Features

Wide input voltage range: 3.6 V to 30 V; reconciliation (3.3 V, 5 V) output options integrated 1 A power switch; use small surface paste components to limit flow; peak values; peak values value; peak value Entering voltage (100 ms): 60 V; can be configured to be buck, buck boost, and sepic regulator; provides 8 lead SOIC packaging; ADISIMPOWER supports #8482; design tools.

Application

Industrial power system PC peripheral power system; pre -adjustor of linear regulator; distributed power system automotive system battery charger.

General instructions

ADP3050 is a current mode single -chip antihypertensive (antihypertensive) pulse width adjustment switch staber, which contains a large current 1A power switch and all all Control, logic and protection functions. It uses a unique compensation scheme to allow any types of output capacitors (钽, ceramics, electrolytic, OS-Con). Unlike some antihypertensive regulators, this design is not limited to using specific types of output capacitors or ESR values.

A special boost driver is used for saturated NPN power switch, which provides higher system efficiency than traditional bipolar buck switches. The internal working current of the device is provided by using the low -voltage adjustment output, which further improves efficiency. High -open frequency allows small external surface installation components. You can use a variety of standard ready -made equipment to provide a lot of design flexibility. A complete regulator design requires only a few external components.

ADP3050 includes a closed input, putting the device in a low power mode, and lowering the total power supply to less than 20 micro -security. The internal protection function includes the weekly limitation of the thermal shutdown circuit and the power switch, providing complete equipment protection under failure conditions.

ADP3050 provides excellent lines and load adjustments. Under all input voltage and output current conditions, the output voltage accuracy is usually kept below ± 3%at temperature.

ADP3050 is specified between the industrial temperature range -40 ° C to+85 ° C. It can be used for thermal reinforcement 8-lead (non-lead) SOIC packaging and standard 8-lead (only lead-free lead (only leading-free leader-free ) SOIC packaging that conforms to ROHS.

Typical performance features

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Operation theory

ADP3050 is a fixed frequency, a current mode antihypertensive regulator. The current mode system provides a good transient response, and it is easier to compensate than the voltage mode system (see Figure 1). At the beginning of each clock cycle, the oscillator sets the lock memory and turn on the electricitySource switch. The signal of the comparator non -vertical input is a copy of the switching current (added to the oscillator slope). When the signal reaches the appropriate level of the output settings of the error amplifier, the comparator reset the locks and turn off the power switch. In this way, the error amplifier sets the correct current check level to keep the output within the adjustment range. If the output of the error amplifier increases, the output current is more; if the output of the error amplifier is reduced, the output current is less.

The current detection amplifier provides a signal that is limited to the comparison switching current and weekly current. If the current limit is exceeded, the locks are reset and the switch is turned off until the next clock cycle starts. The ADP3050 has a folding current limit, which can reduce the switching frequency under the fault conditions to reduce the stress on IC and external components.

Most of the control circuits deviate from 2.5 volts of internal regulators. When the bias pin is kept open, or when the voltage of the pin is less than 2.7 V, all working currents of the ADP3050 are drawn out of the input power supply. When the partial pressure pin is higher than 2.7V, most of the working current comes from the pin (usually connected to the low -voltage output of the regulator), not from the high -voltage input power. This can significantly improve efficiency under light load conditions, especially for systems that are far higher than output voltage than output voltage.

ADP3050 uses a special drive level to allow the power switch to saturate. The external diode and capacitors provide a boost voltage higher than the input power supply voltage to the drive level. The use of this type of saturation driver can significantly improve the overall efficiency.

Pull the SD pin below 0.4V, so that the equipment is in a low -power mode, turn off all internal circuits, and reduce the power current to less than 20μA.

Set output voltage

The output of the adjustable version (ADP3050AR and ADP3050ARZ) can be set to 1.25 V to 1.25 V to the FB pin to 1.25 V. Any voltage between 12 V, as shown in Figure 25.

Application information

Adisimpower Design Tool

ADP3050 supported by the Adisimpower Design Tools. Adisimpower is a set of tools to generate a complete power supply design for specific design target optimization. These tools enable users to generate a complete schematic diagram and material list, and calculate performance in minutes. Adisimpower can optimize the design of cost, area, efficiency and number of parts, and consider the operating conditions and restrictions of all actual external components. For more information about the adisIMPOWER design tool, see/adisimpower. The tool set can be obtained from this website, and users can request unpopular boards through this tool.123]

The following sections provide the complete process of using ADP3050 designing a lower -voltage switch regulator. Each part contains a list of recommended devices. These lists do not include all available equipment or manufacturers. They only include surface installation equipment. If necessary, replace the equivalent pilot device. When selecting components, remember what is most important to design, such as efficiency, cost and size. They eventually determine which components using. It is also important to ensure that the design specifications are clearly defined and reflect the worst situation. The main specifications include minimum and maximum input voltage, output voltage and ripples, minimum and maximum load currents.

Sensor selection

The inductance value determines the working mode of the regulator: continuous mode, continuous flow of inductance current; or non -continuous mode, inductor currents dropped to zero during each switch cycle. Continuous mode is the best choice for many applications. It provides higher output power, low peak currents in switches, inductors and diode, and lower inductive ripple currents, which means lower output ripple voltage. The non -continuous mode allows the use of smaller magnetics, but the cost is: lower load current and higher peak and ripple current. The design of high input voltage or low load current usually works in discontinuous mode to minimize the inductance value and size. The ADP3050 can work normally in both operating modes.

Continuous mode

The inductor current in the continuous mode system is a triangular waveform (equal to the ripple current) centered on DC value (equal to load current). The size of the ripple current is determined by the inductance value, usually between 20%and 40%of the maximum load current. In order to reduce the inductance size, in the continuous mode design of high input voltage or low output current, 40%to 80%of the ripple current is usually used.

The calculation formula of the inductance value is as follows:

Among them, V is the maximum input voltage, V is the regulating output voltage, F is the switch frequency (200 kHz). The initial choice of ripple current seeking is arbitrary, but it can be used as a good starting point for finding standards for the standard for ready -made electrical, such as 10μH, 15 μH, 22 μH, 33 μH, and 47 μH. If you want to use a specific electrical sensing value, you only need to re -arrange equation 2 to find the ripple current. For 800 mAh, 12 volts to 5 volts, and 320 mAh (40%of 800 mA), the ripple current, the inductance is:

47μH inductance It is the closest standard value, and its ripple current is about 310 mAh. The peak switch current is equal to half of the load current plus the ripple current (this is also the peak current of the inductance and capture the diode).

Select a DC (or saturated) rated current 20%larger than ISW (PK) to ensure that the inductor will not run near the edge of the saturation. In this example, 1.20 × 0.95 A 1.14 A, using the DC rated current at least 1.2 A inductor. The maximum switching current is limited to 1.5 A internally. This limit and ripple current determine the maximum load current that the system can provide.

If the load current drops to less than half of the ripple current, the regulator works in a discontinuous mode.

Intermittent mode

For load currents less than 0.5 A, you can use discontinuous mode operations. This allows the use of smaller inductors, but the ripple current is much higher (which means higher output ripple voltage). If a larger output capacitor must be used to reduce the output ripple voltage, the entire system may occupy more board area than when using a larger inductance. The operations and equations of these two modes are completely different, but when the ripple current is twice the load current (Iripple 2 × IOUT), the boundary between the two modes will appear. As a result, Formula 2 is used to find the minimum inductance value required for the system to keep the system (Iriple 2 × IOUT find the inductance value).

Using sensors below this value will cause the system to run in a discontinuous mode.

For 400 mAh, 24 volts to 5 volts:

If the option is too small, the internal current limits each cycle to stick, and The regulator cannot provide the necessary load current.

The iron core type and material of the inductor

There are currently many types of inductors. Many core styles and many core materials often make the selection process more chaotic. Quickly overview the type of inductors can make the selection process easier to understand.

The core geometric shape (wire core) is usually cheaper than the closure core (ring core), which is a good choice for some applications, but you must be careful when used. In the core inductance, the magnetic flux is not completely included inside the core. The radiation magnetic field will generate electromagnetic interference (EMI), and the voltage is usually introduced to the nearby circuit board trajectory. These inductors may not be suitable for systems that contain very high -precision circuits or sensitive magnetism. Some manufacturers have semi -closed and shielded magnetic cores, where the external magnetic shields surround the line axis core. The electromagnetic interference of these devices is smaller than the standard open magnetic core, usually smaller than the closed magnetic core.

The magnetic core materials used on the surface of the surface are mostly iron powder or iron oxygen. For many designs, the choice of materials is arbitrary, but the performance of each material should be recognized. The iron heart loss of the iron oxygen is lower than the iron powder, but the lower the loss, the higher the price. The degree of saturation of powder -shaped iron heart is mild (when the rated current is exceeded, the inductance gradually decreases), and the saturation of iron oxygen iron heart is suddenly (rapid decrease). KOOL mμ It is a kind of iron oxygen, which is specially designed for minimizing magnetic magneticCore loss and fever (especially when the switching frequency is higher than 100 kHz), but the same is more expensive.

The winding DC resistance (DCR) of the inductor cannot be ignored. In the case of low load, high DCR can reduce system efficiency by 2%to 5%. To obtain a lower DCR, it means that the use of a larger inductance, so weigh the size and efficiency. The power loss caused by this resistor is i × DCR. For a system of 800 mA, 5 volts to 3.3 volts, and inductance DCR is 100 mega Euro, winding resistance (0.82) × 0.1Ω 64 MW. This means that the power loss of the system is 64mW/(3.3V × 800mA) 2.4%. The typical DCR value is between 10 MΩ and 200 MΩ. 2

Select the sensor

Consider several factors when selecting an inductor: cost, size, electromagnetic interference, magnetic core and copper loss, and maximum rated current. Use the following steps to select the inductors that are suitable for the system (see the calculation and instructions in the electrical sensor selection part). Please contact the manufacturer to learn about its complete product supply, availability and pricing. Manufacturers provide more value and packaging size to adapt to multiple applications.

1. Select a working mode, and then use the appropriate equation to calculate the electrical value. For the continuous mode system, the ripple current is 40%of the maximum load current is a good starting point. If necessary, you can increase or reduce the inductance value.

2. Calculate the peak switch current (this is the maximum current seen by the sensor). Ensure that the DC (or saturated) current of the inductor is high enough (about 1.2 times the peak switch current). All designs should be an inductor with a DC rated current at least 1A. This provides security and stability for the startup and fault conditions of the inductive current than the normal value. If the rated current of the inductor is exceeded, the magnetic core will be saturated, causing the inductive value to decrease and the temperature of the inductors increases.

3. Estimated the DC winding resistance according to the inductance value. The general rule is that the inductance per μH allows about 5 mΩ per μH.

4. Select the core material and type. First, decide whether to use the design of an open core electromoter. If it is not sure, try several samples (opening, semi -closed core, shielding core and closed core) of each type. Don't encourage the use of open magnetic core inductors because you need to be careful; as long as you know what you use. They are small and cheap, and they have been successfully applied in many different applications.

Output capacitor select

ADP3050 can be used for any type of output capacitors. The balance between price, component size and regulator performance can be evaluated to determine the best choice for each application. The effective series resistance (ESR) of the capacitor has an important impact on loop compensation and system performance. ESR provides 0 in the feedback loop; therefore, must, mustKnow the ESR value so that it can correctly compensate the loop (most manufacturers specify the maximum ESR in their data table). Capacitor ESR also helps output ripple voltage (VRIPPLE ESR × Iriple). It is recommended to use solid or multi -layer ceramic capacitors to provide good performance at a smaller size and reasonable cost. The solid pillar capacitor has a good combination of low ESR and high capacitors, which can be obtained from several different manufacturers. The capacitor value is available from 22μF to more than 500 μF, but the value of 47μF to 220 μF is sufficient for most designs. You can use smaller values, but ESR depends on size, so smaller devices have higher ESR. Ensure that the ripple current of the capacitor rated value is greater than that of the inductance ripple current (the ripple current flows into the output capacitor).

Multi -layer ceramic capacitors can be used to use the minimum application of output voltage ripples. They have very low ESR (22 μF ceramics can have one -fifth of ESR of 22 μF solid), but for the same output capacitance value, more board area may be required. Some manufacturers have recently improved their low-voltage ceramic capacitors and provide a small package with lower ESR (NEC-TOKIN, MUATA, TAIYO-YUDEN, and AVX). Several types of ceramics can be used in parallel to provide extremely low ESR and good capacitance. If the design is sensitive to cost and is not limited by space, multiple aluminum electrolytic capacitors can be used parallel (their size and ESR are larger than ceramic and solid 钽). You can also use OS-CON capacitors, but they are usually larger and more expensive than ceramic or solid electric containers.

Select the output capacitor

Use the following steps to select the appropriate capacitor.

1. Determine the maximum ripple voltage of the design, which determines your maximum ESR (remember VRIPPLE≈ESR × Iripple). The typical output ripple voltage range is between 0.5%and 2%of the output voltage. There are only two options to reduce the output voltage ripple: either increase the inductance value or use the low output capacitance of ESR.

2. Determine which capacitor (钽, ceramic or other). For more values, size and voltage rated values, please contact each manufacturer's complete product list. If a type of capacitor must be used and space permits, multiple devices are used in parallel to reduce the total ESR.

3. Check the voltage rated value and ripple current rated value of the capacitor to ensure that it is suitable for related applications. These rated values will be reduced due to increased temperature, so be sure to view the manufacturer's data table.

4. Make sure the final choice of output capacitors has been optimized in terms of cost, size, availability and performance, but still meets the required capacitors. The recommended capacitance is between 47 μF and 220 μF.

Capture 2Selection of the polar pipe

The recommended capture diode is 1N5818 Schottky or the same type. The fast switching speed of the low -forward voltage drop (450 MV typical AT1 A) and the Schartky rectifier provides the best performance and efficiency. The rated voltage of 1N5818 is 30 V reverse voltage and 1 A average forward current. For lower input voltage, the lower voltage Schartki uses a lower voltage to reduce the forward voltage of the diode and improve the overall system efficiency; for example, the system with 12V to 5V does not require 30V diode. For car applications, 60V Schartky may be required. The average positive current of capturing the diode passes:

For previous continuous mode example (12 V to 5 V AT800 mAh), the average diode current is:

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For the system, 1N5817 is a good choice (the rated voltage is 20V and 1A). Do not use the rated current to capture the diode with less than 1A. Even under normal working conditions, the average current can be less than 1A because the diode current is much higher under the condition. When the regulator is slightly overloaded (sometimes called soft short circuit), the worst failure of the diode. When the ratio of input voltage to the output voltage is greater than 2.5, this is usually just a problem. In this case, the required load current is slightly higher than the current provided by the regulator. The output voltage decreases slightly, and the switch is connected at each cycle until it reaches the internal current limit. In this case, the load current can reach about 1.2 A. For example, when using a system with an input voltage of 24 V and 5 V in the output voltage, if the output voltage is reduced to 4 V, the average diode current is:

] If the system must survive for a long time under such a gradual overload, please make sure that the selected diode can survive under these conditions. If necessary, you can use a larger 2 A or 3 A diode.

Select the capture of the diode

Use the following steps to select the appropriate capture of the diode. Table 5 shows the Schottky rectifier with different reverse voltage and forward current rated value.

The average diode rated current must be sufficient to provide the required load current (see the calculation in the previous section). Even if the average diode current is much lower, the diode with a rated current below 1A should not be used.

The reverse voltage rated value to capture the diode should be at least the maximum input voltage. Generally, a higher rated value (1.2 × maximum input voltage) is used to provide security habits.

Enter the capacitor selection

Enter the bypass electric container plays an important role in the normal operation of the regulator. It can minimize the voltage of the input terminal It provides a short local circuit for the switching current. Short -term andThe wide records are placed near the ADP3050 between the input and ground pins. The rated of the balanced ripple wave current of the input capacitor should be at least:

This rated value is very important, because the input capacitor must be able to withstand the input terminal of the antihypertensive regulator input terminal Large -current pulse. 20 μF to 50 μF is a typical value, but the main criteria for choosing capacitors are ripple current and voltage rated values.

Ceramics is the best choice for entering bypass due to its low ESR and high -grained wave current. Ceramics are particularly suitable for high input voltage and can be from many different manufacturers. Generally used to enter bypass, but preventive measures must be taken, because in the process of power -powered, when the current is influxed into the current, 钽 occasionally fails. When the regulator input is connected to a battery or a high -capacitor power supply, these rush are common. Some manufacturers now provide solid pyrone capacitors that are tested on the surface of the surface, but even these devices, if the capacitor voltage is close to its maximum rated value, there will be faults. Therefore, it is recommended to use the volume of the capacitor in the application of the existence of large rushing flow to 2: 1. For example, 20 volts can only be used for input voltage below 10. Aluminum electrolytic is the cheapest choice, but it takes a few parallel parallel to obtain a good setal root current rated value. OS-Con capacitor has good ESR and ripple current rated values, but they are usually larger and cost higher.

The list of capacitor manufacturers is shown in Table 4.

Non -continuous mode ringing

Under the non -continuous working mode, when the inductor current drops to zero, the opening node will appear high -frequency oscillation. This kind of bell is normal, not the result of unstable ring circuit. This is caused by a switch and diode capacitance and inductance reactions. Such bells are usually within a few mega -horses, and there is no harm to the normal work of the circuit.

Set output voltage

The ADP3050 (3.3 volts and 5 volts) of the fixed voltage version has a feedback resistor separator on the chip. For adjustable versions, the output voltage is set with two external resistors. Refer to Figure 25, select the R1 value between 10 kΩ and 20 kΩ, and then use the following formula to calculate the appropriate value of R2:

It needs to be noted that these resistances are that these resistances are that these resistors need to note that these resistors need to pay attention to these resistors. The accuracy of the output voltage directly affects the accuracy of the output voltage. The FB tube threshold change is ± 3%, and the tolerance of R1 and R2 is added together to determine the total output change. Use a 1%resistor near the FB pin to prevent noise pickup.

Frequency compensation

ADP3050 adopts a unique compensation scheme to allow the use of any type of output capacitors. The designer is not limited to a specific type of capacitor or a specific ESR range. External compensation allows designers to optimize circuits to obtain transient response and system performance. The value setting error of R and CC is largeThe poles and zero positions of the device to compensate the regulator circuit.

For [output capacitors, the typical system compensation value is RC 4KΩ, CC 1NF; for ceramics, the typical value is RC 4kΩ, CC 4.7NF. These values may not be optimized for all design, but they provide a good starting point for the selection of final compensation values. Other types of output capacitors require different C values between 0.5NF and 10NF. Generally, the lower the ESR output capacitor, the greater the value of the CC. The normal changes of capacitor ESR, output capacitors and inductance values (due to production tolerances, changes in working points, and temperature changes) will affect the width and phase response. Be sure to check the final design throughout the work scope to ensure the normal work of the regulator.

Adjusting R and CC values can optimize compensation. Use the above typical values as the starting point, then try to increase and reduce each value, and observe the transient response. A simple way to check the design transient response is to observe the output, and at the same time, the load load current is pulled at a rate of about 100 Hz to 1 kilo. When the load pulse, there should be some slight bell at the output end, but this should not be too much (just a few bells). The frequency of this kind of bell represents the frequency of nearly unit gains in the ring. Third, always check the design input voltage, output current and temperature within the entire work range to ensure that the circuit is correctly compensated.

In addition to setting zero, R also sets a high -frequency gain of an error amplifier. If this gain is too large, the output ripple voltage appears on the COMP pin (the output of the error placing the large device), and its amplitude is enough to interfere with the normal operation of the regulator. If this happens, the sub -harmonic switch will occur (even if the output voltage remains stable, the pulse width of the switch waveform will change). The voltage ripples at the COMP pin should be kept below 100 MV to prevent subsequent harmonic switching. The amount of ripples can be estimated by the following formulas, where G is an error amplifier cross -guided (GM 1250 μmHo):

RC 4 kΩ and CC 1 nf 100 μF 钽 output capacitors, then 12 V to 5 V 800mho regulators with L 47 μH with an inductance of Iripple 310 mAh (see examples of the continuous mode part). The ripple voltage of the COMP pin is:

If the voltage of the ripple is greater than 100mV, it needs to reduce RC to prevent secondary harmonic switching. The typical value of RC is between 2 kΩ and 10 kΩ.

For the output voltage greater than 5V, a small capacitor may need to be added parallel with R2, as shown in Figure 25. This improves stability and transient response. For 钽 output capacitors, the typical value of C is 100pf. For ceramic output capacitors, the typical value of CF is 400 PF.

current limit/frequency folding

ADP3050 uses weekly current limitation to protect the device under failure and high stress conditions. When the current limit is exceeded, the power switch is turned off until the next oscillator cycle starts. If the voltage on the feedback foot is reduced to less than 80%of its nominal value, the frequency of the oscillator starts to decrease (see Figure 17 of the typical performance characteristics part). The frequency gradually decreases to the minimum value of about 80 kHz (when the feedback voltage drops to 30%of its nominal value, this minimum value appears). This reduces the power consumption of integrated circuits, external diodes and inductors under short circuit conditions. This frequency folding method provides complete equipment failure protection without interference equipment.

Partial voltage sales connection

In order to improve efficiency, most of the internal working currents can be obtained from lower voltage adjustment output voltage instead of input power. For example, if the input voltage is 24V and the output voltage is 5V, the static current of 4MA will consume 96MW from the input power supply, but the adjustment 5V output only consumes 20MW. This energy -saving effect is most obvious under high input voltage and low load current. To use this function, the output voltage must be 3 V or higher.

The booster drive level

External capacitors and diodes are used to provide the voltage voltage required for special drive levels. If the output voltage is higher than 4V, the anode of the boost diode is connected to the voltage voltage output; if the output voltage is less than or equal to ≤3V, it will be connected to the input power supply. For some low -voltage systems, such as 5V to 3.3V converters, the anode of the voltage diode can be connected to the input or output voltage. During the closure, the voltage of the voltage capacitor is charged to the voltage of the voltage diode anode. When the switch is turned on, the voltage is added to the switching voltage (the voltage diode is reverse) to provide voltage higher than the input power supply. The peak voltage on the Boost pin is the sum of the input voltage and the Boost voltage (VIN+VOUT or 2 × VIN). Make sure that the maximum rated value of this peak voltage does not exceed the boost pins 45 V.

For most applications, 1N4148 or 1N914 diode can be used with 220 NF capacitors. When the output voltage is between 3 V and 4 V, 470 NF capacitors may be needed. The ESR of the voltage capacitor should be less than 2Ω to ensure that it is fully charged during the closure. Almost any type of film or ceramic capacitors can be used.

Starting/minimum input voltage

In m