Features

Wide power supply range: ± 10V to ± 45V

High conversion rate: 15V /μs

Low input bias current: 10Pa

SO-8 PowerPad #63722; and SO-8 surface installation package

Application

Test equipment

# 8226;

High -voltage regulator

Power amplifier

Data Collection

Signal adjustment

Audio

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Explanation OPA445 is a single -piece operational amplifier that can work under the output current of up to ± 45V and 15mA. It is suitable for various applications that require high output voltage or volatile voltage fluctuations in the community.

The high conversion rate of OPA445 provides a wide power bandwidth response, which is usually required for high -voltage applications. The FET input circuit allows the use of high impedance feedback networks to minimize its output load effect. Laser fine -tuning input circuit generates low input offset voltage and drift.

OPA445 provides standard pins to-99, DIP-8, and SO-8 surface installation packaging and SO-8 PowerPad packaging to reduce the temperature. It is fully stipulated in 25 ° C to+85 ° C, and work between 55 ° C to+125 ° C. SPICE macro model can be used for design and analysis.

Typical features When TA u003d+25 ° C and vs u003d ± 40V, there are other descriptions.

Application FIG Non -conversion amplifier connection. OPA445 can be used for almost any computing amplifier configuration. The power supply terminal should be attached to the power supply feetUse 0.1 μF or larger capacitor to bypass. Ensure that the rated value of the capacitor matches the voltage of the power supply.

Power supply

OPA445 can work under the power supply of up to ± 45V or a total voltage of 90V, which has excellent performance. Without the entire working voltage range, most characteristics remain unchanged. The typical feature shows the parameters of significant changes with the working voltage.

Some applications do not require equal positive and negative output voltage. The power supply voltage does not need to be equal. The voltage of OPA445 between the power supply is only 20 volts, and the voltage between the power supply can reach up to 90 volts. For example, the positive power supply can be set to 80V, and the negative power supply is 10V, and vice versa.

Input protection

The input of the traditional FET input computing amplifier should be protected to prevent the destructive current that flows when the input fET grid to the substrate isolation diode isolates the bias. This is the case if the input voltage exceeds the power supply or the VS u003d 0V input voltage. The protection can be easily achieved by the resistor that is connected in series. Be careful, because the resistor connected with the input capacitor may affect the stability. Many input signals have inherent current limit; therefore, the resistor may not be required.

Filter the bias voltage

OPA445 provides a bias voltage mini -connection on the pinna 1 and 5. As shown in Figure 2, the offset voltage can be adjusted by the connection potential meter. This adjustment is only used to make the operational amplifier's offset to zero, rather than adjusting the system's offset or signal source. The offset of the zero system will reduce the offset voltage drifting behavior of the computing amplifier. Although the exact change of drift cannot be predicted, the impact is usually small.

Capacity load

The dynamic characteristics of OPA445 have been optimized for common gain, load and operating conditions. The combination of low -closed cycle gain and capacitance load will reduce phase margin, and may lead to peak or oscillation of gain. Figure 3 shows a circuit that maintains phase margin under the capacity load. The circuit will not be dropped by voltage due to the load current; however, input impedance at high frequency will be reduced. Refer to the application announcement SBOA015, you can download the website from the following URL to introduce the analysis technology and application circuits in detail.

Increase the output current

In the application of the 15mA output current, it is not enough to drive the required load application, which can be connected to two or more OPA445 to increase the output. The current, as shown in Figure 4. The amplifier A1 is the main amplifier, which can be configured in almost any computing amplifier circuit. From the amplifier A2 to the unit gain buffer. Alternatively, you can use an external output transistor to increase the output current. The circuit in FIG. 5 can provide a loser up to 1AOut current.

The safety operation area

The stress on the output transistor is determined by the output voltage of the output current and the conductive output transistor vs VO. The power consumption of the output transistor is equal to the output current and the voltage of the voltage of the conductive transistor, VS VO. Safety operation area (SOA curve, Figure 6 to Figure 10) illustrates the allowable range of voltage and current. The curve indicates the welding equipment for the radiator -free chip on the printing circuit board (PCB). Increasing the area of u200bu200bthe printing circuit line or the use of the heat sink (to-99 packaging) can significantly reduce the thermal resistance (), thereby adding the output current (see Figure 11, Figure 12, and the heat sink section) under a given output voltage.

With the increase of vs VO, the safe output current decreases. The output short circuit is a very harsh situation for SOA. The short-circuit of the ground forced the entire power supply voltage (V+or V-) through the conductive transistor and generated a typical output current of 25 mA. For ± 40V power, this will cause 1W internal loss.

This is beyond the maximum rated value and is not recommended. If the operation is inevitable in this area, the radiator is needed. To learn more about SOA, see the application announcement SBOA022.

Power loss The power consumption is determined For power, signal and load conditions. For DC signals, power consumption is equal to the output current multiplication of the voltage of the voltage on the conductive output transistor, PD u003d IL (vs vo). By using the required as much as possible to ensure the required output voltage, the power consumption can be minimized.

For the resistance load, the maximum power consumption occurs at the DC output voltage of half of the power supply voltage. The loss of the exchange signal is lower. The application announcement SBOA022 explains how to calculate or measure the dissipation of abnormal loads or signals.

OPA445 can provide 15mA and above output current. This will not cause any problems for the standard operations amplifier using ± 15V power supply. However, at a high power supply voltage, the internal power consumption of the computing amplifier may be quite large. The operation of a single power supply (or unbalanced power supply) can generate greater power consumption because a larger voltage is applied to the electrical output transistor. The application of power consumption may require radiator. Heating

The power consumed in OPA445 will cause the knot temperature to rise. To ensure reliable operation, the connector temperature should be limited to 125 ° C (to-99 packaging at 150 ° C). Some applications require a radiator to ensure that it will not exceed the highest work knot temperature. In addition, in order to improveReliability, the temperature should be as low as possible. The knot temperature can be determined by the following formula:

The packaging thermal resistance JA is affected by the installation technology and environment. Poor air circulation and the use of sockets can significantly increase thermal resistance. The best thermal performance is to welded the computing amplifier to the circuit board with a wide printed circuit traces to allow greater conduction by the computing amplifier lead. Simple clamping radiator (such as thermaloloy 2257) can reduce the thermal resistance of the to-99 metal packaging up to 50 ° C/W. SO-8 PowerPad package will provide lower thermal resistance, especially simple heat sinks with radiator tablets or even lower. For more information on the requirements for determining the radiator, see the application announcement SBOA021.

PowerPad thermal enhancement component

In addition to SO-8, DIP-8, and to-99 software packages, OPA445 also has a SO-8 PowerPad. SO-8 PowerPad is a standard size SO-8 package. The naked lead frame of the bottom of the packaging can be directly welded to the PCB to generate extremely low thermal resistance. This structure greatly enhances the power consumption capacity of OPA445 and eliminates the use of bulky radiator and segmentation that is traditionally used for hot packaging. This package can easily install the standard PCB assembly technology. Note: Because the pins of SO-8 PowerPad are compatible with standard SO-8 packaging, OPA445 can directly replace the calculation amplifier in the existing socket. Always welding PowerPad to PCB, even low -power applications. Welded the device to the PCB, and provides necessary thermal connections and mechanical connections between the lead framework and PCB.

The design of PowerPad packaging makes the lead frame mold pad (or hot pad) exposed to the bottom of the IC; see Figure 13. This design provides a very low heat resistance (JC) 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.

The layout guide of the general power board

OPA445 provides a thermal enhanced PowerPad package. This packaging is installed on it with a lower -loading frame. This arrangement causes the lead framework to be exposed to the package as a hot pad. The thermal pads directly contact the mold; therefore, it can obtain excellent thermal performance by providing a good heat path away from the hot pad.

PowerPad package allows assembly and thermal management at the same time in a manufacturing operation. During the surface of the surface (when welding), the thermal pads must be welded to the copper area below the packaging. By using the heat path in this copper area, heat can beTo transmit from packaging to the ground floor or other heat dissipation devices. Always welding PowerPad to PCB, even low -power applications. Please execute the following steps:

1. The power board must be connected to the most negative power supply voltage on the device V .

2. Prepare PCB with top etched patterns. Both wires and hot pads should be etched.

3. Recommended hole in the thermal pad area. FIG. 14 shows the size and heat-passing mode of the SO-8 DDA component. The diameter of these holes should be 13 dense ears. Keep them very small, so that the weld core is not a problem during the period of the pores. SO-8 PowerPad's minimum recommended hole is 5.

4. Put an additional hole in any position of the thermal plane outside the thermal pad area. These pores help dissipate the heat generated by the OPA445 integrated circuit. These additional holes may be larger than the pores with 13 dense ears in the front diameter of the hot pad. They can be larger because they are not welded with hot pads; therefore, core suction is not a problem.

5. Connect all holes to the internal power plane with the correct voltage (V-).

6. When connecting these holes to the plane, do not use a typical abdomen or wheel spoke connection method. The network connection has a high thermal resistance connection, which helps to slow down the heat transfer in the welding operation, making it easier for the welding of the pores with a flat connection. However, in this application, in order to achieve the most effective heat transfer, low thermal resistance is required. Therefore, the holes under OPA445 PowerPad should be connected to the internal plane and a complete connection around the entire electroplated hole.

7. The welding mask at the top should expose the packaging terminal and thermal pad. The welding mask at the bottom should cover the hole in the hot pad area. This cover can prevent the welded from being pulled away from the thermal pads during the return welding process.

8. Apply the tiny paste to the exposed thermal pad area and all IC terminals.

9. With these preparation steps, PowerPad IC can simply place it in place, and complete the welded back welding operation like any standard SurfaceMount component. This preparation work can make the parts correctly installed.

Details on the PowerPad software package, including thermal demand precautions and maintenance procedures, see the technical introduction SLMA002 PowerPad thermal enhancement package.

Typical application