General description

LM2612 antihypertensive DC-DC converter is a single lithium ion supply mobile phone for ultra-low voltage circuit. It provides up to 400 mAh (Class B is 300 mAh) and exceeds 2.8V to 5.5V in the input voltage range. The pins programmable output voltage is 1.05V, 1.3V, 1.5V, or 1.8V. It allows adjustment to adjust the MPU voltage option without re -designing or external feedback resistors. The device has three pins to choose from, to maximize mobile phones and battery life similar to portable applications. The low noise PWM mode provides the application of 600kHz fixed frequency to reduce the application of radio frequency interference and data collection. In the PWM mode, the internal simultaneous rectification provides high efficiency (91%typical value. 1.8 volts). Synchronous input allows the synchronous switching frequency to avoid noise with the system frequency from 500kHz to 1MHz. Low -current stagnation back PFM mode reduces the static current by 150 μA (typical value) during the system standby. Shut off the device and reduce the battery consumption to 0.1 μA (typical value). The additional functions include soft startup and current overload protection. LM2612 provides 10 -needle micro -patch packaging. This packaging uses a national wafer -level chip -level micro -patch technology and provides as small as possible. There are only three small outer planes, electrical sensors, and two ceramic capacitors.

Main specifications

Working through a single lithium -ion battery (2.8V to 5.5V)

pins programmable output voltage (1.05V, 1.3V, 1.5V, 1.8 1.8 Volume)

400 mAh maximum load capacity (B -class is 300 mAh)

± 2%PWM mode DC output voltage accuracy

2mv typical PWM mode output voltage lines Wave

150 μA typical PFM mode static current

0.1 μA typical shutdown mode current

The internal rectification of N internal rectification of the high PWM mode

efficiency (2.8vin, 1.8VOUT 91%) N 600kHz PWM mode switch frequency is used for the PWM mode frequency synchronous N synchronous input from 500kHz to 1MHz

feature

Ultra micro 10 -pin micro -micro -patch pack

Only three tiny surface stickers are required for external components

Use small ceramic capacitors.

Internal soft start

current overload protection

No external compensation

Mobile phone

Handheld radio

Battery power supply equipment

Absolutely maximum rated value (Note 1)

PVIN, VDD, to SGND 0.2V to+6V

pGND to SGND 0.2V to++++++++++++++++++++++++++++++++++geward 0.2V

EN, synchronous/mode, vid0, vid1 to SGND 0.2V to+6V

FB, SW (GND 0.2V) to (VDD+0.2V )

Storage temperature range 45 ; C to+150 ; C

Diversion temperature (welding, 10 seconds) 260 ; C

] Jianwen (Note 2) 25 ; C to 125 ; C

The smallest ESD rated value

Human model, C u003d 100pf, R u003d 1.5 thousand Euros ± 2.5 kV

Thermal resistance (θja)

LM2612ABP and LM2612BBP (Note 3) 170 ; C/W

Electricity

Standard The font specifications are suitable for TA u003d TJ u003d 25 ; Unless there are other regulations, pvin u003d vdd u003d EN u003d Sync u003d 3.6V, vid0 u003d vid1 u003d 0 volts.

Electrical characteristics (continued)

Standard font specifications are suitable for TA u003d TJ u003d 25 ; C.

Note 1: Absolute maximum rated value indicates the limit value that may be damaged by the device. The operating rated value is normal for the working conditions of the device, but the parameter specifications may not be guaranteed. For guarantee specifications and related test conditions, please refer to the conditions in the minimum and maximum limit and electrical characteristics table. Electrical characteristics table limits are guaranteed by the correlation of production testing, design or use standards to ensure statistical quality control methods. Typical (typical) specification refers to the average or average value at 25 ° C, which is not guaranteed.

Note 2: In the PWM mode, if the knot temperature exceeds the maximum knot temperature of the device 150 ; C, the heat shutdown will occur.

Note the heat resistance specified by PCB (0.5/0.5 oz.cu) at 3: 2 layer.

Note 4: 3 layers of PCB (2/1/1 oz.cu) and 12 thermal resistance specified in the pores with a diameter of 0.33mm (see application annotation An-1187).

Note 5: LM2612 is designed for mobile phone applications. After power -on, it is unnecessary by the system processor and internal UVLO (owed voltage) control) circuit. The LM2612 does not have a UVLO circuit, and it should be kept shutdown by keeping EN pins until the input voltage exceeds 2.8V. Although the LM2612 shows safe behavior during the pre -production assessment, this cannot be guaranteed.

Note 6: The feedback voltage is adjusted at the 1.5V output settings. Other output voltage from the internal DAC frequency pin ratio choice. The accuracy of this feedback voltage is ± 2%, but 1.05V is set to 5%. Contact the National Semiconductor Corporation's portable power application group to fine -tune other voltage.

Note 7: The stagnation voltage is the minimum voltage switch on the FB. It causes internal feedback and control circuit to turn on the internal PFET switch, and then close it in PFM mode.

Note 8: The current limitation is built -in, fixed, non -adjustable. If the output voltage reaches the current limit when the output voltage is lower than about 0.7V, the internal PFET switch is turned off 2.5 μs to reduce the current to the allowable electrical sensor.

Note 9: EN is a CMOS Schmidt trigger digital input. The logical threshold changes with the power supply voltage of the VDD pin. The nominal logic threshold is about 0.71VDD and 0.55VDD, respectively.

Note 10: Synchronous driver, the external clock is switched between VIN and GND. When the external clock is in a synchronization state, the IC will be frequently in the outer clock. LM2612 is synchronized with the rising along the external clock.

Typical operating characteristics

LM2612ABP, Figure 1 circuit, VIN u003d 3.6V, TA u003d 25 ; C, L1 u003d 10 μH, unless otherwise explained.

Typical working characteristics LM2612ABP, Figure 1 circuit, vin u003d 3.6V, TA u003d 25 ; Unless otherwise indicated. (Continuous)

Equipment information

LM2612 is a simple antihypertensive DC-DC converter for low-voltage CPUs or in the unit. DSP power supply phone and other small battery power supply equipment. It provides 1.05V, 1.3V, 1.5V, or a single 2.8V to a 1.8V voltage of a single 2.8V to 5.5V lithium -ion battery. It is the maximum load capacity of 400 mAh (300 mAh level). The device has three pins to choose the mode device required for mobile phones and other complex portable devices. Such applications usually only spend their time running at full speed. During the full power operation,The PWM mode of synchronous or fixed frequency provides a complete output current capacity, while minimizing the interference of sensitive mid -frequency and data collection circuits. PWM mode uses synchronization rectification to improve efficiency: usually 91%for 100mA load, 1.8V output, 2.8V input. The remaining time of these applications is used in low -current standby state running or shutdown to save battery power. During the period of standby operation, the lagging PFM mode reduced the static current to 150 μA (typical value), and the maximum extension of the battery life. Close the mode to close the device and reduce the battery consumption to 0.1 μA (typical value). LM2612 has good performance and a full set of characteristics. It is based on a current mode switch buck circulation flow limit structure. For most output voltage, the output voltage accuracy of the mode is ± 2%. For 1.05V, the accuracy is ± 3%. Synchronous/mode input accepts the external clock between 500kHz and 1MHz. Output voltage selection pin eliminates external feedback resistors. The additional functions include soft startup, current overload protection, overvoltage protection and heat overload protection. The LM2612 uses a chip size 10 -pin micro -chip to form SMD packaging. Micro SMD packaging provides the minimum spatial key type application, such as unit calls. There are only a small part of the required external component 10UH induction, 10UF and 22UF ceramic capacitors to reduce the circuit board area.

Circuit Operation

Reference Figure 1, Figure 2, and 3 LM2612 Operation as follows: In the first part of each switch, the control block in LM2612 Open the internal PFET switch. This allows the current to output the filter capacitance and load through the inductive output of the induction. The inductor limits the current to the slope -Vout/L on the slope (VIN), and stores the energy in the magnetic field. In the second part of each cycle, the controller rotates the PFET to cut off the power, blocks the input current, and then opens the NFET synchronization rectifier. In response to the magnetic field crash of the inductor, a voltage forced current outputs the filter capacitance and load from the ground through the synchronous rectifier. Because the storage energy is returned to the circuit and the current is exhausted, the current is decreased at the slope of VOUT/L. If the electric sensor current reaches zero before the next cycle, the rectifier is turned off synchronously to prevent the current from turning on the current. The output is released when the inductance current is high, and the voltage load is smooth when low. The output voltage is adjusted by adjusting the PFET to control the connection time to control the loading. The effect of the duty -ratio of the switch and synchronization rectifier is sent to the inductance and output filter capacitor. The output voltage is equal to the average voltage at the SW pin.

PWM operation

LM2612 can be set to the current mode PWM operation to connect the synchronization/mode pins to the VDD. When PWM (pulse width modulation) mode, the output voltage is used to adjust the output voltage by the constant frequency,Then adjust the energy of each cycle to control the power of the load. Set the energy -to -width of each cycle to control the peak of the inductance current by adjusting the PFET switch. This is used to compare the slope from the current detection amplifier by using the PFET switch driven by a trigger to compare the slope from the current detection amplifier. The error signal comes from the voltage feedback error amplifier. At the beginning cycle, the oscillator sets the trigger and turns on the PFET switch, causing the electric sensor current to rise. When the current influenza signal is placed by an error, the PWM comparator resets the trigger and turns off the PFET switch to end the first part of the cycle. NFET synchronizes the rectifier to open until the next clock pulse or current rises to zero. If the output voltage is pulled, the output of the error amplifier increases, so that the sensor current is rising before the comparator is turned off. This will increase the average current sent to the output end and adjust the increase in load. Before entering the PWM comparator, the current influenza signal is used to compensate the slope and the current feedback to the stable oscillator. In the second part of the cycle, the zero -zero detector shuts down the NFET synchronization rectifier if the inductive current slope returns to zero.

A: Electrochemical current, 500mA/DIV

b: switch pins, 2V/DIV

c: vout, 10mv, 10mv /div, AC coupling

A: Electrochemical current, 500mA/DIV

b: switch pins, 2V/DIV

c: vout, 50mv/div, communication Coupling

PFM operation

Connect the synchronous/mode pins to the SGND setting of the lagging PFM operation of LM2612. In PFM (pulse frequency modulation) mode, the output voltage is adjusted through the switch, the discrete energy of each cycle, and then adjust the loop or frequency of the control load power. This is to detect the output voltage and control the PFET switch by using an error comparator. The device will be used as a load discharge output filter capacitor until the output voltage drops below the lower limit of the PFM error comparator. Then open the PFET switch through a cycle. This makes the current from the input terminal, through the induction to the output terminal, the charging output filter capacitor. When the output voltage is higher than the PFM error comparator. After the PFET switch is turned off, the output voltage increases with the transfers of the inductor. Therefore, the PFM output voltage ripple mode is proportional to the lag of the error comparison of the error comparison and the sensor current. In the PFM mode, the device can only switch load as needed. This consumes the transitional loss in the internal MOSFET during the switching action of the current consumption in the switching action of the current in the circuit, and also proves that the light load voltage adjustment also proves. In the second part in the cycle, NFET synchronizes the rectifierThe diodes of this signs are turned on until the inductance current rises to zero. LM2612 does not turn on the synchronous rectifier in PFM mode.

Work mode Selection

(Synchronous/Mode pin) synchronous/mode digital input pin is used to select PWM or PFM working mode. Set the synchronization/mode high (higher than 1.3V) for 600kHz PWM operations. When the system is contributed, the load is greater than 50mA. Set the synchronization/mode low (below 0.4V) when the load is less than 50mA, which is used to accurately regulate and reduce the current current consumption of the system running. 50mA), if the device is maintained in the PWM mode, the function may be activated to prevent excessive output voltage. For more information, see voltage protection. Use synchronous/mode pins to select mode conversion rate greater than 5V/100 μs. Use a trigger or logical door of the comparator Schmitt to drive synchronous/mode pins. Do not keep the pin floating and allow it to linger between logical levels. These measures will prevent the output voltage error, otherwise, response to the uncertain logical state. When frequent switching mode, make sure the minimum load is maintained to keep the output voltage adjustment. The minimum load requires changes according to the frequency of the mode changes. When the mode is replaced every 100 milliseconds, 85 Weian 10 milliseconds, 800 Weian 1 milliseconds.

Frequency synchronization

(synchronization/mode pin) synchronization/mode input can also be used for frequency synchronization. When the LM2612 and the external clock are raised to 12.2V, the starting voltage exceeds 1V clock. When synchronization with the external clock, it is in the PWM mode. The device can synchronize to the 50%frequency from 500kHz to 1MHz. When applying the external clock to the synchronous/pattern pin. The height of each clock cycle should be between 1.3 μs and 200ns, and the duty cycle is between 30%and 70%. This total clock cycle should be less than equal to 2 μs. Pickup/overcutting should be less than 100 millivolttilow below the ground or above the seller to investigate. When a noisy clock signal is applied, especially during the sharp assessment period, the edge signal issued by the long cable terminated the cable under its characteristic impedance; in synchronous pins, if necessary, softening the conversion rate and overwhelming/owed. Note that the sharp signal or function generator from the pulse can generate high owl/overwhelming cable at the end of the cable is 10V. Use a signal driver with a conversion rate to drive synchronization/mode pin speed of more than 5V/100 μs. Use the logical door of the comparator Schmidt trigger or drive synchronization/mode pins. Do not move the needle floating allows it to linger between logical levels. These measures will prevent the output voltage error, which may occur in an uncertain logical state.

Overvoltage protection

LM2612 has an overvoltage comparator to prevent it from being a deviceWhen leaving, the output voltage is too high and low in PWM mode. Otherwise, the output voltage may increase from the minimum value to exceeding the regulatory range. Because the minimum 200ns, the energy of each cycle is transferred to the connection time of the PFET switch in the PFET switch in the PWM mode. When the output voltage exceeds its adjustment threshold 30 millivolt, OVP comparator inhibits PWM operations to skip the pulse under the output voltage back to the adjustment threshold. In the overvoltage protection, the output voltage and ripples increased slightly.

Shipping mode

Set the EN digital input pin to as low as SGND to the LM2612 at 0.1UA (typical) stop mode. During the shutdown, the PFET switch, NFET synchronization rectifier, benchmark, and turn off the control and bias of LM2612. Set up EN to VDD to allow normal operations. When opening, the soft start is activated. EN is a CMOS Schmidt trigger digital input threshold changes with the VDD input voltage. This nominal logic threshold is about 71D high and low thresholds, respectively 0.55VDD, respectively. Drive EN uses CMOS logic reference to the VDD pin of LM2612. EN must be set to low to turn off the LM2612 during the power -power period as the minimum working voltage of the power supply less than 2.8V. The LM2612 is designed for mobile phones and similar applications. The system controller is determined by the system controller. It does not require the internal UVLO (under pressure lock) circuit. LM2612 has no UVLO circuit. Although the LM2612 shows a safety behavior assessment before production, it is enabled under low input voltage.

Internal simultaneous rectification

In the PWM mode, LM2612 uses internal NFET as a synchronous rectifier to reduce the positive voltage drop and correlation loss by reducing the front flower. Generally speaking, when the output voltage is relatively low, synchronous rectification can significantly improve the efficiency rectifier diode. Under the middle and heavy loads, the internal NFET synchronization rectifier is turned on the second part of each cycle during the inductance current. Synchronous rectifiers are closed before the next cycle, or the electrical sensor current is close to zero when light loading. NFET is designed to be used for a short interval before opening without an external diode. Synchronous rectification is disabled, and in the second part of each rectifier, the NFET CON is circulated in PFM mode through its body diode to reduce static current related to the synchronous rectifier control circuit. This synchronous rectifier can also be kept off in PWM mode. When the high input output voltage causes a short time, there is no enough time to synchronize the rectifier to start. The main diode NFET can also be used under these conditions. In order to improve the efficiency of PFM or short occupation ratio PWM conditions, please please from PGND to SW outer Schutki diode. Contact the National Semiconductor Corporation's portable power application group, if you are interested in the PFM mode for synchronous rectifier devices.

Flowing

The current limit function allows LM2612 to protect yourself and overload conditionsExternal components. Currently using an independent internal communication device to implement restrictions, the maximum headbroken current is 850mA (B -level equipment is 980mA). In the PWM mode, the circular current limit is not commonly used. If the excessive load is increased, the output voltage is reduced to about 0.7V, and the device switch to the time limit mode. After the current comparison of the current in the timing limit mode, the internal P-FET switch is turned off. The next cycle is prohibited from 2.5 μs to force the instantaneous inductors current to reduce the slope to the safe value. PFM mode also uses regular current limitation operations. Synchronous rectifier is closed under the timing current limit mode. Timing current limits to prevent severe overload, when the output voltage is pulled down, the current control can be seen in some products.

Flow limit and PWM mode

Inspector response

Considering matters

LM2612 is a loading step designed for moderate rapid response. The harsh transient conditions during the above load 300mA will cause the electrical sensor current to rise to the 850mA current limit, resulting in unstable when the PWM mode jitter or the current limit comparator activation. Avoid such jittering or instability, please do not call or start the LM2612 full load (the load is close or higher than 400 mAh). Do not change the working mode or output voltage of the full load. Avoid loading steps with extremely sharp and wide range, such as from u0026 lt; 30ma to u0026 gt; 350ma.

The selected output voltage can be selected

LM2612 has a selected output voltage that can be selected to eliminate the need for external feedback resistors. The output can be set to 1.05V, 1.3V, 1.5V, or 1.8VVID0 and VID1 pins through configuration. See the setting voltage application information part of the setting output voltage, and learn more details.

Soft start

LM2612 has a soft startup function, which can be powered on and started. This reduces the pressure of LM2612 and external components. It can also reduce the startup transient on the power supply.

Soft start (continued)

Soft start is realized by increasing the internal reference of LM2612 to gradually increase the output voltage. When power is powered, the reference value rises within about 400 μs in the PWM mode. Soft starting may require additional 200US to compensate the network for the error amplifier to keep the time charging.

Heat overload protection

LM2612 has the effects of heat -loading protection function to be exempted from short -term misuse and overload. When the knot temperature exceeds about 155 ° C, the device starts soft startup cycle, that is, it is completed after the temperature drops below 130 ° C. It is considered a bad approach if it can be damaged for a long time under the heat overload conditions.

Application information

Set output voltage

LM2612 has an output voltage that can be selected by pins to eliminate the needs of external feedback resistors. Select the configuration, the output voltage is 1.05V, 1.3V, 1.5V, or 1.8VVID0 and VID1 pins, as shown in Table 1.

VID0 and VID1 are digital input. They may be connected to VDD or LOW because they are connected to SGND. It is optional that VID0 and VID1 can provide more than 1.2V voltage by digital door -driven high voltage state, lower than 0.4V voltage to ensure effective logic levels. Each input of VID0 and VID1 has an internal 1.8μA drop -down menu to pull them off when they are disconnected, and the default 1.5V output is low. Opening these sales is acceptable, but the sales are set to high or the recommendation is low.

The sensor selects

The saturated current rated value of 10 μH (B -level 980mA) is recommended for most applications. The resistance of the inductor should always be less than 0.3 u0026#8486; efficiency. Table 2 lists recommended inductors and suppliers.

Suggestion. For noise critical application, the ring or shielding line axis sensor should be used. A good approach is to use two types of overlapping footprints to arrange the flexibility of the circuit board design. This can replace the low -noise circular sensor, in case the noise comes from the low -cost line shaft model is unacceptable. The saturated current rated value is that the current level exceeds the induction of the induction. More than this level, the inductor lost the restricted current to switch to the slope by PFET and allow the switching current to increase rapidly. This can lead to low efficiency, incorrect supervision or stress to DC-DC converter, such as LM2612. When the magnetic flux density generated by the current is exceeded by the electrical sensor, surpassing the corresponding magnetic field.

Capacitor selection

Use 10 μF, 6.3V, X7R or X5R ceramic input filter capacitors and 22UF, X7R Or X5R ceramic output filter capacitor. In small size, cost, and reliability and performance. Do not use Y5V ceramic capacitors. Table 3 Recommended capacitors and suppliers. The output filter can use 10 μF ceramic capacitors capacitors to be suitable for the worst case of the transient load level less than 200mA. Use 10 μF output capacitors to increase the output voltage ripple with smaller size, and the lower line and load transient response. The input filter capacitor provides a voltage ripple applied to the PFET switch in the first part of each cycle. The output filter capacitor smooths the current of the load from the power, which helps maintain a stable output voltage transient load change and reduce the output voltage ripple. These capacitors must have enoughThese functions are executed with capacity and low ESR. ESR or equivalent series resistance of the filter capacitor is the main factor of voltage ripples. From most electrolytes, ESR's impact on voltage ripples is about 75-95%of capacitors, and ceramic capacitors are less. The remaining part of this ripple comes from charge storage, which is due to capacitors.

Selection of diode

The optional Shantky diode (D1 in Figure 1) can be added to the efficiency of improving the PFM mode and light load PWM mode. Increasing the efficiency ratio of battery life increases with Schartki diode. Generally, the efficiency of the PFM mode is increased from 72.7%to 85.0%(20 mAh load, VOUT u003d 1.8V, VIN u003d 3.6V) from 72.7%to 85.0%. See the efficiency curve in typical operating characteristics. The rated current is higher than 850mA, such as MBRM140T3. Using the rated value of 30V or higher voltage can reduce the reverse leakage of diode in high temperature applications.

Hot Design

LM2612 has a thermal overload protection function. The knot temperature exceeds about 155 ° C until the device cools to 130 ° C. However, continuously running the device may damage its bad exercises. A sufficient heat design should keep the equipment below the prescribed 125 ° C working temperature. Micro-sticker packaging assembly and use of micro-pad packaging requires dedicated board layout, precise installation and careful return welding technology. For details, see the ""National Semiconductor Application Description"" An-1112. See ""Surface Installation Technology"" section (SMT) assembly precautions. In order to obtain the best assembly effect, the alignment serial number on the PC board should be used to easily place the device. Because micro -stickers are a new technology, all layouts and assembly methods must be thoroughly tested before production. In particular, the weld return and heat resistance must be verified. The 10 convex packaged for LM2612 has 170 microns for 6.7mil (6.7/1000 in.) Pack is installed on the circuit board. The traces of each cushion should enter the cushion from an entry angle of 90 to prevent debris from falling into the abyss. Initially, the width of each pad should be 6 mIL. For a length of 6 mil or longer, such as heat release pressure. Then each trajectory should reach the optimal state width of more than 11 dense ears or larger, so that the conicalness exceeds the edge of the bag. The important standard is symmetry. This can ensure that the LM2612 returns evenly, and the equipment weld level should be particularly paid special attention to the buffer pad 6-9. Because PVIN and PGND are usually connected to large copper plates, insufficient heat dissipation may cause these convex points to delay or deficiency. The pads used to encapsulate with Micro SMD must be NSMD (non -welded mask definition) type. This means that the weld cover is greater than the size of the pad or 9.7mils for LM2612. This can prevent the formation of the lips, if the welding mold and the pads overlap. This lips can be accommodatedNaver device breaks away from the surface of the circuit board and interfere with the installation. For details, see application annotations AN-1112. Micro -stickers packaging is optimized for the minimum possible size and is suitable for applications with opaque shells with red or infrared. Due to the plastic packaging characteristics of lack of large devices, it is easy to be illuminated. The back metallic and/or epoxy coating, and the front shadow by the printing circuit board, reduce this sensitivity. However, the packaging is exposed to the edge of the mold. In particular, the micro -patch device to the red -sensitive infrared range on the upper edge of the exposed mold of the package.

Application information (continued)

When using LM2612, do not use or power -on high -strength red or infrared light, otherwise it will cause operations that decrease, unpredictable or unstable operation. The light sources with high red or infrared content include sun and halogen lamps with high red or infrared content. Pack the circuit in an opaque red case or infrared.

Note for the layout of the circuit board

PC plate layout is an important part of the DC-DC converter. The bad circuit board layout will destroy the DC-DC converter and its peripheral circuit EMI, ground bouncing, and resistance voltage loss in the trajectory. These will send an error signal IC to the DC-DC converter, causing poor adjustment or instability. Poor layout can also lead to the problem of reflux welding, resulting in poor welding joints between micro SMD packaging and plate pads. Poor solder joints may cause performance instability or decline in performance. The good layout of LM2612 can be implemented by following some simple design rules:

1 Put LM2612 on a micro -patch pack of 6.7 ml. As a thermal release, connect to each pad with 6mil to each pad (Micro SMD), 6mILS is long or longer, and then gradually adds each trace line to its best width to extend the taper to the package. The important criterion is to ensure that the symmetrical return occurs evenly (see micro SMD packaging assembly and use).

2. Put LM2612, electrical sensors and filter capacitors shorten the traces. Traces of traces carry relatively high switching currents as antenna. Following this rule can reduce radiation noise. Put the capacitor and inductors at 0.2 inches (5 mm) of LM2612.

3. Arrange components to curl the switch current ring in the same direction. At each cycle, the current flows out of the input filter capacitor, and the current circulation is formed by the LM2612 and the induction capacitor to the output filter capacitor. In the second part of each cycle, the current is pulled into the