Tri p ath Techn o l o g y, I n c. - T echn i cal I n fo rmation

10

TCA2002 – KLi/0.95/04.06

Inpu t Ca pa c i tor Se le c t ion

I

P

I

R

f

2

1

C

π

=

where:

I

P

Mo d u lato r F eed b ack Desig n

The modulator feedback converts the high-voltage output-switching signal to voltage levels that the

TCA2002 can process. The optimum gain of the modulator is determined from the maximum

allowable feedback level for the modulator and maximum supply voltage for the power stage.

Depending on the maximum supply voltage, the feedback ratio will need to be adjusted for proper

define the gain of the modulator. In addition, the amplifier architecture affects the value of the

feedback resistor values. Once these values are chosen, based on the maximum supply voltage, the

gain of the modulator will be fixed even as the supply voltage changes. Thus, an amplifier based on

TCA2002 has inherent PSRR unlike many other commercially available switching amplifiers.

For the best signal-to-noise ratio and lowest distortion, the maximum differential modulator feedback

voltage should be approximately 4Vpp. This will keep the gain of the modulator as low as possible

and still allow headroom so that the feedback signal does not clip the modulator feedback stage.

Mo d u lato r F eed b ack Desig n

For SPLIT-SUPPLY, SINGLE ENDED operation:

Figure 3: Split Supply, Single Ended Circuit (One Channel)

Figure 3 shows the basic split supply, single ended amplifier using a TCA2002. The MOSFET output

stage operates from two power supplies, VPP and VNN, that are equal magnitude, but opposite

polarity (for instance +/-60VDC). One terminal of the load is driven by the half-bridge MOSFET

output stage. The other load terminal is ground referenced. Differential feedback is taken from the

FET Driver

TCA2002

MOSFETS

Y1

Y1B

HIN

LIN

HS OUT

LS OUT

HS GATE

LS GATE

VPP

VNN

FBKN1

FBKP1

HB OUT

R

FBB

V5

R

FBC

R

FBB

V5

R

FBC