UM11057
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© NXP B.V. 2017. All rights reserved.
User Manual
Rev. 1.0 — 9 June 2017
12 of 14
NXP Semiconductors
UM11057
User Manual
7.4 Speaker driver
The LPC845 DACOUT output PIO0_29 is route to an IS31AP4991 speaker driver (see
Integrated Silicon Solutions web site for datasheet). This device can drive 8 to 32 ohm
speakers; a 32 ohm speaker is supplied with the board and resistors have been selected
to provide a reasonable volume level for musical tones. If desired, a capacitor can be
added in parallel with the speaker driver feedback resistor, in order to reduce the speaker
circuit bandwidth and reject DAC output sampling artifacts. This capacitor can be added
using the through holes with circuit reference designator C26 (also called CAP NP in the
schematic.)