PTB48520WAH

Not Recommended For New Designs PTB48520W www.ti.com SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 25-A, 48-V INPUT ISOLATED DC/DC CONVERTER WITH AUTO-TRACK™ SEQUENCING FEATURES • • • • • • • • • • • • • • • Input Voltage: 36 V to 75 V 25-A Total Output Current 91% Efficiency Wide-Adjust Output Voltage: 1.8 V to 3.6 V Overcurrent Protection Output Overvoltage Protection Overtemperature Shutdown Output Enable Control Auto-Track Compatible Sequenced Output Smart-Sense Remote Sensing Undervoltage Lockout Industry Standard Size Surface Mountable 1500-Vdc Isolation Agency Approvals (Pending): UL/cUL 60950, EN 60950 APPLICATIONS • • • 3.3-V Intermediate Bus Architectures Telecom, High-End Computing Platforms Multi-Rail Power Systems with Power-Up Sequencing DESCRIPTION The PTB48520W is a 25-A rated, 48-V input isolated dc/dc converter that incorporates Auto-Track™ power-up sequencing. This allows these modules to simultaneously power up with any other downstream non-isolated, Auto-Track compliant module. The PTB48520W module provides two outputs, each regulated to the same voltage. During power up, the voltage at Vo Bus rises first, allowing this output to provide input power to any downstream non-isolated module. The voltage from Vo Seq is then allowed to rise simultaneously, under the control of Auto-Track, along with the outputs from the downstream modules. Whether used to facilitate power-up sequencing, or operated as a stand-alone module, the PTB48520W includes many features expected of high-performance dc/dc converter modules. The wide output adjust enables the output voltage to be set to to any voltage over the range, 1.8 V to 3.6 V, using a single external resistor. Precise output voltage regulation is ensured with a differential remote sense that intelligently regulates the sequenced output, depending on its sequence status. Other operational features include an input undervoltage lockout (UVLO) and an output enable control. Overcurrent, overvoltage, and overtemperature protection ensures the module ability to survive any load fault. Typical applications include distributed power architectures in both telecom and computing environments, particularly complex digital systems requiring power sequencing of multiple power supply rails. Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. Auto-Track is a trademark of Texas Instruments. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright © 2004–2005, Texas Instruments Incorporated Not Recommended For New Designs PTB48520W www.ti.com SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Typical Circuit Simultaneous Power Up V1 Track 4 V2 PTB48520W +Sense +VI 1 2 +VI VOSeq VOBus VOEnable V Adjust O VOCOM −VI 3 −VI −Sense 8 V1 = 3.3 V 10 9 2 Track 7 3 5 RSET 887 W C1 100 mF 6 VI PTH03050W V2 = 1.8 V 6 VO Inhibit GND Adjust 4 1 5 R1 5.49 kW C2 100 mF ORDERING INFORMATION PTB48520 (Basic Model) Output Voltage Part Number DESCRIPTION 1.8 V to 3.6 V PTB48520WAH Horizontal T/H 1.8 V to 3.6 V (1) (2) PTB48520WAS SMD, Standard Package Ref. (1) ERP (2) ERQ See the applicable package reference drawing for the dimensions and PC board layout. Standard option specifies 63/37, Sn/Pb pin solder material. ABSOLUTE MAXIMUM RATINGS UNIT V(Track) Track input voltage I(Track) max Track input current TA 0 V to VO Bus + 0.3 V From external source Operating temperature range Over VI range Overtemperature protection PCB temperature (near pin 1) T(reflow) Solder reflow temperature Surface temperature of module or pins Tstg Storage temperature (1) (2) 2 10 mA (1) –40°C to 85°C 115°C 235°C (2) –40°C to 125°C When the Track input is fed from an external voltage source, the input current must be limited. A 2.74-kΩ value series resistor is recommended. During solder reflow of SMD package version, do not elevate the module PCB, pins, or internal component temperatures above a peak of 235°C. Not Recommended For New Designs PTB48520W www.ti.com SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 PACKAGE SPECIFICATIONS PTB48520W (Suffixes AH and AS) Weight 28.5 grams Flammability Meets UL94V-O Mechanical shock Per Mil-STD-883D, Method 2002.3 1 msec, 1/2 Sine, mounted Mechanical vibration Mil-STD-883D, Method 2007.2 20-2000 Hz, PCB mounted (1) 250 Gs (1) Horizontal SMD (Suffix AS) 150 Gs (1) Horizontal T/H (Suffix AH) 15 Gs Horizontal SMD (Suffix AS) 5 Gs Horizontal T/H (Suffix AH) (1) (1) Qualification limit. ELECTRICAL CHARACTERISTICS (Unless otherwise stated, TA = 25°C, VI = 48 V, VO = 3.3 V, CO = 0 µF, and IO = IOmax) PARAMETER IO Output current TEST CONDITIONS Over VI range MIN IO Bus 0 IO Seq 0 Sum total IO Bus + IO Seq VI Input voltage range VO η MAX 25 10 Over IO range 25 36 48 75 UNIT A A V (3) %Vo ±0.8 %Vo ±0.6 -40°C ≤ TA ≤ 85°C (1) (1) (2) 0 Set-point voltage tolerance Temperature variation TYP Line regulation Over VI range ±1 mV Load regulation Over IO range ±1 mV Total output voltage variation Includes set-point, line, load, –40°C ≤ TA≤ 85°C Adjust range Over VI range Efficiency IO = 15 A VO Ripple (peak-to-peak) 20 MHz bandwidth ±1.5 1.8 ±3 (3) 3.6 RSET = 887 Ω, VO = 3.3 V 91% RSET = 6.98 kΩ, VO = 2.5 V 90% RSET = 35.7 kΩ, VO = 2.0 V 89% RSET = open cct. VO = 1.8 V 88% 20 %Vo V mVpp 1 A/µs load step, 50% to 100% IOmax Transient Response Input current Track input (pin 4) Recovery time 75 µs VO over/undershoot ±3 %Vo Pin connected to VO COM -0.13 Open-circuit voltage 0 Vo Bus Input slew rate limits (4) 1 0.1 mA V V/ms Referenced to -VI (pin 3) Output enable input (pin 2) Input high voltage (VIH) 2 Input low voltage (VIL) -0.2 Input low current (IIL) Standby input current Pin 2 open No-load input current Pins 2 and 3 connected, IO Tot = 0 Overcurrent threshold, IO (tot) Shutdown, followed by autorecovery (1) (2) (3) (4) (5) Open (5) 0.8 V –480 µA 2 mA 50 mA 40 A See temperature derating curves for safe operating area (SOA), or consult factory for appropriate derating. When load current is supplied from the VO Seq output, the module exhibits higher power dissipation and slightly lower operating efficiency. The set-point voltage tolerance is affected by the tolerance and stability of RSET. The stated limit is unconditionally met if RSET has a tolerance of 1%, with 100 ppm/°C temperature stability. When controlling the Track input from an external source, the slew rate of the applied signal must be greater than the minimum limit. Failure to allow the voltage to completely rise to the voltage at the VO (bus) output, at no less than the minimum specified rate, may thermally overstress the converter. The VO Enable input has an internal pull-up, and if left open the converter output isturned off. A discrete MOSFET or bipolar transistor is recommended to control this input. The open-circuit voltage is approximately 20% of the input voltage. If the output enable feature is not used, this pin should be permanently connected to –VI. See the application information for other interface considerations. 3 Not Recommended For New Designs PTB48520W www.ti.com SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 ELECTRICAL CHARACTERISTICS (continued) (Unless otherwise stated, TA = 25°C, VI = 48 V, VO = 3.3 V, CO = 0 µF, and IO = IOmax) PARAMETER TEST CONDITIONS OVP Output overvoltage protection Output shutdown and latch off UVLO Undervoltage lockout ƒS Switching frequency MIN MAX 125 Over VI range UNIT %Vo 30 34 36 V 225 275 325 kHz 5000 µF Internal input capacitance MTBF TYP 3 0 µF External output capacitance Between both outputs and VO COM Isolation voltage Input-output Isolation capacitance Input-output Isolation resistance Input-output 10 MΩ Reliability Telcordia SR-332 50% stress, TA = 40°C, ground benign 1.2 106 Hrs 1500 Vdc 1000 pF TERMINAL FUNCTIONS TERMINAL NAME NO. DESCRIPTION +VI (1) 1 The positive input for the module with respect to –VI. When powering the module from a negative input voltage, this input is connected to the input source ground. –VI (1) 3 The negative input supply for the module, and the 0-V reference for the VO Enable input. When powering the module from a positive source, this input is connected to the input source return. 2 An open-collector (open-drain) negative logic input that is referenced to –VI. This input must be pulled to –VI potential to enable the output voltage. A high impedance connection disables the module output. If the output enable feature is not used, pin 2 should be permanently connected to –VI. The module then produces an output whenever a valid input source is applied. VO Bus 9 Produces a positive power output with respect to VO COM. This is the main output from the converter when operated in a stand-alone configuration. It is dc isolated from the input power pins and is the first output to rise when the converter is either powered or enabled. In power-up sequencing applications, this output can provide a 3.3-V standby source to power the downstream non-isolated modules. VO Seq 10 This is the sequenced output voltage from the converter. This voltage can be directly controlled from the Track pin. During power up, VO Seq rises with the Track pin voltage, typically 20 ms after the VO Bus output has reached regulation. VO COM 5 This is the output power return for both the VO Bus and VO Seq output voltages. This node should be connected to the load circuit common. 4 The voltage at this pin directly controls the voltage VO Seq regulated output. It is primarily used to sequence the voltage VO Seq with the regulated outputs from any downstream non-isolated modules that are powered from the converter +VO Bus output. In these applications, the Track pin is simply connected to the track control of each of the non-isolated modules. The Track pin has an internal transistor, which holds it at VO COM potential for approximately 20 ms after the VO Bus output is in regulation. Following this delay, the Track voltage and VO Seq rises simultaneously with the output voltage of all the non-isolated modules that are under the control of Auto-Track. 7 A resistor must be connected between this pin and –Sense to set the converter output voltage. A 0.05-W rated resistor may be used, with tolerance and temperature stability of 1% and 100 ppm/°C, respectively. If this pin is left open, the converter output voltage defaults to its lowest value. The specification table gives the preferred resistor values for the popular bus voltages. +Sense 8 The +Sense pin can be connected to either the VO Bus or VO Seq outputs. When connected to VO Seq, remote sense compensation will be delayed until the power-up sequence is complete. The voltage at VO Bus is raised slightly. The pin may be left open circuit, but connecting it to one of the output terminals improves load regulation of that output. –Sense 6 Provides the converter with a remote sense capability when used with +Sense. For optimum output voltage accuracy, this pin should always be connected to VO COM. This pin is also the reference connection for the output voltage set-point resistor. VO Enable Track VO Adjust (1) (2) 4 (1) (2) These functions indicate signals electrically common with the input. Denotes negative logic: Low (–VI) = Normal operation, Open = Output off Not Recommended For New Designs PTB48520W www.ti.com SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 TYPICAL CHARACTERISTICS Characteristic Data; VI = 48 V (1) EFFICIENCY vs OUTPUT CURRENT (VO Bus) OUTPUT VOLTAGE RIPPLE vs OUTPUT CURRENT (VO Bus) 50 100 VO = 2.5 V V O − Output Voltage Ripple − mV PP VO = 3 V Efficiency − % 90 80 VO = 1.8 V VO = 2 V 70 60 50 0 5 10 15 20 40 30 VO = 2.5 V 10 VO = 2 V VO = 1.8 V 0 25 VO = 3.3 V 20 0 5 10 15 20 25 IO − Output Current − A IO − Output Current − A Figure 1. Figure 2. POWER DISSIPATION vs OUTPUT CURRENT (VO Bus) PD − Power Dissipation − W 10 8 VO = 2 V 6 VO = 2.5 V VO = 3.3 V 4 2 0 VO = 1.8 V 0 5 10 15 20 25 IO − Output Current − A Figure 3. (1) All data listed in Figure 1, Figure 2, and Figure 3 have been developed from actual products tested at 25°C. This data is considered typical data for the dc-dc converter. 5 Not Recommended For New Designs PTB48520W www.ti.com SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 TYPICAL CHARACTERISTICS (continued) Safe Operating Areas; VI = 48 V (2) TEMPERATURE DERATING vs OUTPUT CURRENT (VO Seq) 90 90 80 80 TA − Ambient Temperature 5 C TA − Ambient Temperature 5 C TEMPERATURE DERATING vs OUTPUT CURRENT (VO Bus) 70 400 LFM 60 200 LFM 50 100 LFM Nat Conv 40 30 Airflow 20 0 5 100 LFM 70 60 50 40 30 Airflow 20 10 15 20 IO − Output Current − A 25 0 Figure 4. (2) Nat Conv 2 4 6 8 IO − Output Current − A 10 Figure 5. The temperature derating curves represent operating conditions at which internal components are at or below manufacturer's maximum rated operating temperature. See Figure 4 and Figure 5. APPLICATION INFORMATION Operating Features and System Considerations for the PTB48520W DC/DC Converter Overcurrent Protection To protect against load faults, these converters incorporate output overcurrent protection. Applying a load to the output that exceeds the converter overcurrent threshold (see applicable specification) causes the output voltage to momentarily fold back, and then shut down. Following shutdown, the module periodically attempts to automatically recover by initiating a soft-start power up. This is often described as a hiccup mode of operation, whereby the module continues in the cycle of successive shutdown and power up until the load fault is removed. Once the fault is removed, the converter automatically recovers and returns to normal operation. Output Overvoltage Protection The converter continually monitors for an output overvoltage (OV) condition, directly across the +VO Bus output. The OV threshold automatically tracks the output voltage set point to a level that is 25% higher than that set by the external R(SET) voltage adjust resistor. If the output voltage exceeds this threshold, the converter is immediately shut down and remains in a latched-off state. To resume normal operation, the converter must be actively reset. This can only be done by momentarily removing the input power to the converter. For fail-safe operation and redundancy, the OV protection uses circuitry that is independent of the converter internal feedback loop. Differential Output Voltage Sense A differential remote sense allows a converter regulation circuitry to compensate for limited amounts of IR drop, that may be incurred between the converter and load, in either the positive or return PCB traces. Connecting the (+)Sense and (–)Sense pins to the respective positive and ground reference of the load terminals improves the load regulation of the converter output voltage at that connection point. The (–)Sense pin should always be connected to the VO COM. The (+)Sense pin may be connected to either the +VO Bus or +VO Seq outputs. When the (+)Sense pin is connected to the VO Seq output, the voltage at VO Bus voltage regulates slightly 6 Not Recommended For New Designs www.ti.com PTB48520W SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 APPLICATION INFORMATION (continued) higher. Depending on the load conditions on the VO Seq output, the voltage at VO Bus may be up to 100 mV higher than the converter set-point voltage. In addition, the Smart-Sense feature (incorporated into the converter) only engages sense compensation to the VO Seq output when that output voltage is close to the set point. During other conditions, such as power-up and power-down sequencing events, the sense circuit automatically defaults to sensing the VO Bus voltage, internal to the converter. Leaving the (+)Sense and (–)Sense pins open does not damage the converter or load circuitry. The converter includes default circuitry that keeps the output voltage in regulation. If the remote sense feature is not used, the (–)Sense pin should always be connected to VO COM. Note: The remote sense feature is not designed to compensate for the forward drop of nonlinear or frequency dependent components that may be placed in series with the converter output. Examples include OR-ing diodes, filter inductors, ferrite beads, and fuses. When these components are enclosed by the sense pin connections, they are effectively placed inside the regulation control loop, which can adversely affect the stability of the converter. Overtemperature Protection Overtemperature protection is provided by an internal temperature sensor, which monitors the temperature of the converter PCB (close to pin 1). If the PCB temperature exceeds a nominal 115°C, the converter shuts down. The converter then automatically restarts when the sensed temperature falls to approximately 105°C. When operated outside its recommended thermal derating envelope (see data sheet derating curves), the converter typcially cycles on and off at intervals from a few seconds to one or two minutes. This is to ensure that the internal components are not permanently damaged from excessive thermal stress. Undervoltage Lockout The undervoltage lockout (UVLO) is designed to prevent the operation of the converter until the input voltage is close to the minimum operating voltage. The converter is held off when the input voltage is below the UVLO threshold, and turns on when the input voltage rises above the threshold. This prevents high start-up current during normal power up of the converter, and minimizes the current drain from the input source during low input voltage conditions. The converter meets full specifications when the minimum specified input voltage is reached. The UVLO circuitry also overrides the operation of the VO Enable control. Only when the input voltage is above the UVLO threshold is the VO Enable control functional. Primary-Secondary Isolation These converters incorporate electrical isolation between the input terminals (primary) and the output terminals (secondary). All converters are tested to a withstand voltage of 1500 VDC. This complies with UL/cUL 60950 and EN 60950 and the requirements for operational isolation. It allows the converter to be configured for either a positive or negative input voltage source. The data sheet Terminal Functions table provides guidance as to the correct reference that must be used for the external control signals. Output Voltage Adjustment The VO Adjust control sets the output voltages to a value higher than 1.8 V. For output voltages other than 1.8 V a single external resistor, R(set), must be connected directly between VO Adjust (pin 7) and (–)Sense (pin 6) pins. A 0.05-W rated resistor can be used. The tolerance should be 1%, with a temperature stability of 100 ppm/°C (or better). Place the resistor close to the converter and connect it directly between pins 7 and 6 using dedicated PCB traces (see typical application). Table 1 gives the preferred value of the external resistor for a number of standard voltages, along with the actual output voltage that this resistance value provides. For other output voltages the value of the required adjust resistor may be calculated using Equation 1. 1.225 V R set + 6.49 kW * 4.42 kW V set * 1.805 V (1) 7 Not Recommended For New Designs PTB48520W www.ti.com SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 Table 1. Standard Values of RSET for Common Output Voltages VO (Required) RSET (Standard Value) VO (Actual) 3.6 V 0Ω 3.604 V 3.3 V 887 Ω 3.303 V 2.5 V 6.98 kΩ 2.503 V 2.0 V 35.7 kΩ 2.003 V 1.8 V Open 1.805 V Input Current Limiting The converter is not internally fused. For safety and overall system protection, the maximum input current to the converter must be limited. Active or passive current limiting can be used. Passive current limiting can be a fast-acting fuse. A 125-V fuse, rated no more than 10 A, is recommended. Active current limiting can be implemented with a current limited Hot-Swap controller. Thermal Considerations Airflow may be necessary to ensure that the module can supply the desired load current in environments with elevated ambient temperatures. The required airflow rate is determined from the safe operating area (SOA). The SOA is the area beneath the applicable airflow rate curve on the graph of temperature derating vs output current. (See Typical Characteristics.) Operating the converter within the SOA limits ensures that all the internal components are at or below their stated maximum operating temperatures. 8 Not Recommended For New Designs PTB48520W www.ti.com SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 Using the Output Enable Control on the PTB48520 Auto-Track Compatible DC/DC Converter The VO Enable (pin 2) control is an active low input that allows the output voltage from the converter to be turned on and off while it is connected to the input source. The VO Enable input is referenced to the –VI (pin 3) (1), on the primary side of the converter isolation, and has its own internal pullup. The open-circuit voltage is approximately 20% of the applied input source voltage. For the converter to function normally, pin 2 must be pulled low to –VI potential (2). The converter output then produces a regulated voltage whenever a valid source voltage is applied between +VI (pin 1) and –VI (pin 3) (3). If the voltage at pin 2 is allowed to rise above VIH(min), (see specification table), the output from the converter is turned off. Figure 6 is an application schematic that shows the typical use of the Output Enable function. Note the discrete transistor (Q1). Either a discrete MOSFET or bipolar transistor is recommended to control this input. Table 2 gives the threshold requirements. When placed in Off state, the output neither sources or sinks output current. The load voltage then decays as the output capacitance is discharged by the load circuit. With the output turned off, the current drawn from the input source is typically reduced to 2 mA. (1) (2) (3) The VO Enable control uses –VI (pin 3) as ground reference. All voltages are with respect to –VI. Use an open-collector (or open-drain) discrete transistor to control the VO Enable input. A pullup resistor is not necessary. To disable the converter, the control pin should be pulled low to less than +0.8 V. If the Output Enable feature is not used, pin 2 should be permanently connected to –VI (pin 3). The converter incorporates a UVLO. The UVLO does not allow the converter to power up until the input voltage is close to its minimum specified operating voltage. This is regardless of the state of the Output Enable control. Consult the specifications for the UVLO thresholds. Table 2. Output Enable Control Requirements (1) PARAMETER MIN VIH TYP V 0.8 VO/C [Open-Circuit] V 15 II [pin 1 at –Vin] V –0.8 mA The VO Enable control uses –VI (pin 3) as its ground reference. All voltages are with respect to –VI. Track PTB48520W +Sense +VI 1 1 = Enable 2 R1 10 kW −VI UNIT 2 VIL (1) MAX +VI VOSeq VOBus VOEnable VOAdjust Q1 BSS138 3 VOCOM −VI −Sense 4 8 10 9 7 5 R2 887 W L O A D 6 Figure 6. Output Enable Operation Turn-On Time: In the circuit of Figure 6, turning Q1 off allows the voltage at pin 2 to rise to its internal pullup voltage. This disables the converter output. When Q1 is then turned on, it applies a low-level voltage to pin 2, 9 Not Recommended For New Designs PTB48520W www.ti.com SLTS233A – NOVEMBER 2004 – REVISED APRIL 2005 and enables the output of the converter. The converter produces a regulated output voltage within 50 ms. Figure 7 shows the output response of the converter after Q1 is turned on. The turnon of Q1 corresponds to the drop in the Q1 Vds waveform. Although the output voltage rise time is short (