614

0.713

MIN

10.10

11.35

12.60

15.20

17.70

MIN

–

0.38

3.18

1.40

0.41

1.27

0.20

18.92

0.13

7.62

6.10

–

2.92
0˚

0.398

16

0.447

18

0.496

20

0.598

24

0.697

28

INCHES MILLIMETERS

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˚

21-0042A

2.54 BSC



7.62 BSC



MAX

10.50

11.75

13.00

15.60

18.10

MAX

5.08
–

3.81

2.03

0.56

1.65

0.30

19.43

0.76

8.26

7.11




10.16

3.81

15˚

21-587A

16-PIN PLASTIC

e

B1

B

Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are

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.

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 [phone]

12

__________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 [phone]

© 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

© 1994 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

C

e

A

e

B

DUAL-IN-LINE

PACKAGE