19-1988; Rev 0; 3/01 +72V SOT23 Simple Swapper Hot-Swap Controllers Features ♦ Wide +9V to +72V Operation ♦ Requires No External Sense Resistor ♦ Drives External P-Channel MOSFET ♦ Limits Inrush Current ♦ Circuit Breaker Function ♦ Less than 2mA Quiescent Current ♦ ON/OFF Input Permits Load Power-Supply Control and Sequencing ♦ Adjustable Undervoltage Lockout ♦ Power-Good Output with +72V Rating ♦ Latching or Automatic Retry Fault Management ♦ Thermal Shutdown Helps Protect the External MOSFET ♦ Space-Saving SOT23-6 Package Ordering Information PART TEMP. RANGE PIN-PACKAGE MAX5902_ _EUT* -40°C to +85°C 6-SOT23 MAX5903_ _EUT* -40°C to +85°C 6-SOT23 *For specific part numbers see Selector Guide at end of data sheet. Typical Operating Circuits Applications Network Routers Network Switches Base Station Line Cards Servers RAID Industrial Systems 50W ISOLATED POWER SUPPLY BACKPLANE CIRCUIT CARD +48V IRFR5410 HOT SWAP CONTROLLER Pin Configuration MAX5902 VS TOP VIEW ON/OFF VS 1 6 GND ON/OFF VIN (+) LUCENT JW050A1 GATE DRAIN PGOOD ON/OFF VIN (-) GND DRAIN 2 MAX5902 MAX5903 GATE 3 SOT23-6 ( ) ARE FOR MAX5903 ONLY. 5 PGOOD (PGOOD) 4 GND Typical Operating Circuits continued at end of data sheet. Simple Swapper is a trademark of Maxim Integrated Products Inc. ________________________________________________________________ Maxim Integrated Products For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at 1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com. 1 MAX5902/MAX5903 General Description The MAX5902/MAX5903 are SOT23 hot-swap controllers that allow a circuit card to be safely hot plugged into a live backplane without causing a glitch on the power-supply rail. These devices operate from +9V to +72V and provide the simplest hot-swap solution by eliminating all external components except the external P-channel MOSFET. The MAX5902/MAX5903 limit the inrush current to the load and provide a circuit breaker function for overcurrent protection. During startup the circuit breaker function is disabled and the MAX5902/MAX5903 limit the inrush current by gradually turning on the external MOSFET. Once the external MOSFET is fully enhanced, the circuit breaker function is enabled and the MAX5902/MAX5903 provide overcurrent protection by monitoring the voltage drop across the external MOSFET’s on-resistance. The MAX5902/MAX5903 include an undervoltage lockout (UVLO) function, ON/OFF control input and a power-good status output, PGOOD (MAX5902) or PGOOD (MAX5903). A built in thermal shutdown feature is also included to protect the external MOSFET in case of overheating. The MAX5902/MAX5903 offer latched or auto-retry fault management and are available with 300mV, 400mV or 500mV circuit breaker thresholds. Both the MAX5902 and MAX5903 are available in a small SOT23 package, and are specified for the extended -40°C to +85°C temperature range. For specific ordering information refer to the selector guide at the end of the data sheet. MAX5902/MAX5903 +72V SOT23 Simple Swapper Hot-Swap Controllers ABSOLUTE MAXIMUM RATINGS Terminal Voltage (with respect to GND unless otherwise noted) VS, DRAIN, PGOOD, PGOOD ................................-0.3V to +76V ON/OFF ....................................................................-0.3V to +4V GATE to VS ............................................................-12V to +0.3V Current into any Pin ............................................................±3mA Continuous Power Dissipation at TA = +70°C 6-Pin SOT23 (derate 9.1mW/°C above +70°C)..........727mW Maximum Junction Temperature .....................................+150°C Storage Temperature Range .............................-60°C to +150°C Lead Temperature .............................................................Note 1 Note 1: This device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile the device can be exposed to during board level solder attach and rework. This limit permits only the use of solder profiles recommended in the industry standard specification, JEDEC 020A, paragraph 7.6, Table 3 for IR/VPR and convection reflow. Preheating is required. Hand or wave soldering is not allowed. 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 (VS = +9V to +72V, GND = 0, ON/OFF open circuit, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VS = +48V and TA = +25°C.) (Notes 2, 3) PARAMETER Supply Voltage SYMBOL VS CONDITIONS Supply Current IGND Measured out of GND, PGOOD or PGOOD open circuit, DRAIN = VS External Gate Drive VGS VS - VGATE Load Voltage Slew Rate Magnitude SR | dVDRAIN/dt | CL = 10µF VUVLO VS increasing Default Undervoltage Lockout MIN 9 MAX 72 UNITS V 1 2 mA 11 VS = +36V to +72V 9 10 VS = +9V 8 8.5 VS = +36V to +72V 5 9 18 VS = +9V 3 6 11 28.5 31.5 34.5 Undervoltage Lockout Hysteresis 3.5 ON/OFF Pin Input Resistance RON/OFF DRAIN to GND Resistance RDGND 900 RDS 650 DRAIN to VS Resistance ON/OFF Reference Threshold VON/OFF 19 VON/OFF Increasing tON ON/OFF Off Delay (Note 5) tOFF VS - VGATE < 1V Circuit Breaker Threshold VCB VS - VDRAIN tCB (VS - VDRAIN) > VCB until (VS - VGATE) < 1V, 200mV overdrive step V/ms V V 52 kΩ kΩ kΩ 1.26 1.38 80 150 280 ms 5 10 18 ms MAX590_ _AEUT 200 300 460 MAX590_ _BEUT 280 400 540 MAX590_ _CEUT 400 500 660 CGATE = 1nF 2 6.5 CGATE = 4.7nF 4 11 CGATE = 10nF 7 17 150 280 ms 0.3 0.6 V 140 Start Delay (Note 4) Circuit Breaker Delay (Note 6) 32 V 1.14 ON/OFF Hysteresis 2 TYP Restart Delay (Note 4) tRS After circuit breaker event, MAX590_ A_EUT only Power Good Output Low Voltage VOL IOL = 1mA 80 _______________________________________________________________________________________ V mV mV µs +72V SOT23 Simple Swapper Hot-Swap Controllers (VS = +9V to +72V, GND = 0, ON/OFF open circuit, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VS = +48V and TA = +25°C.) (Notes 2, 3) PARAMETER SYMBOL CONDITIONS Power-Good Output Open-Drain Leakage Current IOH V PGOOD = 72V (MAX5902) V PGOOD = 72V (MAX5903) Thermal Shutdown Temperature TSD Junction temperature Thermal Shutdown Hysteresis THY MIN TYP MAX UNITS 10 µA +125 °C 15 °C Note 2: All currents into device pins are positive, all currents out of device pins are negative, and all voltages are referenced to GND, unless otherwise noted. Note 3: All specifications are 100% tested at TA = +25°C, unless otherwise noted. Specifications over -40°C to +85°C are guaranteed by characterization. Note 4: This is the delay time from a valid on condition until VGS begins rising. Valid on conditions are: the device is not in undervoltage lockout; ON/OFF is not driven low; and the device is not in thermal shutdown. Note 5: This is the delay from a valid low on ON/OFF until VGS falls. Pulses on ON/OFF less than tOFF are ignored, offering glitch immunity. Note 6: Guaranteed by characterization, not production tested. CGATE is a capacitor from GATE to VS. Typical Operating Characteristics (VS = +48V, GND = 0, and TA = +25°C, unless otherwise noted. See Figure 2 for test circuits.) SUPPLY CURRENT vs. INPUT VOLTAGE SUPPLY CURRENT vs. TEMPERATURE 0.9 1.0 VIN = +12V 0.8 0.7 0.7 MAX5902 toc03 MAX5902 toc02 VIN = +48V 0.9 0.8 35 34 33 LOCKOUT VOLTAGE (V) 1.0 VIN = +70V 1.1 SUPPLY CURRENT (mA) 1.1 SUPPLY CURRENT (mA) 1.2 MAX5902 toc01 1.2 VUVLO THRESHOLD vs. TEMPERATURE INCREASING VIN 32 31 30 29 DECREASING VIN 28 27 26 0 15 30 45 INPUT VOLTAGE (V) 60 75 25 -40 -15 10 35 TEMPERATURE (°C) 60 85 -40 -15 10 35 60 85 TEMPERATURE (°C) _______________________________________________________________________________________ 3 MAX5902/MAX5903 ELECTRICAL CHARACTERISTICS (continued) Typical Operating Characteristics (continued) (VS = +48V, GND = 0, and TA = +25°C, unless otherwise noted. See Figure 2 for test circuits.) GATE DRIVE VOLTAGE vs. INPUT VOLTAGE TURN-ON WAVEFORMS RL = 60Ω, CL = 100µF RETRY TIMEOUT vs. TEMPERATURE 200 TIMEOUT PERIOD (ms) 13 11 9 7 MAX5902 toc05 225 MAX5902 toc04 15 GATE DRIVE (V) MAX5902/MAX5903 +72V SOT23 Simple Swapper Hot-Swap Controllers 0 B 175 0 150 C 0 125 D 100 0 75 5 0 15 30 45 60 -40 75 -15 10 35 60 TURN-ON WAVEFORMS RL = OPEN, CL = 100µF A : VOUT, 50V/div B : IIN, 1A/div C : VGATE, 50V/div D : VIN, 50V/div TURN-ON WAVEFORMS RL = 60Ω, CL = 10µF MAX5902 toc08 MAX5902 toc07 TURN-ON WAVEFORMS RL = 60Ω, CL = 100µF MAX5902 toc09 0 0 0 B B B 0 0 C 0 C C 0 0 0 t = 2ms/div t = 2ms/div t = 2ms/div A : VOUT, 50V/div B : IIN, 0.5A/div C : VGATE, 20V/div A : VOUT, 50V/div B : IIN, 1A/div C : VGATE, 20V/div A : VOUT, 50V/div B : IIN, 1A/div C : VGATE, 20V/div CIRCUIT BREAKER EVENT VOVERDRIVE = 200mV, CGATE = 1000pF CIRCUIT BREAKER EVENT VOVERDRIVE = 20mV, CGATE = 1000pF MAX5902 toc10 MAX5902 toc11 0 0 A A B t = 20ms/div A A A 85 TEMPERATURE (°C) INPUT VOLTAGE (V) 0 0 B 0 0 C C 4 MAX5902 toc06 A t = 1µs/div A : VDS, 0.5V/div B : VGS, 10V/div C : VPGOOD TO VS, 50V/div t = 1µs/div A : VDS, 0.5V/div B : VGS, 10V/div C : VPGOOD TO VS, 50V/div _______________________________________________________________________________________ +72V SOT23 Simple Swapper Hot-Swap Controllers PIN NAME FUNCTION MAX5902 MAX5903 1 1 VS 2 2 DRAIN Drain Sense Input for External P-Channel MOSFET. Connect DRAIN as close as possible to the MOSFET’s drain and use wide circuit traces to assure good thermal coupling between the MAX5902/MAX5903 and the MOSFET. See Layout Guidelines. 3 3 GATE Gate Drive Output for External P-Channel MOSFET 4 4 GND Positive Supply Voltage Input and External P-Channel MOSFET Source Connection Ground Connection 5 — PGOOD Power Good Output. PGOOD is an N-channel, open-drain, active-low output, referenced to GND. — 5 PGOOD Power Good Output. PGOOD is an N-channel, open-drain, active-high output, referenced to GND. ON/OFF ON/OFF Control Input. ON/OFF is referenced to GND. Drive ON/OFF above 1.38V or leave unconnected to enable the device. Drive ON/OFF below 1V to disable the device. ON/OFF is also used to adjust the UVLO threshold. Internally clamped to nominally 3V through a 1kΩ resistor. (See Figure 1.) (See Undervoltage Lockout in the Applications section of this data sheet.) 6 6 Detailed Description The MAX5902/MAX5903 are integrated hot-swap controller ICs contained in 6-pin SOT23 packages. They allow a board to be safely hot-plugged into a live backplane without causing a glitch on the power-supply rail. They are well suited for +48V power systems allowing cost-effective, simple, and compact design. The MAX5902/MAX5903 operate from +9V to +72V to cover a wide range of end equipment hot-swap needs. They require only an external P-channel power MOSFET to provide hot-swap control. Figure 1 shows a functional block diagram of the MAX5902/MAX5903. The MAX5902/MAX5903 controls an external P-channel power MOSFET placed in the positive power-supply pathway. When power is first applied, the MAX5902/ MAX5903 keep the MOSFET turned off. The MAX5902/MAX5903 hold the MOSFET off indefinitely if ON/OFF is held low, if the supply voltage is below the undervoltage lockout level, or if the die temperature exceeds +125°C. If none of these conditions exist for 150ms (typ), the MAX5902/MAX5903 begin to gradually turn on the MOSFET. During this turn-on phase, the MAX5902/MAX5903 slowly enhance the MOSFET, allowing the voltage on the load, i.e. the drain of the MOSFET, to rise at a rate of 9V/ms (typ). The inrush current to the load is thus limited to a level proportional to the load capacitance, and the constant slew rate. After the MOSFET is fully enhanced, and the load voltage is MAX5902 MAX5903 VS * 828kΩ ON/OFF 1kΩ * 34.5kΩ 3V PGOOD (PGOOD) CONTROL LOGIC GND GND *900kΩ GND *650kΩ DRAIN GATE ( ) ARE FOR THE MAX5903 ONLY * RELATIVE TOLERANCE ±1%, ABSOLUTE TOLERANCE ±50% (TYP) Figure 1. Functional Block Diagram settled to its final value, the MAX5902A/ MAX5903A and MAX5902L/MAX5903L monitor the voltage drop across the MOSFET. If the voltage drop exceeds the circuit breaker threshold the MAX5902A/MAX5903A and MAX5902L/MAX5903L turn off the MOSFET, discon- _______________________________________________________________________________________ 5 MAX5902/MAX5903 Pin Description MAX5902/MAX5903 +72V SOT23 Simple Swapper Hot-Swap Controllers necting the load immediately. If no circuit breaker fault exists, the MAX5902/MAX5903 assert the power-good output. Then, if any of four conditions exist, the power good output deasserts and the MAX5902/MAX5903 turn off the MOSFET. The four conditions are: the voltage across the MOSFET exceeds the circuit breaker threshold; the supply voltage falls below the undervoltage lockout level; the die temperature exceeds +125°C; or ON/OFF is forced low. After a circuit breaker fault, the MAX5902L/MAX5903L keep the MOSFET off until the power is cycled, or the part is reset by toggling ON/OFF low for 10ms (typ). After a circuit breaker fault, the MAX5902A/MAX5903A automatically restarts in 150ms (typ). All versions automatically restart after a VS VIN V GATE thermal fault, or an undervoltage shutdown, if the fault condition goes away for at least 150ms (typ). ON/OFF offers external control of the MAX5902/ MAX5903, facilitating power-supply sequencing, and may also be used to change the undervoltage lockout (UVL) level. UVLO keeps the external MOSFET switched off as long as the input voltage is below the desired level. A power good output, PGOOD (MAX5902) or PGOOD (MAX5903), asserts when the external MOSFET is fully enhanced and the source-drain voltage is below the circuit breaker threshold. PGOOD and PGOOD are open-drain outputs referenced to GND, and can withstand up to +72V. SCOPE 48V MAX5902 ON/OFF GND SCOPE 50kΩ DRAIN VS GATE DRAIN 0 TO 0.5V MAX5902A PGOOD ON/OFF I (a) SUPPLY CURRENT GND PGOOD (d) RETRY TIMEOUT SCOPE SCOPE IRFR5410 VS DRAIN 50kΩ VS 48V V VIN GATE SCOPE SCOPE MAX5902 ON/OFF GND PGOOD GATE DRAIN RL CL MAX5902 V ON/OFF (b) VUVLO GND PGOOD (d) STARTUP WAVEFORMS SCOPE 50Ω VS V VIN GATE DRAIN V MAX5902 ON/OFF GND SCOPE 48V VS DRAIN 50kΩ PGOOD MAX5902 ON/OFF (b) GATE DRIVE VOLTAGE GATE GND PGOOD SCOPE (d) CIRCUIT BREAKER EVENT Figure 2. Test Circuits 6 _______________________________________________________________________________________ +72V SOT23 Simple Swapper Hot-Swap Controllers +24V OPTIONAL ON/OFF R2 40.2kΩ VS MAX5902N/MAX5903N ignore the MOSFET drain-tosource voltage for applications where a circuit breaker function is not desired. MAX5902 MAX5903 Applications Information ON/OFF Control Input ON/OFF DGND R1 3.01kΩ GND GND Figure 3. Programmed +18V Lockout, with Optional Optocoupler On/Off Control. A thermal shutdown feature protects the external MOSFET by turning it off if the die temperature of the MAX5902/MAX5903 exceeds +125°C. The MAX5902/ MAX5903 must be in good thermal contact with the external MOSFET. See Layout Guidelines in the Applications section of the data sheet. A circuit breaker function monitors the voltage across the external MOSFET, VSD, and turns off the MOSFET if VSD exceeds the circuit breaker threshold, VCB. The circuit breaker function is enabled after the MOSFET is fully enhanced. Three threshold voltage options are available—300mV, 400mV, and 500mV. One version is available with no circuit breaker function. Fault management for the MAX5902/MAX5903 is offered with two different configurations; latched and automatic retry. Latched Circuit Breaker The ON/OFF control input provides three functions: external ON/OFF control; setting of the UVLO level; and resetting after a circuit breaker event has caused the MAX5902L/MAX5903L to turn off the external MOSFET. Pulling ON/OFF to GND for at least 10ms (tOFF) forces the MAX5902/MAX5903 to turn off the external MOSFET (see Figure 3 for a circuit example). To reset the MAX5902L/MAX5903L after a circuit breaker event, toggle ON/OFF to GND for at least 10ms (tOFF). ON/OFF can be used to sequence power supplies. Connecting a capacitor from ON/OFF to GND will delay the rise of ON/OFF proportional to the capacitance and input impedance of ON/OFF, typically 33kΩ (Figure 4). The MAX5902/MAX5903 can be controlled by logic level signals. Logic level signals of 3.3V or 1.8V may be directly connected to ON/OFF. For 5V logic level control, insert a series 47kΩ resistor as shown in Figure 5. HOT SWAP CONTROLLER #1 VS After a circuit breaker trip event the latched versions (MAX5902L/MAX5903L) drive GATE to V S , turning off the external MOSFET, and PGOOD (PGOOD) is deasserted. A latched off condition needs to be reset by toggling ON/OFF low for at least 10ms, or by cycling the power supply, VS. VS MAX5902 MAX5903 ON/OFF C GND Automatic Retry Circuit Breaker After a circuit breaker trip event the automatic retry versions (MAX5902A/MAX5903A) drive GATE to VS, turning off the external MOSFET, and PGOOD (PGOOD) is deasserted. If the start conditions are met for a full 150ms (tRS) the start sequence is re-initiated. The start conditions are: the device is not in UVLO; ON/OFF is not driven low; and the device is not in thermal shutdown. No Circuit Breaker For the versions without a circuit breaker, MAX5902N (MAX5903N), PGOOD (PGOOD) are asserted when the MOSFET is fully enhanced. Once powered up the HOT SWAP CONTROLLER #2 VS MAX5902 MAX5903 ON/OFF 2C GND GND Figure 4. Power-Supply Sequencing _______________________________________________________________________________________ 7 MAX5902/MAX5903 HOT SWAP CONTROLLER MAX5902/MAX5903 +72V SOT23 Simple Swapper Hot-Swap Controllers HOT-SWAP CONTROLLER MAX5902 MAX5903 47kΩ GND MAX5902 100kΩ ON/OFF 5V LOGIC HOT-SWAP CONTROLLER +9V TO +72V VS ON/OFF GND GND LOGIC CONTROL OF 3.3V OR LESS MAY BE CONNECTED DIRECTLY TO THE MAX5902/MAX5903. FOR 5V LOGIC CONTROL INSERT A SERIES 47kΩ RESISTOR AS SHOWN. Figure 6. Defeating Undervoltage Lockout Figure 5. Logic Control Turn-On and Turn-Off Delays After power is applied, or ON/OFF is released, there is a 150ms delay (tON) before the gate ramp is started. This delay is also the automatic restart time delay. In the event of a circuit breaker condition or an overtemperature fault condition, the turn-off delay is less than 4µs. An undervoltage condition must exist for at least 10ms (tOFF) before the MAX5902/MAX5903 turns off the external MOSFET. ON/OFF must be held low for at least 10ms (t OFF) before the MAX5902/MAX5903 turns off the external MOSFET. Turn-off delay minimizes spurious shutdowns due to noisy signals or momentary voltage spikes, as well as preventing accidental resetting of the circuit breaker latch (MAX5902L/MAX5903L). Thermal Shutdown A thermal shutdown feature helps protect the external MOSFET. If the die temperature of the MAX5902/ MAX5903 exceeds +125°C, the MOSFET is turned off. For accurate performance the MAX5902/MAX5903 must be in close thermal contact with the external MOSFET. See Layout Guidelines for information. Due to the low power dissipation of the MAX5902/MAX5903, its junction temperature will typically be within a few degrees of the MOSFET. All versions of the MAX5902/ MAX5903 automatically restart from a temperature fault when the junction temperature drops below +110°C. Undervoltage Lockout The MAX5902/MAX5903 turns off the external MOSFET if the magnitude of the input voltage is below the level set by ON/OFF for longer than 10ms (tOFF). If ON/OFF is left unconnected, the lockout voltage (V UVLO ) defaults to 31.5V. VUVLO may also be set to any value within the power-supply range by using external resistors. To set the lockout voltage to a value between +9V 8 GND and +72V use a resistor divider connected between VS and GND, with the center node of the divider connected to ON/OFF. For example, use a 3kΩ resistor (R1 in Figure 3) from ON/OFF to GND and calculate the other resistor, R2, using: V R2 = R1 × UVLO − 1 VON / OFF where V UVLO is the desired lockout voltage, and VON/OFF is the ON/OFF reference threshold specified in the Electrical Characteristics table (typically 1.26V). Figure 3 shows an example circuit with VUVLO set for +18V. To defeat the UVLO simply connect a single 100kΩ resistor between ON/OFF and VS, as shown in Figure 6. The Power Good Output The power good output, PGOOD (PGOOD), is opendrain and asserts when the external MOSFET is fully enhanced and V SD is less than the circuit breaker threshold (VCB). For versions without the circuit breaker function (MAX5902N/MAX5903N), PGOOD (PGOOD) asserts when the external MOSFET is fully enhanced. PGOOD (PGOOD) deasserts within 4µs when a circuit breaker event occurs or if the die temperature exceeds +125°C. PGOOD (PGOOD) deasserts if VS < VUVLO for longer than 10ms or ON/OFF is held low for longer than 10ms. The MAX5902 PGOOD is active-low and the MAX5903 PGOOD is active-high. Both are open-drain N-channel MOSFETs with their sources connected to GND, and can withstand up to +72V. _______________________________________________________________________________________ +72V SOT23 Simple Swapper Hot-Swap Controllers VCB > (RDS(ON)) ✕ (IOUT(MAX)) where RDS(ON) is the on-resistance of the MOSFET and IOUT(MAX) is the maximum expected output current. The MAX5902N/MAX5903N have no circuit breaker function. For these parts choose an external MOSFET which meets the load requirements. The circuit breaker function is intended to protect against gross overcurrent or short-circuit conditions. During a gross overcurrent or short-circuit condition, the MAX5902/MAX5903 disconnect the load by disabling the external MOSFET. For calculating the circuit breaker threshold use the MOSFET’s RON at the worst possible operating condition, and add a 20% overcurrent margin to the maximum circuit current. For instance, if a MOSFET has an RON of 0.06Ω at TA = +25°C, and a normalized on-resistance factor of 1.75 at TA = +130°C (from the MOSFET data sheet), the RON used for calculation is the product of these two numbers, or (0.06Ω) x (1.75) = 0.105Ω. Then, if the maximum current is expected to be 2A, using a 20% margin, the current for calculation is (2A) x (1.2) = 2.4A. The resulting minimum circuit breaker threshold is then a product of these two results, or (0.105Ω) x (2.4A) = 0.252V. The next highest minimum available threshold is 0.280V of the MAX5902ABEUT, which is an ideal choice given these parameters. Using this method to choose a circuit breaker threshold allows the circuit to operate under worst case conditions without causing a circuit breaker fault, but the circuit breaker function will still operate if a short circuit, or a gross overcurrent condition exists. GROUND U1 SOT23-6 MAX5902/MAX5903 POWER IN M1 SOT-223 S D G POWER OUT Figure 7. Circuit Board Layout Example. Determining Inrush Current Determining a circuit’s inrush current is necessary to help choose the proper MOSFET. The MAX5902/ MAX5903 regulate the inrush current by means of controlling the load voltage slew rate, but inrush current is also a function of load capacitance. Determine inrush current using: I=C dV = C × SR dt where C is the load capacitance, and SR is the MAX5902/MAX5903 Load Voltage Slew Rate Magnitude from the Electrical Characteristics table. For example, assuming a load capacitance of 100µF, and using the typical value of 9V/ms for the slew rate, the inrush current is 0.9A typical. If the maximum possible Load Voltage Slew Rate is used, the maximum inrush current calculates to 1.8A. Choose a MOSFET with a maximum pulsed current specification that exceeds the maximum inrush current. Suggested External MOSFETs MAXIMUM ILOAD (A) SUGGESTED EXTERNAL MOSFET SUGGESTED MAXIM PART 0.5 IRF9540NS MAX5902AAEUT 1 IRF9540NS MAX5902ABEUT 2 IRF5210S MAX5902ABEUT 3 IRF5210S MAX5902ACEUT VIN = +9V to +72V _______________________________________________________________________________________ 9 MAX5902/MAX5903 Selecting a Circuit Breaker Threshold The MAX5902A/MAX5903A and the MAX5902L/ MAX5903L offer a circuit breaker function to protect the external MOSFET and the load from the potentially damaging effects of excessive current. As load current flows through the external MOSFET, a voltage, VSD, is generated from source to drain due to the MOSFET’s on-resistance, R DS(ON) . The MAX5902A/MAX5903A and MAX5902L/MAX5903L monitor VSD when the external MOSFET is fully enhanced. If VSD exceeds the circuit breaker threshold the external MOSFET is turned off, and PGOOD (PGOOD) is deasserted. To accommodate different MOSFETs and different load currents the MAX5902/MAX5903 are available with circuit breaker threshold voltages of 300mV, 400mV, and 500mV. To determine the proper circuit breaker threshold for an application use: MAX5902/MAX5903 +72V SOT23 Simple Swapper Hot-Swap Controllers Layout Guidelines Chip Information Good thermal contact between the MAX5902/ MAX5903 and the external MOSFET is essential for the thermal shutdown feature to operate effectively. Place the MAX5902/MAX5903 as close as possible to the drain of the external MOSFET, and use wide circuit board traces for good heat transfer. See Figure 7 for an example of a PC board layout. TRANSISTOR COUNT: 658 PROCESS TECHNOLOGY: BiCMOS Selector Guide PART CIRCUIT BREAKER FUNCTION CIRCUIT BREAKER THRESHOLD POWER GOOD OUTPUT LOGIC TOP MARK MAX5902NNEUT*† None None Active-Low AASM MAX5902AAEUT*† Auto Retry 300mV Active-Low AASA MAX5902ABEUT* Auto Retry 400mV Active-Low AASB MAX5902ACEUT*† Auto Retry 500mV Active-Low AASC MAX5902LAEUT*† Latched 300mV Active-Low AASD MAX5902LBEUT*† Latched 400mV Active-Low AASE MAX5902LCEUT* Latched 500mV Active-Low AASF None None Active-High AASN MAX5903AAEUT* Auto Retry 300mV Active-High AASG MAX5903ABEUT*† Auto Retry 400mV Active-High AASH MAX5903ACEUT*† Auto Retry 500mV Active-High AASI MAX5903LAEUT*† Latched 300mV Active-High AASJ MAX5903LBEUT*† Latched 400mV Active-High AASK MAX5903LCEUT*† Latched 500mV Active-High AASL MAX5903NNEUT*† *Requires special solder temperature profile described in the Absolute Maximum Ratings section. †Future products—contact factory for availability. Typical Operating Circuits (continued) 50W ISOLATED POWER SUPPLY BACKPLANE CIRCUIT CARD +48V IRFR5410 HOT SWAP CONTROLLER V+ MAX5903 VS ON/OFF GND 1MΩ GATE DRAIN PGOOD MAX5003* INDIV 39kΩ GND GND *THE MAX5003 IS A 110V PWM CONTROLLER 10 ______________________________________________________________________________________ +72V SOT23 Simple Swapper Hot-Swap Controllers 6LSOT.EPS 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 ____________________ 11 © 2001 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products. MAX5902/MAX5903 Package Information