19-0326; Rev 0; 12/94
Signal-Line Circuit Protectors
_______________General Description
The MAX366 and MAX367 are multiple, two-terminal circuit
protectors. Placed in series with signal lines, each two-ter-
minal device guards sensitive circuit components against
voltages near and beyond the normal supply voltages.
These devices are used at interfaces where sensitive cir-
cuits are connected to the external world and could
encounter damaging voltages (up to 35V beyond the sup-
ply rails) during power-up, power-down, or fault conditions.
The MAX366 contains three independent protectors and
the MAX367 contains eight. They can protect analog sig-
nals using either unipolar (4.5V to 36V) or bipolar (±2.25V
to ±18V) power supplies. Each protector is symmetrical.
Input and output terminals may be freely interchanged.
These devices are voltage-sensitive MOSFET transistor
arrays that are normally on when power is applied and
normally open circuit when power is off. With ±10V sup-
plies, on-resistance is 100Ω max and leakage is less than
1nA at +25°C.
When signal voltages exceed or are within approximately
1.5V of either power-supply voltage (including when
power is off), the two-terminal resistance increases dra-
matically, limiting fault current as well as output voltage to
sensitive circuits. The protected side of the switch main-
tains the correct polarity and clamps approximately 1.5V
below the supply rail. There are no “glitches” or polarity
reversals going into or coming out of a fault condition.
____________________________Features
o
±40V Overvoltage Protection
o
Open Signal Paths with Power Off
100Ω Signal Paths with Power On
o
1nA Max Path Leakage at +25°C
o
44V Maximum Supply Voltage Rating
o
Automatic Protection; No Programming or
Controls
MAX366/MAX367
______________Ordering Information
PART
†
MAX366CPA
MAX366CSA
MAX366C/D
MAX366EPA
MAX366ESA
MAX366MJA
MAX367CPN
MAX367CWN
MAX367C/D
MAX367EPN
MAX367EWN
MAX367MJN
TEMP. RANGE
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
-55°C to +125°C
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
-55°C to +125°C
PIN-PACKAGE
8 Plastic DIP
8 SO
Dice*
8 Plastic DIP
8 SO
8 CERDIP**
18 Plastic DIP
18 Wide SO
Dice*
18 Plastic DIP
18 Wide SO
18 CERDIP**
________________________Applications
Process Control Systems
Redundant/Backup Systems
Hot-Insertion Boards/Systems ATE Equipment
Data-Acquisition Systems
Sensitive Instruments
†
MAX367 available after January 1, 1995.
* Dice are tested at T
A
= +25°C only.
* Contact factory for availability.
Pin Configurations appear at end of data sheet.
___________________________________________________Typical Operating Circuit
ELECTRONICS
FAULT!
REMOTE SENSOR
+10V REG.
+28V
1
(SHORT)
IN1
PROTECTOR
MAX366
V+
OUT1
8
7
+12V
2
3
4
IN2
IN3
V-
OUT2
OUT3
6
5
SENSITIVE
AMPLIFIER
(OPEN)
FAULT!
________________________________________________________________
Maxim Integrated Products
1
Call toll free 1-800-998-8800 for free samples or literature.
Signal-Line Circuit Protectors
MAX366/MAX367
ABSOLUTE MAXIMUM RATINGS
V+ to V-......................................................................-0.3V, +44V
IN_, OUT_ ..................................................(V- + 44V), (V+ - 44V)
Continuous Current into Any Terminal..............................±30mA
Peak Current into Any Terminal
(pulsed at 1ms, 10% duty cycle)...................................±70mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin Plastic DIP (derate 9.09mW/°C above +70°C) ....727mW
8-Pin SO (derate 5.88mW/°C above +70°C).................471mW
8-Pin CERDIP (derate 8.00mW/°C above +70°C).........640mW
18-Pin Plastic DIP (derate 11.11mW/°C above +70°C) ...889mW
18-Pin Wide SO (derate 9.52mW/°C above +70°C) .....762mW
18-Pin CERDIP (derate 10.53mW/°C above +70°C).....842mW
Operating Temperature Ranges
MAX36_C_ _ ........................................................0°C to +70°C
MAX36_E_ _......................................................-40°C to +85°C
MAX36_M_ _ ...................................................-55°C to +125°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10sec) .............................+300°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, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
PARAMETER
Analog Signal Range
Fault-Free Analog Signal Range
Analog-Signal Output
Range (Fault)
SYMBOL
V
IN
, V
OUT
V
IN
, V
OUT
V
OUT
CONDITIONS
(Note 1)
V+ = 15V, V- = -15V (Note 2)
V
IN
= V+ or V-,
100kΩ < R
OUT
< 1000MΩ (Note 1)
V+ = 15V, V- = -15V, V
IN
= ±10V,
I
OUT
= 1mA
Analog-Signal-Path Resistance
R
(IN-OUT)
V+ = 10V, V- = -10V, V
IN
= ±5V,
I
OUT
= 1mA
V+ = 5V, V- = -5V, V
IN
= ±2V,
I
OUT
= 1mA
Signal-Path Resistance Match
Signal-Path Leakage
(Power Off)
Signal-Path Leakage
(without Fault Condition)
Signal-Path Leakage
(with Fault Condition)
Signal-Path Leakage
(with Overvoltage)
POWER SUPPLY
Power-Supply Range
Power-Supply Range
(without Fault Condition)
Power-Supply Current
V+, V-
V+, V-
I+, I-
R
(IN-OUT)
< 1000Ω (Note 2)
+25°C,
C, E, M
+25°C,
C, E, M
+25°C
C, E, M
0
±2.25
-1
-10
±18
±18
1
10
V
V
µA
∆R
(IN-OUT)
I
IN(OFF)
I
OUT(ON)
I
IN(ON)
I
IN(OFF)
V
IN
= ±10V, I
OUT
= 1mA
V+ = V- = 0V, V
IN
= ±35V,
V
OUT
= open circuit
V
IN
= V
OUT
= ±10V
V
IN
= ±25V, V
OUT
= open circuit
V+ = V- = 0V, V
OUT
= 0V,
V
IN
= ±35V
TEMP.
RANGE
All
All
All
+25°C
C, E
M
+25°C
C, E
M
+25°C
C, E, M
+25°C
C, E, M
+25°C
C, E, M
+25°C
C, E, M
+25°C
C, E, M
+25°C
C, E, M
140
62
MIN
(V+ - 40)
-11
(V- + 3)
62
TYP
MAX
(V- + 40)
11
(V+ - 1.5)
85
100
125
100
125
150
350
400
7
10
10
1000
1
100
10
1000
10
1000
Ω
UNITS
V
V
V
Ω
nA
nA
nA
nA
-10
-1000
-1
-100
-10
-1000
-10
-1000
Note 1:
Guaranteed, but not tested.
Note 2:
See
Typical Operating Characteristics
curves for fault-free analog signal range at various supply voltages.
2
_______________________________________________________________________________________
Signal-Line Circuit Protectors
__________________________________________Typical Operating Characteristics
(V+ = +15V, V- = -15V, T
A
= +25°C, unless otherwise noted.)
MAX366/MAX367
TRANSFER CHARACTERISTICS
(BIPOLAR SUPPLIES)
MAX366/7-02
TRANSFER CHARACTERISTICS
(SINGLE SUPPLY)
OUTPUT VOLTAGE (V),
INPUT & OUTPUT CURRENT (µA)
OUTPUT LOAD = 1MΩ
V- = 0V
20
V+ = 25V
MAX366/7-03
15
OUTPUT VOLTAGE (V),
INPUT & OUTPUT CURRENT (µA)
10
5
0
-5
V+ = +15V, V- = -15V
V+ = +10V, V- = -10V
V+ = +3V,
V- = -3V
25
15
V+ = 15V
10
V+ = 10V
5
V+ = 5V
0
V+ = +5V,
V- = -5V
V+ = +10V, V- = -10V
OUTPUT
LOAD = 1MΩ
-35
-25
-15
V+ = +15V, V- = -15V
-5 0 5
15
25
35
-10
-15
0
5
10
15
20
25
30
35
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
V
IN
> (V+ - 35V)
PATH RESISTANCE vs. INPUT VOLTAGE
(BIPOLAR SUPPLIES)
MAX366/7-04
PATH RESISTANCE vs. INPUT VOLTAGE
(BIPOLAR SUPPLIES)
V± = ±3V
V± = ±15V
450
PATH RESISTANCE (Ω)
400
350
300
250
200
150
100
50
V± = ±5V
V± = ±10V
MAX366/7-05
1E+08
1E+07
PATH RESISTANCE (Ω)
1E+06
V± = ±10V
1E+05
1E+04
1E+03
1E+02
1E+01
Circuit of Fig. 6
-15
-10
-5
V± = ±15V
500
V± = ±3V
V± = ±5V
0
0
5
10
15
Circuit of Fig. 6
-15
-10
-5
0
5
10
15
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
_______________________________________________________________________________________
3
Signal-Line Circuit Protectors
MAX366/MAX367
____________________________Typical Operating Characteristics (continued)
(V+ = +15V, V- = -15V, T
A
= +25°C, unless otherwise noted.)
PATH RESISTANCE vs. INPUT VOLTAGE
(SINGLE SUPPLY)
100M
PATH RESISTANCE (Ω)
10M
1M
100k
10k
1k
100
V+ = 5V
10 Circuit of Fig. 6
1
V+ = 15V
V+ = 10V
V+ = 35V
V+ = 25V
MAX366/7-06
PATH RESISTANCE vs. INPUT VOLTAGE
(SINGLE SUPPLY)
450
PATH RESISTANCE (Ω)
400
350
300
250
200
150
100
V+ = 5V
V+ = 35V
V+ = 25V
V+ = 10V
V+ = 15V
MAX366/7-07
1G
500
V- = 0V
10
100
50
0
Circuit of Fig. 6
1
10
INPUT VOLTAGE (V)
V- = 0V
100
INPUT VOLTAGE (V)
OVERVOLTAGE RAMP
0
-2
-4
LOSS (dB)
-6
-8
-10
-12
V+ = 5V, V- = -5V
CHAN 1: INPUT OVERVOLTAGE RAMP ±7V, 2V/div
CHAN 2: OUTPUT; OUTPUT LOAD = 1000Ω, 2V/div
10
MAX366 FREQUENCY RESPONSE
MAX366-TOC9
SOURCE = 50Ω
LOAD = 50Ω
V+ = 5V
V- = -5V
100
1k
10k 100k 1M
10M 100M
FREQUENCY (Hz)
4
_______________________________________________________________________________________
Signal-Line Circuit Protectors
______________________________________________________________Pin Description
PIN
NAME*
MAX366
1, 2, 3
–
4
–
5, 6, 7
8
MAX367
1, 2, 3
4–8
9
10–14
15, 16, 17
18
IN1, IN2, IN3
IN4–IN8
V-
OUT8–OUT4
OUT3, OUT2,
OUT1
V+
Signal Inputs 1, 2, 3
Signal Inputs 4–8
Negative Supply Voltage Input
Signal Outputs 4–8
Signal Outputs 1, 2, 3
Positive Supply Voltage Input
FUNCTION
MAX366/MAX367
* Inputs and outputs are names for convenience only; inputs and outputs are identical and interchangeable.
___________Background Information
When a voltage outside the supply range is applied to
most integrated circuits, there is a strong possibility they
will be damaged or “latch up” (that is, fail to operate prop-
erly even after the offending voltage is removed). If an
IC’s input or output pin is supplied with a voltage when the
IC’s power is off, and power is subsequently applied, the
device may act as an SCR and destroy itself and/or other
circuitry. Such “faults” are commonly encountered in
modular control systems where power and signals to inter-
connected modules may be interrupted and re-estab-
lished at random. They can happen during production
testing, maintenance, start-up, or a power “brownout.”
The MAX366/MAX367 are designed to protect delicate
input and output circuitry from overvoltage faults up to
±40V (with or without power applied), in devices such as
op amps, analog-to-digital/digital-to-analog converters,
and voltage references. These circuit protectors automati-
cally limit signal voltages and currents to safe levels with-
out degrading normal signal performance, even in very
high-impedance circuits. They are powered by the power
supply of the protected circuit and inserted into the signal
lines. There are no control lines, programming pins, or
adjustments.
Unlike shunt diode networks, these devices are low-
impedance FETs that become high impedance during a
fault condition, so fault current and power dissipation are
extremely low. Equally important, leakage current during
normal and fault conditions is extremely low. In addition,
unlike most discrete networks, these parts protect circuits
both when power is off and during power transitions.
_______________Detailed Description
Internal Construction
Figure 1 shows the simplified internal construction of
each protector inside the MAX366/MAX367. Each circuit
consists of two N-channel FETs and one P-channel FET.
All the FETs are enhancement types; that is, the N chan-
nels must have approximately 1.3V of positive gate volt-
age in order to conduct, and the P channel must have
approximately 2V of negative gate voltage in order to
conduct.
During normal operation, V+ is connected to a positive
potential and V- is connected to a negative potential.
Since their gates are tied to V+, transistors Q1 and Q3
conduct as long as their sources are at least 1.3V below
V+ (the N-channel gate threshold.) Transistor Q2’s gate
is tied to V-, so it conducts as long as its source is 2V or
more above V- (the P-channel gate threshold.)
V-
P
IN
Q2
N
Q1
V+
Q3
N
OUT
Figure 1. Simplified Internal Structure
_______________________________________________________________________________________
5
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