EXB30 SERIES Application Note 108 Rev. 02 - July 2000 NEW Product * Ultra high efficiency topology, 92% typical at 5V * Operating ambient temperature of -40C to +85C (natural convection) * Approved to EN60950, UL/cUL1950 * Complies with ETS 300 019-1-3/2-3 * Complies with ETS 300 132-2 input voltage and current requirements * Fully compliant with ETS 300 386-1 * Basic insulation (input to output) * Industry standard half-brick pin-out 1. Introduction 1. Introduction . . . . . . . . . . . . . . . . . . . . . .1 2. Models and Features . . . . . . . . . . . . . .1 Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 3. General Description . . . . . . . . . . . . . . .2 Electrical Description . . . . . . . . . . . . . . . . . . . .2 Physical Construction . . . . . . . . . . . . . . . . . . .2 4. Features and Functions . . . . . . . . . . . .2 Wide Operating Temperature Range . . . . . . . . .2 Remote Sense Compensation . . . . . . . . . . . . .2 Output Voltage Adjustment . . . . . . . . . . . . . . .2 Remote On/Off . . . . . . . . . . . . . . . . . . . . . . . .2 Constant Switching Frequency . . . . . . . . . . . .3 Brickwall Current Limit and Short Circuit Prot. .3 Over Temperature Protection . . . . . . . . . . . . . .3 Output Overvoltage Protection . . . . . . . . . . . . .3 Input Undervoltage and Overvoltage Protection 3 5. 6. 2. Models and Features The EXB30 series comprises five separate models as shown in Table 1. All popular integrated circuit operating voltages are covered by the entire range. Model Input Voltage Output Voltage 36-75VDC 4.0V to 5.5V Safety . . . . . . . . . . . . . . . . . . . . . . . . . .4 EXB30-48S3V3 36-75VDC 2.64V to 3.63V Isolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Input Fusing . . . . . . . . . . . . . . . . . . . . . . . . . . .4 EXB30-48S2V5 36-75VDC 2.0V to 2.75V EXB30-48S2V0 36-75VDC 1.6V to 2.2V EXB30-48S12 36-75VDC 7.2V to 13.2V EMC . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Table 1 - EXB30 Models Use in a Manufacturing Environment . .6 Resistance to Soldering Heat . . . . . . . . . . . . . .6 Water Washing . . . . . . . . . . . . . . . . . . . . . . . . .6 ESD Control . . . . . . . . . . . . . . . . . . . . . . . . . . .6 8. In addition the automated manufacture methods and use of planar magnetics together with an extensive qualification program have produced one of the most reliable range of converters on the market. EXB30-48S05 Radiated . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4 Conducted . . . . . . . . . . . . . . . . . . . . . . . . . . . .5 7. The EXB30 series is a new generation of DC/DC converters which were designed in response to the growing need for low operating voltage and higher efficiencies. They offer unprecedented efficiency figures and a wide range of low output voltage solutions. Applications . . . . . . . . . . . . . . . . . . . . .6 Optimum PCB Layout . . . . . . . . . . . . . . . . . . .6 Optimum Thermal Performance . . . . . . . . . . . .7 Remote ON/OFF Control . . . . . . . . . . . . . . . . .8 Positive Logic . . . . . . . . . . . . . . . . . . . . . . . . .8 Specification for the Remote On/Off . . . . . . . .8 Isolated Closure Remote On/Off . . . . . . . . . . .8 Level Controlled Remote On/Off . . . . . . . . . . .8 Remote Sense Compensation . . . . . . . . . . . . .8 Output Voltage Adjustment . . . . . . . . . . . . . . .9 Output Capacitance . . . . . . . . . . . . . . . . . . . . .9 Output Noise and Ripple Measurement . . . . .10 Compatibility with Hot Swap Controller . . . . .11 PAGE 1 Features * Industry standard half-brick pinout and footprint: 61.0 x 57.9 x 10.9mm (2.40 x 2.28 x 0.43 inches) * Wide operating ambient temperature range of -40C to +85C * Output voltage adjustability * Remote sense compensation * Primary-side controlled remote on/off * Constant switching frequency * Brickwall overcurrent protection * Continuous short circuit protection * Overtemperature protection * Output overvoltage protection * Input undervoltage and overvoltage protection EXB30 SERIES 3. General Description Electrical Description The EXB30 power module is a DC/DC converter that operates over an input voltage range of 36VDC to 75VDC and provides an isolated regulated DC output. The modules have maximum power ratings of 30W and excellent efficiencies are achieved by optimum driving of the synchronous rectification stage. The standard feature set includes remote on/off, remote sense and output trim for maximum flexibility in distributed power applications. Input LC Filter + Rectification Stage OTP Current limit PWM Control OptoCoupler Feedback & Adjustability OptoCoupler OVP Detection Trim On/Off | Application Note 108 In the low voltage models the rectification stage consists of synchronous rectifiers that are controlled by proprietary circuitry on the secondary side which optimise the driving scheme for high efficiency power conversion. The rectification stage for the 12V model consists of schottky diodes. Physical Construction The EXB30 is constructed using a single multi-layer FR4 PCB. SMT components are placed on both sides of the PCB and in general, the heavier power components are mounted on the top side in order to optimise heat dissipation. The converter is sold as an open-frame product and no case is required. The open frame design has several advantages over encapsulated closed devices. Among these advantages are: * Cost: No potting compound, case or associated process costs involved. * Thermals: The heat is removed from the heat generating components without heating more sensitive, less tolerant components such as opto-couplers. * Environmental: Some encapsulants are not kind to the environment and create problems in incinerators. In addition open frame converters are more easily re-cycled. * Reliability: Open Frame modules are more reliable for a number of reasons. Figure 1 - Simplified Schematic The DC input is filtered by an LC filter stage before it reaches the main power transformer. A current controlled PWM controller is used to provide a precisely regulated output voltage. The main power switch is a MOSFET running at a constant switching frequency of 300kHz approximately. The output voltage at the sense pins of the module is sensed and compared with a secondary side reference and a compensated error signal is fed back via an optocoupler to the PWM controller. The secondary side trim pin allows the user to adjust the output voltage by connecting a resistor between trim and either the positive or negative output voltage sense pin. The output overvoltage clamp consists of a second control loop, independent from the main regulation loop, that senses the voltage on the output power pins. This OVP loop has typically a 15% higher setpoint relative to the main loop. Further details on the OVP feature can be found in the applications section. An Over-Temperature Protection (OTP) circuit on the primary side shuts down the PWM controller if the converter is in danger of being damaged. There is typically 5C of thermal hysteresis which is used to protect the unit. The remote on/off function allows the user to disable the converter, hence forcing the unit into a lower power dissipation mode. The power transformer which is a planar construction uses the PCB for the primary winding while SMT copper windings are used for the secondary winding. Electrically, the transformer operates just the same as a conventional transformer. However, the advantages of a planar design are as follows: * Excellent thermal characteristics * Low leakage inductance * Excellent repeatability properties http://www.artesyn.com A separate paper discussing the benefits of `open frame low to medium DC/DC converters' Design Note 102 is available from Artesyn Technologies. The effective elimination of potting and a case has been made possible by the use of modern automated manufacturing techniques and in particular the 100% use of SMT components, the use of planar magnetics and the exceptionally high efficiencies. 4. Features and Functions Wide Operating Temperature Range The wide ambient temperature range of the EXB30 module is a consequence of the extremely high efficiency achieved and consequent low power dissipation. Operation from -40C to a maximum ambient temperature of +85C is achieved without the requirement for heatsinks or forced air cooling, making the EXB30 ideally suited to cost and space sensitive applications. Remote Sense Compensation The EXB30 models have a remote sense feature to compensate for moderate voltage drops in the distribution system. Thus accurate voltage regulation can be achieved directly at the load terminals. Further details concerning the remote sense compensation feature are presented in the applications section. Output Voltage Adjustment The output voltage on the 2V, 2.5V, 3.3V and 5V models is trimmable by -20% to +10% of the nominal output voltage. The 12V output voltage can be trimmed by -40% to +10%. Details on how to trim all models are provided in the applications section. PAGE 2 EXB30 SERIES | Application Note 108 Remote On/Off The Remote On/Off function allows the unit to be controlled by an external signal which puts the module into a low power dissipating sleep mode. Methods of using this function are given in the applications section. None of the specifications are guaranteed when the unit is operated in an overcurrent condition. The unit can be operated continuously in this condition. However the lifetime of the unit will be reduced. Constant Switching Frequency The switching frequency for all models is fixed at approximately 300kHz and is independent of line and load levels. This makes the overall power system more predictable and greatly simplifies the design of the input filter required for EMC compliance. Over Temperature Protection This feature is included as standard in order to protect the converter and the circuitry it powers from overheating in the event of a runaway thermal condition such as a fan failure at high temperatures or continuous operation above Tmax at full power. Brickwall Current Limit and Short Circuit Protection All models of the EXB30 have a built in brickwall current limit function and full continuous short circuit protection. Thus, the V-I (output voltage - output current) characteristic will be almost vertical at the current limit inception point, as shown in Figure 2. A slight tailout characteristic may be evident in some models when the output voltage is reduced to very low values, i.e. under short circuit conditions. A short circuit is defined as a resistance of 20m or less. For all models under full load conditions the trip point will be at a minimum ambient of 90C in still air using the recommended layout in the Applications section. Still air or natural convection is defined as less than 0.1m/s airflow. As the load is decreased and the unit is operated at higher temperatures, the trip point also rises. This trip point will at all times protect the unit and will be a minimum of 5C within the safe operating temperature of the device. Vout 100% Iout Figure 2 - Typical Brickwall V-I Characteristic The current limit inception point is dependent on the input voltage, ambient temperature and has a parametric spread also. For all models the inception point is typically 115% of rated full load. It may go as high as 150% or as low as 100% over all operating conditions and the lifetime of the product. None of the specifications are guaranteed when the unit is operated in an overcurrent condition. The unit will not be damaged in an overcurrent condition as it will protect itself through the use of the OTP function before any damage occurs. However the lifetime of the unit may be reduced. In a severe short circuit the unit may enter a `hiccup' current mode and may be operated continuously in this condition. The duty cycle of this hiccup is dependent on input voltage, temperature etc. While the unit is specified to operate into a continuous short circuit, extended or frequent short circuits will reduce the lifetime of the converter. The current limit characteristic for the EXB30-48S12 is unlike that for the low voltage models. The unit will exhibit brickwall current limit for approximately 100ms after which the unit enters a hiccup mode. The duty cycle of the hiccup depends on the level of overcurrent. This mode of operation will continue indefinitely until the overcurrent condition is corrected. PAGE 3 Prolonged operation under short circuit conditions at high ambient temperatures might also cause the OTP circuit to trip. The actual ambient temperature it trips at is dependent on quite a number of factors. The airflow over the unit is the most dominant parameter. The trip point is also affected by the input voltage, output trim voltage, user PCB layout, output load and model. Output Overvoltage Protection The clamped overvoltage protection (OVP) feature is used to protect the module and the user's circuitry when a fault occurs in the main control loop. Faults of this type include optocoupler failure, blown sense resistor or error amplifier failure. The unit is also protected in the event that the output is trimmed above the recommended maximum specification. The OVP circuit consists of an auxiliary control loop running in parallel to the main control loop using a separate optocoupler. However, unlike the main loop, the OVP loop senses the voltage at the output power terminals of the module, Vo+ and Vo-. The sensed voltage is compared to a separate OVP reference and a compensated error signal is generated such that the output voltage is regulated to the OVP clamp level. The clamp levels are set quite accurately and are given in Table 2. Output Voltage Clamp Level 12V 14.2V 5V 5.6V 3.3V 3.8V 2.5V 3.0V 2.0V 2.3V 12.0V 14.2V Table 2 - OVP Trip Point Input Undervoltage and Overvoltage Protection The EXB30 series is fitted with a detection circuit at the input side which inhibits operation of the converter when the input voltage is outside the normal operating range. For 48V models, the converter is disabled when the input voltage is below 32V or above 78V approximately. The lower trip value protects against deep discharge of telecom batteries while the upper level protects the module from operating beyond the maximum input voltage rating. The thresholds EXB30 SERIES also have inherent hysteresis to provide immunity against slow ramping input voltages. The module operates in a low power dissipation mode when protected. 5. Safety Isolation The EXB30 has been submitted to independent safety agencies and has EN60950 and UL1950 Safety approvals. Basic insulation is provided and the unit is approved for use between the classes of circuits listed in Table 3. Insulation Between And TNV-1 Circuit Earthed SELV Circuit Unearthed SELV Circuit TNV-2 Circuit TNV-3 Circuit Earthed SELV Circuit Unearthed SELV Circuit or TNV-1 Circuit Earthed or Unearthed Hazardous Voltage Secondary Circuit Earthed SELV Circuit ELV Circuit Unearthed Hazardous Voltage Secondary Circuit TNV-1 Circuit Table 3 - Insulation Categories for Basic The TNV or Telecommunication Voltage definitions are given in Table V.1 of IEC950 from which EN60950 and UL1950 are derived. The EXB30 has an approved insulation system that satisfies the requirements of the safety standards. | Application Note 108 has complied with. Radiated emissions The applicable standard is EN55022 Class B (FCC Part 15). Testing DC/DC converters as a stand-alone component to the exact requirements of EN55022 (FCC Part 15) is very difficult to do as the standard calls for 1m leads to be attached to the input and output ports and aligned such as to maximise the disturbance. In such a set-up it is possible to form a perfect dipole antenna that very few DC/DC converters could pass. However the standard also states that `An attempt should be made to maximise the disturbance consistent with the typical application by varying the configuration of the test sample'. In addition ETS 300 386-1 states that the testing should be carried out on the enclosure. The EXB30 is primarily intended for PCB mounting in Telecommunication Rack systems. For the purpose of the radiated test, an EXB30-48S3V3 was mounted on a test PCB (230 x 170mm) with Vin- connected to a copper ground plane on the PCB. A resistive load was connected by lead lengths of approximately 10cm and the lead length to the power source was 50cm. The unit was supplied with 48V input and the output was 3.3V at 8A. The measurements were carried out at a 10m measurement distance on an open area test site using a Rhode & Schwarz ESV receiver and a Farnell 352C Spectrum Analyser with a Schwarzbeck BBA9106 broadband VHF antenna. An independent test house performed the testing and a copy of the report is available on request. The results of the test are given in Table 4. All the responses were broadband in nature and there was no detectable response above 147.41MHz. (The `V' denotes the antenna polarization for maximum response was Vertical). As evident, Class A radiated emission requirements of EN55022 are met with margin (limit is 40dBV/m). Frequency (MHz) Response (dBV/m) Limit (dBV/m) In order for the user to maintain the insulation requirements of these safety standards it is necessary for the required creepage and clearance distances to be maintained between the input and output. 35.56 22.30V 40.00 42.28 25.60V 40.00 44.03 29.60V 40.00 Creepage is the distance along a surface such as a PCB and for the EXB30 the creepage requirement between primary and secondary is 1.4mm or 55 thou. Clearance is the distance through air and the requirement is 0.7mm or 27 thou. 48.34 21.30V 40.00 61.96 18.10V 40.00 78.88 20.20V 40.00 Input Fusing In order to comply with safety requirements the user must provide a fuse in the unearthed input line if an earthed input is used. The reason for putting the fuse in the unearthed line is to avoid earth being disconnected in the event of a failure. If an earthed input is not being used then the fuse may be in either input line. 81.97 20.90V 40.00 109.62 27.40V 40.00 110.47 26.00V 40.00 147.41 35.30V 40.00 Table 4 - Radiated Emissions on EXB30-48S3V3 with Ground Plane (within Class A limits) A 2A HRC (High Rupture Capacity) is the recommended fuse rating for the EXB30 product. Secondly, an external pi-filter was connected at the input to the unit, details of which are given in Figure 5. The measured emission levels are given in Table 5. There was no detectable response above 146.54MHz. As evident, Class B radiated emission requirements of EN55022 are met with margin (limit is 30dBV/m). 6. EMC The EXB30 has been designed to comply with the EMC requirements of ETSI 300 386-1. It meets the most stringent requirements of Table 5; Public telecommunications equipment, locations other than telecommunication centres, High Priority of Service. Following is the list of standards which apply and which it http://www.artesyn.com PAGE 4 EXB30 SERIES | Application Note 108 Frequency (MHz) Response (dBV/m) Limit (dBV/m) 75.38 19.25V 30.00 81.20 21.20V 30.00 80 70 dBV 90 84.43 26.80V 30.00 116.78 24.50V 30.00 118.23 24.70V 30.00 119.99 25.95V 40.00 50 146.54 21.80V 30.00 40 60 Table 5 - Radiated Emissions on EXB30-48S3V3 with Ground Plane and External pi-filter (within Class B limits) 55022BAV 30 20 10 In both cases the unit passed the Class B limit which is 30 dBV/m with a significant margin. 0 0.02 Conducted emissions The required standard for conducted emissions is EN55022 Class A (FCC Part 15). The EXB30 has a substantial LC filter on board which greatly reduces conducted emissions. However, to meet Class A and Class B, external pi-filters are connected as described in Figures 5 and 6 respectively. Putting these extra components on board the EXB30 would have added to the cost and footprint of the module. Additionally, this would have removed the flexibility that end users have to add a single filter to the input of all converters on a card thereby reducing cost and space. 0.1 1 10 30 MHz Figure 4 - Conducted Noise Measurements on EXB30-48S05 (meets Class B average) L2 R L1 C The conducted noise plots for the EXB30-48S05 are shown in Figures 3 and 4. The filter circuits to achieve these results are shown in Figures 5 and 6. All other models have similar curves and are available on request. dBV 90 C C C EXB30 Figure 5 - Required Filter for Class A 80 70 L2 60 R 55022AAV L1 50 C C C C C C 40 EXB30 30 20 10 Figure 6 - Required Filter for Class B 0 0.02 0.1 1 10 30 MHz The part numbers for the parts used in each case are given below: Figure 3 - Conducted Noise Measurements on EXB30-48S05 (meets Class A average) PAGE 5 C 470nF 100V AVX ceramic capacitor part number 18121C474KATMA L1 47H TDK inductor part number SLF10145T-470M1R4 L2 27H Siemens inductor part number B82422-H1273-K100 R 10 1206 1/4W resistor Bead MMG SM Ferrite Bead part number B82422-H1273-K100 EXB30 SERIES For the wave soldering test the UUT was again mounted on a test PCB. The unit was wave soldered using the conditions shown in Table 8. VIEW IS FROM TOP SIDE ISOLATION 0.079 (2.00) CL VIN+ VOUT+ REM VSENSE+ CL 2.400 (60.97) For the soldering iron test the UUT was placed on a PCB with the recommended PCB layout pattern shown in the applications section. A soldering iron set to 350C 10C was applied to each terminal for 5 seconds. The UUT was then removed from the test PCB and was examined under a microscope for any reflow of the pin solder or physical change to the terminations. None was found. These recommended PCB layouts will maintain the creepage and clearance requirements discussed in the Safety section of this application note. However, the end user must ensure that other components and metal located in the vicinity of the EXB30 meet the spacing requirements that the system is approved to. 0.353 (8.97) Resistance to Soldering Heat The EXB30 is intended for PCB mounting. Artesyn has determined how well it can resist the temperatures associated with the soldering of PTH components without affecting its performance or reliability. The method used to verify this is MIL-STD-202 method 210D. Within this method two test conditions were specified, Soldering Iron condition A and Wave Solder condition C. Application Note 108 TRIM VSENSE- VIN- VOUT- 0.758 (19.26) 7. Use in a Manufacturing Environment | 1.204 (30.59) 0.292 (7.42) Temperature Time Temperature Ramp 2.280 (57.91) 260C 5C 10s1 Preheat 4C/s to 160C. 25mm/s rate TOP SIDE LAYER 1 OF 2 ALL DIMENSIONS INCHES (MM) Table 8 - Wave Solder Test Conditions THERMAL RELIEF IN CONDUCTOR PLANES REFERENCE IPC-D-275 SECTION 5.3.2.3 Water Washing The EXB30 is suitable for water washing as it doesn't have any pockets where water may congregate long-term. The user should ensure that a sufficient drying process and period is available to remove the water from the unit after washing ESD Control The EXB30 units are manufactured in an ESD controlled environment and supplied in conductive packaging to prevent ESD damage occurring before or during shipping. It is essential that they are unpacked and handled using an approved ESD control procedures. Failure to do so could affect the lifetime of the converter. ALL DIMENSIONS IN INCHES (mm) ALL TOLERANCES ARE 0.10 (0.004) Figure 7 - Optimum PCB Layout for EMC and Thermals for Single Outputs on a Single-Sided PCB VIEW IS FROM TOP SIDE ISOLATION 0.079 (2.00) CL VIN+ VOUT+ REM VSENSE+ CL TRIM VSENSE- VIN- 2.400 (60.97) The UUT was inspected after soldering and no physical change on pin terminations was found. VOUT- 8. Applications 2.280 (57.91) Optimum PCB Layout 2Oz/ft2 or 70m copper should be used for connection to the pins. The PCB acts as a heatsink and draws heat from the unit via conduction through the pins and radiation. The two layers also act as EMC shields. (The recommended layouts do not guarantee system EMC compliance as this is dependent on the end application). If the recommended layout or 2Oz/ft2 copper isn't used then the user needs to ensure that the hot-spots highlighted in the thermal section are kept within their limits. BOTTOM SIDE LAYER 2 OF 2 All DIMENSIONS INCHES (MM) THERMAL RELIEF IN CONDUCTOR PLANES REFERENCE IPC-D-275 SECTION 5.3.2.3 ALL DIMENSIONS IN INCHES (mm) ALL TOLERANCES ARE 0.10 (0.004) Figure 8.1 - Optimum PCB Layout for EMC and Thermals for Single Outputs on a Double-Sided PCB (Top) http://www.artesyn.com PAGE 6 EXB30 SERIES | Application Note 108 VIEW IS FROM TOP SIDE ISOLATION 0.079 (2.00) 85C VOUT+ REM VSENSE+ TRIM VSENSE- 2.400 (60.96) VIN+ Rated Output Current 100% 80% 60% 40% VOUT- VIN- 20% 0% -40C 0 -20C 20C 40C 60C 80C 100C Ambient Temperature 2.280 (57.91) BOTTOM SIDE LAYER 2 OF 2 Figure 10a - Output Power vs. Ambient Temperature in Natural Convection for EXB30 series (Low Voltage Models) THERMAL RELIEF IN CONDUCTOR PLANES REFERENCE IPC-D-275 SECTION 5.3.2.3 Rated Output Current ALL DIMENSIONS IN INCHES (mm) ALL TOLERANCES ARE 0.10 (0.004) 100% (3A) Figure 8.2 - Optimum PCB Layout for EMC and Thermals for Single Outputs on a Double-Sided PCB (Bottom) 83% (2.5A) 50% (1.5A) ISOLATION REQUIREMENTS FOR TOP SIDE (LAYER 1 OF 2) 2.030 (51.55) SECONDARY CORE 1.794 (45.57) 1.256 (31.90) -40C 80C 85C 90C SECONDARY CAPACITORS Ambient Temperature Natural Convection (<0.1 m/s) 2.248 (57.09) 0.959 (24.36) 1.497 (38.01) 1.743 (44.27) 1.450 (36.83) 1.218 (30.95) 0.758 (19.26) 0.100 (2.54) 0.436 (11.07) 0.518 (13.16) 1.591 (40.41) 0% CONVERTER OUTLINE 1.112 (28.23) 0.758 (19.26) 1.730 (43.95) SECONDARY CAPACITOR Figure 10b - Output Power vs. Ambient Temperature in Natural Convection for EXB30 12V model. If forced air cooling is used then the converter may be used up to 95C at full output power dependent on the airflow. Figure 11 is a graph of the increased maximum ambient temperature at full power versus the airflow across the converter. PRIMARY / SECONDARY OPTOCOUPLER PRIMARY CORE 2.042 (51.87) Increase in Ambient Vs. Airflow Figure 9 - Keep Out Areas on Top Side of User PCB to Meet Safety Spacing Requirements Optimum Thermal Performance The EXB30 can operate in still air up to a maximum ambient temperature of 85C using the recommended PCB layouts shown in the previous section. Still air, which is sometimes called natural convection is defined as <0.1m/s airflow (20CFM). The output power may be derated so that the maximum ambient operating temperature can be extended to 95C as shown in Figure 10a. The 12V output is rated to supply an output current of 2.5A at an operating ambient temperature of 85C. At 80C the output current can be increased to 3.0A as shown in figure 10b. PAGE 7 Increase in Max. Ambient Temperature (C) All DIMENSIONS INCHES (MM) 20 15 10 5 0 0 0.5 1.0 1.5 2.0 Airflow (m/s) Figure 11 - Increased Maximum Ambient Temperature at Full Power with Forced Airflow With an airflow of 1.5m/sec the allowed increase in ambient temperature is 15C. Figure 12 shows the new derating curve for the 48S05 model operating with 1.5m/s forced airflow. EXB30 SERIES Application Note 108 In order to maintain the Artesyn derating criteria and comply with safety standards the temperatures of the hotspots should never rise above 120C. 100C 100% Remote On/Off Control The remote on/off control feature allow the user to switch the converter on and off electronically when the appropriate signal is applied to the remote pin. This is a primary referenced function which allows the converter to be put in a low dissipating sleep mode. 80% Rated Output Current | 60% 40% 20% 0% -40C -20C 0 20C 40C 60C 80C 100C 110C Ambient Temperature Figure 12 - Thermal Derating for 48S05 with 1.5m/s Forced Airflow For extreme environments the most accurate method of ensuring that the converter is operating within its guidelines in a chosen application is to measure the temperature of a hot-spot. There are three such positions on the EXB30. The hottest is dependent on the input line voltage, output load and even the ambient temperature. In general they will be within 10C of each other. These hot spots are shown in Figure 13 for the low ouput voltage models and are the main primary switch, two synchronous rectifiers (the thermocouples should be mounted as closely as possible to the tabs of the devices) and the bias supply controller. For the 12V model, three hot spot locations are shown in Figure 13B (i.e. main switch, diode rectifier and bias supply controller) The EXB30 models are available in a positive logic remote on/off configuration. The control pin is held high through an internal resistor. Positive Logic This means that for the active high model, no connection is needed to the control pin for the module to be enabled. However, the control pin needs to be driven low and kept low to put the module into sleep mode. Specification for the Remote On/Off See signal electrical interface on the EXB30 data sheet. Isolated Closure Remote On/Off An isolated closure is a closure with both high and low impedance states that sinks current, but does not source current. For on/off control the closure is between the on/off pin and Vi(-), this can be a device such as a mechanical switch, open collector transistor or opto-isolator. VI(+) Ion/off + Remote On/Off On/Off EXB30 VOn/Off RB RBE VI(-) Figure 13a - Hot Spot Locations on EXB30 2V, 2.5V, 3.3V and 5V Models Figure 14 - Isolated Closure using a Transistor Note in the data sheet, the `acceptable high level leakage current'. The maximum acceptable leakage current is 50A. The isolation device should have a leakage current less than this value or the module may go into a low power dissipation mode (remote off). Figure 13b - Hot Spot Locations on EXB30 12V Model http://www.artesyn.com PAGE 8 EXB30 SERIES | Application Note 108 Level Controlled Remote On/Off Units can also be controlled by applying a voltage to the remote on/off pin. The figure below shows a TTL output control. If the remote sense feature is not required, it is necessary to short the sense terminals to the respective power terminals as shown in Figure 17. VI(+) Io TTL Gate Vo+ Vi+ Ion/off + Remote On/Off On/Off Vsense+ Vin Load EXB30 VsenseVi- VOn/Off VoContact and Distribution Losses VI(-) Figure 17 - Circuit Configuration when Remote Sense is not required Figure 15 - Level Control using TTL Output As per the data sheet the TTL must be capable of sinking the maximum low level input current of 100A. Remote Sense Compensation The remote sense compensation feature minimises the effects of resistance in the distribution system and facilitates accurate voltage regulation at the load terminals or other selected point. The remote sense lines will carry very little current and hence do not require a large cross-sectional area. However, if the sense lines are routed on a PCB, they should be located close to a ground plane in order to minimise any noise coupled onto the lines that might impair control loop stability. In a discrete wiring situation, the use of a twisted pair or any other technique to reduce noise susceptability is recommended. A small 100nF ceramic capacitor can be connected at the point of load to decouple any noise on the sense wires as outlined in Figure 16. Output Voltage Adjustment The output can be externally trimmed by -20% to +10% for low voltage models or -40% to +10% for the 12V model by connecting an external resistor between the TRIM pin and either the Vsense + or Vsense - pins. With an external resistor between TRIM and Vsense-, (RTRIM_DOWN) the output voltage setpoint decreases (See Figure 18). Conversely, connecting an external resistor between TRIM and Vsense+ (RTRIM_UP), the output voltage setpoint increases (See Figure 19). + Sense Rtrim_down Trim - Sense Io Figure 18 - Circuit Configuration to Decrease Output Voltage Vo+ Vi+ Vsense+ + Sense 100n Vin Load Trim VsenseVi- Rtrim_up Vo- Sense Contact and Distribution Losses Figure 19 - Circuit Configuration to Increase Output Voltage Figure 16 - Circuit Configuration for Remote Sense Operation The power module will typically compensate for a maximum drop of 10% of the nominal output voltage. In other words, the voltage difference between the power terminals and the sense terminals must not exceed the maximum output sense range specified in the data sheet, i.e. The equations used to determine the value of the external resistor (specified in k) required to obtain the desired output voltage are shown below ( = % change expressed in decimals): RTRIM_DOWN = [ RTRIM_UP [ I- ] 10k for all models [Vo+ - Vo-] - [Vsense+ - Vsense-] < 10% Vo(nom) However, if trim up and remote sense are used in combination, the overvoltage setpoint might be reached and the output voltage at the power terminals will be clamped at this level. = Vo(nom) -1 Vref ][ I+ ] 10k Where Vo (nom) is the default output voltage of the module. PAGE 9 EXB30 SERIES Vref = 2.5V, 5V and 12V models Vref = 1.225V for 2.0V, 2.5V and 3.3V models RTRIM_UP The resistor required to achieve the desired trimmed up output voltage | Application Note 108 To Input Curent Measurement device +Vin 12H RTRIM_DOWN resistor required to achieve the desired trimmed down output voltage Example: To trim up the 5V model by 5% to 5.25V the required external resistor is: RTRIM_UP = 5 [ 2.5 -1 ][ Cin 220F Electrolytic ESR<0.12 @100kHz EXB30 -Vin 1 + 0.05 10k = 210k 0.05 ] Figure 20 - Reflected Ripple Current Measurement Set-up with Recommended Filter for Ripple Current Reduction To trim down by 10% the required resistor is: RTRIM_DOWN = - 0.1 [ 1 0.1 ] 10k = 90k Note that the resistor required to trim down is independent of output voltage, whereas the resistor required to trim up is largely dependent on output voltage. Parallel Operation Because of the absence of an active current sharing feature, parallel operation of multiple EXB30 converters is generally not recommended. If unavoidable, Oring-diodes have to be used to decouple the outputs. Droop resistors will support some passive current sharing. It should be noted that both measures will adversely affect the power conversion efficiency. When the output voltage is trimmed up a certain percentage, the output current must be derated by the same amount so that the maximum output power is not exceeded. Output Capacitance The EXB30 series of DC/DC converters has been designed to be stable operation without the need for external capacitors at the input or output terminals when powered from a low impedance source. However, when powering loads with large dynamic current requirements, improved voltage regulation can be obtained by inserting decoupling capacitors as close as possible to the load. Low ESR ceramic capacitors will handle high frequency current components while tantalum capacitors can be used to supply the lower frequency dynamic current variations. Note that the absolute maximum value of output capacitance is 10,000F for the 2V, 2.5V, 3.3V and 5V models and 2,000F for the 12V model. For larger capacitance values than this please contact the local Artesyn Technologies representative. Reflected Input Current Measurement: The circuit shown in Figure 20 has been used to measure the reflected input current. Capacitor Cin is used to offset any impedance that may occur between the converter and the battery. This filter may also be connected on the input side of the EXB30 to reduce the reflected input ripple current. http://www.artesyn.com PAGE 10 EXB30 SERIES | Application Note 108 Output Noise and Ripple Measurement 100nF Low Loss, Low Inductance Type Capacitor Vout+ Vout- 50 50 Coax 50 Low Inductive Type Resistor Measuring Instrument/ Oscilloscope Low Inductive Type Resistor TX36/23/15 3E25 Material High Ferrite Torroid 5 Turns or More NOTE: Readings must be multiplied by 2 Figure 21 - Output Noise and Ripple Set-up The above circuit has been used for noise measurement on EXB30 series converters. The large toroid will act as a common mode filter to noise which would otherwise flow through the measuring instrument or oscilloscope to disturb the measurement of the differential mode noise. A 50 coax lead should be used with source and termination impedances of 50. This will prevent impedance mismatch reflections which would otherwise disturb the noise reading at higher frequencies. PAGE 11 The 50 resistor which is added in series with the output of the power supply will form a voltage divider with the termination 50 and so ripple and noise measurement readings should be multiplied by 2. EXB30 SERIES | Application Note 108 UVLO and OVLO trip levels. Compatibility with LT(R)1640L/LT1640H Hot Swap Controller The PWRGD output can be used to directly enable the EXB30. This is an open collector output with minimum output impedance of 2k. The pull-up resistor (R7) required to ensure that the Remote on/off pin voltage is greater than 2V at an input voltage of 30V is 33k. This results in a maximum power dissipation in R7 at Vinmax (75V) to be approximately 0.2W. The LT(R)1640L/LT1640H is an 8-pin, negative voltage Hot Swap(R) controller that allows a board to be safely inserted and removed from a live backplane. The EXB30 modules are compatible with LT1640H part. It provides the following features: Typically the PWRGD signal is not required for inrush current control and thus, this 0.2W maximum power dissipation can be avoided if the user controls the Remote on/off pin voltage level by other means. 1 Inrush current is limited to a programmable value by controlling the gate voltage of an external N-channel pass transistor. 2 The pass transistor is turned-off if the input voltage is less than the programmable undervoltage threshold or greater than the overvoltage threshold. A programmable electronic circuit breaker protects the system against shorts. 3 The LT1640H is designed for modules with a high enable input. The PWRGD signal can be used to directly enable a power module. The UV (pin 3) and OV (pin 2) pins can be used to detect undervoltage and overvoltage conditions at the power supply unit. The EXB30 has already got undervoltage and overvoltage protection in-built to ensure that the unit does not draw power from the power source for voltages less than 32V and greater than 78V. Resistors R4, R5 and R6 determine the undervoltage and overvoltage levels. Users should refer to data sheet of the LT1640 for formulae to set the required GND R7 R4 8 3 VDD UV 1 PWRGD R5 LT1640H 2 OV R6 VEE SENSE 4 GATE 5 C1 33nF -48V DRAIN 6 R1 0.02R R2 10R 7 R3 10k C2 3n3 Remote ON/OFF Q1 IRF530 Vin+ C3 0.1 100V C4 100 100V EXB30-48SXXX Vo+ Vsense+ Vsense- C5 100 16V VoVin- Figure 22 - LT1640H Hot Swap Controller Interface with EXB30-48SXXX http://www.artesyn.com PAGE 12 AN_EXB30_20001020.PDF Application Note (c) Artesyn Technologies(R) 2000 The information and specifications contained in this application note are believed to be correct at time of publication. However, Artesyn Technologies accepts no responsibility for consequences arising from printing errors or inaccuracies. Specifications are subject to change without notice. No rights under any patent accompany the sale of any such product(s) or information contained herein.