Function description

LM4670 is a completely integrated single power supply high no output filter inductance load high -efficiency switch audio amplifier. It is characterized by an external -configured gain innovation modulator to eliminate the very fast opening time of LC output: 1.35ms (typical value) filter with typical switch amplifiers. Eliminate the output filter to reduce the count of external component components, simplify the circuit design, and ""click the pop -up"" to suppress the circuit to reduce the circuit board area. The LM4670 processing simulation micro-power closing mode input is used to use incremental-Sigma modulation technology. This technology short-circuit protection reduces the output noise and THD traditional pulse width modulator. Provide space -saving DSBGA and WSON to meet the requirements of the LM70 for mobile phones and other portable communication application devices. Runing on a 5V power supply, it can continuously drive 4 speaker load from 2.4V to 5.5V.

The main specifications compared to typical AB amplifiers. 3.6 volts

Power driver an 8 speakers, the efficiency of the integrated circuit is 3.6 volts, 100 mile to 8 speakers,

100MW power level is 77% of 77% It reached 88%at 600MW 77%(typical) output power.

LM4670's speaker load efficiency is high

The main specifications compared to typical AB amplifiers. 3.6 volts

Power driver an 8 speakers, the efficiency of the integrated circuit is 3.6 volts, 100 mile to 8 speakers,

100MW power level is 77% of 77% It reached 88%at 600MW 77%(typical) output power.

The average output power of the mobile phone is 2.3W, THD+N.ITS is less than 1%

PDA flexible power supply allows operation

Portable electronic equipment

] LM4670's speaker load efficiency is high

The main specifications compared to typical AB amplifiers. 3.6 volts

Power driver an 8 speakers, the efficiency of the integrated circuit is 3.6 volts, 100 mile to 8 speakers,

100MW power level is 77% of 77% It reached 88%at 600MW 77%(typical) output power.

8 speaker 3.6V and 600MW efficiency,

LM4670 is characterized by low power consumption of 88%(typical value)

shutdown mode. Close can pass

Efficiency is 5V, 1W input 8 speakers, 87%drive shutdown pins to logical low (GND). (Typical)

The gain of LM4670 is an external configuration

static current, 3.6V power supply, 4.8mA (typical value), allowed from multiple

Total shutdown power supply Current, 0.01 μA source, summarize the signal. (Typical)

Single power range, 2.4 to 5.5V

[1) Unless otherwise regulations, all voltage is measured relative to the ground needle foot measurement. Essence

(2) Absolute maximum rated value indicates the limit that may cause damage. The work rated value indicates that the device can work normally, but cannot guarantee specific performance restrictions. DC and AC electrical states of electrical characteristics to ensure specifications under specific test conditions for specific performance limit. This assumes that the device is at the rated value. For parameters without restrictions, the specifications cannot be guaranteed, but the typical value is a good instruction equipment performance.

(3) The maximum power consumption must be reduced at high temperature, and the teaching assistant is determined by TJMAX, θJa and environmental temperature. The maximum allowable power consumption is PDMAX u003d (TJMAX -TA)/θJa or the given values u200bu200bgiven in the absolute maximum rated value. For LM4670, tjmax u003d 150 ° C. The typical θja package package is 220 ° C/W, and the WSON packaging is 64 ° C/W.

(4) Human model, 100pf passes 1.5k resistance.

(5) Machine model, 220pf – 240pf Power electricity through all pins.

Electrical characteristics (1) (2)

The following specifications are applicable to AV u003d 2V/V (ri u003d 150k ), RL u003d 15 μH+8 +15μH, unless unless There are other regulations. Restricted applicable to TA u003d 25 ° C

(1) Unless there are other regulations, all voltages are measured relative to the ground needle foot.

(2) Absolute maximum rated value indicates the limit that may cause damage. The work rated value indicates that the device can work normally, but cannot guarantee specific performance restrictions. DC and AC electrical states of electrical characteristics to ensure specifications under specific test conditions for specific performance limit. This assumes that the device is at the rated value. For parameters without restrictions, the specifications cannot be guaranteed, but the typical value is a good instruction equipment performance.

(3) The typical specifications are specified under 25 ° C, representing parameter specifications.

(4) The test limit specifies the AOQL (Average quality level).

(5) The minimum/maximum specification limit of the data table is determined by design, testing or statistical analysis.

(6) Measure the shutdown current under normal room environment. Under the direct sunlight, ISD's maximum increase of 2 μA shutdown pin should be as close to GND as much as possible to achieve the minimum shutdown current. See the following application information closing function to get more information.

(7) The typical output power number is suitable for LM4670 in ITL (DSBGA) packaging. In the WSON (SDA) package, the output power will be low because of higher resistance from IC output pad to PCB traces, so it will be lower. As the impedance load decreases, this difference increases.

(8) When the driver 4 load to 10%THD+N, the maximum working voltage of LM4670 in the SDA (WSON) component is 5.0 volts.

Electrical characteristics (1) (2) (continued)

The following specifications are applicable to AV u003d 2V/V (ri u003d 150k ), RL u003d 15μH+8 + 15 μH, unless there are other regulations. Restricted to TA u003d 25 ° C.

] Application information

Universal amplifier function

Output consists of two signals, consisting of two signals from near -ground potential to VDD. The two outputs can be independent of the vein, except that they may never have the same pulse, because this will cause the voltage on the BTL load to be zero. The width of the minimum value of each pulse is about 350ns. However, the pulse on the same output can appear in order. In this case, they are connected in series and displayed as a single wider pulse to achieve an effective 100%duty cycle. This will generate the maximum audio output power under the given power supply voltage and load impedance. LM4670 can achieve higher efficiency than class AB, while maintaining acceptable THD performance. The short (350ns) driving arteries emitted at the LM4670 output end means that the minimum load can be used. The typical sensor load on the audio amplifier is very unresponsive (induction). For this, the load can be used as its own filter. This ""filter -free"" switch amplifier/sensor load has saved the cost of circuit board space and external component costs. This combination is more economically attractive and does not require filter.

Power consumption and efficiency

Generally speaking, efficiency is considered to be useful for the total energy output of the required total energy to generate its power consumption, usually in integrated circuits. HereThe key is ""useful"" job. For the audio system, the energy transmitted in the hearing band is considered useful, including the input signal. Yinyin speed (DC) and supersonic components (u0026 gt; 22kHz) do not work. The difference between the two comes from the power of the power supply and the transformed audio frequency band power in LM4670 and the sensor load. The power consumption of LM4670 is very low. This is because the informant resistance for forming a switch for output waveforms is usually less than 0.25 This leaving only a small part of the sensor load as the potential ""sink"" is a small part of the input power exceeding the audio band output power. LM4670 only consumes a small part of excess power, and does not require additional PCB area or copper plane as a heat sink.

Differential amplifier description

As the analog voltage continues to narrow, the designer is constantly shrinking the digital signal to maintain a signal -to -noise ratio when limiting voltage swing. LM4670 is a completely different amplifier with differential input and output. Differential amplifier amplifies the two input signals. Traditional audio power amplifiers usually only provide single -end input relative to differential inputs, and the signal -to -noise ratio is reduced by 6 decibels. The LM4670 also provides DC input coupling, eliminating two external AC coupling and DC closed lock capacitors. LM4670 can be used as a single -end input amplifier, while still retaining its completely different advantages. In fact, a completely irrelevant signal can be placed on the input pin. LM4670 only enlarged this difference between signals. One of the main advantages of differential amplifiers is that the co -mode suppression ratio (CMRR) is improved on a single input amplifier. The co -mode inhibitory characteristics of the differential amplifier reduce the sensitivity of the injection of noise -related noise in the ground, which is particularly important in high noise applications.

PCB layout precautions

As the output power increases, the amplifier, load and power supply generate voltage drop. The voltage loss on the record channel between LM4670 and the load result is reduced to the output power and the efficiency is reduced. The high -track resistance between the power supply and the LM4670 is the same as that of improper adjustment of the power supply. Increasing the ripple on the power line will also reduce the peak output power. Due to the high output power, the impact of the residual tracking resistance increases as the output current increases, and the load impedance decreases or both. Maintain the maximum output voltage swing and the corresponding peak output power supply, and the PCB trajectory of the connected output pins to the PCB trajectory of the load and the power supply foot to the power supply should be as wide as possible to minimize the trace resistance. The use of power and ground aircraft will provide the best THD+N performance. While reducing the amount of trace resistance, the use of electric aircraft can also produce parasitic capacitors, which helps filter the power cord.

The rising edge and decline edge must be short relative to the minimum pulse width (350ns), and it has a typical up and down time of about 16ns, depending on the parasitic output capacitor. One or two sides of the inductive sensor load will also cause overwhelming, and the parasitic diode is cut to each case.GND and VDD. From the perspective of electromagnetic interference, this is a kind of aggressive waveform that can radiate or transmit to other components in the system. Keeping power and output trajectory is crucial. If possible, it should be short and well protective. The use of ground plane, beads, and micro -band layout techniques are useful to prevent unnecessary interference. As the distance between LM4670 and speakers increases, EMI radiation volume will become more effective as the output line or trace line of the antenna as the length of the antenna. What is acceptable electromagnetic interference is high -specific to the application. The ferrous oxygen -type electromoter placed near LM4670 may need to reduce EMI radiation. Special application value of iron oxygen chip.

Power bypass

Like any power amplifier, the correct power bypass is important for low noise performance and high power supply (PSRR). The position of the capacitor (CS) should be as close to LM4670 as possible. In a typical application, the voltage regulator has 10 μF and 0.1 μF bypass electrical container, which can improve the stability of power supply. These capacitors cannot eliminate the need for the LM4670 power pins. 1 μF 议 It is recommended to use a capacitor.

Shipping function

In order to reduce power consumption without use, the LM4670 contains the reduction of the current consumption of less than 0.01 μA. Typical values u200bu200bin the shutdown trigger point are displayed in the parking characteristics and stagnation voltage diagrams in the electrical system. The typical performance characteristics are found. It is best switched between ground and power in the shutdown state to achieve minimum current use. The LM4670 may be suspended under the stop voltage between the ground and the power supply, and the idling current will be higher than the typical 0.01μA value. When the voltage is lower than the VDD, you can also observe that THD increases the pins in the playback mode. LM4670 has an internal resistor connected between GND and shutdown pins. The role of this resistor is to eliminate any unwanted state changes when the shutdown pin floats. LM4670 will enter the shutdown state when the shutdown pin is kept floating, or if there is no floating, the shutdown voltage exceeds the threshold. In order to minimize the power current when shutting down, the shutdown pins should be driven to GND or left. If the stop pin is not driven to GND, the internal turnover resistance can be obtained by Formula 1. (VSD-grounding)/300K

In the case of only 0.5V difference, it will consume an additional 1.7 μA current in a shutdown state. Correctly select the gain of the external component LM4670 is set by the external resistance RI. In Figure 1, the gain is given by Formula 2. The best THD+N performance reaches the gain of 2V/V (6DB). The average u003d 2*150 k /RI (5/5) It is recommended to use a resistor with a tolerance of 1%or better to set the gain of LM4670. The international support social resistance should be close to the input pin of LM4670. Keep input trajectoryIt is close to each other in a high noise environment. The CMRR of the same length is good, helping to suppress noise LM4670. The noise on the input trajectory that is coupled to physical close to each other will be co -models, and it is easily rejected by LM4670. In some applications or when the power supply is a single -end, a capacitor may be required (see Figure 27 and Figure 29). The input capacitor needs to block any DC voltage at the power supply so that you can see that the input terminal of the DC voltage LM4670 is 0V. The input capacitor uses input to generate a high -pass filter resistance, RI. The -3DB point of Qualcomm filter can be found through Formula 3. FC u003d 1/(2πri Ci) (Herz)

Input capacitors can also be used to remove bass frequency. Small speakers cannot reproduce the bass low audio therefore may need to be filtered. When the LM4670 uses a single -ended power supply, the noise on the power supply is coupled by the+input pin on the ground to the ground (see Figure 29 to 31). Set the high -pass filter point to a higher than the power noise frequency of 217Hz (A), for example, the GSM mobile phone will filter these noise, so that it will not be enlarged and hear it at the output end. Capacitor impedance matching is recommended to 10%or better.

Differential circuit configuration

LM4670 can be used for a variety of different circuit configurations. The simplest and best performance is the DC coupling differential input configuration as shown in Figure 26. The above equivalence 2 is used to determine the resistance required by the international support agency. The input capacitor can be used in the differential configuration shown in FIG. 27. The above formula 3 is used to determine the value of the CI capacitor to obtain the frequency response of expectations, which is from CI and RI. The above formula 2 is used to determine the value of the RI value. The resistor LM4670 can be used to enhance most of the audio sources. Figure 28 shows a dual -differential input configuration. Each input gain can be set up independently to obtain the maximum design flexibility for each input and equation 2 resistor. The input capacitor can be used for one or more power supply, and different frequency responses depends on whether the power or DC voltage needs to be blocked with the power supply.

Single -end circuit configuration

LM4670 can also be used for single -end power supply, but you need to enter a capacitor to block any DC AT input terminal. Figure 29 shows a typical single -end application configuration. The gain equation, equation 2 and frequency response equation 3 are suitable for single -end structure, as shown in Figure 29. When multiple single -end power supply is used, as shown in Figure 30, the impedance terminals of each input terminal should be equal. To find the correct value of CI3 and RI3 connected to the input pin+in, all single -end source impedance is calculated. Single -ended sources are parallel to each other. By calculating the parallel combination of all capacitors and resistors, the equivalent capacitance and resistance CI3 and RI3CIVALUES are obtained and then all RI values. The following equations 4 and Formula 5 are suitable for a single -end source of any amount.

CI3 u003d CI1+CI2+CIN. Essence Essence (F)

RI3 u003d 1/(1/RI1+1/RI2+1/Rin… ( )

LM4670 can also use a combination of single -ended and differential sources. A typical example The application single -end source and a difference source are shown in Figure 31. The value of the external component of the superposition principle can be determined by the above -mentioned equations corresponding to the configuration.

In addition to the minimum parts required for the application circuit, the circuit board is evaluated, so that traditional audio measure No additional equipment is required. This is a balanced input, the ground differential output low -pass filter, the 3DB frequency is about 35kHz, the upper terminal resistance is 300 Common modular suppression is not the best, but because the independent pulse format has a large number of components on each output end. Analyze the high -frequency co -mode suppression ratio of the instrument. Even if the ground filter is used, the audio signal is still different, so the instrument is connected to any analysis. Instruments, they are not different because BNC's ring is often grounded. Common audio accuracy analyzers are different, but it can accurately reject the width of the pulse 350ns. Therefore, it is necessary to install a car measurement filter. When there is Questions or signals require a single -end, using a audio signal converter to convert the differential output to a single -end output. According to the characteristics of the audio converter, there may be some attenuation of the audio signal to measure the performance correctly. The measurement performed by the output terminal is attenuated than an audio output compared to the unique main filter. This is the resistor (300 ) caused by the resistance of an inductor that interacts with the terminal, usually about -0.25db (3%). In other words, the voltage level (and the corresponding power is slightly lower than the actual value when the level displayed by the filter is placed on the unique output. The lower output power reading ratio is actually in the case where the output and the load that occurs in unique.