3 Detailed Descriptions

VOUT connectors connect to the power inductor and output capacitors. Connect the load between the VOUT connector and the GND connector to provide load current. Connect the loading device to the board with short and thick wires to handle the large DC output current.

The GND is connected to the PGND and AGND pins of the device as well as the ground of the input and output capacitors. The GND connections next to VIN, VIN_EMI, and VOUT connectors are meant for current return path for the supply voltage and load, respectively. Connectors are provided in pairs to allow easy and accurate sensing of voltages. Connect to supply and load grounds with short and thick wires. Other GND connectors are for signal measurement and probing.

The V_IN connector connects to the input capacitors and the VIN pins of the LMQ61460-Q1. Connect the supply voltage from a power supply or a battery between VIN and GND connectors as power input to the device. The input voltage (V_IN) range must be higher than 3.9 V for the device to start up and above 3 V to maintain operation. A V_IN higher than 6 V provides a regulated 5-V output voltage. Maximum V_IN is limited to 36 V to avoid damaging the device. The current limit on the supply must be high enough to provide the needed supply current. The supply voltage must be connected to the board with short and thick wires to handle the required input current at maximum load current. If long cables are used to power up the board, damping must be provided by adding CFLT3 and RFLT3 to avoid oscillation between the cable parasitic inductance and the existing low-ESR ceramic capacitors.

If the input filter is required, connect the supply voltage between VIN_EMI and GND_EMI. The supply voltage must be connected to the board with short and thick wires.

The input filter consists of the following: CF1, CF2, CF3, CF4, CF5, CF6, and L2. CD1, CD2, RD1, and RD2 are provided to allow more options for filter optimization. To include the input filter in the power path, connect the supply voltage between the VIN_EMI and GND_EMI connectors. The output of the filter is connected to V_IN, which is connected to the V_IN pins of the LMQ61460-Q1.

Conducted EMI arises from the operation of switching circuits.

This is the current return path for the supply connected to VIN_EMI. It provides a short-loop connection to the input filter capacitors to best filter the conducted noise generated from the PCB. Use VIN_EMI and GND_EMI connection if input filter is used and conducted EMI test is desired.

The CLK input connector is designed for external clock input to the EN/SYNC pin. Switching action of the buck is synchronized to the external clock when it is present. The operation mode automatically changes to forced PWM mode, maintaining a constant switching frequency over the entire load range while the clock signal is present.

This test point is used to monitor the voltage on the device EN pin. By default, the EN pin is connected to the mid-point of an enable divider. Note that the lower resistor in this divider, RENB, is not populated so the IC turns on by default. Populate RENB to adjust UVLO. Apply a voltage to EN to externally enable or disable the device.

The PGOOD flag indicates whether the output voltage is within the regulation band. The RESET pin (synonymous with PGOOD pin) of the device is an open-drain output and is pulled up to V_OUT through a 100 k resistor. This pin pulls to GND when the output voltage is out of regulation.

A low value resistor, Rinj, is placed between VOUT and this node. The feedback divider of the board is connected to this node. An AC signal is applied across Rinj when taking measurements for bode plots.

This connector is provided for measuring the output voltage accurately.

This connector is provided for measuring the input voltage accurately.