FAN7031 Datasheet, PDF (17/20 Pages) Fairchild Semiconductor – 2W Stereo Power Amplifier with Four Selectable Gain Setting and Headphone Drive

FAN7031
BLT Mode of Operation vs. Single Ended Mode of Operation
The FAN7031 offers both BTL (Bridge-Tied Load) and SE (Single Ended) operation. When SE/BTL pin is low, BTL
operation is selected. In BTL operation, maximum output power is increased 4 times comparing with SE operation
at the same load, output swing and supply condition because output swing is doubled. Thus, BTL mode is useful to
drive a speaker load. On the other hand, when SE/BTL pin is high, one amplifier configured BTL driver is turned off
and only single amplifier is activated. In this mode, maximum output power is reduced and the quiescent power
consumption is saved about half. Thus, SE mode is adequate for head-phone load. The output power of BTL and
SE are expressed as follows respectively:
PBTL = ₂---^V--_â‹--^p-_R---²--_L-- ,
PSE
=
---^V----^p----²----
8 ⋅ RL
.
To use the amplifier in SE mode, the output DC voltage must be blocked not to increase power consumption. Thus,
the load is tied to output via output DC blocking capacitor. The capacitor size can be chosen using above f-3dB
equation. For example, assuming the load impedance is 32W, 249uF capacitor guarantees 20Hz signal transmis-
sion to the load without gain reduction.
Shutdown Mode
The device moves to a shutdown mode when the shutdown pin is at 0V. For normal operation the shutdown pin
should be at VDD. This pin should never be left unconnected.
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