QPO-1-EVAL1

USER GUIDE | UG:313 QPO-1-EVAL1 QPO™ Active Output Filter Evaluation Board Contents Page Introduction 1 Features 1 QPO-1-EVAL1 BOM 3 Installed Components 3 User Defined Components 3 Function Descriptions 4 Introduction The QPO-1-EVAL1 is designed to allow full testing of the QPO-1LZ, along with its various performance options, to fully optimize a final system design. The board offers two terminal options for vertical or horizontal mounting. The user must select the required values for the RHR, RSCSET and RSA resistors and solder them in the designated positions before applying power to the EVAL1. Please refer to the QPO-1LZ product data sheet, schematics and the following pages for the proper application of this board. The QPO-1 output ripple attenuator SiP uses active filtering to reduce output ripple and noise (PARD) over 30dB from 500Hz to 500kHz and can be extended down to 50Hz with additional capacitance added to the VREF pin. The QPO-1LZ operates over a voltage range from 3 to 30VDC and supports load currents as high as 10A. Output regulation is maintained with remote sense or trim adjustment of the power supply. The closed loop architecture improves transient response and ensures quiet point-of-load regulation when used in conjunction with the power supply’s control loop or trim node. Slope Adjust 4 Headroom Adjust 4 SC Function 4 Remote Sense 4 Start-up Circuit 6 Features Peak Detector 6 nn > 30dB PARD attenuation, 1 – 500kHz Ordering Information 8 nn 3 – 30VDC operating range nn 10A rating nn Supports precise point-of-load regulation through use of remote sensing or converter trimming nn Optional start-up circuit included nn User-selectable performance optimization for attenuation, power dissipation and transient response nn Horizontal or vertical mounting options nn Evaluation board includes a Johnson Jack for low-noise measurement of the QPO’s filtering performance Figure 1 Top view of evaluation board UG:313 Page 1 QPO-1 Performance The waveforms in Figure 2 highlight the QPO-1’s ability to both filter a converter’s output ripple and maintain a constant output voltage during a load transient. The input voltage of the QPO-1 (dark blue) shows varying amplitude and frequency PARD before and during the load transient, but the QPO-1 output voltage (light blue) remains relatively unaffected. The load transient is a 1 – 10A load step (green). The converter used is a Vicor Mini, 48V to 5V converter (Model number: V48B5C200BN). Figure 2 PARD and Transient Attenuation Figure 3 Evaluation board schematic J11 J12 J8 C1 15µF RSENSE 51.1 J7 J6 J5 J3 RP RSA 1.00kΩ J9 QPO OUT Peak Det CESR SC Set SC TBD CESR RHR CHR CP TBD Opt Opt R2 DZ1 18V 100Ω RSU Q1 IRLML5103TRPBF 20.0kΩ Gnd CSU 1µF J10 J6 Start-up Circuit TBD VREF VREF Gnd J2 15µF RSCSET Slope Adj J1 J4 QPO IN J1 UG:313 Page 2 QPO-1-EVAL1 BOM Qty Description Value Designator Vendor 2 Capacitor, X7R eramic, 15µF, 25V, 1812 15µF C1, CESR TDK C4532X7R1E156MT 1 Capacitor, X7R Ceramic, 1µF, 50V, 1206 1µF CSU TDK C3216X7R1H105K 1 Diode, Zener, 12V, 0.15W, SOT-23 18V DZ1 ON Semi 8 Samtec, 0.2in, Rt-Angle Header J1, J2, J3, J4, J5, J6, J7, J8 Samtec 2 Connector, Johnson Jack Johnson Jack Vendor Part Number BZX84C18LT1G FWS-08-02-T-S-RA J11, J12 Tektronix RLML5103TRPBF Q1 International Recifier 131503100 QPO-1LZ QPO-1 VICOR QPO-1LZ F 1 Transistor, PFET, 30V, 0.6A IRLML5103TRPB 1 QPO-1LZ 1 Resistor, 5%, 0.25W, 1206 100 R2 Rohm MCR18EZPJ101 1 Resistor, 5%, 0.25W, 1206 1.00kΩ RP Rohm MCR18EZHF1001 1 Resistor, 5%, 0.25W, 1206 51.1 RSENSE Rohm MCR18EZPF51R1 1 Resistor, 1%, 0.25W, 1206 20kΩ RSU Rohm MCR18EZHF2002 Installed Components The QPO-1-EVAL1 board comes with the following components pre-stuffed: Remote Sense Components C1, RSENSE Start-up Assist Circuit CSU, RSU, DZ1, R2, Q1 Peak Detector RP CESR CESR User-Defined Components The QPO-1-EVAL1 board comes with the following components not installed; values to be determined by customer: Headroom Resistor RHR (not optional, must be installed for proper operation) Headroom Capacitor CHR (optional) Slope Adjust RSA (optional) SC Function CSC, RSCSET (optional) Peak Detector CP (optional) UG:313 Page 3 Function Descriptions Slope Adjust The slope adjust function allows the user to modify the voltage drop across the QPO-1 (headroom voltage) dependent on the current passing through the QPO-1. This function is used to maintain a constant power across the QPO-1 over a varying range of load currents. The RSA resistor can be calculated by using the following equation: RSA = 0.05V ∆ IOUT Ÿ ∆V Ÿ 2.5kΩ A HR (1) Where: ∆IOUT = Maximum change in load current (A) ∆VHR = headroom voltage change over load range (V) RSA = slope adjust resistor (Ω) The slope adjust feature can be disabled by either using a large resistor value (100kΩ or greater) for RSA or by omitting this resistor entirely. Headroom Adjust The RHR resistor is used to program the desired voltage drop across the QPO-1. This voltage must be greater than the ripple voltage that the QPO-1 is to filter, with additional voltage added for the voltage drops in the attenuation path. Like the RP resistor, the RHR resistor must always be installed for proper operation. The value of RHR can be calculated using this equation: RHR = QPOOUT Ÿ 2.5kΩ VHR (2) Where: RHR = headroom setting resistor value (Ω) QPOOUT = the voltage on the QPO’s output (V) VHR = the target headroom voltage (V) If this resistor is omitted, then the reference pin will be at the same voltage as the input pin, forcing the output pin to be the same voltage as the input pin. SC Function The function of the SC circuit is to use a converter’s trim or SC (secondary control) pin to compensate for the voltage drop across the QPO-1, thereby maintaining the desired output voltage on the QPO’s output. The RSCSET resistor (listed as RSC in the data sheet) determines the amount of current the SC pin of the QPO-1 will source. The current is calculated by dividing the headroom voltage (the voltage drop from QPOIN to QPOOUT ) by RSCSET. RSCSET = RIN  VOUT VRPT (3) Where: VOUT = nominal converter output voltage (V) VRPT = internal reference voltage (V) RIN = internal series resistor (Ω) When using one of the Vicor Micro, Mini or Maxi converters, the RIN = 1kΩ and the VRPT = 1.23V. Figure 4 shows the QPO-1-EVAL1 board connected so as to use the SC function to compensate for the QPO-1’s voltage drop. Remote Sense Compensation for the QPO-1’s voltage drop can be done using the converter’s remote-sense pins, if available. The on-board sensing network can be attached as is shown in Figure 5. UG:313 Page 4 Figure 4 Evaluation board in SC configuration – – QPO-1 US AND FOREIGN PATENTS, PATENTS PENDING Figure 5 Evaluation board in remote‑sense configuration – – QPO-1 US AND FOREIGN PATENTS, PATENTS PENDING UG:313 Page 5 Figure 6 Start-up waveforms; without (top) and with (bottom) the optional start-up circuit Start-up Circuit The start-up circuit (Figure 3) on the evaluation board is used to connect the QPO-1’s reference pin to its input pin during start up. In both waveform pictures of Figure 6, the Output Voltage (light blue) follows the VREF voltage (purple) of the QPO-1. In the picture on the top in Figure 6, without the optional start-up circuit, the QPO-1 input voltage (the converter’s output voltage) can be seen to be greater than the nominal 5V output of the converter. This is due to the QPO-1’s SC circuit having greater headroom voltage during start up and therefore over‑driving the SC of the converter. After about 40ms, the VREF voltage reaches its 5V pre-set limit and the converter’s output voltage starts to drop, eventually steadying out at 5.35V, the nominal output voltage plus the QPO-1’s headroom voltage. The potential problem with this start up is that the converter could fault due to its output being forced to be greater than 110% of the nominal value. For converters with lower nominal output voltages, this could be very serious condition. The waveforms on the bottom are the same converter with the optional start-up circuit enabled. Here, the VREF is forced to follow VIN, so VOUT follows as well. After about 25ms, the start-up circuit releases the VREF pin and it adjusts it value down to generate the proper headroom voltage across the QPO-1. Using this method, there is no possibility of over-driving the converter and causing a fault. Peak Detector The QPO-1 peak detector is used to adapt the headroom voltage in response to increasing converter ripple. The greater the ripple on the QPO-1’s input, the greater the headroom voltage across the QPO-1. This feature can be disabled by adding the CP capacitor to the evaluation board. The addition of this capacitor creates an RC filter network that filters out the converter’s ripple to the peak detector. The RP resistor must always be installed for proper operation. The peak detector creates the internal reference voltage rail that gets divided down by the headroom resistor RHR. UG:313 Page 6  UG:313 Page 7 QPO-1 US AND FOREIGN PATENTS, PATENTS PENDING Figure 7 Mounting options Figure 8 Mechanical drawing QPO-1 EVAL1 Ordering Information Carrier Board Part Number QPO-1-EVAL1 Compatible VI Chip® Evaluation Boards (sold separately) [b] Evaluation Board for QPO-1L UG:313 Page 8 Limitation of Warranties Information in this document is believed to be accurate and reliable. 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