Datasheet

www.ti.com
5-V VERSUS 3.3-V OPERATION
TPA4861
SLOS163C – SEPTEMBER 1996 – REVISED JUNE 2004
The TPA4861 was designed for operation over a supply range of 2.7 V to 5.5 V. This data sheet provides full
specifications for 5-V and 3.3-V operation, as these are considered to be the two most common standard
voltages. There are no special considerations for 3.3-V versus 5-V operation as far as supply bypassing, gain
setting, or stability. Supply current is slightly reduced from 3.5 mA (typical) to 2.5 mA (typical). The most
important consideration is that of output power. Each amplifier in TPA4861 can produce a maximum voltage
swing of V
DD
– 1 V. This means, for 3.3-V operation, clipping starts to occur when V
O(PP)
= 2.3 V as opposed to
when V
O(PP)
= 4 V while operating at 5 V. The reduced voltage swing subsequently reduces maximum output
power into an 8-Ω load to less than 0.33 W before distortion begins to become significant.
Operation at 3.3-V supplies, as can be shown from the efficiency formula in Equation 4 , consumes approximately
two-thirds of the supply power for a given output-power level than operation from 5-V supplies. When the
application demands less than 500 mW, 3.3-V operation should be strongly considered, especially in
battery-powered applications.
20