Datasheet

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_______________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 cur-

rent 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 first-

generation fault-protected muxes. First, the Maxim protec-

tion scheme limits fault currents to nanoamp leakage

values rather than many milliamperes. This prevents dam-

age to sensors or other sensitive signal sources. Second,

the MAX378/MAX379 fault-protected muxes can withstand

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 requir-

ing 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

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).

MAX378/MAX379

High-Voltage, Fault-Protected

Analog Multiplexers

________________________________________________________________

Maxim Integrated Products

GND

V+

IN1

V-

TOP VIEW

MAX378

IN5

IN6

IN7

IN8

OUT

IN4

IN3

IN2

DIP

GND

V+

IN1B

IN1A

V-

MAX379

IN2B

IN3B

IN4B

OUTB

OUTA

IN4A

IN3A

IN2A

DIP

__________________________________________________________Pin Configurations

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

19-1902; Rev 1; 8/94

PART

MAX378CPE

MAX378CWG

MAX378CJE 0°C to +70°C

0°C to +70°C

TEMP. RANGE PIN-PACKAGE

16 Plastic DIP

24 Wide SO

16 CERDIP

MAX378EPE

MAX378EWG -40°C to +85°C

-40°C to +85°C 16 Plastic DIP

24 Wide SO

MAX378EJE

MAX378MJE -55°C to +125°C

-40°C to +85°C 16 CERDIP

16 CERDIP

MAX378MLP -55°C to +125°C 20 LCC*

Pin Configurations continued at end of data sheet.

MAX378C/D 0°C to +70°C Dice**

Summary of content (12 pages)

PAGE 1
9-1902; 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.
PAGE 2
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- .........................................................
PAGE 3
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.
PAGE 4
__________________________________________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.
PAGE 5
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.
PAGE 6
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.
PAGE 7
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.
PAGE 8
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.
PAGE 9
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.
PAGE 10
_____________________________________________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.
PAGE 11
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.
PAGE 12
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.