Gain control BTL D audio power amplifier and its application TPA3007D1

1 Overview

PWM modulation technique using D (switch type) audio power amplifier with its high efficiency, low power consumption characteristics, than other types (such as A Class, B Class and Class AB) power amplifiers for more advantages and thus with audio-enabled devices, especially portable applications dominate.

Texas Instruments (TI) is the production of audio-power chip is one well-known manufacturers. The company's Class D audio power amplifier has been developed to the third generation.

TI's third-generation Class D audio power amplifier ICs are controlled with less than 1μA shutdown current, and typically 7mA or low 8mA supply current, which are innovative modulation technique does not require or require only low-cost small output filter. As the package to solve the heat problem, so no need to use the heat sink. This new generation of Class D power amplifier chip output power and the relationship between the temperature curve was flat, and this is class AB amplifier can not be compared. They are all the devices are built to bang sound / to a click circuitry, which can effectively eliminate the on / off noise, while chips are built-in short circuit protection and thermal shutdown circuit, thus increasing the device itself and the system reliability.

TPA3007D1 is TI's recently launched BTLD 6.5W mono audio power amplifier chip, the chip's efficiency up to 85% @ Vcc = 12V or more, and with 12dB, 18dB, 23.6dB and 36dB gain to the four for control and choice. Applications include LCD monitors, TVs, PCs, car hands-free kit and power powered loudspeakers. 2 TPA3007D1 the structure and function

24-pin TSSOP package, the TPA3007D1 chip pin arrangement shown in Figure 1.

Gain control BTL D TPA3007D1 audio power amplifier and its application

TPA3007D1 with bias and internal voltage reference, and gain control circuit, PWM modulation circuit, gate driver, consisting of four MOSFET H-bridge power pole and short-circuit detection and thermal shutdown protection circuit, Figure 2 is a block diagram of its internal structure.

TPA3007D1's supply voltage (Vcc / PVcc) range of 8 ~ 18V (typically 12V); load impedance RL is greater than 7Ω; its GAIN0, GAIN1 and SHUTDOWN pin high level input voltage VIH should be greater than 2V; low input voltage VIL should be less than 0.8V; TPA3007D1 working temperature range of -40 ~ +85 ℃.

Gain control BTL D audio power amplifier and its application TPA3007D1

3 third-generation modulation scheme

TPA3007D1 innovative modulation schemes. Although each output (OUTP and DUTN) range is still from 0V to VCC (12V), but no input, OUTP and OUTN the same phase. For the positive output voltage, OUTP is greater than 50% duty cycle, while the OUTN is less than 50% duty cycle. The negative output voltage, OUTP is less than 50% duty cycle, while OUTN duty cycle greater than 50%. Most of the switching cycle time, the voltage across the load is 0V. In this modulation, the load on the differential voltage magnitude is not 2VCC, but the VCC, thus greatly reducing the switching current and ripple current and load losses (I2R). As the load on the differential voltage pulse is very narrow, which can save the output filter. Only in the output power is large, because the output pulse broadening, the ripple current increases, in order to improve efficiency, it needs a hole in a small ferrite bead (ferrite bead) filter.

Figure 3 is the third generation of modulation schemes for voltage and current waveforms.

Gain control BTL D TPA3007D1 audio power amplifier and its application

4 Application Circuit

Formed by a 6.5W BTLD TPA3007D1 audio power amplifier circuit shown in Figure 4. The figure, U1 (TPA3007D1) oscillator frequency fosc by 20 feet and 21 feet outside the resistor R1 outside the capacitor C12 is set to 250kHz fosc = 6.6 / (R5 · C12). Amplifier gain can be 3 feet by U1 and 4 feet to set it up.

When the TPA3007D1 to 5 feet (SHUTDOWN pin) is high (greater than 2V) when, IC work. If the pin is pulled low, IC will enter the closed mode. In the closed state, the amplifier output mute, time consuming only 1μA of supply current.

Gain control BTL D audio power amplifier and its application TPA3007D1

U1's output OUTP and OUTN connections L1, C14 and L2, C15 may form the output filter. Where, L1 and L2 is small chip ferrite beads with holes (ferritechip bead) model for the Fair Rote2512067007Y3. Filter cutoff frequency of 1MHz, can be used to reduce the EMI, in order to meet FCC and CE standards requirement. The L1 and L2 should be present at high frequencies with high impedance, low impedance at low frequencies present. OUTP and OUTN feet and connect the Schottky diode D1 and D2 B130 for the transient absorption peak output pulse and to output short circuit protection. D1 and D2 in the forward voltage drop under 1A should be less than 0.5V, voltage should be greater than 30V.

TPA3007D1 internal short-circuit detection circuit. When short circuit occurs, the output drivers rapidly closing, so the device into shut down mode.