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19-1514; Rev 0; 7/99
Fault-Protected, High-Voltage, Signal-Line Protector
General Description
The MAX4505 is a single signal-line protector featuring a fault-protected input and Rail-to-Rail(R) signal handling capability. The input is protected from overvoltage faults up to 36V with power on or 40V with power off. During a fault condition, the input terminal becomes an open circuit and only nanoamperes of leakage current flow from the source, while the switch output (AOUT) furnishes typically 19mA from the appropriate polarity supply to the load. This ensures an unambiguous rail-to-rail output when a fault begins and ends. The MAX4505 protects both unipolar and bipolar analog signals using either unipolar (+9V to +36V) or bipolar (8V to 18V) power supplies. The device has no logic control inputs; the protector is always on when the supplies are on. On-resistance is 100 max, and on-leakage is less than 0.5nA at TA = +25C. The MAX4505 is available in 5-pin SOT23 and 8-pin MAX packages.
Features
o Overvoltage Protection 40V with Power Off 36V with Power On o Open Signal Paths with Power Off o Output Clamps to Either Rail with an Input Overvoltage o 100 max On-Resistance o 10ns Overvoltage Turn-On Delay o No Latchup During Power Sequencing o Rail-to-Rail Signal Handling o 500 Output Clamp Resistance During Overvoltage o Tiny 5-Pin SOT23 Package
MAX4505
Applications
Process Control Systems Hot-Insertion Boards/Systems Data-Acquisition Systems Redundant/Backup Systems ATE Equipment Sensitive Instruments
PART MAX4505EUK-T MAX4505EUA
Ordering Information
TEMP. RANGE -40C to +85C -40C to +85C PINPACKAGE 5 SOT23-5 8 MAX TOP MARK ADLW --
Typical Operating Circuit
TOP VIEW
VV-
Pin Configurations
MAX4505
VV+
V+
V+ AIN 1 5 V-
V+ 2 RAIL SENSOR AOUT 3 IN AIN AOUT OUT
ROUT
MAX4505
4
N.C.
SOT23-5
Pin Configurations continued at end of data sheet. Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
________________________________________________________________ Maxim Integrated Products 1
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Fault-Protected, High-Voltage, Signal-Line Protector MAX4505
ABSOLUTE MAXIMUM RATINGS
(Voltages referenced to GND) V+ ........................................................................-0.3V to +44.0V V- .........................................................................-44.0V to +0.3V V+ to V-................................................................-0.3V to +44.0V AIN, AOUT (Notes 1, 2) .......................................................44V AIN Overvoltage with Power On ..........................................36V AIN Overvoltage with Power Off ..........................................40V Continuous Current into Any Terminal..............................30mA Peak Current into Any Terminal (pulsed at 1ms, 10% duty cycle)...............................70mA Continuous Power Dissipation (TA = +70C) 5-Pin SOT23-5 (derate 7.10mW/C above +70C) ...571mW 8-Pin MAX (derate 4.10mW/C above +70C) ........330mW Operating Temperature Ranges MAX4505C_ _ ..................................................0C to +70C MAX4505E_ _ ...............................................-40C to +85C Storage Temperature Range .............................-55C to +150C Lead Temperature (soldering, 10sec) .............................+300C
Note 1: The AOUT pin is not fault protected. Signals on AOUT exceeding V+ or V- are clamped by internal diodes. Limit forward diode current to maximum current rating. Note 2: The AIN pin is fault protected. Signals on AIN exceeding -36V to +36V may damage the device. These limits apply with power applied to V+ or V-, or 40V with V+ = V- = 0.
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.
RECOMMENDED OPERATING GUIDELINES
V+ to GND ..............................................................-0.3V to +40V V- to GND ...............................................................-32V to +0.3V V+ to V- ..................................................................................40V AIN .......................................................................................40V AOUT...............................................................................V+ to VAIN to AOUT.........................................................40V differential Continuous Current into Any Terminal ..............................30mA Peak Current into Any Terminal (pulsed at 1ms, 10% duty cycle) ...............................70mA
ELECTRICAL CHARACTERISTICS--Dual Supplies
(V+ = +15V, V- = -15V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 3) PARAMETER ANALOG SWITCH Fault-Free Analog Signal Range (Note 4) Analog Signal-Path Resistance Signal-Path Leakage Current (Note 5) Input Capacitance FAULT PROTECTION Fault-Protected Analog Signal Range (Notes 4, 6) Input Signal-Path Leakage Current, Supplies On Input Signal-Path Leakage Current, Supplies Off Output Clamp Current, Supplies On Output Clamp Resistance, Supplies On Fault Output Turn-On Delay Time 2 VAIN IAIN(ON) IAIN(OFF) IAOUT RAOUT Applies with power on Applies with power off VAIN = 25V, VAOUT = open VAIN = 40V, VAOUT = open V+ = 0, V- = 0 VAIN = 25V VAIN = -25V IAOUT = 1mA VAIN = 25V VAIN = -25V E E +25C E +25C E +25C +25C +25C +25C +25C -36 -40 -20 -200 -20 -500 13 -26 19 -19 0.5 0.4 10 0.2 0.1 36 40 20 200 20 500 26 -13 1.0 1.0 V nA nA mA k ns VAIN RON IAOUT(ON) CAIN VAIN = 15V VAIN = 10V, IAOUT = 1mA VAOUT = 10V, VAIN = 10V or floating VAIN = 0, f = 1MHz E +25C E +25C E +25C -0.5 -20 20 V65 V+ 100 125 0.5 20 V nA pF SYMBOL CONDITIONS TA MIN TYP MAX UNITS
RL = 10k, VAIN = 25V
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Fault-Protected, High-Voltage, Signal-Line Protector
ELECTRICAL CHARACTERISTICS--Dual Supplies (continued)
(V+ = +15V, V- = -15V, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 3) PARAMETER Fault Recovery Time POWER SUPPLY Power-Supply Range V+, VI+ Power-Supply Current IVAIN = 15V VAIN = 15V E +25C E +25C E -150 -240 -45 8 45 18 150 240 A V SYMBOL CONDITIONS RL = 10k, VAIN = 25V TA +25C MIN TYP 25 MAX UNITS s
MAX4505
ELECTRICAL CHARACTERISTICS--Single Supply
(V+ = +12V, V- = 0, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 3) PARAMETER ANALOG SWITCH Fault-Free Analog Signal Range (Note 4) Analog Signal-Path Resistance Signal-Path Leakage Current (Note 5) FAULT PROTECTION Fault-Protected Analog Signal Range (Notes 4, 6) Input Signal-Path Leakage Current, Supply On (Note 7) Input Signal-Path Leakage Current, Supply Off (Note 7) Output Clamp Current, Supply On Output Clamp Resistance, Supply On Fault Output Turn-On Delay Time Fault Recovery Time POWER SUPPLY Power-Supply Range Power-Supply Current Note 3: Note 4: Note 5: Note 6: Note 7: Note 8: V+, VI+ VAIN = 12V E +25C E +9 5 +36 25 40 V A VAIN IAIN(ON) IAIN(OFF) IAOUT RAOUT Applies with power on Applies with power off VAIN = 25V, VAOUT = 0 VAIN = 40V VAIN = 25V VAIN = 25V RL = 10k, VAIN = 25V RL = 10k, VAIN = 25V E E +25C E +25C E +25C +25C +25C +25C -36 -40 -20 -200 -20 -500 3 5.5 1.0 10 2.5 0.2 0.2 36 40 20 200 20 500 10 2.5 V nA nA mA k ns s VAIN RON IAOUT(ON) VAIN = 12V VAIN = 10V, IAOUT = 1mA VAIN = 10V or floating E +25C E +25C E -0.5 -20 0.05 0 125 V+ 200 250 0.5 20 V nA SYMBOL CONDITIONS TA MIN TYP MAX UNITS
The algebraic convention is used in this data sheet; the most negative value is shown in the minimum column. See Fault-Free Analog Signal Range vs. Supply Voltage graph in the Typical Operating Characteristics. Leakage parameters are 100% tested at maximum rated hot temperature and guaranteed by correlation at TA = +25C. Guaranteed by design. Guaranteed by testing with dual supplies. SOT packaged parts are 100% tested at +25C. Limits at the maximum rated temperature are guaranteed by design and correlation limits at +25C. Leakage tests are typical for SOT packaged parts. _______________________________________________________________________________________ 3
Fault-Protected, High-Voltage, Signal-Line Protector MAX4505
Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
ON-RESISTANCE vs. OUTPUT VOLTAGE (DUAL SUPPLIES)
MAX4505 toc01
ON-RESISTANCE vs. OUTPUT VOLTAGE (SINGLE SUPPLY)
V- = 0 V+ = +9V 200 V+ = +12V
MAX4505 toc02
ON-RESISTANCE vs. OUTPUT VOLTAGE AND TEMPERATURE (DUAL SUPPLIES)
MAX4505 toc03
140 120 100 RON () 80 60 40 20 0 -20 -15 -10 -5 0 VOUT_ (V) 5 10 15 V+ = +18V V- = -18V V+ = +10V V- = -10V V+ = +15V V- = -15V V+ = +8V V- = -8V
250
120 100 80 RON () 60 TA = +25C 40 20 TA = -40C
TA = +125C TA = +85C TA = +70C
RON ()
150 V+ = +20V V+ = +30V 50 V+ = +36V
100
TA = -55C V+ = +15V V- = -15V -15 -10 -5 0 VOUT_ (V) 5 10 15
20
0 0 5 10 15 20 25 30 35 VOUT_ (V)
0
ON-RESISTANCE vs. OUTPUT VOLTAGE AND TEMPERATURE (SINGLE SUPPLY)
MAX4505 toc04
OUTPUT CLAMP RESISTANCE (SUPPLIES ON) vs. TEMPERATURE
MAX4505 toc05
OUTPUT CLAMP CURRENT (SUPPLIES ON) vs. TEMPERATURE
20 15 10 IOUT (mA) 5 0 -5 -10 -15 V- = -15V V+ = +15V
MAX4505 toc06
250
V+ = +12V V- = 0 TA = +125C TA = +85C
0.7 0.6 0.5 ROUT (k) 0.4 0.3 0.2 0.1 VIN = -25V V+ = +15V V- = -15V VIN = 2.5V VIN = +25V
25
200
RON ()
150
TA = +70C 100 TA = -40C TA = +25C TA = -55C 50
-20 -25 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 TEMPERATURE (C) -55 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
0
0 0 2 4 6 VOUT_ (V) 8 10 12
OUTPUT TRANSFER CHARACTERISTICS (DUAL SUPPLIES)
MAX4505 toc07
OUTPUT TRANSFER CHARACTERISTICS (SINGLE SUPPLY)
35 OUTPUT CLAMP VOLTAGE (V) 30 25 20 15 10 5 0 0 5 V+ = +9V INPUT VOLTAGE LINEARLY SWEPT BETWEEN 0 AND 36V 10 15 20 25 30 35 40 INPUT VOLTAGE (V) -15 -20 V+ = +15V V+ = +12V V+ = +25V OUTPUT LOAD = 1M V- = 0 V+ = +36V
MAX4505 toc08
FAULT-FREE ANALOG SIGNAL RANGE vs. SUPPLY VOLTAGE
15 OUTPUT VOLTAGE (V) 10 5 0 -5 -10
MAX4505 toc09
20 15 OUTPUT CLAMP VOLTAGE (V) 10 5 0 -5 -10 -15 -20 -30 -20
(V+ = +18V, V- = -18V) (V+ = +15V, V- = -15V) (V+ = +10V, V- = -10V) (V+ = +8V, V- = -8V) INPUT VOLTAGE LINEARLY SWEPT BETWEEN -30V AND +30V
40
20
(V+ = +8V, V- = -8V) (V+ = +10V, V- = -10V)
(V+ = +15V, V- = -15V) (V+ = +18V, V- = -18V) OUTPUT LOAD = 1M -10 0 10 20 30 INPUT VOLTAGE (V)
-20
-15
-10
-5
0
5
10
15
20
INPUT VOLTAGE (V)
4
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Fault-Protected, High-Voltage, Signal-Line Protector
Typical Operating Characteristics (continued)
(TA = +25C, unless otherwise noted.)
FAULT-FREE OUTPUT LEAKAGE CURRENT (SUPPLIES ON)
MAX4505 toc10
MAX4505
INPUT FAULT LEAKAGE CURRENT (SUPPLIES ON)
MAX4505 toc11
POWER SUPPLY CURRENT vs. TEMPERATURE
60 SUPPLY CURRENT (A) 40 20 0 -20 -40 -60 -80 II+ SINGLE SUPPLY +12V V+ = +15V V- = -15V
MAX4505 toc12
100n 10n LEAKAGE CURRENT (A) 1n 100p 10p 1p 0.1p 0.01p -55
VOUT = 10V IOUT (V+ = +15V, V- = -15V)
1 100n LEAKAGE CURRENT (A) 10n 1n IIN AT +25V (V+ = +15V, V- = -15V)
80 I+
IOUT (V+ = +12V, V- = 0)
100p 10p 1p 0.1p IIN AT +25V (V+ = +12V, V - = 0)
-30
-5
20
45
70
95
120 145
-55 -35 -15
5
25
45
65
85 105 125
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80 TEMPERATURE (C)
TEMPERATURE (C)
TEMPERATURE (C)
SUPPLY CURRENT vs. INPUT VOLTAGE
MAX4505 toc13
FREQUENCY RESPONSE
MAX4505 toc15
FAULT-FREE SIGNAL PERFORMANCE
MAX4505 toc16
60 I+ 40 SUPPLY CURRENT (A) 20 0 -20 -40 I-60 -15 -10 -5 0 5 10
10 0 -10 -20 BANDWIDTH (dB) -30 -40 -50 -60 -70 -80 -90 -100 0.01 V+ = +15V V- = -15V 0.1 1 10 100
+15V IN_ 10V/div -15V +15V OUT_ 0 10V/div -15V
15
1000
5s/div FAULT-FREE RAIL-TO-RAIL SIGNAL HANDLING WITH 15V SUPPLIES
INPUT VOLTAGE (V)
FREQUENCY (MHz)
INPUT OVERVOLTAGE vs. OUTPUT CLAMPING
MAX4505 toc17
FAULT RECOVERY
MAX4505 toc18
+25V +16V IN_ 0 +15V -25V 0 OUT_ 0 -15V 5s/div 25V OVERVOLTAGE INPUT WITH THE OUTPUT CLAMPED AT 15V 0 OUT_ 5V/div 0 V+ = +15V V- = -15V +15V IN_ 5V/div
5s/div
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5
Fault-Protected, High-Voltage, Signal-Line Protector MAX4505
Pin Description
PIN SOT 1 2 3 4 5 MAX 3 8 1 2, 5, 6, 7 4 NAME AIN V+ AOUT N.C. VAnalog Fault-Protected Input Positive Supply Voltage Input Analog Signal Output No Connection. Not internally connected. Negative Supply Voltage Input FUNCTION
-15V
COMPARATOR
-15V
N3 SENSE SWITCH
N-CHANNEL DRIVER
-V(-15V)
CLAMP N2 N1 OUT CLAMP P2
IN
also occur when signal voltage is applied before the power-supply voltage. When in a latchup state, the circuit draws excessive current and may continue to draw excessive current even after the overvoltage condition is removed. A continuous latchup condition may damage the device permanently. Such "faults" are commonly encountered in modular control systems where power supplies to interconnected modules may be interrupted and reestablished at random. Faults can happen during production testing, maintenance, startup, or a power failure. Figure 1 shows the normal complementary pair (N1 and P1) found in many common analog switches. In addition to these transistors, the MAX4505 also contains comparators, sensing circuitry, and clamping circuitry to control the state of N1 and P1. During normal operation, N1 and P1 remain on with a typical 65 onresistance between IN and OUT. The on-board comparators and sensing circuitry monitor the input voltage for possible overvoltage faults. Two clamp circuits limit the output voltage to within the supply voltages. When the power supplies are off, any input voltage applied at IN turns off both N1 and P1, and OUT is clamped to 0V.
P3 SENSE SWITCH +15V
P1 +V(+15V) P-CHANNEL DRIVER
+15V
COMPARATOR
Figure 1. Simplified Internal Structure
Normal Operation
_______________Detailed Description
The MAX4505 protects other ICs from overvoltage by clamping its output voltage to the supply rails. If the power supplies to the device are off, the device clamps the output to 0V. The MAX4505 provides protection for input signals up to 36V with the power supplies on and 40V with the power supplies off. The MAX4505 protects other integrated circuits (ICs) connected to its output from latching up. Latchup is caused by parasitic SCR(s) within the IC turning on, and can occur when the supply voltage applied to the IC exceeds the specified operating range. Latchup can
6
When power is applied, the protector acts as a resistor in series with the signal path. A voltage on the "input" side of the switch conducts through the protector to the output (Figure 2). When the output load is resistive, it draws current through the protector. The internal resistance is typically less than 100. The MAX4505 does not affect highimpedance loads. The protector's path resistance is a function of the supply voltage and the signal voltage (see Typical Operating Characteristics).
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Fault-Protected, High-Voltage, Signal-Line Protector MAX4505
+3V O NEW COM 1 1 +5V 2 AO EN VA1 16 A2 15 GND 14
MAX4505
VVV+ V+
-15V 3 8 +15V 7 4 5 6 7
NO1 MAX4508 V+ 13 +15V NO2 NO3 NO4 COM NO5 12 NO6 11 NO7 10 NO8 9
2
MAX4505
VIN AIN AOUT
3 -15V 4 6 5
8
ROUT
Figure 4. Demultiplexer Application Using MAX4505 with MAX4508 Figure 2. Application Circuit
+3V OV 1 +5V 2 -5V 3 1 2 8 +15V 7 4 5 6 7 -15V 4 5 8 AO EN VNO1 MAX338 NO2 NO3 NO4 VOUT A1 16 A2 15 GND 14 V+ 13 +15V NO5 12 NO6 11 NO7 10 NO8 9
control pins. For example, with the V- pin grounded, the output of a CMOS gate can drive the V+ pin to turn the device on and off. Ensure that the driving source(s) does not drive the V+ pin more negative than the V- pin.
Protector as Circuit Elements
Figure 3 shows a MAX4505 used in front of a MAX338 unprotected 1-to-8 multiplexer. With supplies at 15V, VAOUT of the MAX4505 clamps to 15V and VOUT of the MAX338 goes to 14V. With supplies off, VAOUT goes to 0 even though the input remains at 25V.
MAX4505
+25V 3 6
Multiplexer and Demultiplexer
The MAX4505 can be used in series with the output of a MAX4508 (1-to-8 multiplexer) to act as multiplexer or demultiplexer. The MAX4508 is a fault-protected multiplexer whose inputs are designed to interface with harsh environments; however, its common output is not fault protected if connected to outside signals (i.e., demultiplexer use). If the common output can see fault signals, then it needs to be protected, and the MAX4505 can be added to provide complete protection. As seen in Figure 4, the signal input can now be put into pin 3 of the MAX4505 (new common output for system), and outputs can be taken at MAX4508 pins 4 to 7, and 9 to 12. This is the classic demultiplexer operation. This system now has full protection on both of the multiplexers' inputs and outputs.
Figure 3. Protecting a MAX338 with a MAX4505
Fault Protection with Power Off
When power is off (i.e., V+ = V- = 0), the protector is a virtual open circuit. The output stays at 0 with up to 40V applied to the input.
Fault Protection with Power On
A fault condition exists when the voltage on AIN exceeds either supply rail. This definition is valid when power is on or off, as well as during all states while power ramps up or down.
Applications Information
Supplying Power Through External ICs
The MAX4505 has low supply current (<250A), which allows the supply pins to be driven by other active circuitry instead of connected directly to the power sources. In this configuration, the part can be used as a driven fault-protected switch with V+ or V- used as the
Measuring Path Resistance
Measuring path resistance requires special techniques, since path resistance varies dramatically with the AIN and AOUT voltages relative to the supply voltages. Do not use conventional ohmmeters. Their applied voltage and currents are usually unpredictable. The true resis-
_______________________________________________________________________________________
7
Fault-Protected, High-Voltage, Signal-Line Protector MAX4505
Pin Configurations (continued)
TOP VIEW
100mV A
MAX4505
VAIN AIN ADJUSTABLE ANALOG VOLTAGE VV+ V+ AOUT VAOUT AOUT 1 N.C. 2 8 7 V+ N.C. N.C. N.C.
MAX4505
AIN 3 6 5 V- 4 PATH RESISTANCE = 100mV/A
Figure 5. Path-Resistance Measuring Circuit
MAX
tance is a function of the applied voltage, which is dramatically altered by the ohmmeter itself. Autoranging ohmmeters are particularly unreliable. Figure 5 shows a circuit that gives reliable results. This circuit uses a 100mV voltage source and a low-voltagedrop ammeter as the measuring circuit, and an adjustable supply to sweep the analog voltage across its entire range. The ammeter must have a voltage drop of less than 1mV (up to the maximum test current) for accurate results. A Keithley model 617 electrometer has a suitable ammeter circuit, appropriate ranges, and a built-in voltage source designed for this type of measurement. Find the path resistance by setting the analog voltage, measuring the current, and calculating the path resistance. Repeat the procedure at each analog and supply voltage. Note that it is important to use a voltage source of 100mV or less. As shown in Figure 5, this voltage and the VAIN voltage form the VAOUT voltage. Using higher voltages could cause AOUT to go into a fault condition prematurely.
Chip Information
TRANSISTOR COUNT: 56
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.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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