MAX366ESA+T

19-0326; Rev 0; 12/94 Signal-Line Circuit Protectors ____________________________Features ♦ ±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 Controls ______________Ordering Information PART† TEMP. RANGE PIN-PACKAGE MAX366CPA 0°C to +70°C 8 Plastic DIP MAX366CSA MAX366C/D MAX366EPA 0°C to +70°C 0°C to +70°C -40°C to +85°C 8 SO Dice* 8 Plastic DIP MAX366ESA MAX366MJA MAX367CPN -40°C to +85°C -55°C to +125°C 0°C to +70°C 8 SO 8 CERDIP** 18 Plastic DIP MAX367CWN MAX367C/D MAX367EPN 0°C to +70°C 0°C to +70°C -40°C to +85°C 18 Wide SO Dice* 18 Plastic DIP MAX367EWN MAX367MJN -40°C to +85°C -55°C to +125°C 18 Wide SO 18 CERDIP** ________________________Applications † MAX367 available after January 1, 1995. Process Control Systems Redundant/Backup Systems Hot-Insertion Boards/Systems ATE Equipment Data-Acquisition Systems Sensitive Instruments * Dice are tested at TA = +25°C only. * Contact factory for availability. Pin Configurations appear at end of data sheet. ___________________________________________________Typical Operating Circuit ELECTRONICS PROTECTOR FAULT! REMOTE SENSOR MAX366 +28V +10V REG. (SHORT) 8 1 IN1 OUT1 7 2 IN2 OUT2 6 3 IN3 OUT3 5 4 (OPEN) V+ +12V SENSITIVE AMPLIFIER V- FAULT! ________________________________________________________________ Maxim Integrated Products Call toll free 1-800-998-8800 for free samples or literature. 1 MAX366/MAX367 _______________General Description The MAX366 and MAX367 are multiple, two-terminal circuit protectors. Placed in series with signal lines, each two-terminal device guards sensitive circuit components against voltages near and beyond the normal supply voltages. These devices are used at interfaces where sensitive circuits are connected to the external world and could encounter damaging voltages (up to 35V beyond the supply rails) during power-up, power-down, or fault conditions. The MAX366 contains three independent protectors and the MAX367 contains eight. They can protect analog signals 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 supplies, 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 dramatically, limiting fault current as well as output voltage to sensitive circuits. The protected side of the switch maintains 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. MAX366/MAX367 Signal-Line Circuit Protectors 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 (TA = +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, TA = TMIN to TMAX, unless otherwise noted.) PARAMETER SYMBOL Analog Signal Range Fault-Free Analog Signal Range VIN, VOUT VIN, VOUT Analog-Signal Output Range (Fault) VOUT TEMP. RANGE MIN (Note 1) V+ = 15V, V- = -15V (Note 2) All All VIN = V+ or V-, 100kΩ < ROUT < 1000MΩ (Note 1) All CONDITIONS MAX UNITS (V+ - 40) -11 (V- + 40) 11 V V (V- + 3) (V+ - 1.5) V +25°C V+ = 15V, V- = -15V, VIN = ±10V, IOUT = 1mA Analog-Signal-Path Resistance R(IN-OUT) V+ = 5V, V- = -5V, VIN = ±2V, IOUT = 1mA Signal-Path Resistance Match ∆R(IN-OUT) 62 C, E M 125 VIN = ±10V, IOUT = 1mA Signal-Path Leakage (Power Off) IIN(OFF) V+ = V- = 0V, VIN = ±35V, VOUT = open circuit Signal-Path Leakage (without Fault Condition) IOUT(ON) VIN = VOUT = ±10V Signal-Path Leakage (with Fault Condition) IIN(ON) VIN = ±25V, VOUT = open circuit Signal-Path Leakage (with Overvoltage) IIN(OFF) V+ = V- = 0V, VOUT = 0V, VIN = ±35V 62 C, E 100 125 M Ω 150 +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 85 100 +25°C V+ = 10V, V- = -10V, VIN = ±5V, IOUT = 1mA TYP 140 350 -10 -1000 -1 -100 -10 -1000 -10 -1000 400 7 10 10 1000 1 100 10 1000 10 1000 +25°C, C, E, M 0 ±18 V +25°C, C, E, M ±2.25 ±18 V +25°C C, E, M -1 -10 1 10 µA Ω nA nA nA nA POWER SUPPLY Power-Supply Range V+, V- Power-Supply Range (without Fault Condition) V+, V- Power-Supply Current I+, I- R(IN-OUT) < 1000Ω (Note 2) 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 TRANSFER CHARACTERISTICS (BIPOLAR SUPPLIES) V+ = +3V, V- = -3V 5 0 V+ = +5V, V- = -5V -5 V+ = +10V, V- = -10V OUTPUT LOAD = 1MΩ -35 -25 -15 MAX366/7-03 15 V+ = 15V 10 V+ = 10V 5 V+ = 5V 0 -5 0 5 15 25 35 0 5 10 15 20 25 30 35 PATH RESISTANCE vs. INPUT VOLTAGE (BIPOLAR SUPPLIES) PATH RESISTANCE vs. INPUT VOLTAGE (BIPOLAR SUPPLIES) V± = ±3V 500 V± = ±10V 1E+04 1E+03 V± = ±5V V± = ±3V 450 V± = ±15V 1E+05 400 V± = ±15V 350 V± = ±10V 300 250 200 150 V± = ±5V 100 1E+02 MAX366/7-05 INPUT VOLTAGE (V) VIN > (V+ - 35V) 1E+06 1E+01 V+ = 25V 20 INPUT VOLTAGE (V) 1E+08 1E+07 OUTPUT LOAD = 1MΩ V- = 0V V+ = +15V, V- = -15V PATH RESISTANCE (Ω) -15 25 OUTPUT VOLTAGE (V), INPUT & OUTPUT CURRENT (µA) 10 -10 PATH RESISTANCE (Ω) MAX366/7-02 V+ = +15V, V- = -15V V+ = +10V, V- = -10V MAX366/7-04 OUTPUT VOLTAGE (V), INPUT & OUTPUT CURRENT (µA) 15 TRANSFER CHARACTERISTICS (SINGLE SUPPLY) 50 Circuit of Fig. 6 -15 -10 -5 0 0 5 INPUT VOLTAGE (V) 10 15 Circuit of Fig. 6 -15 -10 -5 0 5 10 15 INPUT VOLTAGE (V) _______________________________________________________________________________________ 3 MAX366/MAX367 __________________________________________Typical Operating Characteristics (V+ = +15V, V- = -15V, TA = +25°C, unless otherwise noted.) ____________________________Typical Operating Characteristics (continued) (V+ = +15V, V- = -15V, TA = +25°C, unless otherwise noted.) PATH RESISTANCE vs. INPUT VOLTAGE (SINGLE SUPPLY) PATH RESISTANCE vs. INPUT VOLTAGE (SINGLE SUPPLY) 10M V+ = 10V 1M V+ = 35V V+ = 15V 10k 1k MAX366/7-07 450 PATH RESISTANCE (Ω) V+ = 25V 100k 500 MAX366/7-06 1G 100M PATH RESISTANCE (Ω) V+ = 10V 400 V+ = 15V 350 V+ = 25V 300 250 V+ = 5V 200 V+ = 35V 150 100 100 V+ = 5V 10 Circuit of Fig. 6 1 50 V- = 0V 10 V- = 0V Circuit of Fig. 6 0 1 100 100 10 INPUT VOLTAGE (V) INPUT VOLTAGE (V) OVERVOLTAGE RAMP MAX366 FREQUENCY RESPONSE MAX366-TOC9 0 -2 SOURCE = 50Ω LOAD = 50Ω V+ = 5V V- = -5V -4 LOSS (dB) MAX366/MAX367 Signal-Line Circuit Protectors -6 -8 -10 -12 V+ = 5V, V- = -5V CHAN 1: INPUT OVERVOLTAGE RAMP ±7V, 2V/div CHAN 2: OUTPUT; OUTPUT LOAD = 1000Ω, 2V/div 4 10 100 1k 10k 100k 1M FREQUENCY (Hz) _______________________________________________________________________________________ 10M 100M Signal-Line Circuit Protectors PIN NAME* MAX366 MAX367 1, 2, 3 1, 2, 3 IN1, IN2, IN3 – 4–8 IN4–IN8 FUNCTION Signal Inputs 1, 2, 3 Signal Inputs 4–8 4 9 V- – 10–14 OUT8–OUT4 Negative Supply Voltage Input Signal Outputs 4–8 5, 6, 7 15, 16, 17 OUT3, OUT2, OUT1 Signal Outputs 1, 2, 3 8 18 V+ Positive Supply Voltage Input * 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 properly 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 interconnected modules may be interrupted and re-established 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 automatically limit signal voltages and currents to safe levels without 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 lowimpedance 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 channels must have approximately 1.3V of positive gate voltage 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.) VP IN OUT Q2 N N Q1 Q3 V+ Figure 1. Simplified Internal Structure _______________________________________________________________________________________ 5 MAX366/MAX367 ______________________________________________________________Pin Description MAX366/MAX367 Signal-Line Circuit Protectors As long as the signal is within these limits, all three transistors 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. Normal Operation In normal operation, the protector is placed in series with the signal line and the power supplies are connected 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.) 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 resistance is a function of the supply voltage and the signal voltage (see Typical Operating Characteristics). MAX366 4 VVIN 1 V- V+ IN1 OUT1 8 7 V+ VOUT ROUT VLOW Power Off 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 signal pin is within about 1.5V of either supply rail 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. 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 symmetrical. It is approximately 1.3V down from the positive supply (V+ pin) or approximately 2.0V up from the negative supply (V- pin). Each fault knee voltage varies slightly with supply voltage, with output current, and from device to device. 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 current have the same polarity as the fault. The maximum input fault voltage is 40V from the “opposite-polarity supply rail.” This means the input can go to ±35V with ±5V supplies or to ±25V with ±15V supplies. The fault voltage is highest (±40V) when the supplies are off (V+ = V- = 0V). Using the circuit of Figure 2, the approximate fault currents are as follows: 1) For positive faults: I(F) ≈ (V+ - 1.3V - VLOW) ÷ ROUT 2) For negative faults: I(F) ≈ (V- + 2V + VLOW) ÷ ROUT where VLOW is the terminating voltage at the far end of ROUT. VLOW = 0V when ROUT is grounded. Figure 2. Application Circuit 6 _______________________________________________________________________________________ Signal-Line Circuit Protectors Single-Supply Output Operation Single-supply operation is a special case. Signals cannot go to ground, since from 0V to approximately +2V is a fault condition. Extremely Low-Current Operation 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. When the protector’s output side is connected to very high-resistance, very low-current loads (such as opamp inputs), a small leakage current flows from the input to the output during fault conditions. This current is typically below a nano-ampere (