Power Golden Oxygen Crystal

MOST needs two N -channel power MOSFET LTC3830 circuit. These should be considered by the main considerations and resistance. In high -efficiency design, thermal consumption is usually secondary factor. The required MOSFET threshold shall be driven according to the available power supply voltage and/or the complexity of the door to drive the charge pump scheme. In the 3.3V input design, the auxiliary 12V power supply can be used for PVCC1 and PVCC2, the standard MOSFET, and the RDS (ON) 5V or 6V is specified on the VGS, which is good. According to the different MOSFETs used, the current extracted from the power supply is also different from the LTC3830 working frequency of less than 50mA. With 5V or lower VIN voltage and generating PVCC1 and PVCC2, there is no enough gate -drive voltage enhancement standard power MOSFET. In this case, the RDS (on) of effective MOSFET may be quite high, which improves the loss and efficiency of the field effect transistor. For 5V or lower voltage, it is recommended to choose the level FET voltage system. The logical grade FET can be fully enhanced with a double/three -fold charge pump and will be the highest efficiency. After selecting the MOSFET threshold voltage, select the input voltage, output voltage, allowing power consumption and maximum output current. In a typical LTC3830 circuit, in continuous mode, the average inductor current is equal to the output load current. The current is split power consumption through the Q1 or Q2 according to the duty cycle ratio:

PMAX should mainly calculate the efficiency or allow the heat dissipation according to the requirements. Typical climax 5V input and 3.3V 10A efficiency circuit design output may allow no more efficiency to lose the load of each MOSFET. Suppose the efficiency is about 90%at the current level, which gives the PMAX value:

Please note that the RDS (on) required in the second quarter is about this value. Two times in this example. This application may specify a single 0.03 the device is used for Q2, and two or more devices are connected in parallel. It is also important to note that the RDS (ON) value indicates that the MOSFET is large, and the power difference is only 1.1W or less each device; the large To-220 package and the heat sink may not necessarily be needed in high-efficiency applications. Silkone SI4410DY or international rectifier IRF7413 (both SO8) or SiliconixSud50n03-10 (to-252) or semiconductor MTD20N03HDL (DPAK) is a small surface installed under 5V of VGS. The RDS (ON) value is lower than 0.03 The device works well in the LTC3830 circuit. The higher PMAX value is calculated in RDS (on). MOSFET usually reduces cost and circuit efficiency and increases MOSFET heat sink requirements. Table 1 listsVarious power MOSFETs are applied in LTC3830.

Sensor selection

The inductor is usually the largest component design and must be carefully selected in the LTC3830. Select the value and type of sensor based on the output conversion requirements. The maximum increase rate of this sensor current is used by the inductance value, the input and output voltage difference, and the maximum occupation ratio of the LTC3830. In the typical 5V input, 3.3V output application, the maximum rise time is:

Note: For test conditions and details Manufacturer's data table.

, LO is an inductive value and the unit is μH. Under the appropriate frequency compensation, the combined output capacitor value of the inductors determines the transient recovery time. Generally speaking, a smaller inductor improves the cloidal value of the heap core at the cost of ripples and inductors. The time in the application of 2 μH inductor is 0.81A/μs, leading to a response 5A load current jump. During these 6.2μs period, the difference between the electrical sensor current and the output consists of an output capacitor. This operation caused a temporary voltage of the output end. To minimize this effect, the inductor value should usually be input to the circuit in the range of most 5V input LTC3830 in the range of 1 μH to 5 μH. In order to optimize performance, different combination input and output voltage and expected load may require different inductors values. Once the required value is known, the type of inductor iron core can be selected according to the peak current and efficiency. The peak current in the inductor is equal to the maximum output load current plus half of the ripple current of the inductance peak. The ripple current consists of electrical sensor value, input and output voltage, and working frequency. The ripple current is about equal to:

The peak inductor current at the load of 10A: 10A+(2.8A/2) 11.4A

Circuit current current Generally at 10%and 40%of the output current. The sensor must be able to withstand the copper resistance in the peak current winding in the case of unsaturated conditions to minimize the resistance of the resistance power. Please note that the current in the circuit induction that does not use a current limit may exceed this maximum value under short circuit or failure; the inductor should adjust the size accordingly to bear the additional current. Ultimate options of inductors with gradient saturation characteristics are usually the best choice.

Input and output capacitors

The typical LTC3830 design pairs of input and output capacitors. Under normal circumstances, stable load running, similar to the LTC3830 antihypertensive converter from the switching frequency of the input power supply. The peak current value is equal to the output load current plus 1/2 peak ripple current. Most current provides capacitors from input bypass. The input -end -generated square -rooted current current capacitor is heated, causing the capacitor premature damage to the extreme situation. The maximum balance of the root current occurs at the 50%pulse width adjustment ratio, so that the amount of the current square current current is equal to IOUT/2. Low EThe SR input capacitor must use the ripple current rated value to ensure reliable operation. Please note that the ripple current rated value of the capacitor manufacturer is usually based on the lifespan of the rated temperature of 2000 hours (3 months). Entering further reduction is recommended to be a capacitor line current exceeding the manufacturer's specifications to extend its service life circuit. The lower working temperature affects the maximum capacitor life.

Under steady -state conditions, the ripple current of the output capacitor of the BUCK converter ratio an input capacitor. The peak current is equal to the electrochemical ripple current, which usually accounts for 10%to 40%of the total load. The capacitor does not occupy power consumption, but on ESR. During the transient state of the output load, the output capacitor must provide all the additional load current LTC3830 required to adjust the sensor current to the new value. The ESR in the output capacitor causes the step voltage in the output to multiply the ESR value by load current. With 0.05 ESR output 5A load -order jump capacitors cause 250 millivol to output voltage offset; this is 7.6%of the output voltage of 3.3V power! Because the output capacitor ESR and the output load transient response, select the output capacitor of ESR instead of the capacitor value. The appropriate ESR of the capacitor usually has a large capacitor value. This is required to control the steady -state output ripple. The electrolytic capacitor for the rated switching power supply has a specified ripple current rated value and the power supply of ESR CAN is effective in the LTC3830 application. OS-Cons Sanyo and other manufacturers produce an excellent electrolytic container performance, with high performance/size ratio of electrolytic capacitors. The surface installation application can use electrolytic or dry 钽 capacitors.浪 The capacitors must be tested and specified for switching power. As we all know, the low -cost ordinary alloy has a very short switching power supply application after explosive death. Other capacitors include Sanyo POSCAP and MV-WX series.

The ability to reduce ESR and increase ripple current is parallel to several capacitors. A typical LTC3830 application may appear 5A input ripple current. Sanyo OS-CON capacitor, part number 10SA220M (220 μF/10V), has 2.3A allowed ripple current 85 ° C; three in the input end parallel (to inherit the input ripple current) to meet the above requirements. Similarly, Sanyo POSCAP 4TPB470M (470 μF/4V) capacitor maximum rated ESR is 0.04 three parallel and lower net output capacitors ESR is 0.013 .

Feedback loop compensation

LTC3830 voltage feedback loop is compensation pins, error placing output nodes of large device. The feedback loop usually uses RC to compensate+C networks from COMP to GND, as shown in Figure 10A. The stability of the ring circuit is affected by the electrical sensitivity value of the output capacitor, the output capacitor ESR, the error placing the large -guided and error amplifier compensation network. Inductor and output electricityThe container creates the bipolar with the following frequencies:

ESR frequency of the output capacitor and output capacitor is zero:

The compensation network of the error placement of the discharge must be provided at the 0db intersection. The frequency of the entire loop transmission function of the entire loop of the phase of the phase is sufficient. The zero and pole points of this compensation network are:

Figure 10B shows the BODE diagram function of the entire transmission.

When the low ESR output capacitor (Sanyo OS-Con) is used, the frequency of the zero point of ESR can be high enough. It provides a small phase improvement at the cross frequency of the ring. Therefore, phase margin becomes equal, and the load transient state is not optimized. To solve this problem, a small electric container can connect the top of the resistor division network and VFB pin to create a zero -polar point compensation in the ring. The zero position is before the pole position, so the phase of the phase can increase the cross frequency of the phase of the loop. The position of the pole and zero point is

Address:

fzc2 1/[2π (R2) (C2) (C2)] and fpc2 1/[2π (R1 | R2) (C2)]]]]] Among the R1 | | R2 is the parallel combination resistance and R2 of R1. Choose C2, so that the zero point is more frequent compared with the FCO, and the high point position makes the closed loop stabilize sufficient phase margin. Figure 10C shows the use of the BODE Figure LTC3830 resistor to compensate the network around the pressure of the LTC3830 resistor. Note: Only when R1 u0026#9251; u0026 GT; u0026 GT; u0026#9251; R2, that is, under the high output voltage, only the extremely zero is fully separated.

Although the mathematical method can be used for frequency compensation, the input and/or output filter, the unknown capacitor ESR, and the change of the total working point with the change of the input voltage and the load current method. This can be the final point and zero point through the load and the use of the RC network box, or to find the actual circuit pole and zero point by using the network analyzer.

Table 2 shows that the recommended compensation part is worth 4SP820M low ESR output capacitors based on 5V to 3.3V applications based on Sanyo OS-Con.

表2。5V至3.3V的推荐补偿网络使用多个820μF Sanyo OS-CON的应用程序4SP820M输出电容器

[ 123]

Table 3 shows that the recommended compensation part is based on the value of 5V to 3.3V applications of 470 μF Sanyo.

Table 3.5V to 3.3V Recommended compensation network uses multiple 470 μF Sanyo POSCAP applications 4TPB470M output capacitors

]

Table 4 shows the recommended compensation part based on the value of 5V to 3.3V applications of 1500 μF Sanyo.

Table 4.5V to 3.3V Recommended compensation network uses multiple 1500 μF Sanya MV-WX parallel parallel output capacitors

Layout Note

When arranging the printing circuit board, use the following inspection form to ensure the normal operation of the LTC3830. In the layout, there are also diagrams in the layout. Figure 11. The thick line shows the high current path. Note that at a current level of 10A or above, the current density of the PC board itself is a serious problem. Traces of high current should be as wide as possible. For example, the minimum tracking width of PCB made with 2OZ copper is 0.15 "