MAX366C/D [MAXIM]
Signal-Line Circuit Protectors; 信号线电路保护器
| 型号： | MAX366C/D |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Signal-Line Circuit Protectors |
| 文件： | 总12页 (文件大小：104K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-0326; Rev 0; 12/94
S ig n a l-Lin e Circ u it P ro t e c t o rs
/MAX367
_______________Ge n e ra l De s c rip t io n
____________________________Fe a t u re s
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.
♦ ±40V Overvoltage Protection
♦ Open Signal Paths with Power Off
100Ω Signal Paths with Power On
♦ 1nA Max Path Leakage at +25°C
♦ 44V Maximum Supply Voltage Rating
♦ Automatic Protection; No Programming or
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.
Controls
______________Ord e rin g In fo rm a t io n
†
PART
TEMP. RANGE
0°C to +70°C
PIN-PACKAGE
8 Plastic DIP
8 SO
MAX366CPA
MAX366CSA
MAX366C/D
MAX366EPA
MAX366ESA
MAX366MJA
MAX367CPN
MAX367CWN
MAX367C/D
MAX367EPN
MAX367EWN
MAX367MJN
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.
0°C to +70°C
0°C to +70°C
Dice*
-40°C to +85°C
-40°C to +85°C
-55°C to +125°C
0°C to +70°C
8 Plastic DIP
8 SO
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.
8 CERDIP**
18 Plastic DIP
18 Wide SO
Dice*
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
18 Plastic DIP
18 Wide SO
18 CERDIP**
†
________________________Ap p lic a t io n s
MAX367 available after January 1, 1995.
* Dice are tested at T = +25°C only.
A
* Contact factory for availability.
Process Control Systems
Hot-Insertion Boards/Systems ATE Equipment
Data-Acquisition Systems Sensitive Instruments
Redundant/Backup Systems
Pin Configurations appear at end of data sheet.
___________________________________________________Typ ic a l Op e ra t in g Circ u it
ELECTRONICS
PROTECTOR
FAULT!
REMOTE SENSOR
8
MAX366
+28V
+12V
V+
+10V REG.
1
IN1
OUT1
7
6
5
(SHORT)
SENSITIVE
AMPLIFIER
2
IN2
IN3
V-
OUT2
OUT3
3
4
(OPEN)
FAULT!
________________________________________________________________ Maxim Integrated Products
1
Ca ll t o ll fre e 1 -8 0 0 -9 9 8 -8 8 0 0 fo r fre e s a m p le s o r lit e ra t u re .
S ig n a l-Lin e Circ u it P ro t e c t o rs
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
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
(pulsed at 1ms, 10% duty cycle)...................................±70mA
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
Continuous Power Dissipation (T = +70°C)
A
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
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 = T
A
to T , unless otherwise noted.)
MAX
MIN
TEMP.
RANGE
PARAMETER
SYMBOL
, V
CONDITIONS
MIN
TYP
MAX
UNITS
/MAX367
Analog Signal Range
V
(Note 1)
V+ = 15V, V- = -15V (Note 2)
V = V+ or V-,
IN
All
All
(V+ - 40)
-11
(V- + 40)
11
V
V
IN OUT
Fault-Free Analog Signal Range
V , V
IN OUT
Analog-Signal Output
Range (Fault)
V
OUT
All
(V- + 3)
(V+ - 1.5)
V
100kΩ < R
< 1000MΩ (Note 1)
OUT
+25°C
C, E
62
62
85
100
125
100
125
150
350
400
7
V+ = 15V, V- = -15V, V = ±10V,
IN
I
= 1mA
OUT
M
+25°C
C, E
Analog-Signal-Path Resistance
Signal-Path Resistance Match
R
Ω
(IN-OUT)
V+ = 10V, V- = -10V, V = ±5V,
IN
I
= 1mA
OUT
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
V+ = 5V, V- = -5V, V = ±2V,
IN
I
= 1mA
OUT
∆R
V
IN
= ±10V, I = 1mA
OUT
Ω
(IN-OUT)
10
-10
-1000
-1
10
Signal-Path Leakage
(Power Off)
V+ = V- = 0V, V = ±35V,
IN
I
nA
nA
nA
nA
IN(OFF)
V
OUT
= open circuit
1000
1
Signal-Path Leakage
(without Fault Condition)
I
V
IN
= V
= ±10V
OUT(ON)
OUT
-100
-10
100
10
Signal-Path Leakage
(with Fault Condition)
I
V
IN
= ±25V, V
= open circuit
IN(ON)
OUT
-1000
-10
1000
10
Signal-Path Leakage
(with Overvoltage)
V+ = V- = 0V, V
= 0V,
OUT
I
IN(OFF)
V
IN
= ±35V
-1000
1000
POWER SUPPLY
+25°C,
C, E, M
Power-Supply Range
V+, V-
V+, V-
I+, I-
0
±18
±18
V
V
Power-Supply Range
(without Fault Condition)
+25°C,
C, E, M
R
< 1000Ω (Note 2)
±2.25
(IN-OUT)
+25°C
-1
1
Power-Supply Current
µA
C, E, M
-10
10
Note 1: Guaranteed, but not tested.
Note 2: See Typical Operating Characteristics curves for fault-free analog signal range at various supply voltages.
2
_______________________________________________________________________________________
S ig n a l-Lin e Circ u it P ro t e c t o rs
/MAX367
__________________________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s
(V+ = +15V, V- = -15V, T = +25°C, unless otherwise noted.)
A
TRANSFER CHARACTERISTICS
(BIPOLAR SUPPLIES)
TRANSFER CHARACTERISTICS
(SINGLE SUPPLY)
15
25
20
15
V+ = +15V, V- = -15V
OUTPUT LOAD = 1MΩ
V+ = +10V, V- = -10V
10
V+ = 25V
V- = 0V
V+ = +3V,
V- = -3V
5
V+ = 15V
V+ = 10V
0
10
5
V+ = +5V,
-5
V- = -5V
-10
-15
V+ = +10V, V- = -10V
V+ = +15V, V- = -15V
OUTPUT
V+ = 5V
30
LOAD = 1MΩ
0
-35 -25 -15
-5
0
5
15
25
35
0
5
10
INPUT VOLTAGE (V)
> (V+ - 35V)
15 20
25
35
INPUT VOLTAGE (V)
V
IN
PATH RESISTANCE vs. INPUT VOLTAGE
(BIPOLAR SUPPLIES)
PATH RESISTANCE vs. INPUT VOLTAGE
(BIPOLAR SUPPLIES)
500
1E+08
1E+07
1E+06
1E+05
1E+04
1E+03
1E+02
1E+01
V± = ±3V
V± = ±3V
450
400
350
300
250
V± = ±15V
V± = ±15V
V± = ±10V
V± = ±10V
200
150
V± = ±5V
V± = ±5V
100
50
0
Circuit of Fig. 6
Circuit of Fig. 6
-15
-10
-5
0
5
10
15
-15
-10
-5
0
5
10
15
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
_______________________________________________________________________________________
3
S ig n a l-Lin e Circ u it P ro t e c t o rs
____________________________Typ ic a l Op e ra t in g Ch a ra c t e ris t ic s (c o n t in u e d )
(V+ = +15V, V- = -15V, T = +25°C, unless otherwise noted.)
A
PATH RESISTANCE vs. INPUT VOLTAGE
(SINGLE SUPPLY)
PATH RESISTANCE vs. INPUT VOLTAGE
(SINGLE SUPPLY)
500
450
400
350
300
250
1G
V+ = 25V
V+ = 10V
V+ = 15V
100M
10M
V+ = 10V
1M
V+ = 25V
V+ = 35V
100k
V+ = 5V
V+ = 15V
10k
200
150
V+ = 35V
/MAX367
1k
100
50
0
100
V+ = 5V
Circuit of Fig. 6
V- = 0V
V- = 0V
100
Circuit of Fig. 6
10
1
10
INPUT VOLTAGE (V)
1
10
100
INPUT VOLTAGE (V)
OVERVOLTAGE RAMP
MAX366 FREQUENCY RESPONSE
0
-2
-4
-6
SOURCE = 50Ω
LOAD = 50Ω
V+ = 5V
V- = -5V
-8
-10
-12
100
10
1k 10k 100k 1M 10M 100M
FREQUENCY (Hz)
V+ = 5V, V- = -5V
CHAN 1: INPUT OVERVOLTAGE RAMP ±7V, 2V/div
CHAN 2: OUTPUT; OUTPUT LOAD = 1000Ω, 2V/div
4
_______________________________________________________________________________________
S ig n a l-Lin e Circ u it P ro t e c t o rs
/MAX367
______________________________________________________________P in De s c rip t io n
PIN
NAME*
FUNCTION
MAX366
MAX367
1, 2, 3
4–8
1, 2, 3
IN1, IN2, IN3
IN4–IN8
Signal Inputs 1, 2, 3
–
4
–
Signal Inputs 4–8
9
V-
Negative Supply Voltage Input
Signal Outputs 4–8
10–14
OUT8–OUT4
OUT3, OUT2,
OUT1
5, 6, 7
8
15, 16, 17
18
Signal Outputs 1, 2, 3
V+
Positive Supply Voltage Input
* Inputs and outputs are names for convenience only; inputs and outputs are identical and interchangeable.
___________Ba c k g ro u n d In fo rm a t io n
_______________De t a ile d De s c rip t io n
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.”
In t e rn a l Co n s t ru c t io n
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.)
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.
V-
P
IN
OUT
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.
Q2
N
N
Q1
Q3
V+
Figure 1. Simplified Internal Structure
_______________________________________________________________________________________
5
S ig n a l-Lin e Circ u it P ro t e c t o rs
As long as the signal is within these limits, all three tran-
Power Off
sistors conduct and a low-resistance path is maintained
from the IN to OUT pin. (Note that, since the device is
symmetrical, IN and OUT pins can be interchanged.)
When the signal is beyond the gate threshold of either
Q2 or Q1/Q3, the path resistance rises dramatically.
When power is off, none of the transistors have gate
bias, so the circuit from IN to OUT is open.
When power is off (i.e., V+ = V- = 0V), the protector is a
virtual open circuit, and all voltages on each side are
isolated from each other up to ±40V. With ±40V applied
to the input pin, the output pin will be 0V, regardless of
its resistance to ground.
Fault Conditions
A fault condition exists when the voltage on either sig-
na l p in is within a b out 1.5V of e ithe r s up p ly ra il or
exceeds either supply rail. This definition is valid when
power is applied and when it is off, as well as during all
the states as power ramps up or down.
No rm a l Op e ra t io n
In normal operation, the protector is placed in series
with the signal line and the power supplies are con-
nected to V+ and V- (see Figure 2). V- is ground when
operating with a single supply. When power is applied,
each protector acts as a resistor in the signal path.
Any voltage source on the “input” side of the switch will
be conducted through the protector to the output. (Note
that, since the protector is symmetrical, IN and OUT
pins can be interchanged.)
During a fault, the protector acts as a variable resistor,
conducting only enough to sustain the other side of the
switch within about 1.5V of the supply rail. This voltage
is known as the “fault knee voltage,” and is not symmet-
rical. It is approximately 1.3V down from the positive
supply (V+ pin) or approximately 2.0V up from the neg-
ative supply (V- pin). Each fault knee voltage varies
slightly with supply voltage, with output current, and
from device to device.
/MAX367
If the output load is resistive, it will draw current, and a
voltage divider will be formed with the internal resistance
so the output voltage will be lower than the input voltage.
Since the internal resistance is typically less than 100Ω,
high-impedance loads will be relatively unaffected by the
presence of the protector. The protector’s path resis-
tance is a function of the supply voltage and the signal
voltage (see Typical Operating Characteristics).
During a fault condition, all the fault current flows
from one signal pin through the protector and out
the other signal pin. No fault current flows through
either supply pin. (There will be a few pico-amps of
leakage current from each signal pin to each supply
pin, but this is independent of fault current.)
During the fault condition, enough current will flow to
maintain the output voltage at the fault knee voltage, so
the fault current is a function of the output resistance
and the supply voltage. The output voltage and cur-
rent have the same polarity as the fault.
The maximum input fault voltage is 40V from the “oppo-
site-polarity supply rail.” This means the input can go
to ±35V with ±5V supplies or to ±25V with ±15V sup-
plies. The fault voltage is highest (±40V) when the sup-
plies are off (V+ = V- = 0V).
MAX366
4
1
8
7
V-
V-
V+
V+
V
IN
V
OUT
IN1
OUT1
Using the circuit of Figure 2, the approximate fault cur-
rents are as follows:
R
OUT
1) For positive faults:
I
(F)
≈ (V+ - 1.3V - V ) ÷ R
LOW OUT
V
LOW
2) For negative faults:
≈ (V- + 2V + V
I
(F)
) ÷ R
LOW OUT
where V
is the terminating voltage at the far end of
LOW
R
. V
= 0V when R
is grounded.
OUT
LOW
OUT
Figure 2. Application Circuit
6
_______________________________________________________________________________________
S ig n a l-Lin e Circ u it P ro t e c t o rs
/MAX367
The current through each protector should never exceed
30mA. Always calculate the power dissipated by all the
protectors in worst-case conditions (maximum voltage
and current through each protector) to ensure the pack-
age dissipation limit is not reached.
5
4
3
2
1
0
V+ = +5V
V- = -5V
R
OUT
= 100MΩ
With single-supply operation, grounded loads will have
zero voltage (and current) whenever the input voltage is
below approximately 2V. In effect, both the IN and OUT
pins are in fault condition.
-1
-2
-3
-4
A special case arises when power is off: The part is in a
p e rp e tua l fa ult c ond ition b ut no fa ult c urre nt flows
because all the internal FETs are off.
S in g le -S u p p ly Ou t p u t Op e ra t io n
Single-supply operation is a special case. Signals can-
not go to ground, since from 0V to approximately +2V is
a fault condition.
-30
-20
-10
0
10
20
30
INPUT VOLTAGE (V)
Ex t re m e ly Lo w -Cu rre n t Op e ra t io n
Figure 3 shows the typical high-impedance transfer
characteristics with a 100MΩ load. Compared to the
transfer characteristic at 1MΩ (see Typical Operating
Characteristics), the two knees are closer to the supply
voltages and the slopes of the flat portions of the curve
(fault conditions) are steeper. As the load resistance is
increased even further, the positive and negative knees
increase, and the slopes in fault conditions increase
even more. Eventually, at some extremely high output
resistance (e.g., Tera ohms), the output voltage can
exceed the supply voltage during fault conditions. This
is due to extremely low leakage currents from the input
to output.
Figure 3. High-Impedance Transfer Characteristic
reserved for use when ultra-low leakage (pA) is needed.
The MAX366/MAX367 have nano-amperes of leakage,
which would negate the low leakage of the unprotected
amplifier.
Lo w -Vo lt a g e Op e ra t io n
The MAX366/MAX367 “operate” with supply voltages
all the way down to 0V, but what they do to the signal is
not obvious. With a total supply voltage of 3.5V, the
protector is in a fault condition with nearly any input that
is not close to 2.0V. Below 3.5V (including power off),
the protector is perpetually in a fault condition (i.e., high
impedance).
When the protector’s output side is connected to very
high-resistance, very low-current loads (such as op-
amp inputs), a small leakage current flows from the
input to the output during fault conditions. This current
When the supply voltage(s) ramps up (and/or down)
from zero, the signal path is initially in a fault condition
(open), until the supply voltage passes the input volt-
age. The output starts at zero and is delayed from
reaching the input voltage as the part comes out of the
fault condition. If the supply voltage exceeds about
3.5V, but never exceeds the input voltage, the output
will follow the supply, always remaining about 1.3V
below the positive supply voltage or 2V above the neg-
ative supply voltage. If the input voltage subsequently
comes out of the fault condition, the output returns to
the inp ut va lue . This s e t of c ond itions is e xa c tly
reversed when power ramps down to zero.
-9
is typically below a nano-ampere (<10 A) but, if the
output resistance is high enough, it can cause the out-
put voltage to exceed the supply voltages during fault
conditions.
This condition can be self-correcting, however, if the
high-resistance load has protection diodes to the sup-
ply rails (either external or internal to the op amp).
These diodes conduct the leakage current to the supply
rails and safely limit the output voltage. An alternative is
to add a high-value resistor to ground in parallel with
the load. This resistor may be as low as 1000MΩ; its
value must be determined experimentally at the highest
anticipated operational temperature.
Since the input and output pins are identical and inter-
changeable, predicting whether or not the part is in a
fault condition is easy: If either IN or OUT exceeds V+
or V-, a fault condition exists and the current that flows
will be just enough to cause the other signal pin (OUT
or IN) to approach the appropriate supply rail.
The fault protectors will not normally be used with high-
impedance FET-input amplifiers that lack input protection
diodes. Such amplifiers are fragile and are normally
_______________________________________________________________________________________
7
S ig n a l-Lin e Circ u it P ro t e c t o rs
Bip o la r Fa u lt s
The MAX366/MAX367 V+ and V- pins are normally con-
nected to a circuit’s most positive and most negative
power supplies. When a circuit has multiple power
supplies (such as ±5V and ±12V) and the MAX366/
MAX367 V+ and V- pins are connected to the lower
supply, it is possible to have fault conditions on both
sides of the signal path at once, if both sides of the
+5V
8
7
6
5
MAX366
V+
10µF
100k
1
2
IN1
OUT1
switch have paths to higher voltages. If the polarity of
these faults is the same, the signal path will be open
and there is no conflict.
IN2
IN3
V-
OUT2
OUT3
If the IN and OUT pins are driven in opposite polarities
from low-imp e d a nc e s ourc e s , the lowe r of the two
impedances will overcome the higher impedance, just
as if the protector were not present. (Make sure the
current does not exceed the 30mA absolute maximum
rating.) As the lower impedance source approaches
and exceeds the fault knee voltage, the protector will
conduct enough current to maintain the other signal pin
near the fault knee voltage. This means when the fault
knee voltage is reached, the current through the pro-
tector shifts from the higher current capability of the
lower impedance source to the lower current capability
of the higher impedance source.
OP AMP
3
4
/MAX367
100k
10µF
-5V
Figure 4. Turn-On Delay
This circuit can be tailored to nearly any rate of turn-
on by selecting the RC time constants in the V+ and
V- p ins , without a ffe c ting the time c ons ta nt of the
measuring circuit.
_______________Typ ic a l Ap p lic a t io n s
Drive n S w it c h e s
The MAX366/MAX367 ha ve low s up p ly c urre nts
(<1µA), whic h a llows the s up p ly p ins to b e d rive n
directly by other active circuitry, instead of connected
directly to the power sources. In this configuration,
the p a rts c a n b e us e d a s d rive n fa ult-p rote c te d
switches with V+ or V- pins used as the control pins.
For example, if the V- pin is grounded, you can turn
the V+ pin on and off by driving it with the output of a
CMOS gate. This effectively connects and discon-
nects three or eight separate signal lines at once. (If
bipolar signals or signals that go to ground are being
switched, the V- pin must be driven simultaneously to
a negative potential.) Always ensure that the driving
source(s) does not drive the V+ pin more negative
than the V- pin.
P ro t e c t o rs a s Circ u it Ele m e n t s
Any of the individual protectors in a MAX366 or MAX367
may be used as a switched resistor, independent of the
functions of other elements in the same package. For
example, Figure 5 shows a MAX366 with two of the pro-
tectors used to protect the input of an op amp, and the
third e le me nt us e d to s e q ue nc e a p owe r s up p ly.
Combining the circuits of Figures 4 and 5 produces a
delayed action on the switched +5V, as well as smooth
application of signals to the amplifier input.
_________Te s t in g Circ u it P ro t e c t o rs
Me a s u rin g P a t h Re s is t a n c e
Measuring path resistance requires special techniques,
since path resistance varies dramatically with the IN
a nd OUT volta g e s re la tive to the s up p ly volta g e s .
Conventional ohmmeters should not be used, for two
reasons: 1) the applied voltage and currents are usual-
ly not predictable, and 2) the true resistance is a func-
tion of the applied voltage, which is dramatically altered
by the ohmmeter itself. Autoranging ohmmeters are
particularly unreliable.
Fig ure 4 s hows a s imp le turn-on d e la y tha t ta ke s
advantage of the MAX366’s low power consumption.
The two RC networks cause gradual application of
power to the MAX366, which in turn applies the input
s ig na ls s moothly a fte r the a mp lifie r ha s s ta b ilize d .
The two diodes discharge the two capacitors rapidly
when power is turned off.
8
_______________________________________________________________________________________
S ig n a l-Lin e Circ u it P ro t e c t o rs
/MAX367
SWITCHED +5V
P
100mV
+5V
A
8
7
6
5
MAX366
MAX366
V+
100k
V
IN_
V-
OUT_
V+
V
OUT
IN
1
2
IN1
OUT1
IN2
IN3
V-
OUT2
OUT3
V-
4
OP AMP
8
3
4
V+
ADJUSTABLE ANALOG VOLTAGE
PATH RESISTANCE = 100mV/A
-5V
Figure 6. Path-Resistance Measuring Circuit
Figure 5. Power-Supply Sequencing
Figure 6 shows a circuit that can give reliable results.
This circuit uses a 100mV voltage source and a low-
voltage-drop ammeter as the measuring circuit, and an
adjustable supply to sweep the analog voltage across
its whole range. The ammeter must have a voltage
drop of less than one millivolt (at any current) for accu-
rate results. (A Keithley Model 617 Electrometer has a
suitable ammeter circuit, appropriate ranges, and a
built-in voltage source designed for this type of mea-
surement.) Measurements are made by setting the
analog voltage, measuring the current, and calculating
the path resistance. The procedure is repeated at
each analog voltage and supply voltage.
Hig h -Fre q u e n c y P e rfo rm a n c e
In 50Ω systems, signal response is reasonably flat up
to s e ve ra l me g a he rtz (s e e Typ ic a l Op e ra ting
Characteristics). Above 5MHz, the response has sev-
eral minor peaks, which are highly layout dependent.
Because the path resistance is dependent on the sup-
ply voltage and signal amplitude, the impedance is not
controlled. Adjacent channel attenuation up to 5MHz is
about 3dB above that of a bare IC socket, and is due
entirely to capacitive coupling.
Pulse response is reasonable, but because the imped-
ance changes rapidly, fast rise times may induce ringing
as the signal approaches the fault voltage. At very high
amplitudes (such as noise spikes), the capacitive cou-
pling across the signal pins will transfer considerable
energy, despite the fact that the DC path is a virtual open
circuit.
It is important to use a voltage source of 100mV or less.
As shown in Figure 4, this voltage is added to the V
IN
voltage to form the V
voltage. Using a higher volt-
OUT
age could cause the OUT pin to go into a fault condi-
tion prematurely.
_______________________________________________________________________________________
9
S ig n a l-Lin e Circ u it P ro t e c t o rs
__Hig h -Vo lt a g e S u rg e S u p p re s s io n
These devices are not high-voltage arresters, nor are they
substitutes for surge suppressers. In systems that use
these forms of protection, however, the MAX366/MAX367
can fill a vital gap. Figure 7 shows a typical circuit.
Although the surge suppressers are extremely fast shunt
elements, they have very soft current knees. Their clamp
voltage must be chosen well above the normal signal
levels, because they have excessive leakage currents as
the knee is approached. This current can interfere with
normal operation when signal levels are low or imped-
ances are high. If the clamp voltage is too high, however,
the input can be damaged.
+5V
8
7
6
5
MAX366
V+
1
2
IN1
OUT1
IN2
IN3
V-
OUT2
OUT3
OP AMP
3
4
Using a MAX366/MAX367 after the surge suppresser
allows the surge-suppresser voltage to be set above
the supply voltage (but within the overvoltage limits),
dramatically reducing the effects of leakage (Figure 7).
During a surge, the surge suppresser clamps the input
/MAX367
-5V
SURGE SUPPRESSERS
(+10V)
volta g e to roug hly ± 10V.
This p rote c ts the
MAX366/MAX367, but the MAX366/MAX367 still dis-
connect the signal from the op amp well within the ±5V
supply.
Figure 7. Surge-Suppression Circuit
_________________P in Co n fig u ra t io n s
___________________Ch ip To p o g ra p h y
IN1
TOP VIEW
IN1
V+
V+
1
2
3
4
5
6
7
8
9
18
17
16
15
14
13
12
11
10
OUT1
OUT2
OUT3
OUT4
OUT5
OUT6
OUT7
OUT8
IN2
IN3
IN4
IN5
IN1
OUT1
V+
1
2
3
4
8
7
6
5
IN2
OUT1
OUT2
OUT3
IN2
0. 112"
(2. 84mm)
IN3
V-
IN6
IN7
IN8
MAX366
OUT2
IN3
DIP/SO
V-
MAX367
OUT3
V-
DIP/SO
0. 085"
(2. 16mm)
TRANSISTOR COUNT: 21
SUBSTRATE CONNECTED TO V+
10 ______________________________________________________________________________________
S ig n a l-Lin e Circ u it P ro t e c t o rs
/MAX367
________________________________________________________P a c k a g e In fo rm a t io n
INCHES
MILLIMETERS
DIM
E
MIN
MAX
0.200
–
MIN
–
MAX
5.08
–
A
–
E1
D
A1 0.015
A2 0.125
A3 0.055
0.38
3.18
1.40
0.41
1.14
0.20
0.13
7.62
6.10
2.54
7.62
–
0.175
0.080
0.022
0.065
0.012
0.080
0.325
0.310
–
4.45
2.03
0.56
1.65
0.30
2.03
8.26
7.87
–
A3
A2
A1
A
L
B
0.016
B1 0.045
0.008
D1 0.005
0.300
E1 0.240
0.100
eA 0.300
C
0° - 15°
E
C
e
e
B1
eA
eB
–
–
B
eB
L
–
0.400
0.150
10.16
3.81
0.115
2.92
D1
INCHES
MILLIMETERS
DIM
Plastic DIP
PLASTIC
DUAL-IN-LINE
PACKAGE
(0.300 in.)
PINS
MIN
MAX MIN
MAX
8
D
D
D
D
D
D
0.348 0.390 8.84
9.91
14
16
18
20
24
0.735 0.765 18.67 19.43
0.745 0.765 18.92 19.43
0.885 0.915 22.48 23.24
1.015 1.045 25.78 26.54
1.14 1.265 28.96 32.13
INCHES
MILLIMETERS
DIM
MIN
0.053
MAX
0.069
0.010
0.019
0.010
0.157
MIN
1.35
0.10
0.35
0.19
3.80
MAX
1.75
0.25
0.49
0.25
4.00
A
D
A1 0.004
B
C
E
e
0.014
0.007
0.150
0°-8°
A
0.101mm
0.004in.
0.050
1.27
e
H
L
0.228
0.016
0.244
0.050
5.80
0.40
6.20
1.27
A1
C
B
L
INCHES
MILLIMETERS
DIM PINS
SO
MIN MAX
MIN
MAX
5.00
8.75
8
0.189 0.197 4.80
D
D
D
SMALL OUTLINE
PACKAGE
E
H
14 0.337 0.344 8.55
16 0.386 0.394 9.80 10.00
(0.150 in.)
21-0041A
______________________________________________________________________________________ 11
S ig n a l-Lin e Circ u it P ro t e c t o rs
___________________________________________P a c k a g e In fo rm a t io n (c o n t in u e d )
INCHES
MILLIMETERS
DIM
MIN
0.093
MAX
0.104
0.012
0.019
0.013
0.299
MIN
2.35
0.10
0.35
0.23
7.40
MAX
2.65
0.30
0.49
0.32
7.60
D
A
A1 0.004
0°- 8°
B
C
E
e
0.014
0.009
0.291
A
0.101mm
0.004in.
1.27
0.050
e
B
A1
H
L
0.394
0.016
0.419
0.050
10.00
0.40
10.65
1.27
C
L
/MAX367
INCHES
MILLIMETERS
MAX
PINS
DIM
MIN MAX MIN
E
H
Wide SO
SMALL OUTLINE
PACKAGE
0.398 0.413 10.10 10.50
0.447 0.463 11.35 11.75
0.496 0.512 12.60 13.00
0.598 0.614 15.20 15.60
0.697 0.713 17.70 18.10
21-0042A
D
D
D
D
D
16
18
20
24
28
(0.300 in.)
INCHES
MIN
MILLIMETERS
DIM
MAX
0.200
0.023
0.065
0.015
0.310
0.320
MIN
–
MAX
5.08
0.58
1.65
0.38
7.87
8.13
E1
E
A
B
–
0.014
0.36
0.97
0.20
5.59
7.37
D
B1 0.038
A
C
E
0.008
0.220
E1 0.290
e
L
0.100
2.54
0.125
0.150
0.015
–
0.200
–
3.18
3.81
0.38
–
5.08
–
0°-15°
C
Q
L1
Q
S
L
L1
0.070
0.098
–
1.78
2.49
–
e
B1
S1 0.005
0.13
B
S1
S
INCHES
MILLIMETERS
DIM PINS
MIN
–
MAX MIN MAX
CERDIP
D
D
D
D
D
D
8
0.405
0.785
0.840
0.960
1.060
1.280
–
–
–
–
–
–
10.29
19.94
21.34
24.38
26.92
32.51
CERAMIC DUAL-IN-LINE
PACKAGE
14
16
18
20
24
–
–
–
(0.300 in.)
–
–
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 __________________Ma x im In t e g ra t e d P ro d u c t s , 1 2 0 S a n Ga b rie l Drive , S u n n yva le , CA 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0
© 1994 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
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