The EVM features a LMZ31520 (20 A) or LMZ31530 (30 A), synchronous buck SIMPLE SWITCHER power module configured for operation with typical 5-V and 12-V input bus applications. The output voltage can be set to one of six popular values by using a configuration jumper. In similar fashion, the switching frequency can be set to one of four values with a jumper. The full 20-A/30-A rated output current can be supplied by the EVM. Input and output capacitors are included on the board to accommodate the entire range of input and output voltages. Monitoring test points are provided to allow the following:

• Measurement of efficiency
• Power dissipation
• Input ripple
• Output ripple
• Line and load regulation
• Transient response

Figure 2-1 highlights the user interface items associated with the EVM. The polarized PVin Power terminal block (J8) is used for connection to the host input supply and the polarized Vout Power terminal block (J11) is used for connection to the load. These terminal blocks can accept up to 16-AWG wire. The polarized VBIAS terminal block (J12) is used along with the VIN SELECT jumper (J4) when optional split power supply operation is desired. Refer to the LMZ31520 20-A Power Module With 3-V to 14.5-V Input Data Sheet and LMZ31530 30-A Power Module With 3-V to 14.5-V Input Data Sheet for further information on split power supply operation.

Figure 2-1 LMZ315x0EVM User Interface

The PVin Monitor (TP1) and Vout Monitor (TP3) test points located near the power terminal blocks are intended to be used as voltage monitoring points where voltmeters can be connected to measure PVIN and VOUT. The voltmeter references should be connected to the PGND test points (TP4 and TP2). Do not use these PVIN and VOUT monitoring test points as the input supply or output load connection points. The PCB traces connecting to these test points are not designed to support high currents.

The PVin Scope (J6) and Vout Scope (J7) test points can be used to monitor PVIN and VOUT waveforms with an oscilloscope. These test points are intended for use with un-hooded scope probes outfitted with a low-inductance ground lead (ground spring) mounted to the scope barrel. The two sockets of each test point are on 0.1-inch centers. The scope probe tip should be connected to the socket labeled PVIN or VOUT, and the scope ground lead should be connected to the socket labeled PGND.

The Vout Scope (J5) test point can be used to monitor the V_OUT waveform with an oscilloscope. This test point is intended for use with an un-hooded scope probe with a 3.5-mm ground barrel.

The control test points located directly above the device are made available to test the features of the device. Refer to Section 3 for more information on the individual control test points.

The Vout Select jumper (J2) and Fsw Select jumper (J3) are provided for selecting the desired output voltage and appropriate switching frequency. Before applying power to the EVM, ensure that the jumpers are present and properly positioned for the intended output voltage. Always remove input power before changing the jumper settings.

Seven wire-loop test points and three scope probe test points have been provided as convenient connection points for digital voltmeters (DVM) or oscilloscope probes to aid in the evaluation of the device. A description of each test point follows:

In order to operate the EVM using a single power supply, the VIN Select jumper (J4) must be in the default PVIN-VIN position shown in Figure 2-1. In this position, the PVIN and VIN pins of the device are connected together. The UVLO threshold of the EVM is approximately 4.2 V with 0.25 V of hysteresis. The input voltage must be above the UVLO threshold to start up the device. After start-up, the minimum input voltage to the device must be at least 4.5 V or (V_OUT + 1.0 V), whichever is greater. The maximum operating input voltage for the device is 15 V. Refer to the product data sheet for further information on the input voltage range, and optional split power supply operation for operating with PVIN as low as 3.0 V when using an external Vbias supply.

After application of the proper input voltage, the output voltage of the device will ramp to its final value in approximately 0.7 ms. If desired, this soft-start time can be increased by increasing the value of the Rss resistor (R6). Refer to the LMZ31520 20-A Power Module With 3-V to 14.5-V Input Data Sheet and LMZ31530 30-A Power Module With 3-V to 14.5-V Input Data Sheet for further information on adjusting the soft-start time.

The EVM includes input and output capacitors to accommodate the entire range of input and output voltage conditions. The actual capacitance required will depend on the input and output voltage conditions of the particular application, along with the desired transient response. In most cases, the required output capacitance will be less than that supplied on the EVM. Refer to the LMZ31520 20-A Power Module With 3-V to 14.5-V Input Data Sheet and LMZ31530 30-A Power Module With 3-V to 14.5-V Input Data Sheet for further information on the minimum required I/O capacitance and transient response.

The LMZ315x0 can be operated in either auto-skip Eco-Mode or in forced continuous conduction mode (FCCM) by selecting the desired mode using J1. Refer to the LMZ31520 20-A Power Module With 3-V to 14.5-V Input Data Sheet and LMZ31530 30-A Power Module With 3-V to 14.5-V Input Data Sheet for further information on selecting the mode of operation.