The size of the door trajectory and the phase trajectory must determine the power MOSFET according to the duties they are transmitted. The robustness of the device allows management applications with powerful functions to stay away from the controller without losing performance. In any case, if possible, it is recommended to minimize the distance between the controller and the power part. The connection between small signal components and application key nodes, as well as power supply to the device, is also important. Positioning the barrier container (VCC and self -lifting capacitors) and feedback compensation elements are as practical as possible as possible. In order to realize the programmability of overcurrent, the RocSet is close to the device and avoids the leakage current path on the LGATE/OC pin because the internal current source is only 10 μA. The system that does not use the Schartki diode and the low -edge MOSFET may show a large number of negative peaks on a large number of defect phase needles. The peak must be limited to the rated value within the absolute maximum range (e.g., a gate resistance is connected in series on the HS MOSFET gate) and the peak of the positive peak, but there is an additional consequence: it causes the self -raising capacitor to over -charge. In the worst case of the maximum input, this additional charge will cause voltage and during a specific transient process. Starting to overcome the maximum voltage of the absolute voltage will also cause equipment failure. In this case, it is recommended to restrict this situation with an additional charging by connecting a small resistance on the self -raising diode.

Application information

inductor design

The inductor value is dynamic response time, efficiency, cost and scale. The inductor must be calculated to maintain the current ( #8710; IL) of 20%to 30%of the maximum output current (typical values) of the ripple. The inductance can use the following relationship calculation value:

Among them, the FSW is the switch frequency, VIN is the input voltage, and VOUT is the output voltage. Figure 9 shows the relationship between the ripple current of different values u200bu200band the output voltage, vin u003d 5V, VIN u003d 12V. Increasing the inductance value can reduce the current ripple, but at the same time, increase the response time of the frequency frequency to dynamic load changes. The response time is the time required to change the current from the initial value to the final value. Until the charging time of the sensor is not over, the output current is provided by the output capacitor. The minimum response time can minimize the required output capacitance. If the compensation network design is good, during the load change, the device can set the duty cycle ratio and the stable state value (0%or 80%). In this case, the time required to change the current is determined by the time required by the sensor.

Output capacitor

The output capacitor is the basic component of the output ripple voltage and the rapid transient response of the power supply. They depend on the requirements of the output voltage ripple and any output voltage deviation during the load period. Under the steady condition, the output voltage ripple is E.The capacitance value of SR and output capacitors is as follows:

In the type #8710; IL is an inductor current ripple. In particular, the expression of the definition #8710; Vout_c considers the charging and discharge of the output capacitor as an inductive current ripple. During the load change, the output capacitor provides current providing current or absorbing current stored in the inductor until the converter reacts. In fact, even if the controller immediately recognizes the load transient and sets the duty cycle to 80%or 0%current slope is limited by electrical value. The output voltage also declines depends on the effective charging/discharge of ESR and capacitors, as shown below:

20 A Demonstration Board

L6728 Demonstration board implemented on the four -layer PCB The antihypertensive DC/DC converter shows the operation of the device in the general application. The input voltage can be from 5V to 12V bus, and the output voltage is fixed at 1.25V. Applications can output currents up to 30A. The switch frequency is 300kHz.

Circuit board description

Power input

This is the input voltage of power conversion. The high -voltage side drainage pipe is connected to this. The voltage range is 1.5 V to 12 V's bus. If the voltage is between 4.5 V and 12 V, it can also supply the device (via VCC pin) in this case. In this case, there must be R16 (0 ) resistors.

Output (VOT)

The output voltage is fixed at 1.25 volts, but it can be changed by replacing the resistor R8 (the underlying resistance) and R13 (feedback partition resistance). R18 allows adjustment of OCP thresholdEssence

Signal input (VCC)

Use the input voltage Vin to power the controller. This input does not require a power supply. However, the controller can supply power input (4.5-12 V) and in this case through VCC and power level, and in this case, R16 (0 ) resistors must not be welded.

Test point

Provide multiple test points to facilitate the use of devices in all important signal feature descriptions:

--Comp: Output of Error Player

123] –FB: The inverter input of the error release

–PGOOD: The signal of the normal function (high activity)

--vgdhs: the self -lifting diode anode

- phase position : Phase node

– Lgate: The low -voltage side door of the device

– Hgate:

Demonstration Board 5 A

L6728 Demonstration Board achieved the antihypertensive DC/DC converter on the two layers of PCB displaying the device in the universal small current application Operation. The input voltage range from 5 V to the 12 V bus, and the output voltage is fixed at 1.25 V application to provide an output current of more than 5A. The switch frequency is 300 kg.

Circuit board description

Power input

This is the input voltage of power conversion. The high -voltage side drainage pipe is connected to this. If the voltage agency is between 4.5 V and 12 V, it can also supply power (via VCC pin) in this case. In this case, there must be R16 (0 ) resistors.

Output (VOT)

The output voltage is fixed at 1.25 volts, but it can be changed by replacing the resistor R8 (the underlying resistance) and R13 (feedback partition resistance). R18 allows adjustment of the OCP threshold.

Signal input (VCC)

Use the input voltage Vin to power the controller. This input does not require a power supply. However, the controller can supply power input (4.5-12 V) and in this case through VCC and power level, and in this case, R16 (0 ) resistors must not be welded.

Test point

Provide multiple test points to facilitate use in all important signal feature descriptions

Device:

--Comp: error amplifier: error amplifier Output

–FB: The inverter input of the error release

–pgood: NormalSignal (high activity)

--vgdhs: self -lifting diode anode

- phase: phase node

– Lgate: The low -pressure side door sales of the device

--Hgate: The high side gate of the device.enter.The voltage range is 1.5 V to 12 V's bus.