TA3020 Ver la hoja de datos (PDF) - Tripath Technology Inc.

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componentes Descripción

Fabricante

TA3020

Stereo 300W (4Ω) Class-T Digital Audio Amplifier Driver using Digital Power Processing™ Technology

Tripath Technology Inc. 

TECHNICAL INFORMATION

One apparent method to generate the VN10 supply voltage is to use a negative IC regulator to drop

PGND down to 10V (relative to VNN). This method will not work since negative regulators only sink

current into the regulator output and will not be capable of sourcing the current required by VN10.

Furthermore, problems can arise since VN10 will not track movements in VNN.

Output Transistor Selection

The key parameters to consider when selecting what MOSFET to use with the TA3020 are drain-

source breakdown voltage (BVdss), gate charge (Qg), and on-resistance (RDS(ON)).

The BVdss rating of the MOSFET needs to be selected to accommodate the voltage swing between

VSPOS and VSNEG as well as any voltage peaks caused by voltage ringing due to switching transients.

With a ‘good’ circuit board layout, a BVdss that is 50% higher than the VPP and VNN voltage swing

is a reasonable starting point. The BVdss rating should be verified by measuring the actual voltages

experienced by the MOSFET in the final circuit.

Ideally a low Qg (total gate charge) and low RDS(ON) are desired for the best amplifier performance.

Unfortunately, these are conflicting requirements since RDS(ON) is inversely proportional to Qg for a

typical MOSFET. The design trade-off is one of cost versus

lower I2RDS(ON) losses but the associated higher Qg translates

performance. A lower RDS(ON) means

into higher switching losses (losses =

Qg x 10 x 1.2MHz). A lower RDS(ON) also means

means lower cost and lower switching losses but

a larger silicon

higher I2RDSON

die and

losses.

higher

cost.

A higher RDS(ON)

The following table lists BVdss, Qg and RDS(ON) for MOSFETs that Tripath has used with the

TA3020:

Manufacturer

ST Microelectronics

ST Microelectronics

International Rectifier

International Rectifier

Fairchild

Manufacturer’s

Part Number

STW34NB20

STP19NB20

IRFB41N15D

IRFB31N20D

FQA34N20

BVdss

200

200

150

200

200

Qg

(nanoCoulombs)

60

29

67

70

60

RDS(ON) (Max)

(Ohms)

0.075

0.18

0.045

0.082

0.075

Gate Resistor Selection

The gate resistors, RG, are used to control MOSFET switching rise/fall times and thereby minimize

voltage overshoots. They also dissipate a portion of the power resulting from moving the gate

charge each time the MOSFET is switched. If RG is too small, excessive heat can be generated in

the driver. Large gate resistors lead to slower MOSFET switching, which requires a larger break-

before-make (BBM) delay.

Break-Before-Make (BBM) Timing Control

The half-bridge power MOSFETs require a deadtime between when one transistor is turned off and

the other is turned on (break-before-make) in order to minimize shoot through currents. BBM0 and

BBM1 are logic inputs (connected to logic high or pulled down to logic low) that control the break-

before-make timing of the output transistors according to the following table.

24

TA3020, Rev 2.1, 01.01

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