SMH4812

SUMMIT MICROELECTRONICS, Inc. Distributed Power Hot-Swap Controller SMH4812 Preliminary FEATURES ! Soft Starts Main Power Supply on Card Insertion or System Power Up ! Senses Card Insertion via Short Pins or Ejector Switches ! Master Enable to Allow System Control of Power Up or Down " Can be used as a Temperature Sense Input ! Programmable Independent Controls of a DC/DC Converter " Not Enabled until Host Supply Fully Soft Started " Programmable Time Delay " Available Input to hold off Dependant Enables until Conditions are Satisfied ! Highly Programmable Circuit Breaker " Programmable Quick-TripTM Values " Programmable Current Limiting " Programmable Duty Cycle Times " Programmable Over-current Filter ! Programmable Host Voltage Fault Monitoring " Programmable Under-Voltage Hysteresis " Programmable UV/OV Voltage Filter " Programmable Fault Mode: Latched or Duty Cycle ! Programmable Forced Shutdown Timer ! 2.5V and 5.0V Reference Outputs " Eliminates the Need for Other Primary Voltages " Easy Expansion of External Monitor Functions ! Supply Range +20VDC to >+500VDC SIMPLIFIED APPLICATION DRAWING 0V Disable/Enable VDD Pin Detect PD1# ENPG FS# FAULT# UV SMH4812 OV PG2# DC/DC Pin Detect PD2# VSS CBSENSE VGATE 2.5VREF 5.0VREF –48V Characteristics subject to change without notice 2055 4.0 12/22/00 2055 SAD 1.1 ©SUMMIT MICROELECTRONICS, Inc., 2000 • 300 Orchard City Dr., Suite 131 • Campbell, CA 95008 • Phone 408-378-3970 • FAX 408-378-6586 • www.summitmicro.com 1 SMH4812 Preliminary DESCRIPTION The SMH4812 is designed to control hot swapping of plugin cards operating from a single supply, which can have an output range from 20V to 500V. The SMH4812 hot-swap controller provides under-voltage and over-voltage monitoring of the host power supply, it drives an external power MOSFET switch that connects the supply to the load, and it protects against over-current conditions that might disrupt the host supply. When the input and output voltages to the SMH4812 controller are within specification it provides a Power Good logic output that may be used to enable a DC-DC converter. Additional features of the device include: temperature sense or master enable input, 2.5V and 5V reference outputs for expanding monitor functions, two Pin-Detect enable inputs for fault protection, and duty-cycle or latched over-current protection modes. All of these features can be programmed by the factory according to the user's requirements. FUNCTIONAL BLOCK DIAGRAM ENPG 14 VDD 16 12VREF PROGRAMMABLE SHUTDOWN TIMER + 13 FS# 12 2.5VREF DRAIN 1 SENSE 50kΩ 50kΩ 50kΩ – 11 5.0VREF EN/TS 3 PD1# 4 PD2# 5 + – PROGRAMMABLE DELAY 15 PG# UV 9 + – FILTER + OV 10 5V 12V 2.5V 2 VGATE VSS 8 PROGRAMMABLE DELAY 50mV CBSENSE 7 Programmable Quick Response Ref. Voltage 2 – 50kΩ VGATE SENSE + – + – 6 FAULT# DUTY CYCLE TIMER 2055 BD 3.0 2055 4.0 12/22/00 SUMMIT MICROELECTRONICS, Inc. SMH4812 Preliminary PIN CONFIGURATION DRAIN SENSE VGATE EN/TS PD1# PD2# FAULT# CBSENSE VSS 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 VDD PG# ENPG FS# 2.5VREF 5VREF OV UV 2055 PCon 2.0 PIN DESCRIPTIONS DRAIN SENSE (1) The DRAIN SENSE input monitors the voltage at the drain of the external power MOSFET switch with respect to VSS. An internal 10µA source pulls the DRAIN SENSE signal towards the 5V reference level. DRAIN SENSE must be held below 2.5V to enable the PG outputs. EN/TS (3) The Enable/Temperature Sense input is the master enable input. If EN/TS is less than 2.5V, VGATE will be disabled. This pin has an internal 200kW pull-up to 5V. PD1#, PD2# (4, 5) These are logic level active low inputs that can optionally be employed to enable VGATE and the PG outputs when they are at VSS. These pins each have an internal 50kW pull-up to 5V. CBSENSE (7) The circuit breaker sense input is used to detect overcurrent conditions across an external, low value sense resistor (RS) tied in series with the Power MOSFET. A voltage drop of greater than 50mV across the resistor for longer than tCBD will trip the circuit breaker. A programmable Quick-Trip sense point is also available. UV (9) The UV pin is used as an under-voltage supply monitor, typically in conjunction with an external resistor ladder. VGATE will be disabled if UV is less than 2.5V. Programmable internal hysteresis is available on the UV input, adjustable in increments of 62.5mV. Also available is a filter delay on the UV input. OV (10) The OV pin is used as an over-voltage supply monitor, typically in conjunction with an external resistor ladder. VGATE will be disabled if OV is greater than 2.5V. A filter delay is available on the OV input. VGATE (2) The VGATE output activates an external power MOSFET switch. This signal supplies a constant current output (100µA typical), which allows easy adjustment of the MOSFET turn on slew rate. FAULT# (6) FAULT# is an open-drain, active-low output that indicates the fault status of the device. 5VREF (11) This is a precision 5V output reference voltage that may be used to expand the logic input functions on the SMH4812. The reference output is with respect to VSS. 2.5VREF (12) This is a precision 2.5V output reference voltage that may be used to expand the logic input functions on the SMH4812. The reference output is with respect to VSS. FS# (13) The Forced Shutdown (FS#) pin is an active low input that causes VGATE and PG outputs to be shut down at any time after an internal hold-off timer has expired. The holdoff timer allows supervisory circuits on the secondary side (which are not powered up initially) to control shut down of the SMH4812 via an opto-isolator. This input has no pullup resistor. SUMMIT MICROELECTRONICS, Inc. 2055 4.0 12/22/00 3 SMH4812 Preliminary ENPG (14) The ENPG input controls the PG# output. When ENPG is pulled low the PG# output is immediately placed in a high impedance state. If ENPG is driven high then the PG# output will immediately be driven low. PG# (15) PG# is an open-drain, active-low output with no internal pull-up resistor. It can be used to switch a load or enable a DC/DC converter. PG# is enabled immediately after VGATE reaches VDD – VGT and the DRAIN SENSE voltage is less than 2.5V. Voltage on these pins cannot exceed 12V, as referenced to VSS. VDD (16) VDD is the positive supply connection. An internal shunt regulator connected between VDD and VSS develops approximately 12V that supplies the SMH4812. A resistor must be placed in series with the VDD pin to limit the regulator current (RD in the application illustrations). VSS (8) VSS is connected to the negative side of the supply. 4 2055 4.0 12/22/00 SUMMIT MICROELECTRONICS, Inc. SMH4812 Preliminary ABSOLUTE MAXIMUM RATINGS* Temperature Under Bias ...................... –55°C to 125°C Storage Temperature ........................... –65°C to 150°C Lead Solder Temperature (10 secs) ................... 300 °C Terminal Voltage with Respect to VSS: VDD ................................. –0.5V to VDD OV, UV, DRAIN SENSE, FS#, CBSENSE ..... –0.5V to VDD+0.5V PD1#, PD2#, ENPG, EN/TS ......... 10V FAULT#, PG# ........ –0.5V to VDD+0.5V VGATE ................................ VDD+0.5V *COMMENT Stresses 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 outside those listed in the operational sections of this specification is not implied. Exposure to any absolute maximum rating for extended periods may affect device performance and reliability. AC OPERATING CHARACTERISTICS Symbol Description Min. Typ. 5 tCBD Programmable 50mV Circuit Breaker delay (filter) 50 * 150 400 50 250 500 tVGD Programmable Power Good delay 1500 5* 20 80 160 tFSTSHTDN tCYC tCBRST Fast shutdown delay from Fault to VGATE off Circuit breaker cycle time CBRESET pulse width 200 OFF * tPUVF Programmable Under-Voltage filter 5 80 160 0.5 tPDD Programmable Pin Detect 5 80 * 160 * = Default value Max. Units µs µs µs µs µs µs µs µs ms ms ms ms ns s ns — ms ms ms ms ms ms ms 2055 Prog Table 200 2.5 SUMMIT MICROELECTRONICS, Inc. 2055 4.0 12/22/00 5 SMH4812 Preliminary DC OPERATING CHARACTERISTICS (Over Recommended Operating Conditions; Voltages are relative to VSS, except VGT) Symbol VDD 5VREF ILOAD5 2.5VREF ILOAD2.5 IDD VUV VUVHYST VOV VOVHYST VGATE IGATE VSENSE ISENSE VCB Parameter Supply voltage 5V reference output 5V reference output current 2.5V reference output 2.5V reference output current Power supply current Under-Voltage threshold Under-Voltage hysteresis Over-Voltage threshold Over-Voltage hysteresis VGATE output voltage VGATE current output DRAIN SENSE threshold DRAIN SENSE current output Circuit breaker threshold Programmable Quick Trip circuit breaker threshold Off VENTS VENTSHYST VIH VIL VOL IIL VGT (1) TA = 25ºC. Conditions IDD = 3mA IDD = 3mA IDD = 3mA IDD = 3mA (1) IDD = 3mA IDD = 3mA (1) IDD = 3mA IDD = 3mA (1) IDD = 3mA Min. 11 4.75 –1 2.475 –0.2 2.475 2.475 Typ. 12 5.00 2.500 Max. 13 5.25 1 2.525 1 10 Units V V mA V mA mA V mV V mV V µA V µA mV mV mV mV — 2.500 63 2.500 10 2.525 2.525 VDD 100 IDD = 3mA (1) VSENSE = VSS (1) IDD = 3mA 2.475 9 40 2.500 10 50 200 100 60 IDD = 3mA (1) IDD = 3mA 3 0 IOL = 3mA IOL = 3mA VIL = VSS 0.7 0 0 100 1.8 3.0 2.475 2.500 10 5VREF 2 0.4 0.4 2.525 2.525 11 60 VQCB EN/TS threshold EN/TS hysteresis Input high voltage: ENPG Output low voltage: FAULT# Output low voltage: PG# Input current: PD1#, PD2#, EN/TS Gate threshold V mV V V V V µA V 2055 Elect Table RECOMMENDED OPERATING CONDITIONS Temperature –40°C to 85°C. 6 2055 4.0 12/22/00 SUMMIT MICROELECTRONICS, Inc. SMH4812 Preliminary FUNCTIONAL DESCRIPTION GENERAL OPERATION The SMH4812 is an integrated power controller for hot swappable add-in cards. The device operates from a wide supply range and generates the signals necessary to drive an isolated output DC/DC converter. As a typical add-in board is inserted into the powered backplane physical connections must first be made with the chassis to discharge any electrostatic voltage potentials. The board then contacts the long pins on the backplane that provide power and ground. As soon as power is applied the device starts up, but does not immediately apply power to the output load. Under-voltage and over-voltage circuits inside the controller check to see that the input voltage is within a user-specified range, and pin detection signals determine whether the card is seated properly. These requirements must be met for a Pin Detect Delay period of tPDD, after which time the hot-swap controller enables VGATE to turn on the external power MOSFET switch. The VGATE output is current limited to IVGATE, allowing the slew rate to be easily modified using external passive components. During the controlled turn-on period the VDS of the MOSFET is monitored by the drain sense input. When drain sense drops below 2.5V, and VGATE gets above VDD – VGT, the power good output can begin turning on the DC/DC controller. The Power Good Enable input may be used to activate or deactivate the output load. Steady state operation is maintained as long as all conditions are normal. Any of the following events may cause the device to disable the DC/DC controller by shutting down the power MOSFET: an under-voltage or overvoltage condition on the host power supply; an overcurrent event detected on the CBSENSE input; a failure of the power MOSFET sensed via the DRAIN SENSE pin; the pin detect signals becoming invalid; the master enable (EN/TS) falling below 2.5V; the FS# input being driven low by events on the secondary side of the DC/DC controller. The SMH4812 may be configured so that after any of these events occur the VGATE output shuts off and either latches into an off state or recycles power after a cooling down period, tCYC. Powering VDD The SMH4812 contains a shunt regulator on the VDD pin that prevents the voltage from exceeding 12V. It is necessary to use a dropper resistor (RD) between the host power supply and the VDD pin in order to limit current into the device and prevent possible damage. The dropper resistor allows the device to operate across a wide range of system supply voltages, and also helps protect the device against common-mode power surges. Refer to the Applications Section for help on calculating the RD resistance value. System Enables There are several enabling inputs, which allow a host system to control the SMH4812. The Pin Detect pins (PD1# & PD2#) are two active low enables that are generally used to indicate that the add-in circuit card is properly seated. This is typically done by clamping the inputs to VSS through the implementation of an injector switch, or alternatively through the use of a staggered pins at the card-cage interface. Two shorter pins arrayed at opposite ends of the connector force the card to be fully seated (not canted) before both pin detects are enabled. Care must be taken not to exceed the maximum voltage rating of these pins during the insertion process. Refer to details in the Applications Section for proper circuit implementation. The EN/TS input provides an active high comparator input that may be used as a master enable or temperature sense input. These inputs must be held low for a period of tPDD before a power-up sequence may be initiated. Under-/Over-Voltage Sensing The Under-Voltage (UV) and Over-Voltage (OV) inputs provide a set of comparators that act in conjunction with an external resistive divider ladder to sense when the host supply voltage exceeds the user defined limits. If the input to the UV pin rises above 2.5V, or the input to the OV pin falls below 2.5V for a period of tPDD, the power-up sequence may be initiated. The tPDD filter helps prevent spurious start-up sequences while the card is being inserted. If UV falls below 2.5V or OV rises above 2.5V, the PG and VGATE outputs will be shut down immediately. Under-/Over-Voltage Filtering The SMH4812 may also be configured so that an out of tolerance condition on UV/OV will not shut off the output immediately. Instead, a filter delay may be inserted so that only sustained under-voltage or over-voltage conditions will shut off the output. When the UV/OV filter option is enabled an out of tolerance condition on UV/OV for longer than the filter delay time, tUOFLTR, activates the FAULT# output, and the VGATE and PG outputs will be latched in the off state. See Figure 1. To initiate another power-up sequence the FAULT# output must first be reset. Refer to the appropriate section on resetting the FAULT# output. The Under-/Over-Voltage Filtering feature is disabled in the default configuration of the device. SUMMIT MICROELECTRONICS, Inc. 2055 4.0 12/22/00 7 SMH4812 Preliminary 2.5V OV / UV CBSENSE TCBD 50mV TCBD tUOFLTR TCYC FAULT# VGATE 2055 Fig01 2055 Fig02 Figure 1. Under-/Over-Voltage Filter Timing Figure 2. Circuit Breaker Cycle Mode VDD 11 ≤ VDD ≤ 13