19-4168; Rev 0; 2/09 Signal-Line Overvoltage Protector for Low-Voltage Devices The MAX9940 signal-line overvoltage protector for lowvoltage digital communication ports provides protection against high-voltage faults and ESD strikes. The MAX9940 is especially useful for sensitive communication protocols such as Maxim 1-Wire ® that cannot afford standard means of fault protection, such as large series resistors or large line capacitances. The MAX9940 operates from a single supply voltage of +2.2V to +5.5V and consumes only 13µA of quiescent supply current. The EXT port is protected up to 28V. The device features a reaction time of 60ns for fast action during fault conditions and operates over the -40°C to +125°C automotive temperature range. Features ♦ 28V Protection on EXT ♦ Extended ESD Protection ±4kV IEC 61000-4 Contact on EXT ♦ +2.2V to +5.5V Supply Voltage Range ♦ 13µA Quiescent Supply Current ♦ 60ns Fault Reaction Time ♦ Small, 5-Pin SC70 ♦ -40°C to +125°C Temperature Range Applications Ordering Information Notebook Computers PART TEMP RANGE PINPACKAGE TOP MARK MAX9940AXK+ -40°C to +125°C 5 SC70 ATC Portable Devices Industrial Equipment +Denotes a lead(Pb)-free/RoHS-compliant package. 1-Wire is a registered trademark of Maxim Integrated Products, Inc. Block Diagram/Typical Application Circuit ADAPTER NOTEBOOK VDD = 3.3V LOAD ENABLE NOTEBOOK BATTERY CHARGER VCC MAX9940 MICROCONTROLLER + 2kΩ - PROTECTION CIRCUIT DATA EXT Rx INT Tx Rx N P 20V 1-Wire DEVICE Tx GND ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX9940 General Description MAX9940 Signal-Line Overvoltage Protector for Low-Voltage Devices ABSOLUTE MAXIMUM RATINGS (All voltages with respect to GND.) VCC ...........................................................................-0.3V to +6V INT ............................................................................-0.3V to +6V EXT .........................................................................-0.3V to +30V Continuous Input Current into Any Terminal.....................±20mA Continuous Power Dissipation (TA = +70°C) 5-Pin SC70 (derate 3.1mW/°C above +70°C) ..............245mW Operating Temperature Range .........................-40°C to +125°C Junction Temperature ......................................................+150°C Storage Temperature Range .............................-65°C to +150°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 CC = +3.3V, R INT_PULLUP = 2kΩ to V DD, V DD = 3.3V, T A = T MIN to T MAX, unless otherwise noted. Typical values are at TA = +25°C.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS POWER SUPPLY Power-Supply Voltage VCC Quiescent Supply Current ICC 2.2 VINT = 0 13 5.5 V 21 µA DC CHARACTERISTICS INT Voltage Range VINT EXT Voltage Range VEXT EXT Rising Threshold VTHR VCC + 0.19 EXT Falling Threshold VTHF VCC + 0.09 (Note 2) 0 5.5 V -0.7 +28 V VCC + 0.26 VCC + 0.30 V VCC + 0.13 VCC + 0.16 V 43.5 77.5 SWITCH CHARACTERISTICS Ω On-Resistance RON 0 < VEXT < VCC, IEXT = ±10mA On-Capacitance CON Capacitance to GND 38 pF INT Off-Capacitance COFF Capacitance to GND 27 pF INT Normal Operation Leakage Current (to GND) 0 < VINT < VCC, VCC = 5.5V 3 4.2 µA EXT Normal Operation Leakage Current (to GND) 0 < VEXT < VCC, VCC = 5.5V 3 5 µA INT Fault Leakage Current VINT = 3.3V, VEXT = 28V 2 10 nA EXT Fault Leakage Current VINT = 3.3V, VEXT = 28V 341 510 µA VCC = VDD = 0, 2.2V < VDD < 5.5V, RINT_PULLUP = 2kΩ to VDD 38 70 µA VCC = VDD = 0 1 INT Shutdown Leakage Current (to GND) nA AC CHARACTERISTICS Power-Up Delay Time tPUP Fault Reaction Time tOFF Fault Recovery Time tON 500 Fault, VEXT = 10V, RINT_PULLUP = 200Ω 98 Fault, VEXT = 16V, RINT_PULLUP = 200Ω 60 Fault removed, VEXT < VCC - 0.8V 271 µs 200 375 ns ns Note 1: All devices are 100% production tested at TA = +25°C. Specifications over temperature limits are guaranteed by design. Note 2: Minimum EXT voltage of -0.7V is allowed only with a maximum drawn current of 20mA. 2 _______________________________________________________________________________________ Signal-Line Overvoltage Protector for Low-Voltage Devices 40 VCC = 3.3V VCC = 5.5V 20 TA = +125°C TA = +85°C 40 30 20 TA = +25°C 10 300 TURN-ON/TURN-OFF TIME (ns) ON-RESISTANCE (Ω) VCC = 2.5V 50 MAX9940 toc02 50 ON-RESISTANCE (Ω) 60 MAX9940 toc01 60 30 TURN-ON/TURN-OFF TIME vs. TEMPERATURE ON-RESISTANCE vs. VCM TURN-ON 250 200 150 TURN-OFF 100 EXT = 0 TO 10V SQUARE WAVE RPULLUP = 200Ω 50 10 TA = -40°C 3 4 5 0 6 0.5 1.0 1.5 2.0 2.5 3.0 VCM (V) TURN-ON/TURN-OFF TIME vs. TEMPERATURE SUPPLY CURRENT vs. SUPPLY VOLTAGE SUPPLY CURRENT (µA) 200 150 EXT = 0 TO 16V SQUARE WAVE RPULLUP = 200Ω 100 TA = +125°C TA = +85°C 14.5 14.0 TA = +25°C 13.5 13.0 50 TA = -40°C 0 25 50 75 100 125 150 75 100 125 150 2 1 0 -1 -2 -3 -4 -7 2.0 2.5 TEMPERATURE (°C) 3.0 3.5 4.0 4.5 5.0 5.5 6.0 1k 10k 100k 1M 10M 100M FREQUENCY (Hz) SUPPLY VOLTAGE (V) OFF-ISOLATION vs. FREQUENCY FAULT TURN-ON AND RECOVERY TIME 0 MAX9940 toc07 0 -20 OFF-ISOLATION (dB) -25 50 -6 12.0 -50 25 -5 12.5 TURN-OFF 0 3 MAX9940 toc05 15.5 15.0 -25 INSERTION LOSS vs. FREQUENCY 16.0 MAX9940 toc04 TURN-ON -50 4.0 TEMPERATURE (°C) VCM (V) 250 3.5 MAX9940 toc08 2 INSERTION LOSS (dB) 1 300 TURN-ON/TURN-OFF TIME (ns) 0 0 0 MAX9940 toc06 0 MAX9940 toc03 ON-RESISTANCE vs. VCM EXT 1V/div -40 0 -60 -80 INT 500mV/div -100 VDD = VCC = 3.3V 0 -120 1k 10k 100k 1M 10M 100M TIME (40μs/div) FREQUENCY (Hz) _______________________________________________________________________________________ 3 MAX9940 Typical Operating Characteristics (VCC = +3.3V, RINT_PULLUP = 2kΩ to VDD, VDD = 3.3V, TA = TMIN to TMAX, unless otherwise noted.) Typical Operating Characteristics (continued) (VCC = +3.3V, RINT_PULLUP = 2kΩ to VDD, VDD = 3.3V, TA = TMIN to TMAX, unless otherwise noted.) MAX9940 toc09 RPULLUP = 200Ω EXT 5V/div MAX9940 toc10 FAULT RECOVERY TIME FAULT TURN-ON TIME RPULLUP = 2kΩ EXT 5V/div 0 0 INT 500mV/div INT 2V/div 0 0 FAULT TURN-ON AND RECOVERY TIME (SCHOTTKY DIODE FROM INT TO VCC) FAULT TURN-ON TIME (SCHOTTKY DIODE FROM INT TO VCC) EXT 5V/div EXT 5V/div 0 0 INT 1V/div INT 1V/div 0 0 TIME (40μs/div) TIME (100ns/div) VTHR AND VTHF vs. SUPPLY VOLTAGE VTHR AND VTHF vs. TEMPERATURE VTHR 250 VOLTAGE THRESHOLD (mV) 250 200 VTHF 100 50 MAX9940 toc14 VTHR 150 300 MAX9940 toc13 300 200 VTHF 150 100 50 0 0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 SUPPLY VOLTAGE (V) 4 MAX9940 toc12 TIME (100ns/div) MAX9940 toc11 TIME (100ns/div) RPULLUP = 2Ω VOLTAGE THRESHOD (mV) MAX9940 Signal-Line Overvoltage Protector for Low-Voltage Devices 5.5 6.0 -50 -25 0 25 50 75 100 125 TEMPERATURE (°C) _______________________________________________________________________________________ Signal-Line Overvoltage Protector for Low-Voltage Devices PIN NAME 1 VCC FUNCTION 2 GND Ground 3 N.C. No Connection. Not internally connected. 4 INT Microcontroller I/O Port. Connection to a microcontroller data port. 5 EXT External Connector Port. Connection to a 1-Wire device. Power Supply. Can be connected to a microcontroller enable input. Detailed Description The MAX9940 is a signal-line overvoltage protector for low-voltage devices that provides circuit protection from high-voltage faults and ESD strikes. The device provides protection in digital communication lines such as 1-Wire and I2C protocols where large series resistance and capacitances cannot be used to provide protection due to their impact on VIL/VIH levels and communication timing. The MAX9940 includes a series switch that connects INT to EXT. When a high-voltage fault condition occurs on EXT, the MAX9940 quickly shuts off the series switch and isolates the low-voltage device from the fault condition. In addition to providing DC fault isolation, the MAX9940 also provides up to ±4kV IEC 61000-4 contact ESD protection on EXT. The MAX9940 is ideal for circuits that require low-voltage devices that communicate to the outside world over connector ports that can expose them to hazardous high-voltage DC faults and ESD strikes. Series Switch The MAX9940 features a series switch to connect a low-voltage device such as a microcontroller to an external communication device such as a 1-Wire or I2C slave. The internal switch is turned off when disabled or if a fault condition exists, isolating the microcontroller from any possible damage. The nominal switch resistance is 38Ω (typ). The series switch is composed of parallel DMOS and HV-pMOS devices as shown in the Block Diagram/Typical Application Circuit. The series switch cell contains circuitry that ensures the pMOS device turns off properly when the voltage at EXT exceeds the supply voltage. The switch can withstand a maximum voltage of 28V at EXT. Comparator The MAX9940 features a low-power, high-speed comparator that is used to turn off the series switch if a high-voltage condition is detected on EXT. The nominal hysteresis of the comparator is 128mV (typical). Fault voltages on EXT that are slightly above VCC trigger the comparator to quickly isolate INT and EXT channels from each other. In this mode, the MAX9940 is able to withstand 28V on EXT. Negative voltages on EXT are allowed as long as they are current-limited to less than 20mA. Typical Application Circuits The innovative design of the MAX9940 allows it to withstand large DC voltages up to 28V at INT and EXT even when VCC is 0. This allows application-specific powersaving and fault-protection schemes to be implemented. Figures 1 and 2 show two methods of powering the MAX9940 from an ENABLE digital output port of the microcontroller. Figure 3 shows the conventional method of operating the MAX9940 with both pullup resistor for digital communication on DATA (RP) and VCC being connected directly to VDD of the microcontroller. _______________________________________________________________________________________ 5 MAX9940 Pin Description MAX9940 Signal-Line Overvoltage Protector for Low-Voltage Devices VDD = 3.3V ENABLE VCC MICROCONTROLLER RP 2kΩ MAX9940 1-Wire DEVICE DATA Rx INT Rx EXT GND Tx Tx Figure 1. Recommended Scheme for Battery-Operated Devices that Need to Shut Down the MAX9940 and Prevent Power Draw During Short to GND Faults In all three schemes, the MAX9940 protects the microcontroller from both DC fault voltages above VCC and ESD strikes on EXT. The difference in the three schemes lies in the impact on power consumption in battery-operated devices during normal and short to GND fault conditions. Figure 1 shows a recommended configuration for batteryoperated devices that need to conserve power both on a continuous basis as well as during short to GND fault conditions. In this scheme, the ENABLE port of a microcontroller supplies the quiescent current for the MAX9940 as well as that required for digital communication (i.e., RP pullup resistor). By forcing a 0 on the ENABLE digital output port of the microcontroller, the MAX9940 is in a zero-power shutdown mode, while also preventing any power drain to occur in the event of a short to GND fault on EXT. As stated earlier, EXT maintains the ability to withstand DC voltages up to 28V even when VCC = 0. In Figure 2, the ENABLE port of a microcontroller powers the MAX9940. The low 13µA operating current allows standard digital I/O ports to easily supply the 6 operating current of the MAX9940 without any substantial voltage drop (VOH ≈ VDD). By forcing a 0 on the ENABLE port of the microcontroller, the MAX9940 can be put into a zero-power mode, thus conserving battery power. It should be noted that there is no internal ESD diode from INT to VCC. This allows the voltage at INT to stay at VDD even though VCC = 0, thus drawing no current from RP or the battery. However, an internal diode does exist from INT to EXT, and therefore, in the event of a short to GND fault on EXT, current is drawn through RP, causing a power drain from VDD, and can potentially reduce battery life. In Figure 3, VDD powers the MAX9940 directly, and consumes quiescent current on a continuous basis. In this mode, the internal FET between INT and EXT is kept on as long as the voltage on EXT is below VCC. As a result, in the event of a short to GND fault on EXT, current is drawn through RP, causing a power drain from VDD and potentially reducing battery life. _______________________________________________________________________________________ Signal-Line Overvoltage Protector for Low-Voltage Devices MAX9940 VDD = 3.3V ENABLE VCC MICROCONTROLLER RP 2kΩ MAX9940 1-Wire DEVICE DATA Rx INT Rx EXT GND Tx Tx Figure 2. Recommended Scheme for Applications that Require the MAX9940 to be Put into Shutdown VDD = 3.3V VCC MICROCONTROLLER RP 2kΩ MAX9940 1-Wire DEVICE DATA Rx Rx INT EXT GND Tx Tx Figure 3. Recommended Operating Circuit for Nonbattery-Operated Applications _______________________________________________________________________________________ 7 Signal-Line Overvoltage Protector for Low-Voltage Devices MAX9940 Pin Configuration Chip Information PROCESS: BiCMOS TOP VIEW + VCC 1 GND 2 5 EXT 4 INT MAX9940 N.C. 3 SC70 8 _______________________________________________________________________________________ Signal-Line Overvoltage Protector for Low-Voltage Devices PACKAGE CODE DOCUMENT NO. 5 SC70 X5-1 21-0076 SC70, 5L.EPS PACKAGE TYPE PACKAGE OUTLINE, 5L SC70 21-0076 E 1 1 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. Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 _____________________ 9 © 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc. MAX9940 Package Information For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.