19-2735; Rev 1; 3/04 K ATION EVALU BLE AVAILA IT ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies Features Critical loads often employ parallel-connected power supplies with redundancy in order to enhance system reliability. The MAX8535/MAX8536/MAX8585 are highly integrated but inexpensive MOSFET controllers that provide isolation and redundant power capability in high-reliability systems. The MAX8535/MAX8585 are used in 12V systems, and have an internal charge pump to drive the gates of the n-channel pass elements to VCC + 10V. The MAX8536 is used in 3.3V and 5V systems, with a chargepump output of VCC + 5V. During startup, the MAX8535/MAX8536/MAX8585 monitor the voltage drop across external MOSFETs. Once V CC approaches or exceeds the bus voltage, the MOSFETs are turned on. The MAX8535/MAX8536/ MAX8585 feature a dual-purpose TIMER input. A single external resistor from TIMER to ground sets the turn-on speed of the external MOSFETs. Optionally, the TIMER input can be used as a logic-enable pin. Once the device is turned on, the MAX8535/MAX8536/MAX8585 monitor the load, protecting against overvoltage, undervoltage, and reverse-current conditions. Simple, Integrated, and Inexpensive ORing MOSFET Controller Overvoltage and undervoltage fault thresholds are adjustable and can be disabled. The current-limit trip points are set by the external MOSFETs' R DS(ON) , reducing component count. An open-drain logic-low fault output indicates if an overvoltage, undervoltage, or reverse-current fault occurs. Space-Saving 8-Pin MAX Package All devices come in a space-saving 8-pin MAX (R) package and are specified over the extended -40C to +85C temperature range. ORing MOSFET Drive for 12V (MAX8535/MAX8585) and 3.3V or 5V (MAX8536) Bus Eliminates ORing Diode Power Dissipation and Reverse Leakage Current Provides N + 1 Redundant Supply Capability for Highly Reliable Systems Isolates Failed Supply from Output Bus in <1s Reverse-Current Flow Detection Programmable Soft-Start Logic-Enable Input Adjustable Overvoltage and Undervoltage Trip Points Fault-Indicator Output Ordering Information PART TEMP RANGE PIN-PACKAGE 8 MAX MAX8535EUA -40C to +85C MAX8535AEUA -40C to +85C 8 MAX MAX8536EUA -40C to +85C 8 MAX MAX8585EUA -40C to +85C 8 MAX Typical Operating Circuit MAX is a registered trademark of Maxim Integrated Products, Inc. Applications OUTPUT: 3.3V/5V (MAX8536), 12V (MAX8535) Silver Box Supplies for Servers On-Board Redundant Power Supplies in Blade Servers OUT+ +VO -VO REDUNDANT OUTPUT BUS Network/Telecom Power Supplies Rectifiers Redundant Power Supplies in High-Availability Systems SILVER BOX OR RECTIFIERS GATE VCC TIMER CS FAULT MAX8535 MAX8536 MAX8585 GND UVP N.C. OVP Pin Configuration, Functional Diagrams, and Typical Application Circuits appear at end of data sheet. OUT- ________________________________________________________________ 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 MAX8535/MAX8536/MAX8585 General Description MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies ABSOLUTE MAXIMUM RATINGS GATE to GND (MAX8535/MAX8535A/MAX8585)...-0.3V to +28V VCC to GND (MAX8535/MAX8535A/MAX8585) .....-0.3V to +18V CS, FAULT to GND (MAX8535/MAX8535A/MAX8585) ......................-0.3V to +15V GATE to GND (MAX8536) ............................ -0.3V to (VCC + 6V) VCC, CS, FAULT to GND (MAX8536) .......................-0.3V to +6V OVP, UVP, TIMER to GND........................................-0.3V to +6V Continuous Power Dissipation (TA = +70C) 8-Pin MAX (derate 4.5mW/C above +70C) .............362mW Operating Temperature Range ...........................-40C to +85C Storage Temperature Range .............................-65C to +150C Junction Temperature ....................................................+150C Lead Temperature (soldering, 10s) .................................+300C 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 = 12V (MAX8535/MAX8535A/MAX8585), VCC = 5V (MAX8536), VCS = VCC - 0.1V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, TA = 0C to +85C, unless otherwise noted.) PARAMETER SYMBOL CONDITIONS MIN TYP MAX VCC = 14V (MAX8535/ MAX8535A/MAX8585) 2 4.5 VCC = 6V (MAX8536) 2 3 UNITS VCC SUPPLY VCC Supply Current TIMER = 2.5V VCC Shutdown Current TIMER = 0V VCC Input Voltage TIMER = 2.5V VCC = 14V (MAX8535/ MAX8535A/MAX8585) 4.5 VCC = 6V (MAX8536) 3 MAX8535/MAX8535A/ MAX8585, charge pump on 8 14 MAX8536, charge pump on 3.0 5.5 MAX8535/MAX8535A/ MAX8585, charge pump off TIMER = 2.5V CS Isolation CS = max operating voltage, VCC = 0V, I(VCC) 100 CS = 5.5V (MAX8536) VCC Undervoltage Lockout VCCOK VCC Overvoltage Internal Threshold V A 50 -0.05 -1 6 6.5 7 MAX8536, rising threshold 2.5 2.7 2.9 MAX8535/ MAX8535A/ MAX8585 Rising threshold 14 14.5 15 Falling threshold 13.3 13.9 14.5 Measured from VGATE to VCC, VCC = 3.3V (MAX8536) 5 5.5 6 VCC = 5V (MAX8536) 5 5.5 6 VCC = 12V (MAX8535/MAX8535A/MAX8585) 9 11 12 MAX8535/MAX8535A/MAX8585, rising threshold mA 17 CS = 14V (MAX8535/ MAX8535A/MAX8585) CS Input Current mA A V V CHARGE-PUMP VOLTAGE Gate Voltage 2 VGATE _______________________________________________________________________________________ V ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies (VCC = 12V (MAX8535/MAX8535A/MAX8585), VCC = 5V (MAX8536), VCS = VCC - 0.1V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, TA = 0C to +85C, unless otherwise noted.) PARAMETER SYMBOL Charge-Pump Switching Frequency CONDITIONS MIN TYP RTIMER = 20k 187 RTIMER = 125k 450 RTIMER = open 500 VTIMER = 1.5V 550 MAX UNITS kHz TIMER TIMER Voltage 1.219 1.25 1.281 V 80 100 120 A 10 20 A TIMER Maximum Source Current VTIMER = 1V TIMER High-Input Current VTIMER = 1.5V TIMER Maximum Frequency Select Voltage Input Range MAX8535/MAX8535A/MAX8585 1.5 MAX8536 1.5 1.0 TIMER Logic High VIH Charge pump enabled TIMER Logic Low VIL Charge pump disabled 3.4 VCC - 0.6 V V 0.5 V FAULT Fault Output Low Voltage IFAULT = 0.5mA Fault Sink Current FAULT = 0.8V Fault Leakage Current 0.8 0.5 V mA FAULT = 18V (MAX8535 /MAX8535A/MAX8585) 5 FAULT = 6V (MAX8536) 5 A GATE Gate On Threshold Measured from VCC to CS VGATE = VCC = 12V Gate Drive Current VGATE = VCC = 5V Gate Shutdown Delay Gate Discharge Current Gate Fall Time 0.3 0.4 0.5 ITIMER = 0A (MAX8535/ MAX8535A/MAX8585) 35 50 65 ITIMER = 50A (MAX8535/ MAX8535A/MAX8585) 15 25 36 ITIMER = 0A (MAX8536) 17 25 33 ITIMER = 50A (MAX8536) 8 12 16 200 300 From fault sense to the start of gate voltage falling, or from TIMER to the start of gate voltage falling GATE = VCC + 5V (MAX8535/MAX8536) 100 200 300 GATE = VCC + 5V (MAX8535A/MAX8585) 200 300 400 Gate voltage fall from fault to VGATE = VCC, CGATE = 0.01F (200ns + CV/I = 700ns, typ) (MAX8535/MAX8536) 0.7 MAX8535A/MAX8585 0.55 V A ns mA s CURRENT SENSE Reverse-Current Threshold Measured from CS to VCC (MAX8535/MAX8535A/MAX8536) 20 30 40 MAX8585 -3 0 +3 mV _______________________________________________________________________________________ 3 MAX8535/MAX8536/MAX8585 ELECTRICAL CHARACTERISTICS (continued) MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies ELECTRICAL CHARACTERISTICS (continued) (VCC = 12V (MAX8535/MAX8535A/MAX8585), VCC = 5V (MAX8536), VCS = VCC - 0.1V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, TA = 0C to +85C, unless otherwise noted.) PARAMETER SYMBOL Startup Reverse-Current Blank Time MAX8585 Measured from VCC to CS Forward-Current Threshold OVERVOLTAGE PROTECTION OVP Fault Threshold CONDITIONS MIN TIMER = open (MAX8535/MAX8535A/ MAX8536) VOVP OVP rising TYP MAX 524 ms 5 32 10 15 1.219 1.25 1.281 OVP falling 1.2 OVP Bias Current UNITS 0.2 mV V A UNDERVOLTAGE PROTECTION UVP Fault Voltage VUVP UVP rising threshold 1.219 1.25 1.281 UVP falling threshold 1.119 1.15 1.181 UVP Bias Current 0.4 V A ELECTRICAL CHARACTERISTICS (VCC = 12V (MAX8535/MAX8535A/MAX8585), VCC = 5V (MAX8536), VCS = VCC - 0.1V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, TA = -40C to +85C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS VCC SUPPLY VCC = 14V (MAX8535/ TIMER = 2.5V MAX8535A/MAX8585) VCC Supply Current VCC Shutdown Current TIMER = 0V VCC = 6V (MAX8536) 3 VCC = 14V (MAX8535/ MAX8535A/MAX8585) 4.5 VCC = 6V (MAX8536) 3 MAX8535/MAX8535A/ MAX8585, charge pump on VCC Input Voltage 4.5 TIMER = 2.5V MAX8536, charge pump on 8 14 3.0 5.5 MAX8535/MAX8535A/ MAX8585, charge pump off 17 CS Isolation CS = max operating voltage, VCC = 0V, I(VCC) -1 VCC Undervoltage Lockout (MAX8535/MAX8535A/MAX8585) rising threshold 6.0 7.0 (MAX8536) rising threshold 2.5 2.9 (MAX8535/ MAX8535A/ MAX8585) Rising threshold 14 15 Falling threshold 13.3 14.5 VCC Overvoltage Internal Threshold 4 VCCOK mA mA V A V V _______________________________________________________________________________________ ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies (VCC = 12V (MAX8535/MAX8535A/MAX8585), VCC = 5V (MAX8536), VCS = VCC - 0.1V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, TA = -40C to +85C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS CHARGE-PUMP VOLTAGE Gate Voltage VGATE Measured from VGATE to VCC, VCC = 3.3V (MAX8536) 5 6 VCC = 5V (MAX8536) 5 6 VCC = 12V (MAX8535/MAX8535A/MAX8585) 9 12 1.200 1.281 V 80 120 A 20 A V TIMER TIMER Voltage TIMER Maximum Source Current VTIMER = 1.0V TIMER High-Input Current VTIMER = 1.5V TIMER Maximum Frequency Select Voltage Input Range MAX8535/MAX8535A/MAX8585 1.5 MAX8536 1.5 1.1 TIMER Logic High VIH Charge pump enabled TIMER Logic Low VIL Charge pump disabled 3.4 VCC - 0.6 V V 0.5 V FAULT Fault Output Low Voltage IFAULT = 0.5mA Fault Sink Current FAULT = 0.8V 0.8 Fault Leakage Current FAULT = 18V (MAX8535/ MAX8535A/MAX8585) 5 FAULT = 6V (MAX8536) 5 0.5 V mA A GATE Gate On Threshold Measured from VCC to CS VGATE = VCC = 12V Gate-Drive Current VGATE = VCC = 5V Gate Shutdown Delay 0.3 0.5 ITIMER = 0A (MAX8535/ MAX8535A/MAX8585) 35 65 ITIMER = 50A (MAX8535/ MAX8535A/MAX8585) 15 36 ITIMER = 0A (MAX8536) 17 33 ITIMER = 50A (MAX8536) 8 16 From fault sense to the start of gate voltage falling, or from TIMER to the start of gate voltage falling 300 GATE = VCC + 5V (MAX8535/MAX8536) 100 300 MAX8535A/MAX8585 200 400 Reverse-Current Threshold Measured from CS to VCC (MAX8535/MAX8535A/MAX8586) 20 40 MAX8585 -5 +5 Forward-Current Threshold Measured from VCC to CS 5 15 Gate Discharge Current V A ns mA CURRENT SENSE mV mV _______________________________________________________________________________________ 5 MAX8535/MAX8536/MAX8585 ELECTRICAL CHARACTERISTICS (continued) MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies ELECTRICAL CHARACTERISTICS (continued) (VCC = 12V (MAX8535/MAX8535A/MAX8585), VCC = 5V (MAX8536), VCS = VCC - 0.1V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, TA = -40C to +85C, unless otherwise noted.) (Note 1) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS OVERVOLTAGE PROTECTION OVP Fault Threshold VOVP OVP rising 1.20 OVP Bias Current 1.281 V 0.2 A UNDERVOLTAGE PROTECTION UVP Fault Voltage VUVP UVP rising threshold 1.200 1.281 UVP falling threshold 1.10 1.19 UVP Bias Current Note 1: Specifications to -40C are guaranteed by design and not production tested. 6 _______________________________________________________________________________________ 0.4 V A ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies VCC > VCCOK CS + 0.01V CS ALL TRANSITIONS ARE ASYNCHRONOUS CS - 0.03V CS - 0.4V STANDBY: CPMP: OFF GATE: LOW VCC VSHARE LATCH IREVERSE BLANKING IFORWARD 500ms TIMER >1V IREVERSE VSHARE = (CS - VCC) < 0.4V IFORWARD = (VCC - CS) > 0.01V IREVERSE = (CS - VCC) > 0.03V WAIT FOR VSHARE CS - VCC > 0.4V CS - VCC < 0.4V VCC OR TIMER CYCLED UVP FAULT ON: SET VSHARE LATCH, CHARGE PUMP ON UVP FAULT SHUTDOWN GATE: FAULT NOT LATCHED OVP OK AND IREVERSE DURING FIRST 500ms IFORWARD AND OVP FAULT UVP = OK FAULT SHUTDOWN GATE: FAULT LATCHED UVP = OK (MAX8585) IREVERSE AFTER 32ms BLANK TIME FAULT SHUTDOWN GATE: NOT LATCHED IREVERSE CONDITION DETECTED AFTER 500ms BLANK TIME (MAX8535/MAX8535A/MAX8536) FAULT SHUTDOWN GATE: FAULT LATCHED VCC OR TIMER CYCLED _______________________________________________________________________________________ 7 MAX8535/MAX8536/MAX8585 State Diagram MAX8535 Typical Operating Characteristics (VCC = 12V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, BUS = 100F, TA = +25C, unless otherwise specified.) SUPPLY CURRENT vs. TEMPERATURE GATE-CHARGE CURRENT vs. TIMER RESISTANCE (RTIMER) TA = +25C 40 TA = -40C 30 20 3.2 10 3.0 TIMER = GND 2.8 2.6 TIMER IS UNCONNECTED 2.4 2.2 0 2.0 10 1000 100 -40 -20 0 20 40 60 80 RESISTANCE (k) TEMPERATURE (C) MAX8535 REVERSE-CURRENT THRESHOLD vs. TEMPERATURE UVP AND OVP LEAKAGE CURRENT vs. TEMPERATURE 34 33 32 31 30 29 28 140 120 LEAKAGE CURRENT (nA) MAX8535/MAX8536 toc03 35 UVP 100 80 60 40 27 OVP 20 26 0 25 -40 -15 10 35 60 -40 85 -20 0 20 40 60 80 TEMPERATURE (C) TEMPERATURE (C) POWER-UP WAVEFORM (VBUS = 0V) POWER-UP WAVEFORM (VBUS = 12V) MAX8535/MAX8536 toc05 4ms/div 8 MAX8535/MAX8536 toc02 50 3.4 MAX8535/MAX8536 toc04 GATE-CHARGE CURRENT (A) TA = +85C SUPPLY CURRENT (mA) MAX8535/MAX8536 toc01 60 REVERSE-CURRENT THRESHOLD (mV) MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies MAX8535/MAX8536 toc06 VCC 10V/div VCC 10V/div IMOSFET 10A/div IMOSFET 2A/div VGATE 20V/div VGATE 20V/div VCS 10V/div VCS 10V/div 4ms/div _______________________________________________________________________________________ ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies TIMER-ENABLED STARTUP AND SHUTDOWN WAVEFORMS (VCC = 12V, VBUS = 12V) TIMER-ENABLED STARTUP AND SHUTDOWN WAVEFORMS (VCC = 12V, VBUS = 0V) MAX8535/MAX8536 toc07 MAX8535/MAX8536 toc08 VTIMER 2V/div VTIMER 1V/div IMOSFET 50mA/div IMOSFET 10A/div VGATE 20V/div VGATE 20V/div VCS 10V/div VCS 10V/div 4ms/div 4ms/div UVP FAULT WAVEFORM (R1 = 100) REVERSE-CURRENT FAULT WAVEFORM (R1 = 10) MAX8535/MAX8536 toc10 MAX8535/MAX8536 toc09 VCS 1V/div 12V IMOSFET 5A/div 1.25V VUVP 1V/div VFAULT 10V/div VGATE 20V/div VGATE 20V/div VCS 10V/div VFAULT 10V/div 1s/div 400ns/div SELECTIVE OVP SHUTDOWN WAVEFORM (R1 = 10) MAX8535/MAX8536 toc11 VCS 1V/div 12V VGATE1 (OVP UNIT) 20V/div VGATE2 (GOOD UNIT) 20V/div VFAULT 10V/div 1s/div _______________________________________________________________________________________ 9 MAX8535/MAX8536/MAX8585 MAX8535 Typical Operating Characteristics (continued) (VCC = 12V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, BUS = 100F, TA = +25C, unless otherwise specified.) MAX8536 Typical Operating Characteristics (VCC = 12V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, BUS = 100F, TA = +25C, unless otherwise specified.) GATE-CHARGE CURRENT vs. TIMER RESISTANCE (RTIMER) SUPPLY CURRENT vs. TEMPERATURE 15 10 MAX8535/MAX8536 toc13 TA = -40C TA = +85C 20 2.2 2.0 SUPPLY CURRENT (mA) TA = +25C 25 5 1.8 TIMER IS UNCONNECTED 1.6 TIMER = GND 1.4 1.2 0 1.0 10 1000 100 -40 -20 0 20 40 60 TEMPERATURE (C) MAX8536 REVERSE-CURRENT THRESHOLD vs. TEMPERATURE UVP AND OVP LEAKAGE CURRENT vs. TEMPERATURE 34 33 32 31 30 29 28 140 120 LEAKAGE CURRENT (nA) MAX8535/MAX8536 toc14 35 UVP 100 80 60 40 27 OVP 20 26 25 0 -40 -15 10 35 60 85 -40 -20 0 20 40 60 80 TEMPERATURE (C) TEMPERATURE (C) POWER-UP WAVEFORM (VBUS = 0V) POWER-UP WAVEFORM (VBUS = 5V) MAX8535/MAX8536 toc16 MAX8535/MAX8536 toc17 VCC 5V/div VCC 5V/div IMOSFET 2A/div 4ms/div 10 80 RESISTANCE (k) MAX8535/MAX8536 toc15 GATE-CHARGE CURRENT (A) MAX8535/MAX8536 toc12 30 REVERSE-CURRENT THRESHOLD (mV) MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies IMOSFET 1A/div VGATE 10V/div VGATE 10V/div VCS 5V/div VCS 5V/div 4ms/div ______________________________________________________________________________________ ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies TIMER-ENABLED STARTUP AND SHUTDOWN WAVEFORMS (VCC = 5V, VBUS = 5V) TIMER-ENABLED STARTUP AND SHUTDOWN WAVEFORMS (VCC = 5V, VBUS = 0V) MAX8535/MAX8536 toc18 MAX8535/MAX8536 toc19 VTIMER 2V/div VTIMER 2V/div IMOSFET 50mA/div IMOSFET 1A/div VGATE 10V/div VGATE 10V/div VCS 5V/div VCS 5V/div 4ms/div 10ms/div UVP FAULT WAVEFORM (R1 = 100) REVERSE-CURRENT FAULT WAVEFORM (R1 = 10) MAX8535/MAX8536 toc21 MAX8535/MAX8536 toc20 VCS 1V/div 5V IMOSFET 5A/div 1.25V VUVP 2V/div VFAULT 5V/div VGATE 10V/div VGATE VFAULT 5V/div VCS 1V/div 400ns/div 1s/div SELECTIVE OVP SHUTDOWN WAVEFORM (R1 = 10) MAX8535/MAX8536 toc22 VCS 1V/div 5V VGATE2 (GOOD UNIT) 10V/div VGATE1 (OVP UNIT) 10V/div VFAULT 5V/div 1s/div ______________________________________________________________________________________ 11 MAX8535/MAX8536/MAX8585 MAX8536 Typical Operating Characteristics (continued) (VCC = 12V, RTIMER = 25k, UVP = 2V, OVP = 1V, CGATE = 0.01F, BUS = 100F, TA = +25C, unless otherwise specified.) MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies Pin Description PIN NAME 1 GATE Gate Drive Output. Bypass GATE with a 0.01F capacitor to ground. 2 GND Ground 3 VCC Power-Supply Input. Bypass VCC with a 0.1F capacitor to ground. UVP Undervoltage Input. Connect a resistor-divider from the VCC to GND with the center point connected to UVP. Leave high impedance if not used. UVP fault threshold must be set above VCCOK threshold. 5 TIMER Timer Input. Connect a resistor from TIMER to ground to select the charge-pump operating frequency. The charge-pump frequency is proportional to the TIMER output current. TIMER can source up to 100A. If pulled low (<0.5V), the gate drive is disabled. If pulled high (above 1.25V), the charge pump operates at 550kHz. 6 OVP Overvoltage Input. Connect a resistor-divider from the CS to GND with the center point connected to OVP. Connect to GND if not used. 7 FAULT 8 CS 4 FUNCTION Open-Drain Fault Output. FAULT is low during a fault, high impedance during normal operation. Connect a pullup resistor of 50k or higher value to a voltage rail. Current-Sensing Input. Connect CS to the positive side of the system bus. Bypass with 1nF capacitor to GND. Detailed Description Critical loads often employ parallel-connected power supplies with redundancy to enhance system reliability. The MAX8535/MAX8536/MAX8585 are highly integrated but inexpensive MOSFET controllers that provide isolation and redundant power capability in high-reliability systems. The MAX8535/MAX8585 is used in 12V systems and has an internal charge pump to drive the gates of the n-channel pass elements to VCC + 10V. The MAX8536 is used in 3.3V and 5V systems, with a charge pump output of VCC + 5V. During startup, the MAX8535/MAX8536/MAX8585 monitor the voltage drop across external MOSFETs. Once V CC approaches or exceeds the bus voltage, the MOSFETs are turned on. The MAX8535/MAX8536/ MAX8585 feature a dual-purpose TIMER input. A single external resistor from TIMER to ground sets the turn-on speed of the external MOSFETs. Optionally, the TIMER input can be used as a logic-enable pin. Once the device is turned on, the MAX8535/MAX8536/MAX8585 monitor the load, protecting against overvoltage, undervoltage, and reverse-current conditions. Overvoltage and undervoltage fault thresholds are adjustable and can be disabled. The current-limit trip points are set by the external MOSFETs' RDS(ON) , reducing component count. An open-drain logic-low fault output indicates if an overvoltage, undervoltage, or reverse-current fault occurs. 12 VCC V CC is the power-supply input for the MAX8535/ MAX8536/MAX8585 and the input to the internal charge pump that drives the gate of the external MOSFETs. The MAX8535/MAX8536/MAX8585 monitor VCC at all times. VCC connects directly to the power supply (Silver Box or DC-DC power modules). During startup, the device turns on when VCC rises above the undervoltage threshold V CCOK . After V CC exceeds V CCOK and V CC is greater than (CS - 0.4V), the charge pump turns on, driving GATE high and turning on the external MOSFETs. TIMER The MAX8535/MAX8536/MAX8585 provide a programmable-frequency charge pump and shutdown function through TIMER. Slowing down the charge-pump frequency allows a user to program soft-start. Connecting a resistor from TIMER to GND sets the charge-pump frequency from 100kHz to 500kHz. Connecting TIMER to a logic high sets charge-pump operation to a maximum frequency of 550kHz. Pulling TIMER to GND shuts down the charge pump and turns off the external MOSFET. Reducing the charge-pump frequency increases the IREVERSE startup blank time (see the Reverse-Current Fault section). GATE GATE is the output of the internal charge pump that drives the external MOSFETS. During startup, the GATE voltage ramps up according to the charge-pump frequency. At 250kHz, the GATE drive current for the MAX8535/MAX8585 is 25A and the GATE drive current ______________________________________________________________________________________ ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies CS The voltage drop across the external MOSFETs is measured between the VCC and CS inputs. CS connects to the positive side of the system bus. The voltage drop across the CS and VCC determines operation modes. IFORWARD is defined as VCC - CS > 0.01V. IREVERSE is defined as CS - V CC > 0.03V in all except the MAX8585. In the MAX8585, IREVERSE = 0V. FAULT Conditions The MAX8535/MAX8536/MAX8585 contain a versatile FAULT output that signals overvoltage, undervoltage, or reverse-current conditions. During a FAULT condition, the charge pump shuts down and the GATE discharges to ground. Undervoltage Fault The MAX8535/MAX8536/MAX8585 turn off the external MOSFET if the input voltage falls below the UVP threshold. If UVP is left unconnected, the undervoltage input is disabled. Set the undervoltage threshold to any value above VCCOK. When the input voltage rises above the UVP threshold, FAULT clears and the MOSFET turns back on. Overvoltage Fault The MAX8535/MAX8536/MAX8585 contain an adjustable OVP feature. A resistor-divider from the CS system bus to the OVP input pin sets the overvoltage threshold. When the OVP level is exceeded and the part is in the IFORWARD condition (defined as VCC > CS + 0.01V), the MAX8535/MAX8536/MAX8585 turn off the external MOSFET and a fault is latched. If there is no I FORWARD condition, an OVP detection has no effect. In this way, only the input supply, which is causing the overvoltage condition, is turned off in a redundant power system application. An overvoltage fault is a latching fault condition, and requires VCC or TIMER to be cycled to reset the part. Reverse-Current Fault The MAX8535/MAX8536 contain a reverse-current protection feature. If, after the 500ms (typ) startup blank time, an IREVERSE condition is detected, the MAX8535/ MAX8536 turn off the external MOSFET and a fault is latched. A reverse-current fault forces the MAX8535/ MAX8536 to latch off. Cycle V CC or TIMER to exit a latched fault condition. Startup blanking time allows the incoming power supply to connect to the system bus at V BUS - 0.4V. Reducing charge-pump frequency increases the startup blanking time. The MAX8585 does not latch this fault. Applications Information Selecting the Timer Resistor To set the frequency of the internal charge-pump operation, connect a resistor from TIMER to GND. Determine the frequency by using the equation: 1.25V Frequency = 5 x 100A kHz / A RTIMER Pull TIMER above 1.5V for maximum charge-pump frequency. Pull TIMER below 0.5V to disable the charge pump. Leave TIMER unconnected for a 500kHz charge-pump frequency. Selecting the Gate Capacitor and Gate Resistor The charge pump uses an internal monolithic transfer capacitor to charge the external MOSFET gates. Table 1. MAX8535/MAX8536/MAX8585 Fault Modes FAULT MODE PIN CONDITIONS GATE PIN FAULT PIN LATCHING VCC UVLO VCC < VCCOK Low High impedance No UVP pin undervoltage protection UVP < 1.25V Low Low No OVP > 1.25V VCC > CS + 0.01V Low Low Yes Reverse-current protection (MAX8535/MAX8536) VCC < CS - 0.03V Gate ON for t > 0.5s Low Low Yes Reverse-current protection (MAX8585) VCC < CS Gate ON for t > 0.032s Low Low No VCC > 14.5V Low Low No OVP pin overvoltage protection VCC internal (MAX8535/MAX8585) overvoltage protection ______________________________________________________________________________________ 13 MAX8535/MAX8536/MAX8585 for the MAX8536 is 12A. Increasing the charge-pump frequency increases the GATE drive current. Adding a resistor from GATE to the gate of the external MOSFETs further increases turn-on and turn-off times. MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies Normally, the external MOSFET's gate capacitance is sufficient to serve as a reservoir capacitor. If the MOSFETs are located at a significant distance from the MAX8535/MAX8536/MAX8585, place a local bypass capacitor (0.01F, typ) across GATE and GND. For slower turn-on times, add a small capacitor between GATE and GND and a series resistor between GATE and the gate of the MOSFETs. Set the UVP Fault Threshold To set the undervoltage lockout threshold, use a resistordivider connected between VCC and GND, with the center node of the divider connected to UVP. For example, use a 10k resistor (R4 in Figure 4) from UVP to GND and calculate the other resistor (R3) using: V R3 = R4 UVLO - 1 VUVP where VUVLO is the desired undervoltage lockout voltage and VUVP is the UVP reference threshold specified in the Electrical Characteristics (1.25V, typ). To defeat the UVP, leave UVP unconnected. Set the OVP Fault Threshold To set the OVP threshold, use a resistor-divider connected between CS and GND, with the center node of the divider connected to OVP. For example, use a 10k resistor (R6 in Figure 4) from OVP to GND and calculate the other resistor, R5, using: V R5 = R6 OVLO - 1 VOVP where VOVLO is the desired overvoltage lockout voltage and VOVP is the OVP reference threshold specified in the Electrical Characteristics (1.25V, typ). To defeat the OVP, connect the OVP input to GND. MOSFET Selection The MAX8535/MAX8536/MAX8585 drive n-channel MOSFETs. The most important feature of the MOSFETs is RDS(ON). As load current flows through the external MOSFET, a voltage (VDS) is generated from drain-tosource due to the MOSFET's on-resistance, RDS(ON). The MAX8535/MAX8536/MAX8585 monitor VDS of the 14 MOSFETs at all times. The MAX8535/MAX8536/ MAX8585 determine the state of the monitored power supply by measuring the voltage drop across the external MOSFETs. With two external MOSFETs, the equation becomes: VDSTOTAL = RDS(ON)1 x ILOAD + RDS(ON)2 x ILOAD Selecting a MOSFET with a low RDS(ON) allows more current to flow through the MOSFETs before the MAX8535/MAX8536/MAX8585 detect reverse-current (IREVERSE) and forward-current (IFORWARD) conditions. Using a Single MOSFET Single MOSFETs can be used if the OVP function is not needed. Connect the source of the MOSFET to V CC and the drain of the MOSFET to CS. Layout Guidelines Keep all traces as short as possible and maximize the high-current trace width to reduce the effect of undesirable parasitic inductance. The MOSFET generates a fair amount of heat because of the high currents involved. In order to dissipate the heat generated by the MOSFET, make the power traces very wide with a large amount of copper area, and place the MAX8535/ MAX8536/MAX8585 as close as possible to the drain of the external MOSFET. A more efficient way to achieve good power dissipation on a surface-mount package is to lay out two copper pads directly under the MOSFET package on both sides of the board. Connect the two pads to the ground plane through vias and use enlarged copper mounting pads on the topside of the board. Use a ground plane to minimize impedance and inductance. Refer to the MAX8535 Evaluation Kit data sheet for an example of a PC board layout. In addition to the usual high-power considerations, bypassing prevent false faults by: 1) Bypass VCC with a 0.1F capacitor to ground and bypassing CS with a 1nF capacitor to ground. 2) Making the traces connecting UVP and OVP as short as possible. 3) Kelvin connecting V CC and CS to the external MOSFET. ______________________________________________________________________________________ ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies GATE VCC VCC CHARGE PUMP 400mV CS *0mV OFFSET IN THE MAX8585 10mV 30mV* CLK SHUTDOWN VCC FAULT CONTROL LOGIC VOLTAGE SHARE REVERSE CURRENT FORWARD CURRENT 14.5V OVERVOLTAGE INTERNAL OVP OVERVOLTAGE EXTERNAL UNDERVOLTAGE 1.25V IOSC TIMER ENABLE UVP 1.25V REF MAX8535 MAX8585 1.25V GND Figure 1. MAX8535/MAX8585 Functional Diagram GATE VCC VCC CHARGE PUMP 400mV 30mV CS 10mV CLK SHUTDOWN VCC FAULT CONTROL LOGIC VOLTAGE SHARE REVERSE CURRENT FORWARD CURRENT OVP OVERVOLTAGE EXTERNAL UNDERVOLTAGE 1.25V IOSC TIMER ENABLE 1.25V REF UVP MAX8536 1.25V GND Figure 2. MAX8536 Functional Diagram ______________________________________________________________________________________ 15 MAX8535/MAX8536/MAX8585 Functional Diagrams Typical Application Circuits Q1 AND Q2 2XSUB75N03-04 30V/4m +VO -VO OUTPUT: 12V/20A OUT+ C3 1nF R3 SILVER BOX 53.6k OR RECTIFIERS C1 0.01F, 50V R5 100k GATE R2 51k OUTPUT BUS R1 10 CS FAULT VCC C2 0.1F, 16V MAX8535 MAX8585 UVP R4 10k OVP TIMER GND R6 10k R7 24.9k OUTENABLE Figure 3. Typical Application Circuit for 12V/20A Output with OVP and UVP Q1 AND Q2 2XSUB75N03-04 30V/4m +VO -VO OUTPUT: 3.3V OR 5V/20A OUT+ C3 1nF R1 10 R3 SILVER BOX 13.3k OR RECTIFIERS C1 0.01F, 50V R5 35.7k GATE CS VCC FAULT C2 0.1F, 16V MAX8536 UVP OVP TIMER R4 10k R2 51k OUTPUT BUS MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies GND R7 24.9k R6 10k OUT- Figure 4. Typical Application Circuit for 3.3V or 5V/20A Output with OVP and UVP 16 ______________________________________________________________________________________ ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies MAX8535/MAX8536/MAX8585 Q1 SUB75N03-04 30V/4m +VO -VO OUTPUT: 12V/20A OUT+ SILVER BOX OR RECTIFIERS R2 51k C1 0.01F, 50V GATE ON C2 0.1F, 16V OFF MAX8535 MAX8585 R4 7.5k TIMER ENABLE CS FAULT VCC GND UVP OUTPUT BUS C3 1nF R1 10 N.C. OVP R3 7.5k OUT- Figure 5. Typical Application Circuit for 12V/20A Output without OVP and UVP ______________________________________________________________________________________ 17 MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies V+ Q1A AND Q2A 2XSUB75N03-04 30V/4m +VO -VO VCCA = 12V/20A OUT+ R3A SILVER BOX 53.6k A C1A 0.01F, 50V R5A 100k GATE C2A 0.1F, 16V UVP R4A 10k CS U1 VCC R2A 51k FAULT MAX8535 MAX8585 GND TIMER OUTPUT BUS C3A 1nF R1A 10 OVP R6A 10k R7A 24.9k OUTQ1B AND Q2B 2XSUB75N03-04 30V/4m VCCB = 12V/20A OUT+ R3B SILVER BOX 53.6k B C1B 0.01F, 50V R2B 51k GATE C2B 0.1F, 16V UVP R4B 10k CS U2 VCC FAULT MAX8535 MAX8585 TIMER GND OUTPUT BUS C3B 1nF R1B 10 OVP R7B 24.9k OUT- N+1 Figure 6. N + 1 Redundant Power System Connections 18 ______________________________________________________________________________________ ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies Chip Information TRANSISTOR COUNT: 3011 PROCESS: BiCMOS TOP VIEW GATE 1 8 GND 2 7 FAULT VCC 3 6 OVP UVP 4 5 TIMER MAX8535 MAX8536 MAX8585 CS MAX ______________________________________________________________________________________ 19 MAX8535/MAX8536/MAX8585 Pin Configuration Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information, go to www.maxim-ic.com/packages.) 4X S 8 E y 0.500.1 8 INCHES DIM A A1 A2 b H c D e E H 0.60.1 1 L 1 0.60.1 S BOTTOM VIEW D MIN 0.002 0.030 MAX 0.043 0.006 0.037 0.014 0.010 0.007 0.005 0.120 0.116 0.0256 BSC 0.120 0.116 0.198 0.188 0.026 0.016 6 0 0.0207 BSC 8LUMAXD.EPS MAX8535/MAX8536/MAX8585 ORing MOSFET Controllers with Fastest Fault Isolation for Redundant Power Supplies MILLIMETERS MAX MIN 0.05 0.75 1.10 0.15 0.95 0.25 0.36 0.13 0.18 2.95 3.05 0.65 BSC 2.95 3.05 4.78 5.03 0.41 0.66 0 6 0.5250 BSC TOP VIEW A1 A2 e A c b L SIDE VIEW FRONT VIEW PROPRIETARY INFORMATION TITLE: PACKAGE OUTLINE, 8L uMAX/uSOP APPROVAL DOCUMENT CONTROL NO. 21-0036 REV. J 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. 20 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.