General description

lm4890 is a high -demand application for mobile phones and other communication devices for mobile phones and other communication devices. It has the ability to provide 8 BTL with a 1 -wwww of the power supply (THD+N) power supply with an average power of 5 volts. Boomer audio power amplifier is specifically for providing high -quality output power external components. LM4890 does not require output coupling electrical containers or self -lifting capacitors, so it is very suitable for mobile phones and other low -voltage applications. In these applications, the minimum power consumption is the primary requirement. LM4890 has a low -power shutdown function mode, which is low with logic. In addition, LM4890 also has an internal heat shutdown protection mechanism. The LM4890 contains advanced pop -up and click circuits to eliminate and turn off and turn. The LM4890 is a stable unit gain and can set the resistor through external gain.

Main specifications

J PSRR, VDD 5V (Figure 1) 62DB (typical)

5.0V and 1%Thd 1W power output (typical value value )

3.3V and 1%THD 400MW power output (typical)

The shutdown current 0.1 μA (typical value)

Features

Provide space saving Packaging: Micro SMD, MSOP, SOIC and LLP

Ultra -low current shutdown mode

BTL output can drive capacitance load

improved pop -up and click circuit to eliminate noise [ 123]

Open and close the conversion

2.2-5.5V operation

No output coupling capacitor, buffer network or self-lifting capacitor

Hot shutdown protection

Stable unit gain

External gain configuration capabilities

Application

Mobile phone

pda

Portable electronic device

Absolute maximum rated value (Note 2)

Power voltage (Note 11) 6.0V

Storage temperature 65 #730; C to+150 ; C

Input voltage 0.3V to VDD+0.3V

Power consumption (Note 3) Internal limited

ESD Sensitivity (Note 4) 2000V

Nene temperature 150 ; c

θjc (SOP) 35 #35 ; C/W

θja (SOP) 150 ; C/W

θja (8 convex patch, Note 12) 220 ; c/w

θja (9 convex micro -stickers, Note 12) 180 ; C/W

θjc (mSOP) 56 ; C/W

θja (MSOP) 190 190 Celsius

θja (LLP) 220 ; C/W

Welding information

See AN-1112 micro-chip-grade chip scale package.

See AN-1187 Lead-free Diversion Framework Component (LLP)

Retime-rated value

Temperature range

tmin ≤Ta ≤TMAX 40 # 730; C≤ta ≤ 85 ; C

Power voltage 2.2V ≤VDD ≤ 5.5V

Electric characteristics VDD 5V (Note 1, 2, 8)

] The following specifications are applicable to the circuit shown in Figure 1, unless there are other regulations. The limit at TA 25 ° C

Electric characteristics VDD 3V (Note 1, 2, 8)

The following specifications are applicable to Figure 1 The circuit shown is unless there are other regulations. TA 25 ° C. Applicable limit.

Electric characteristics VDD 3V (Note 1, 2, 8)

The following specifications are suitable for the circuit shown in FIG. 1, unless there are other regulations. Limited to TA 25 ° C (continued)

Electric characteristics VDD 2.6V (Note 1, 2, 8)

The following specifications are applicable to the figure in the figure 1 The circuit shown is unless there are other regulations. TA 25 ° C. Applicable limit.

Note 1: Unless there are other regulations, all voltages are measured relative to ground pins.

Note 2: Absolute maximum rated value indicates the limit that may cause damage. The working rated value represents the functionality of the equipment, but does not guarantee specific performance restrictions. Electrical characteristics illustrate DC and AC electrical specifications under specific test conditions to ensure specific performance restrictions. This assumes that the device is within the scope of the working ratio. For unlimited parameters, the specifications are not guaranteed. However, typical values are good instructions for equipment performance.

Note 3: The maximum power consumption must be reduced at high temperature, and it is determined by TJMAX, θJa and environmental temperature TA. The maximum power consumption is PDMAX (TJMAX -TA)/θJa or absolutely the mostThe given values given in large rated values shall prevail. For LM4890, please refer to the power reduction curve to get more information.

Note 4: Human model, 100 PF discharge through 1.5 k resistor.

Note 5: Machine model, 220 PF -240 PF Power electricity through all pins.

Note 6: The typical value is measured at 25 ° C, which represents parameter standards.

Note 7: The limit is guaranteed to be national AOQL (the average factory quality level).

Note 8: It is only suitable for Micro SMD to measure the shutdown current in a normal indoor environment. Under the direct sunlight, ISD increased by a maximum increase of 2 μA.

Note 9: The minimum/maximum specification limit of the data table is guaranteed by design, test or statistical analysis.

Note 10: ROUT is the measurement value from each output pin to ground. This value represents 10K Ohm output resistance and two 20K resistance parallel combination Om resistors.

Note 11: If the product is in the shutdown mode and VDD exceeds 6V (maximum 8V VDD), most of the over -current will flow through the ESD protection circuit. If the source impedance limits the current to a maximum of 10 mA, the parts will be protected. When VDD is greater than 5.5V less than 6.5V, if the part is enabled, although the service life will be shortened, it will not cause any damage. In the absence of current restrictions, more than 6.5V operations will cause permanent damage.

Note 12: All convex blocks have the same thermal resistance. When used to reduce thermal resistance, the contribution is equal. All bumps must be connected to achieve the specified thermal resistance.

Note 13: The maximum power consumption (PDMAX) in the device occurs when the output power level is significantly lower than the full output power. PDMAX can be displayed in the application part with formula 1. It can also be obtained from the power consumption diagram.

Note 14: PSRR is a function of system gain. Specifications are suitable for the circuit in AV 2 in Figure 1. The higher system gain will increase the PSRR value to increase gain. The system gain is 10 to indicate that the gain increases by 14dB. Power suppression ratio will be reduced by 14 decibels, suitable for all working voltage.

典型性能特征

[123 ] Application information

Bridge configuration instructions

As shown in Figure 1, LM4890 has two operating internal amplifiers, allowing several different amplifiers to configure. The gain of the first amplifier can be configured outside, while the second amplifier is fixed at the unit gain and reversed configuration. The first amplifier of the closed -loop gain is set by selecting the ratio of RF to RIN. The gain of the second amplifier isThe resistor is 20K the resistor. Figure 1 shows one of the output of the amplifier used as an input of amplifier 2. Both of them produce the same signal produced by the amplifier, but the difference between the output phase is 180 ;. Therefore, for IC is the average value 2*(RF/Lien), via output VO1 and VO2, is usually called the establishment of a bridge mode . The bridge mode operation is different from the traditional single -end amplifier configuration, that is, the side of the load. The design of the bridge amplifier is configured in a single -end configuration, because it provides a driver to the load, so that the output swing is doubled the power supply voltage. Four times the output power is possible compared with the single -end amplifier under the same conditions. The increase in the output power assumes that the amplifier has no current limit or current limit. In order to choose a closed -loop gain of a amplifier without causing excessive cutting waves, please refer to the audio power amplifier design part. The configuration of the bridge, such as the LM4890, has a second advantage compared to a single -end amplifier. Because the differential output VO1 and VO2 are half of the power supply, there is no net DC voltage on the load. This does not require output coupling capacitors to be configured in a single -power single -end amplifier configuration. The load deviation without the output coupling container may cause the internal IC power consumption and speaker to damage.

Exposed-DAP package PCB installation

Precautions for LM4890LD

LM4890LD exposure DAP (mold connection blades) packaging (LD) in molds and components installation and welding to PCB. This LM4890LD packaging should be welded to the ground copper pads (the radiator NC pins, non -connected pins and grounding pins should also be connected directly to this copper pad heat sink area). The area of copper pads (radiator) can be determined according to the LD power. If the area of the multi -layer copper heat sink, each area of these inner or back copper heat sinks should be connected to each other through 4 (2 x 2) through the 4 (2 x 2) hole. The diameter of these pores should be 0.02 inches between 0.013 inches and a spacing of 0.050 inches. Make sure high -efficiency thermal conductivity is achieved through electroplating and welded filling holes. For more details about PCB, the layout, manufacturing and installation of LLP packaging can obtain the application comments from the package engineering department of the National Semiconductor. The bridge is still a single -end. The direct consequences of the increase in power are transmitted to the load through the bridge amplifier. Since the LM4890 has two operating amplifiers in one package, the maximum internal power consumption is 4 times that of a single -end amplifier. Given the maximum power consumption of the application can be exported from the power dissipation diagram or equation 1. PDMAX 4*(VDD) 2/(2π2RL) (1) The most important thing is not more than 150 ; C. TJMAX can reduce the power of the PDMAX and PC board foilThe curve area. By adding additional copper foil, the thermal resistance can reduce the number of applications, thereby increasing PDMAX. The additional copper foil can be added to any wire to be connected to LM4890. Refer to the LM4890 reference to the information application on the design board good heat dissipation. If TJMAX still exceeds 150 ; C, and then other changes must be made. These changes can include reducing power supply voltage, increased load impedance, or lowering ambient temperature. Internal power consumption is the output power function. Refer to the output power and output load of typical performance power loss information.

Power bypass

Like any amplifier, the correct power bypass is suppressed in low noise performance and high power supply. The position of the capacitor position on this bypass and power pins should be as close to the device as much as possible. The typical application uses a 5V regulator with 10 μF 钽 or electrolytic capacitors and the supply of ceramic side electric containers. This does not eliminate power nodes that bypass LM4890. Selecting bypass electrical containers, especially CBYPASS, depending on the PSRR requirements, clicking the pop -up performance (as described by the correct selection of external components ), system cost and size limit.

Shipping function

In order to reduce the power consumption LM4890 when not in use, the bias circuit used to turn off the amplifier. When this closure function will turn off the logic of the pins, the amplifier will be closed. By switching the downtime to the ground, the LM4890 power supply will minimize the current consumption. When the device's closing pins voltage may be greater than the 5VDC value of 0.1 μA. (Saying the pin ground when the idling current is stopped). In many applications, the output of microcontrollers or microprocessors is used to control the shutdown circuit to provide a fast and steady transition to the shutdown state. Another solution is to pull the single -single switch with an external pull -up resistor. When the opening is turned off, the pin is turned off and the AM amplifier is disabled. If the switch is turned off, the external pull -up resistor will be enabled by LM4890. This scheme ensures that shutdown sales will not float, thereby preventing unnecessary state changes.

Application information (continued)

The output impedance of the shutdown

For RF 20K ohm: ZOUT1 (between OUT1 and GND) 10K | | 50K | | RF 6K #8486; zout2 (between out2 and gnd) 10K | (40K+(10K | | RF)) 8.3k zout1-2 (between Out1 and Out2) 40K | (10K+(10K | RF ))) 11.7 thousand Euros The -3DB attenuation of these measurements is 600kHz Correct selection of external components In the application of integrated power amplifier, the correct selection of external components is the key and systematic performance of optimization devices. And LM4890 can tolerate external componentsIn a combination, the component value must be considered to maximize the overall quality of the system. LM4890 is a unified gain and stability, which gives designers the greatest system flexibility. LM4890 is used in low -gain configuration to minimize THD+N value, and maximum signal -to -noise ratio. Low -gain configuration requires a large input signal to obtain a given output power. The input signal is equal to or greater than 1VRMS from the source of the audio edit decoder. Please refer to the design of the audio power amplifier to explain the correct gain choice in a comprehensive explanation. In addition to gain, one of the main factors is the closed bandwidth of the amplifier. To a large extent, the bandwidth depends on the selection of external components as shown in Figure 1. Enter the coupling capacitor and CIN to form a first -order high -pass filter that limits low -frequency response. There are several obvious reasons for selecting this value frequency response as needed.

Selection of the size of the input capacitor

Large input capacitors are both expensive and occupying space for portable design. Obviously, capacitors of a certain size need to be coupled at low frequencies without having to pay serious attention. But in many cases, speakers are used for portable systems, whether internally or outside, there is no ability to reproduce signals below 100Hz to 150Hz. Therefore, using large input capacitors may not improve the actual system performance. In addition to the cost and size of the system, the clicks and pop -up performance are also affected by the size of the input coupling electrical container, CIN company. The larger input coupling capacitor requires more charge to reach its static DC voltage (nominal 1/2 VDD). This charge comes from the output by feedback, and it is easy to create POP when the device is enabled. Therefore, through the minimum capacitor size based on the necessary low -frequency response, the open POP can be minimized. In addition to reducing the size of the input capacitor, you should also consider the value of the bypass container carefully. Wingrser -in container, CBYPASS, is the most critical part of micro -opening POPS because it determines the speed of LM4890. The slower the output speed of the LM4890, the smaller the static DC voltage (nominal 1/2VDD). Selecting CBYPASS is equal to 1.0 μF and CIN values less (within 0.1 μF to 0.39μF range). One can produce a function of almost no clicks and pop -up. When the device works normally, (no oscillation or motorboat), when CBYPASS is equal to 0.1 μF, the device will be more likely to be opened and popped up. Therefore, it is recommended to remove the most cost -sensitive design.

Audio power amplifier design

A 1W/8 audio amplifier

In view of: power output 1 WRMS

Load impedance 8 [[[[[[[[

123]

Input level 1 VRMS

Input impedance 20 k

Bandwidth 100 Hz – 20 KHz ± 0.25 DB

SettingThe plan must first determine the specified output power of the minimum supply track. The relationship between the relationship between the output power and the power supply voltage can be easily found in the typical performance characteristics part. The second method of determining the minimum support is to use the Vopeak required to calculate the Formula 2 calculation plus the output voltage. Using this method, the minimum power supply voltage is (VOTOP+VODBOT), where Vodbot and VOTTOP are the feature parts inferred by the voltage-voltage relationship curve under typical performance.

5V is a standard voltage. In most applications, it is the Cho Sen of the power rail. The additional power supply voltage creates head space, so that LM4890 can reproduce too much peak value by 1W, and will not produce sound distortion. At this time, the designer must ensure that the selection of the power supply is explained in the Power Consumption section without violation of conditions. Once the power consumption equation is solved, the required differential gain can be determined by equal 3.

According to Formula 3, the minimum AVD is 2.83; using AVD 3. Since the required input impedance is 20 k , and the AVD gain is 3, the ratio of RF and Rin is 1.5: 1, the allocation result is RIN 20 k and RF 30 k Essence The final design step is to solve the required bandwidth requirements as a pair of 3 db frequency points. Five times a decrease in ± 0.25 dB of 3 dB points from the point of 3 dB and the band by 0.17 DB. FL 100Hz/5 20Hzfh 20kHz*5 100kHz

Application information (continued)

As mentioned in the external component part, the connection of RIN and CIN form high -pass filter. Cin≥1/(2π*20 k *20Hz) 0.397μF; use 0.39μF high -frequency magnetic pole to be polarly fH and differential gain AVD. When AVD 3 and FH 100kHz, the GBWP 300kHz generated is more than 2.5 MM. This calculation shows that if the designer needs to design a amplifier LM4890, which has a higher differential gain, it can still use limitations without occupying bandwidth.

LM4890 is a stable unit gain. It does not require components except for the gain setting resistance, an input coupling capacitor, and the appropriate power sources in typical applications. However, if the closed -loop micro -score gain is greater than that of more than 10, the feedback capacitor (C4) can need to limit the bandwidth of the amplifier as shown in Figure 2. This feedback capacitor generates a low -pass filter to eliminate possible high -frequency oscillations. Be careful when calculating the -3db frequency, because R3 and C4 are notThe correct combination will lead to a 20 -kilometer roll. The typical combination of feedback resistors and capacitors will not produce audio frequent high -frequency attenuation is R3 20K and C4 25PF. These components cause -3DB points to be about 320 kHz.

PCB layout guide

Practical guidelines for hybrid signals in this section involve various digital/simulation power sources and ground traces. Designers should notice that these are just the rule of empirical suggestions and actual effects that will largely depend on the final layout. The total layout diagram of the hybrid signal is recommended to design the 2 -layer hybrid signal design, the digital power supply and grounding track of the simulation power supply and the ground tracking path. Star tracking routing technology (bringing a single tracking back to the center point instead of the tracking link together in a serial manner) can have the main effect on the performance of low level signal. Star route refers to providing electricity and grounding to each circuit and even equipment with a separate record channel. This technology will require more design time, but it will not increase the final price of the board. The only additional parts need to be a parachuting athlete.

Single -point power supply/grounding connection

The simulation power tracking should be connected to the number through a single point (link) to track. Pi filter may help to minimize high -frequency noise coupling simulation and digital parts. Further recommend the number and simulation power tracking on the corresponding digital and simulation ground tracking to minimize noise coupling. Full digital components and high -speed digital signal tracking of numbers and simulation components should stay as far away from the simulation components and circuit traces as much as possible. Avoid typical design/layout problems to avoid ground circuits or run numbers and simulation trajectories on the same PCB layer parallel (side by side). When the traces must cross each other, cross at a 90 -degree angle. Run the numbers at 90 degrees and the simulation trajectory will minimize the noise coupling and string of capacitance noise from top to bottom.