19-4168; Rev 0; 2/09 Signal-Line Overvoltage Protector for Low-Voltage Devices General Description Features M The MAX9940 signal-line overvoltage protector for low- ♦ 28V Protection on EXT A voltage digital communication ports provides protection against high-voltage faults and ESD strikes. The ♦ Extended ESD Protection X MAX9940 is especially useful for sensitive communica- ±4kV IEC 61000-4 Contact on EXT 9 tion protocols such as Maxim 1-Wire® that cannot ♦ +2.2V to +5.5V Supply Voltage Range 9 afford standard means of fault protection, such as large series resistors or large line capacitances. ♦ 13µA Quiescent Supply Current 4 0 The MAX9940 operates from a single supply voltage of ♦ 60ns Fault Reaction Time +2.2V to +5.5V and consumes only 13µA of quiescent ♦ Small, 5-Pin SC70 supply current. The EXT port is protected up to 28V. The device features a reaction time of 60ns for fast ♦ -40°C to +125°C Temperature Range action during fault conditions and operates over the -40°C to +125°C automotive temperature range. Applications Ordering Information Notebook Computers PIN- TOP PART TEMP RANGE Portable Devices PACKAGE MARK Industrial Equipment MAX9940AXK+ -40°C to +125°C 5 SC70 ATC +Denotes a lead(Pb)-free/RoHS-compliant package. 1-Wire is a registered trademark of Maxim Integrated Products, Inc. Block Diagram/Typical Application Circuit NOTEBOOK ADAPTER VDD = 3.3V LOAD NOTEBOOK BATTERY CHARGER ENABLE VCC MAX9940 MICROCONTROLLER + 2kΩ - PROTECTION 20V CIRCUIT 1-Wire DATA DEVICE EXT Rx INT N Rx P Tx Tx GND ________________________________________________________________Maxim Integrated Products 1 For pricing, delivery, and ordering information,please contact Maxim Directat 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Signal-Line Overvoltage Protector for Low-Voltage Devices 0 ABSOLUTE MAXIMUM RATINGS 4 (All voltages with respect to GND.) Continuous Power Dissipation (TA= +70°C) 9 VCC...........................................................................-0.3V to +6V 5-Pin SC70 (derate 3.1mW/°C above +70°C)..............245mW 9 INT............................................................................-0.3V to +6V Operating Temperature Range.........................-40°C to +125°C EXT.........................................................................-0.3V to +30V Junction Temperature......................................................+150°C X Continuous Input Current into Any Terminal.....................±20mA Storage Temperature Range.............................-65°C to +150°C A M 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 (VCC = +3.3V, RINT_PULLUP = 2kΩ to VDD, VDD = 3.3V, TA = TMIN to TMAX, 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 2.2 5.5 V Quiescent Supply Current ICC VINT = 0 13 21 µA DC CHARACTERISTICS INT Voltage Range VINT 0 5.5 V EXT Voltage Range VEXT (Note 2) -0.7 +28 V VCC + VCC + VCC + EXT Rising Threshold VTHR V 0.19 0.26 0.30 VCC + VCC + VCC + EXT Falling Threshold VTHF V 0.09 0.13 0.16 SWITCH CHARACTERISTICS On-Resistance RON 0 < VEXT < VCC, IEXT = ±10mA 43.5 77.5 Ω On-Capacitance CON Capacitance to GND 38 pF INT Off-Capacitance COFF Capacitance to GND 27 pF INT Normal Operation Leakage 0 < VINT < VCC, VCC = 5.5V 3 4.2 µA Current (to GND) EXT Normal Operation Leakage 0 < VEXT < VCC, VCC = 5.5V 3 5 µA Current (to GND) 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, INT Shutdown Leakage Current RINT_PULLUP = 2kΩ to VDD 38 70 µA (to GND) VCC = VDD = 0 1 nA AC CHARACTERISTICS Power-Up Delay Time tPUP 500 µs Fault, VEXT = 10V, RINT_PULLUP = 200Ω 98 200 Fault Reaction Time tOFF Fault, VEXT = 16V, RINT_PULLUP = 200Ω 60 ns Fault Recovery Time tON Fault removed, VEXT < VCC - 0.8V 271 375 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 Typical Operating Characteristics M (VCC= +3.3V, RINT_PULLUP= 2kΩto VDD, VDD= 3.3V, TA= TMINto TMAX, unless otherwise noted.) A X ON-RESISTANCE ON-RESISTANCE TURN-ON/TURN-OFF TIME 9 vs. VCM vs. VCM vs. TEMPERATURE 5600 MAX9940 toc01 5600 TA = +125°C MAX9940 toc02 ns)235000 TURN-ON MAX9940 toc03 940 ΩSISTANCE () 4300 VCC = 2.5VVCC V=C 3C. 3=V 5.5V ΩSISTANCE () 3400 TA = +85°C URN-OFF TIME (125000 ON-RE 20 ON-RE 20 TA = +25°C URN-ON/T100 TURN-OFF 10 10 T 50 EXT = 0 TO 10V SQUARE WAVE TA = -40°C RPULLUP = 200Ω 0 0 0 0 1 2 3 4 5 6 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 -50 -25 0 25 50 75 100 125 150 VCM (V) VCM (V) TEMPERATURE (°C) TURN-ON/TURN-OFF TIME SUPPLY CURRENT vs. TEMPERATURE vs. SUPPLY VOLTAGE INSERTION LOSS vs. FREQUENCY TURN-ON/TURN-OFF TIME (ns)112230505000000 TURN-ONESRXPQUTUL =AL RU0PE T =WO 2 A10V60EVΩ MAX9940 toc04 µSUPPLY CURRENT (A)11111113434556.......0055050 TA T=A +=8 +51°C25°C TA = -40T°AC = +25°C MAX9940 toc05 INSERTION LOSS (dB) -----543210123 MAX9940 toc06 50 TURN-OFF 12.5 -6 0 12.0 -7 -50 -25 0 25 50 75 100 125 150 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 1k 10k 100k 1M 10M 100M TEMPERATURE (°C) SUPPLY VOLTAGE (V) FREQUENCY (Hz) OFF-ISOLATION vs. FREQUENCY FAULT TURN-ON AND RECOVERY TIME 0 -20 MAX9940 toc07 EXT MAX9940 toc08 1V/div dB) -40 N ( O TI LA -60 0 O S F-I OF -80 INT 500mV/div -100 VDD = VCC = 3.3V -120 0 1k 10k 100k 1M 10M 100M TIME (40μs/div) FREQUENCY (Hz) _______________________________________________________________________________________ 3

Signal-Line Overvoltage Protector for Low-Voltage Devices 0 Typical Operating Characteristics (continued) 4 (VCC= +3.3V, RINT_PULLUP= 2kΩto VDD, VDD= 3.3V, TA= TMINto TMAX, unless otherwise noted.) 9 9 X FAULT TURN-ON TIME FAULT RECOVERY TIME A M RPULLUP = 200Ω MAX9940 toc09 EXT RPULLUP = 2kΩ MAX9940 toc10 EXT 5V/div 5V/div 0 0 INT INT 500mV/div 2V/div 0 0 TIME (100ns/div) TIME (100ns/div) FAULT TURN-ON AND RECOVERY TIME FAULT TURN-ON TIME (SCHOTTKY DIODE FROM INT TO VCC) (SCHOTTKY DIODE FROM INT TO VCC) EXT RPULLUP = 2Ω MAX9940 toc11 EXT MAX9940 toc12 5V/div 5V/div 0 0 INT INT 1V/div 1V/div 0 0 TIME (40μs/div) TIME (100ns/div) VTHR AND VTHF VTHR AND VTHF vs. SUPPLY VOLTAGE vs. TEMPERATURE mV)235000 VTHR MAX9940 toc13 mV) 235000 VTHR MAX9940 toc14 D (200 D ( 200 VOLTAGE THRESHO110500 VTHF VOLTAGE THRESHOL 110500 VTHF 50 50 0 0 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 -50 -25 0 25 50 75 100 125 SUPPLY VOLTAGE (V) TEMPERATURE (°C) 4 _______________________________________________________________________________________

Signal-Line Overvoltage Protector for Low-Voltage Devices Pin Description M PIN NAME FUNCTION A 1 VCC Power Supply. Can be connected to a microcontroller enable input. X 2 GND Ground 9 3 N.C. No Connection. Not internally connected. 9 4 INT Microcontroller I/O Port. Connection to a microcontroller data port. 4 5 EXT External Connector Port. Connection to a 1-Wire device. 0 Detailed Description Block Diagram/Typical Application Circuit. The series switch cell contains circuitry that ensures the pMOS The MAX9940 is a signal-line overvoltage protector for device turns off properly when the voltage at EXT low-voltage devices that provides circuit protection exceeds the supply voltage. The switch can withstand from high-voltage faults and ESD strikes. The device a maximum voltage of 28V at EXT. provides protection in digital communication lines such as 1-Wire and I2C protocols where large series resis- Comparator tance and capacitances cannot be used to provide The MAX9940 features a low-power, high-speed com- protection due to their impact on VIL/VIH levels and parator that is used to turn off the series switch if a communication timing. The MAX9940 includes a series high-voltage condition is detected on EXT. The nominal switch that connects INT to EXT. When a high-voltage hysteresis of the comparator is 128mV (typical). Fault fault condition occurs on EXT, the MAX9940 quickly voltages on EXT that are slightly above VCC trigger the shuts off the series switch and isolates the low-voltage comparator to quickly isolate INT and EXT channels device from the fault condition. In addition to providing from each other. In this mode, the MAX9940 is able to DC fault isolation, the MAX9940 also provides up to withstand 28V on EXT. Negative voltages on EXT are ±4kV IEC 61000-4 contact ESD protection on EXT. The allowed as long as they are current-limited to less than MAX9940 is ideal for circuits that require low-voltage 20mA. devices that communicate to the outside world over connector ports that can expose them to hazardous Typical Application Circuits high-voltage DC faults and ESD strikes. The innovative design of the MAX9940 allows it to with- stand large DC voltages up to 28V at INT and EXT even Series Switch when VCC is 0. This allows application-specific power- The MAX9940 features a series switch to connect a saving and fault-protection schemes to be implemented. low-voltage device such as a microcontroller to an Figures 1 and 2 show two methods of powering the external communication device such as a 1-Wire or I2C MAX9940 from an ENABLE digital output port of the slave. The internal switch is turned off when disabled or microcontroller. Figure 3 shows the conventional method if a fault condition exists, isolating the microcontroller of operating the MAX9940 with both pullup resistor for from any possible damage. The nominal switch resis- digital communication on DATA (RP) and VCC being tance is 38Ω (typ). The series switch is composed of connected directly to VDDof the microcontroller. parallel DMOS and HV-pMOS devices as shown in the ______________________________________________________________________________________________________________________________________________________________________________ 55

Signal-Line Overvoltage Protector for Low-Voltage Devices 0 4 VDD = 3.3V 9 9 X ENABLE A VCC M MICROCONTROLLER 2kRΩ P MAX9940 1-Wire DATA DEVICE Rx Rx INT 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 micro- operating current of the MAX9940 without any substan- controller from both DC fault voltages above VCC and tial voltage drop (VOH ≈ VDD). By forcing a 0 on the ESD strikes on EXT. The difference in the three ENABLE port of the microcontroller, the MAX9940 can schemes lies in the impact on power consumption in be put into a zero-power mode, thus conserving battery battery-operated devices during normal and short to power. It should be noted that there is no internal ESD GND fault conditions. diode from INT to VCC. This allows the voltage at INT to Figure 1 shows a recommended configuration for battery- stay at VDDeven though VCC= 0, thus drawing no cur- operated devices that need to conserve power both on rent from RP or the battery. However, an internal diode does exist from INT to EXT, and therefore, in the event a continuous basis as well as during short to GND fault of a short to GND fault on EXT, current is drawn through conditions. In this scheme, the ENABLE port of a micro- controller supplies the quiescent current for the RP, causing a power drain from VDD, and can potential- ly reduce battery life. MAX9940 as well as that required for digital communi- cation (i.e., RP pullup resistor). By forcing a 0 on the In Figure 3, VDD powers the MAX9940 directly, and ENABLE digital output port of the microcontroller, the consumes quiescent current on a continuous basis. In MAX9940 is in a zero-power shutdown mode, while also this mode, the internal FET between INT and EXT is preventing any power drain to occur in the event of a kept on as long as the voltage on EXT is below VCC. As short to GND fault on EXT. As stated earlier, EXT main- a result, in the event of a short to GND fault on EXT, tains the ability to withstand DC voltages up to 28V current is drawn through RP, causing a power drain even when VCC= 0. from VDDand potentially reducing battery life. In Figure 2, the ENABLE port of a microcontroller pow- ers the MAX9940. The low 13µA operating current allows standard digital I/O ports to easily supply the 6 _______________________________________________________________________________________

Signal-Line Overvoltage Protector for Low-Voltage Devices M VDD = 3.3V A X 9 ENABLE 9 VCC 4 0 MICROCONTROLLER 2kRΩ P MAX9940 1-Wire DATA DEVICE Rx Rx INT EXT GND Tx Tx Figure 2. Recommended Scheme for Applications that Require the MAX9940 to be Put into Shutdown VDD = 3.3V VCC MICROCONTROLLER 2kRΩ P MAX9940 1-Wire DATA DEVICE 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 0 Pin Configuration Chip Information 4 PROCESS: BiCMOS 9 9 TOP VIEW X + A VCC 1 5 EXT M MAX9940 GND 2 N.C. 3 4 INT SC70 8 _______________________________________________________________________________________

Signal-Line Overvoltage Protector for Low-Voltage Devices Package Information M For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. A PACKAGE TYPE PACKAGE CODE DOCUMENT NO. X 5 SC70 X5-1 21-0076 9 9 S 4 P E L. 0 5 0, 7 C S PACKAGE OUTLINE, 5L SC70 1 21-0076 E 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.