Class AB audio amplifier with mono speaker and stereo headphone outputs
The Texas Instruments LM4851ITL is a Boomer® Class AB audio amplifier that delivers 1.5W into a 4Ω mono speaker load while simultaneously driving 115mW per channel into 32Ω stereo headphones, all from a 2.6V to 5V supply. This output architecture suits portable devices where a single speaker handles ringtones or hands-free calls and a headphone jack provides private listening — the amplifier handles both loads from one IC.
Integrated features for portable audio design
Built-in depop circuitry suppresses the audible pop and click when the amplifier transitions between shutdown and active states, eliminating the need for external muting FETs or series capacitors on the output. A SPI bus provides digital volume control and allows the host processor to adjust gain without a separate potentiometer or resistor network — the interface also reads back fault status from the thermal protection block. Thermal protection shuts down the output stage if the die temperature exceeds the safe operating limit, protecting the speaker load and the IC during sustained high-power playback in a confined enclosure.
Housed in an 18-bump WFBGA (18-uSMD, 1.97x2.23 mm), the LM4851ITL requires a surface-mount reflow profile compatible with lead-free solder — the small footprint saves board area in space-constrained portable designs. The 2.6V to 5V supply range covers single-cell Li-ion battery voltage (3.0-4.2V) with margin for the battery's full discharge curve, so the amplifier continues operating down to the battery's undervoltage lockout threshold.
RoHS compliance is not claimed for this date-code variant — the part is listed as RoHS non-compliant, which matters for BOMs that must meet EU RoHS exemption thresholds or customer-specific green-material declarations.