Features

● High output current: 2A

● Output swing to: 150mv rail, IO u003d 2a

● Hot protection

● Yes, yes possible Restrictions

● Two signs: current limit and temperature warning

● Low -voltage operation: 2.7V to 5.5V

● Output closing function

● Small power component: SO-20 POWERPAD #8482;

Application

● Thermoelectric cooler driver

● Laser diode pump drive

● Valve, valve, Transformer drive

● Synchronous, servo driver

● Sensor excitation

● Common linear power amplifier for operation amplifier

Options

Explanation

OPA569 is a low -cost, large current, computing amplifier. It is designed to drive various loads when running at a low -voltage power supply. In order to design the flexibility, it uses a single power supply or dual power supply, and plans rail on track in input and output. The typical output swing is within the 150mv range of the power rail, and the output current is 2A. The lighter load can make the output swing closer to the power supply track.

OPA569 has the problem of unit gain stability, small DC error, convenient use, and not affected by the phase reversal of certain power amplifiers. Keep high performance under the voltage fluctuations near the output track.

OPA569 provides an accurate user -selected current limit, which is adjusted by digital adjustment through external resistance settings or digital modular converters.

OPA569 output can be disabled by enable pins independently, saving electricity and protective loads.

The iMonitor pin provides 1: 475 two -way copy of the output current. This does not need to be connected in series diversion, which allows more voltage to apply to the load. This pin can be used for simple monitoring or feedback control to establish a constant output current.

Provide two signs: one for warning thermal stress, and the other for current restrictions. The hot standard pins can be connected to the enable pins to provide heat shutdown solutions.

Packaged in the power board of Texas instruments #8482; packaging, small volume and easy to dissipate heat. OPA569 stipulates that it is operated within the range of -40 ° C to+85 ° C in the industrial temperature range.

Typical features

TA u003d+25 ° C, vs u003d+5V, unless otherwise explained.

Application information Basic configuration

FIG. 1 shows OPA569 connected to the basic non -conversion amplifier; however, OPA569 can actually be used for any computing amplifier configuration. The current limit setting the resistor (RSET, Figure 1) is essential for the operation of OPA569 and cannot be omitted.

The power terminal should be bypass with low series resistance resistance. It is recommended to use larger crickets and smaller ceramic types in parallel. The power terminal should have low series impedance.

Power supply

OPA569 has excellent performance when single power supply (+2.7V to+5.5V) or dual power supply power supply. As long as the total voltage is kept below 5.5V, the power supply voltage does not need to be equal. The typical feature part shows the parameters of significantly changes with the working voltage.

adjustable restrictions and current limit signs pins

OPA569 provides overload protection for loads through its accurate, user -adjustable current limit (pin 3). Set the pins control current through the current limit, the current limit value ILIMIT can be set from 0.2A to 2.2A. The current limit ILIMIT will be 9800 ISET; where ISET sets the current of the pins through the current limit. Setting current limit does not require special power resistors. The output current does not flow through the pin.

Set the current limit

As shown in Figure 2, the simplest way to set current limit is based on the following formulas, setting the pin and pin pin and the current limit settings and the setting of A resistor or potential meter connected between the negative power supply V -(negative power supply):

Or, the output current limit can be connected in series with the resistance and resistance by using the following formulas. Settings:

The voltage source will refer to V -.

Flow limit accuracy

Internal independent circuit monitoring positive and negative current limit values. Each circuit output is compared with a single internal benchmark set by the user through a combination of external resistors or resistors/voltage sources. OPA569 uses a patented circuit technology to achieve accurate and stable current restrictions throughout the entire output range. The initial accuracy of the current limit is usually within 3%, but the error may be as high as 15%due to the internal matching limit. The typical feature part shows changes in current limits with factors such as output current level, output voltage, and temperature.

When a current limit (source or trap) accuracy ratio ratio ratioWhen one is more important, the accuracy can be set to 1%by adjusting the external resistance or external voltage. The accuracy of another current limit is still affected by internal matching.

The current limitation flag pins

OPA569 has a current limit logo pin (pin 4), which can determine when the part is at the current limit. The output signal of the current limit signs is compatible with the standard logic in the application of a single power source. The output signal is a CMOS logic door, which is switched from V+to V-to indicate that the amplifier is in the current limit. The source and leakage current of the output pins can reach 25 μA. The additional parasitic capacitance between pin 3 and pin 4 can cause instability of the current limit edge. Avoid these records parallel to each other.

Static current depends on the current limit settings

OPA569 is a low -power amplifier, which has a typical 3.4MA static current (the current limit configuration is 200mA). The static current changes with the current limit settings-the current limit is increased by 0.5mA every 200mA, as shown in Figure 3.

current monitor

OPA569 has an accurate output current monitor (Imonitor) without using series resistance on load. This greatly improves efficiency and provides better overall swing supply performance.

Internal circuits generate a copy of the output current of 1: 475. The copy of this output current can be monitored independently, and it can also be used for current control driving, setting asymmetric positive, negative current limit or two or more devices in parallel to increase the output current driver. When not in use, the current monitor pin may remain floating.

When using a current monitor function, some restrictions are applicable. When the main amplifier is the source current, the current monitoring circuit must be the source current. Similarly, when the main offer is a sink current, the current monitor circuit must also be a sink current. In addition, the swing on the Imonitor pin is smaller than the output swing. When the amplifier provides current, the voltage of the current monitor pins must be at least 200 millivolves than the output voltage of the amplifier. Conversely, when the amplifier is absorbing the current, the voltage of the current monitor pins must be at least 200 millivolves than the output voltage of the amplifier. The resistance load can meet these restrictions. Other types of loads may cause an invalid current monitor value.

A simple way to monitor the load current and meet these requirements is to connect a resistor (resistance less than 400 #8226; rl) from the Imonitor pin to the same potential connected to the other side of the load. Another method is to use a cross -blocking major, as shown in Figure 4. This circuit must ensure that the Imonitor pin is kept within the effective voltage range. The method is to connect it to the same potential connected to the load. For dual power applications, it is likely to be groundedFor single power applications, it is an intermediate power supply.

When the output current is small, the accuracy of the current copy will be reduced. The internal circuit monitor the direction of the output current, and enables a positive current or negative current monitoring circuit accordingly. The changes in the direction of the current are delayed by about 20 μs. The switching point is close to the static state, which may cause an error in the current monitor at the time of the output current.

Enable pins output for disable

Enable pins can be disabled in the microsecond to disable OPA569. When disabled, the current of the amplifier is less than 10 μA, and its output enters a high impedance state that allows multiple reuses. It should be noted that when the amplifier is disabled, the heat label pin circuit will continue to work. This function allows the use of heat signs to be output to achieve thermal protection strategy. For details, see the heat protection part.

OPA569 enables the pins to have an internal pull circuit, so there is no need to connect the positive power supply during normal work. To disable the amplifier, the enable pins must be connected to no (V-)+0.8V. To enable the amplifier, allow the pins to float or connect it to at least (V-)+2.5V.

Enable pins are related to the negative electrode power supply (V-). Therefore, in the single power supply and dual power application, the shutdown operation is slightly different.

In the operation of a single power supply, V -is usually equal to public grounding, so enable/disable logical signals and OPA569 enable pins to reference the same potential. In this configuration, the logic level and OPA569 enable the pipe to pipe can be simply connected. Disables occur when the voltage level is lower than 0.8V. OPA569 is enabled when the logic level is greater than 2.5V.

In dual power operation, logic level reference logic ground. However, OPA569 ENABLE pins still reference v -. To disable OPA569, the voltage level of the logical signal requires the level shift. This can be completed using optocouplers, as shown in Figure 5.

The typical feature part shows the output behavior example under different load impedance under different load impedance. Please note that this behavior is a function of circuit board layout, load impedance and bypass strategy. For sensitive loads, it is recommended to use a low -pass filter or other protection strategies.

Ensure that the compatibility of the microcontroller

Not all micro -controllers output the same logical state after power -on or reset. For example, the 8051 microcontroller outputs high levels of logic on its port, while other models are powered by logic low after reset.

In the configuration (a) shown in FIG. 5, the use/disabled signal is used in the cathode side of the optical diode in the optical coupling internal tube. The logic high level makes OPA569 enable, and the logic low level makes OPA569 ineffective. In the configuration (b) of FIG. 5, the logic signal is applied on the anode side, highThe level is disabled OPA569, and the computing amplifier is enabled at a low level.

Rail output range

OPA569 has an AB output stage with a common source transistor for realizing rail output swing. It is designed to be closer to orbit than other existing linear amplifiers, even if the output current level is high. According to the requirements of different output current, a method of rapidly estimating the output swing is to use the following formulas:

The typical feature part provides the output swing and the output current, the power supply voltage, the power supply voltage The relationship with temperature.

The input range of the rail

The input co -mode voltage range of OPA569 exceeds 100mV of the power rail. This is achieved through the complementary input level of parallel input with an N -channel input input differential parallel. For input voltage near the track, the N channel input is effective, and the P channel input is effective for input voltage nearly negative. The transition point is usually in (V+) -1.3V, and there is a small transition area around the switching point where both transistors are connected. It should be noted that these two inputs have different signs and size offsets. Therefore, when the transition point is crossed, the offset of the amplifier changes. This offset shift indicates the reduction of the co -mode suppression ratio within the entire input co -mode range.

Output protection

The load that generates non -merit and electric momentum can return the load current to the amplifier, causing the output voltage to exceed the power supply voltage. From the output to the clamping diode of the power supply, this damage can be avoided, as shown in Figure 6. It is recommended to use the continuous rated value of 3A or larger Schottky rectifier diode.

Thermal label sales

OPA569 has armal sensing circuit. When the mold temperature exceeds the safety temperature, it will send a warning signal limit. Unless the thermal sign is connected to the enable pin, when the sign is triggered, the component continues to run even if the knot temperature exceeds 150 ° C. This allows the maximum available operation under very harsh conditions, but reduces reliability. The hot standard pins can be used to turn off the system in an orderly manner before the failure. It can also be used to evaluate the heat environment to determine the needs and proper design of the suspension mechanism.

The heat-standard output signal comes from the CMOS logic door. The logic door switches from V+to V-to indicate that the amplifier is in the heat limit. The source and leakage current of the output pins can reach 25 μA. During the normal operation, the hot standard pins are high levels. The power consumed in the amplifier will cause the knot temperature to rise. When the knot temperature exceeds 150 ° C, the heat label pin will become lower and keep it at a lower level until the amplifier cools to 130 ° C. Although there is such a lag phenomenon, through the orderly shutdown method, the hot -standard pins can be interrupted according to the load and signal conditions. This limits the loss of the amplifier, but it may be bad for the loadinfluences. This temperature range exceeds the absolute maximum temperature rated value, which aims to protect the equipment from the impact of excessive temperature that may cause damage. The short -lived and uncontrollable offset within this temperature can be tolerated, but it is not recommended to do it.

The heat signs can be connected directly to the enable pins of automatic shutdown protection. When heat shutdown and amplifier enable/disable functions, the output of the control signal and thermal signs of the external generation should be combined with the door, as shown in Figure 7. Temperature protection design is used to prevent overload. This is not to replace proper heat dissipation. Continuous operation of OPA569 to enter and exit heat shutdown will reduce reliability.

The trend of any activating thermal protection circuit indicates that the power consumption is too large or insufficient heat dissipation. For reliable, long -term, and continuous operation, the highest knot temperature should be limited to 125 ° C. It is estimated that the safety haunterness of the complete design (including the radiator) should be estimated, please increase the ambient temperature until trigger heating protection. Use the load and signal conditions in the worst case. In order to obtain good long -term reliability, thermal protection should trigger a temperature above the maximum expected environmental conditions above the application of 25 ° C. This will generate a 125 ° C knot temperature under the maximum expected environmental conditions.

The rapid transient transformation of large output current (such as fast switching from source 2A to sinking 2A) may cause the heat signs pins to fail. When a large current needs to be switched, it is recommended to use additional bypass or the low -pass filter on the feet on the power supply.

Power consumption and safety operation area

Power consumption depends on power, signals and load conditions. It is mainly determined by the power consumption of the output transistor. For DC signals, power loss is equal to the output current, output current, and the output voltage of the output voltage of the transistor (VS-Vout) through conductive output. The loss of the exchange signal is lower.

The output short circuit requirements are particularly high in the amplifier, because the complete power voltage can be seen on the conductive crystal. It must be noted that the temperature protection will not close the parts at ultra -temperature conditions, unless the thermal signs pins are connected to the enable pin;

FIG. 8 shows the safety operating area of u200bu200bdifferent heat dissipation power at room temperature. Note that the safe output current decreases with the increase of (VS -VOUT). Figure 9 shows the safe operation area at different temperatures, and the power board welded with a 2 ounce copper pad.

The power of safe heat dissipation in the packaging is related to environmental temperature and radiator design. PowerPad packaging is designed specifically for excellent power consumption, but the layout of the circuit board has greatly affected the heat dissipation of the packaging.

When welded to 2OZ copper plane, OPA569 and environmental thermal resistance (θJa) value was 21.6 ° C/W. By adding forced air, this value can be further reduced to 12 ° C/W. Figure 10 shows the knot-environment heat resistance of DWP-20 packaging.

The knot temperature should be kept below 125 ° C to ensure reliable operation. The knot temperature can be calculated through the following formula:

tj u003d knot temperature (° C)

TA u003d Environmental temperature (° C)

pd u003d consumption power (w)

θja u003d knot and environmental heat resistance

θjc u003d the heat from the connector to the shell to the shell The relationship between the maximum power consumption and temperature of the maximum power consumption and temperature listed in Figure 11 in FIG.

The relationship between the heat dissipation and the heat dissipation area should be considered appropriately to determine the relationship between the heat dissipation and the heat dissipation. Once the heat dissipation area is selected, the load conditions should be tested in the worst case to ensure proper heat protection.

For applications with limited plate size, refer to Figure 12 to understand the approximate thermal resistance of the area of u200bu200bthe radiator. Increase the area of u200bu200bthe heat sink to above 2in2, and the thermal resistance has almost no improvement. In order to achieve 21.5 ° C/W specified in the electrical characteristics, a copper plane of 9in2 is used. The SO-20 PowerPad package is very suitable for continuous power levels, as shown in Figure 11. In applications with low switching duty, higher power levels can be achieved.

The feedback capacitor increases the response

The best stability and stability of the best stability and stability of the high impedance feedback network (RF GT; 50K #8486;) It may need to add feedback capacitors to the feedback resistance RF, as shown in Figure 13. The capacitor compensation feedback network impedance and OPA569 input capacitance (and any parasitic layout capacitance) produced zero. This effect becomes more significant in high impedance networks.

The size of the required capacitors is estimated to be used as follows:

Among them, CIN is the sum of the input capacitors of OPA569 plus parasitic layout capacitors.

parallel operation

OPA569 allows multiple computing amplifiers to run parallel to expand the output current capacity or improve the output voltage of the track. Special internal circuits make the load current allocate between two (or more) operations amplifiers.

FIG. 14 shows two methods to connect the input terminal. When the amplifier is input parallel, the effective bias voltage is average, and the bandwidth and conversion ratio are the same as the single amplifier. You can also use a amplifier as the ""Lord"" and connect other inputs to the voltage within the input range of the amplifier co -mode input;However, the conversion rate and bandwidth performance will be reduced.

In order to obtain the best performance, keep the additional capacitor of parallel output at the minimum value, and avoid other lines that may fluctuate in large voltage fluctuations.

PowerPad thermal enhancement package

OPA569 uses SO-20 PowerPad encapsulation. This is a standard-enhanced standard size IC package. It aims to eliminate it to eliminate it The bulky radiator and plug used in traditional hot packaging. This package can easily install the standard PCB assembly technology.

The design of PowerPad packaging makes the lead frame mold pad (or hot pad) exposed to the bottom of the IC, as shown in Figure 15. This provides a very low thermal resistance (θJC) path between the mold and the outside of the packaging. The thermal pad at the bottom of the IC can be welded directly to the PCB and uses PCB as a heat sink. In addition, the electroplated hole (over -perforated) provides a low thermal heating runner on the back of the PCB.

It is always recommended to welded PowerPad to the PCB IA, even if it is a low -power application. This provides necessary thermal connections and mechanical connections for the lead frame of the lead framework and PCB.

PowerPad assembly process

1. The power board must be connected to the most negative power supply voltage of the device. In the application of a single power supply, the voltage will be grounded. The voltage will be grounded in the split power supply application.

2. Prepare PCB with the top etched pattern, as shown in Figure 16. Both wires and thermal pads should be etched.

3. Place a recommended number of electroplating pores (or heating holes) in the hot pad area. The diameter of these holes should be 13 dense ears. They remain very small, so that during the return welding, it is not a problem with the welded core of the hole. The minimum recommended hole of the SO-20 PowerPad is 24, as shown in Figure 16.

4. Suggestion (but not required) Put a small amount of extra holes under the packaging and the hot pad area. These holes provide additional thermal channels between the copper land and the horizon. They may be bigger because they are not in areas that need welding, so core suction is not a problem. As shown in Figure 16.

5. Connect all holes (including holes in the hot pads area and outside the pad area) to the internal ground plane or other internal copper planes (for the application of single power supply applications (for single power supply application ), And V -for split power supply.

6. When arranging these holes to the ground plane, do not use a typical abdomen or wheel spoke connection method, as shown in Figure 17. The network connection has a high thermal resistance connection, which helps to slow the heat transfer during the welding process. This makes welding more easily with holes with ground plane. HoweverIn this application, low thermal resistance is the most effective heat transfer requirement. Therefore, the holes under the PowerPad component should be connected to the internal ground plane and a complete connection around the entire electroplated hole.

7. The welding mold at the top should be exposed to the terminal and thermal pads of the pads connected. The hot pad area should be exposed with 13 dense ears. The large hole outside the thermal pads should cover the welding mask.

8. Apply welded paste on the exposed hot pad area and all packaging terminals.

9. With these preparation steps, PowerPad IC can simply place in place and complete welding back welding operations like any standard surface paste element. This will cause the parts to be installed correctly.

layout guide

OPA569 is a power amplifier, which requires appropriate layout to get the best performance. Figure 18 shows a layout example. According to the requirements of the assembly process, the layout of the example may be refined.

The power cord should be as short as possible. This will maintain low tostes and minimum resistance. It is recommended that the minimum wire thickness of the power cord is No. 18. The length of the wire should be less than 8 inches.

Appropriate power bypass and low ESR capacitors are the key to achieving good performance. The parallel combination of 100NF ceramics and 47μF 钽 wing containers will provide low impedance within a wider frequency range. The barrier capacitor should be as close to the power pins of OPA569 as possible.

PCB lines with high current, if the power pins from output to load or from power connectors to OPA569 should be kept as wide and short as possible.

The 24 holes on the landing pattern of OPA569 are used to connect the power plate of OPA569 to the heat -passing pores that are connected to the PCB. The other four larger holes further strengthened the heat conduction of the heat dissipation area area. The trajectory of all conducting high -current is very wide to achieve the lowest inductance and minimum resistance. Please note that the negative power (—V) pin on OPA569 can be connected through the power board to allow the maximum tracking width of the large current path.

Application circuit