TS4900ID View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

TS4900ID

300mW at 3.3V SUPPLY AUDIO POWER AMPLIFIER WITH STANDBY MODE ACTIVE HIGH

STMicroelectronics 

TS4900

■ BTL Configuration Principle

The TS4900 is a monolithic power amplifier with a

BTL (Bridge Tied Load) output configuration. BTL

means that each end of the load is connected to

two single ended output amplifiers. Thus, we have:

Single ended output 1 = Vout1 = Vout (V)

Single ended output 2 = Vout2 = -Vout (V)

bandwidth by adding a capacitor (Cfeed) in parallel

with Rfeed. Its form a low pass filter with a -3dB cut

off frequency

FCH = --2----π------R-----f--e----1e---d------C----f--e---e----d- (Hz)

■ Power dissipation and efficiency

Hypothesis :

And Vout1 - Vout2 = 2Vout (V)

• Voltage and current in the load are sinusoidal

(Vout and Iout)

The output power is :

t(s) Pout = (2 Vout RMS )2 (W)

RL

uc For the same power supply voltage, the output

rod power in BTL configuration is four times higher

P t(s) than the output power in single ended

configuration.

lete uc ■ Gain In Typical Application Schematic

d (cf. page 1)

so ro In flat region (no effect of Cin), the output voltage

b P of the first stage is :

) - O lete Vout1 = –Vin R-----f-R-e---i-e-n---d---- (V)

t(s so For the second stage : Vout2 = -Vout1 (V)

uc Ob The differential output voltage is

Prod t(s) - Vout2 – Vout1 = 2Vin R-----f-R-e---i-e-n---d---- (V)

lete uc The differential gain named gain (Gv) for more

d convenient usage is :

bso Pro Gv = V-----o---u---t--2--V---–--i--nV-----o---u----t--1-- = 2 R-----f-R-e---i-e-n---d----

O lete Remark : Vout2 is in phase with Vin and Vout1 is

o 180 phased with Vin. It means that the positive

sterminal of the loudspeaker should be connected

Obto Vout2 and the negative to Vout1.

• Supply voltage is a pure DC source (Vcc)

Regarding the load we have:

VO UT = VPEAK sin ω t (V)

and

IOUT = -V----OR----U-L---T--- (A)

and

PO UT = V-----P--2-E--R--A---LK----2--- (W)

Then, the average current delivered by the supply

voltage is:

ICC AVG = 2 V-----πP----ER---A--L-K---- (A)

The power delivered by the supply voltage is

Psupply = Vcc IccAVG (W)

Then, the power dissipated by the amplifier is

Pdiss = Psupply - Pout (W)

Pdi ss = -2--------2---V-----c---c-- POUT – PO UT (W)

π RL

and the maximum value is obtained when:

∂--∂--P--P--d--O--i--sU---s-T--- = 0

■ Low and high frequency response

and its value is:

In low frequency region, the effect of Cin starts.

Cin with Rin forms a high pass filter with a -3dB cut

off frequency

Pdiss max

=

2 Vcc2

π2RL

(W)

FCL = --2----π------R---1--i--n-----C----i--n- (Hz)

Remark : This maximum value is only depending

on power supply voltage and load values.

In high frequency region, you can limit the

The efficiency is the ratio between the output

15/19

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