M4670

Preliminary

CMOS IC

UNISONICTECHNOLOGIESCO.,LTD

6 of 9

www.unisonic.com.tw

QW-R502-442.b

APPLICATION INFORMATION

GENERAL AMPLIFIER FUNCTION

The M4670 output signal consists of two, BTL connected, of course, the output signal can also be a pulse signal,

the minimum width of each pulse is approximately 350ns. The two outputs can pulse independently exception that

they both may never pulse simultaneously as this would result in zero volts across the BTL load. But in the same row

of as the output pulse occurred in this case, they are connected together, as a broader pulse, to achieve an effective

100% duty cycle occurs. For a given supply voltage and load impedance, the maximum audio output power effects.

The M4670 chip can achieve much high efficiencies than the class AB amplifier, while maintaining acceptable THD

performance.

The short driver pulse output means, a good efficiency can be issued with the M4670 inductive load. For the

typical sensor load audio amplifier is a very passive. To this end, the load can act as its own filter.

POWER DISSIPATION AND EFFICIENCY

In general, efficiency is considered useful in the work required to produce a different power dissipated in the

integrated circuit usually it is divided by the total energy output ratio. For audio systems, the energy delivered in the

audible bands is considered useful including the distortion products of the input signal. Sub-sonic (DC) and

super-sonic components (>22kHz) are not useful. The difference between the power flowing from the power supply

and the audio band power being transduced is dissipated in the M4670 and in the transducer load. The amount of

power dissipation in the M4670 is very low. This is because the on resistance of the switches used to form the output

waveforms is typically less than 0.25Ω. This leaves only the transducer load as a potential "sink" for the small excess

of input power over audio band output power. The M4670 dissipates only a fraction of the excess power requiring no

additional PCB area or copper plane to act as a heat sink.

DIFFERENTIAL AMPLIFIER EXPLANATION

The M4670 is a fully differential amplifier with differential input and output stages. A differential amplifier

amplifies the difference between the two input signals. Traditional audio power amplifiers have typically offered only

single-ended inputs resulting in a 6dB reduction in signal to noise ratio relative to differential inputs. The M4670 also

provides the possibility of DC input coupling, eliminating the need for two external AC coupling, DC blocking

capacitors. The M4670 also can be used, but as a single-ended input amplifier while still retaining it is an entirely

different interests. The main advantage of a differential amplifier is to increase common-mode rejection ratio (CMRR)

for a single input amplifier.

SHUTDOWN FUNCTION

In order to reduce power consumption while not in use, the M4670 contains shutdown circuit current

consumption reduced to less than the reduced 0.01μA. For the closure of trigger point is displayed as a table of

electrical characteristics and typical shutdown hysteresis voltage diagram found in some of the typical performance

characteristics. The best is to switch on the ground and use the smallest current supply, while in the closed state.

The M4670 may be disabled chip off the ground and supply voltage, the idle current is larger than the typical value of

reduced 0.01μA. Total harmonic distortion may increase, but also can be observed when the voltage is less than the

diameter of the shutdown pin in PLAY mode.

There has a resistor connected between GND and Shutdown pins in the M4670 internal, and this resistor is

designed to eliminate any unnecessary state changes, when the Shutdown pin is floating. To minimize the supply

current when the M4670 working in the Shutdown mode, if the M4670 don’t working in the Shutdown mode, the

amount of additional resistor current due to the internal shutdown resistor can be found be Equation (1) below.

The difference is only 0.5V, the current additional 1.7μA, lots will be drawn, while in the closed state.