Vicor Pi352x-0x-eval1 Zvs Regulators 60vin Buck Evaluation Board User Guide

VICOR PI352X-0X-EVAL1 ZVS Regulators 60VIN Buck Evaluation Board

Introduction

This evaluation board is designed for the PI352x family of 10 x 14 ZVS Bucks. It can be configured to demonstrate a single product in a stand-alone local sense or a remote sense configuration.
The PI352x family of wide input range DC-DC ZVS-Buck regulators feature high efficiency with integrated controller, power switches, and support components all within a high density 0.4” x 0.55” System-in-Package (SiP). Required components are placed inside a demarcation featuring a solution size of 7.3” x 1.35”. The demarcation includes an external inductor, compensation capacitor, voltage selection resistors, soft-start capacitor, and input-output capacitors to form a complete DC-DC regulator.

IMPORTANT NOTICE: Be sure to read the precautions below entirely BEFORE using the Evaluation Board. Do not operate the evaluation board unless you have the appropriate safety precautions in place on your bench to ensure a successful experience. The list below is not comprehensive and is not a substitute for common sense and good practice.

• Refer to the specific regulator module datasheet for an electrical rating of the device, and thermal and mechanical product details. It is important to remain within the device-rated range when testing.
• When testing electronic products always use approved safety glasses. Follow good laboratory practices and procedures.
• During operation insure the power devices and surrounding structures can be operated safely.
• Care should be taken to protect the user from accidental contact when under power.
• Provide a strain relief for wires and place the system on the bench in such a way as to prevent accidental displacement from the benchtop.
• Review thermal considerations and guidelines associated with operating the evaluation board. Most notably use a benchtop fan and use rubber feet to elevate the PCB as they allow airflow to
  the bottom.
• Remove power and use caution when connecting and disconnecting test probes and interface lines to avoid inadvertent short circuits and contact with hot surfaces.
• Verify power connections to avoid reversing applied voltage polarities.
• Avoid creating ground loops between the SGND and PGND pins when making measurements.
• The product evaluation board is designed for general laboratory evaluation. It is not recommended for installation in end-user equipment.
• The evaluation board is designed to facilitate the evaluation of the performance of Vicor’s mounted ZVS buck products. Sockets are provided to permit quick probing. Input sockets can be used to place a bulk capacitor. The evaluation board provides lugs, and bottom layer banana jack footprint for input and output connections, signal connectors allowing wire, signal test points for easy connection to standard test equipment, and Kelvin Johnson-Jack for accurate voltage measurements of power nodes.

Box Contents

The evaluation board ships with the following contents:

• 1 Customer evaluation board
• 3 x pre-installed jumpers
• 1 x hardware kit: 5 x size 10 screws, lugs and washers

Recommended Test Equipment

The following is a list of recommended test equipment.

1. Safety glasses.
2. DC power supply: Refer to the specific PI352x model datasheet to ensure the supply has sufficient power and current capability.
3. Electronic load: Refer to the specific PI352x model datasheet to ensure the load has sufficient power handling and current capability for testing.
4. Bench top cooling fan.
5. Digital multi-meters (DMMs).
6. Oscilloscope and probes.
7. Interconnect wires, cables and fastening hardware.

Features

1. Input and output lugs for source and load connections.
2. Input sockets to place through-hole input aluminum-electrolytic capacitor.
3. Input source filter (L102, R105).
4. Toggle switch (S101) for enabling and disabling the regulator through the EN pin.
5. Oscilloscope probe jack for accurate, high frequency input (J101) and output (J102) voltage measurement.
6. Signal pins test points and wire connectors.
7. Kelvin voltage test points and sockets for all pins of the SiP product.
8. Access to voltage switching node VS1 with a nearby ground receptacle.
9. Mode selection switch for local (default) and remote sense loop.
10. Trim control selection for both local and remote sense:
    • ADJ: potentiometer to exercise the full output range.
    • Fixed: resistor to set unit to nominal output.
11. Local and remote sense AC signal injection (J201).

Board Operation Modes

• S101 provides control to enable / disable the powertrain.
• In the “OFF” position, the switch will connect SGND pin to the EN net, which disables the regulator output.
• In the “ON” position, the EN net is allowed to float.
• The PI352x evaluation board supports the following operating modes:

Thermal Consideration

A fan blowing across the evaluation board is recommended for operation. The fan should be placed about 4 inches away from the evaluation board edge. A typical benchtop fan is recommended providing about 1000LFM. Using the supplied rubber feet is also required in order to elevate the board about 0.4 inches off a flat surface and enable airflow underneath the PCB.

Power Up Procedure

1. Confirm bench equipment is powered off.
2. Connect input DC power supply positive lead to +VIN input lug, then connect input power supply negative lead to PGND input lug of the evaluation board.
3. Connect the +VOUT lug to the electronic load positive input, connect the PGND output lug to the electronic load negative input.
4. Verify proper polarity of both input and output connections.
5. Verify on-board mechanical switch (S101) desired actuator position. “ON” state allows power up upon application of input voltage. S101 default actuator position is “ON” allowing the unit to power up upon the application of an input voltage greater than VUVLO_START.
6. Verify that three separate two-position jumper sockets are placed on the header (J201) shorting the following J201 pins 1 to 2, 3 to 4, 5 to 6.
7. Verify desired feedback loop operation:
   • On-board mechanical switch (S202) default position is “LS” short for local sense loop
   • On-board mechanical switch (S201) default position is “FIXED” implying the use of the populated exact value resistors producing a regulated, device-specific, nominal output voltage.
8. Place measuring equipment such as DMM, scope probes as desired
9. Direct airflow from the cooling fan towards the evaluation board.
10. Download the latest product datasheet from the Vicor power product page and have it on hand for reference
11. Apply input voltage greater than the minimum Input under-voltage lockout start threshold (VUVLO_START).

Board Description

The following section provides a detailed description of the evaluation board features.

Figure 2: Signal Connector and Header Pinout, Front View

General Components

1. PI352x family product (PS101)
2. Input lugs: Sized for #10 hardware. Use for making connection to the input source. This board does not contain reverse polarity protection. Check for proper polarity before applying power.
3. Input Filtring: Sockets provision can be used for easy installation of aluminum-electrolytic input capacitor and filtering (inductor and ceramic capacitors) allows for stable operation with most input sources. 10 x 2.2µF output ceramic capacitors 1210 (C101- C110) are used to achieve <2% of VIN peak-to-peak ripple.
4. Enable / Disable switch (S101): When actuator is towards “ON” position, the (EN) pin will be open and the regulator will be allowed to power up. When actuator is towards “OFF”, the EN pin will be connected to SGND pin and the regulator will be disabled. When switch (S101) is “ON”, an external voltage source can control the EN pin state using the external EN test point.
5. Wire to board connector (J108): provides access to the regulator signal. All signal pins are reference to SGND.
   • TRK: An external capacitor may be connected between TRK pin and SGND to slow down the internal reference ramp. With this pin connected to an external capacitor the output voltage will track the slope effectively executing a soft-start function. See datasheet for additional tracking options.
   • EAO: Internal transconductance amplifier output pin.
   • EN: Regulator enable pin. Regulator is disabled when (S101) is in “OFF” state as this pin is connected to SGND. In “ON” state the module pin is allowed to float.
   • SGND: Internal logic ground return for all module. SGND to PGND connection is made inside the regulator package.
6. Loop compensation mode selection (S202): Used to select one of the following:
   • Local Sense (LS): default. Single ended feedback loop using the internal to the regulator operational transconductance amplifier. +VOUT Lug is the local sensed location. +VOUT lug is connected to the Error Amplifier Inverting Input (EAIN) through a voltage divider network.
   • Remote Sense (RS): Non-isolated remote sensing option using the internal to the regulator independent differential amplifier which outputs (VDIFF) is in turn connected to the transconductance amplifier input (EAIN) pin. Remote sensing is achieved using +VRS and –VRS test points. Resistors R223 and R224 are 100Ω catch resistor placed to prevent an open loop condition if accidentally switched to this mode.
7. Trim mode selection (S201 or S203): Switch (S201) and trim potentiometer (R206) are associated with local sense loop while switch (S203) and trim potentiometer (R221) are associated with remote sense selection. Both Switches (S201 and S203) provide the following trim modes:
   • Fixed Trim (FIXED): default. Fixed resistor divider is used to set regulator output to the nominal datasheet output voltage.
   • Adjustable Trim (ADJ): selection allows the use of trim potentiometer (R206 or R221) to exercise the full output voltage range. Turn counterclockwise to increase the output voltage and clockwise to decrease the output voltage. The trim potentiometer at either lowest or highest point can only exercise the voltage range defined in the datasheet as valid operational range within tolerance limits. If preferred, through-hole receptacles are available to bypass the potentiometer with external leaded resistor.
8. Header-jumper (J201): Default setting is all three jumper sockets populated. This header provides the following function:
   • Pin 1 and pin 2 can be used to inject the isolated signal of a network analyzer through (R211= 49.9Ω) used for bode plot measurement in order to evaluate the stability in local sense mode.
   • Pin 3 is SGND.
   • Pin 5 and pin 6 can be used to inject the isolated signal of a network analyzer through (R214 = 49.9Ω) used for bode plot measurement in order to evaluate the stability in remote sense mode.
9. Soft-start capacitor (C123): Capacitor connected to regulator TRK pin and SGND. The soft-start time is set with an internal 47nF capacitor to roughly 0.94ms. C123 can be added to further stretch the soft-start ramp CTRK = (tTRK_DESIRED x 50E-6) – 47E-9 where ITRK = 50µA.
10. Internal operational transconductance amplifier compensation network (C201, R212, R225, C202): this network provides flexibility during loop compensation design to adjust the compensation. For the purpose of this evaluation board, C201 in series to the internal R(ZI) of 5kΩ is used.The maximum mid-band gain that can be achieved when using the internal R(ZI) is roughly (20•log(R(ZI)•gm•VREF/VOUT_SET). With a reference voltage of 0.99V and output voltage of 5V max mid band gain is ~14dB. R212 + R(ZI) in series can be used to further increase the mid-band gain. C202 can be used to lower the high-frequency pole if desired. The high-frequency pole is set internally to ~1.7Mhz using a C(HF) = 56pF.
11. Output lugs: Sized for #10 hardware. Use these lugs to connect the output directly to the load.
12. Output oscilloscope probe Jack (J102): Used for making accurate scope measurements of the output voltage (e.g. ripple). The jack is directly compatible with many common passive voltage probes models. Remove the grounding lead and insulating barrel of the probe and insert the probe tip and barrel directly into the jack, ensuring that the probe tip sits in the center socket of the jack. To avoid the risk of an inadvertent short circuit, do not attempt to install while power is applied. This Johnson Jack is kelvin connected to a C126 positive pin.
13. Output filter: 12x 10µF output ceramic capacitors 1210 (C111- C122). Is used to achieve <1.5% of VOUT peak-to-peak ripple.

Test Points Description
Each square point test point can be used with standard probes, clips or hooks. All test points are labeled on the board. Each test point is accompanied with an adjacent socket for adding a test lead or to facilitate wiring to external circuitry.

Sockets Description
Each socket accepts 0.015 – 0.025 inch diameter leads for easy installation of solid wires and through-hole components for use with external circuit and test equipment.

Figure 3: PI352x Evaluation Board Schematic Page 1

Figure 4: PI352x Evaluation Board

Figure 6: PI352x Evaluation Board Assembly, Bottom Side

Bill of Materials

Table 4: PI352x Design Specific Components

Limitation of Warranties

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