600kHz 3A Step-Down Switching Regulator

TJ4519

Jul. 2010 – Preliminary

- 11 -

HTC

Loop Gain T(s)

Power Stage

Mag

Figure 4. Asymptotic diagrams of power stage with current loop closed and its loop gain.

The design guidelines for the TJ4519 applications are as following:

1. Set the loop gain crossover corner frequency

2. Place an integrator at the origin to increase DC and low frequency gains.

3. Select

4. Place a high frequency compensator pole

ripple and high frequency noise with the adequate phase lag at

Layout Guidelines:

In order to achieve optimal electrical and thermal performance for high frequency converters, special attention

must be paid to the PCB layouts. The goal of layout optimization is to identify the high di/dt loops and minimize

them. The following guidelines should be used to ensure proper operation of the converters.

1. A ground plane is suggested to minimize switching noises and trace losses and maximize heat transferring.

2. Start the PCB layout by placing the power components first. Arrange the power circuit to achieve a clean power

flow route. Put all power connections on one side of the PCB with wide copper filled areas if possible.

3. The VIN bypass capacitor should be placed next to the VIN and GND pins.

4. The trace connecting the feedback resistors to the output should be short, direct and far away from any noise

sources such as switching node and switching components.

5. Minimize the loop including input capacitor, the TJ4519 and freewheeling diode D2. This loop passes high di/dt

current. Make sure the trace width is wide enough to reduce copper losses in this loop. 6. Maximize the trace

width of the loop connecting the inductor, freewheeling diode D2 and the output capacitor.

7. Connect the ground of the feedback divider and the compensation components directly to the GND pin of the

TJ4519 by using a separate ground trace.

8. Connect Pin 4 to a large copper area to remove the IC heat and increase the power capability of the TJ4519. A

few feed through holes are required to connect this large copper area to a ground plane to further improve the

thermal environment of the TJ4519. The traces attached to other pins should be as wide as possible for the

same purpose.