Table of Contents
Advertisement
www.ti.com
1.2
TPA3251D2EVM Frequency Adjust
The TPA3251D2EVM offers hardware trimmed oscillator frequency by external control of the FREQ_ADJ
pin. The Frequency adjust can be used to reduce interference problems while using a radio receiver tuned
within the AM band, the switching frequency can be changed from nominal to lower values. These values
should be chosen such that the nominal and the lower value switching frequencies together results in the
fewest cases of interference throughout the AM band. The oscillator frequency can be selected by the
value of the FREQ_ADJ resistor connected to GND in master mode according to
For slave-mode operation, turn off the oscillator by pulling the FREQ_ADJ pin to DVDD. This configures
the OSC_I/O pins as inputs to be slaved from an external differential clock. In a master/slave system inter-
channel delay is automatically setup between the switching phases of the audio channels, which can be
illustrated by no idle channels switching at the same time. This will not influence the audio output, but only
the switch timing to minimize noise coupling between audio channels through the power supply. This will
optimize audio performance and result in better operating conditions for the power supply. The inter-
channel delay will be setup for a slave device depending on the polarity of the OSC_I/O connection such
that slave mode 1 is selected by connecting OSC_I/O of the master device in phase with OSC_I/O of the
slave device (+ to + and – to –), while slave mode 2 is selected by connecting the OSC_I/O's out of phase
(+ to – and – to +).
1.3
TPA3251D2EVM Single-Ended and Differential Input
The TPA3251D2EVM supports both differential and single-ended inputs. For single-ended inputs, J4
and/or J19 jumpers are set to the SE position, so that the TPA3251D2EVM uses the NE5532 to convert
the single-ended input signal to differential to properly drive the differential inputs of the TPA3251D2. The
input RCA jack, J3, is used to provide INA and INB inputs and RCA jack J18 is used to provide INC and
IND inputs with single-ended inputs.
For differential input operation, J4 and/or J19 jumpers are set to the DIFF position, and the
TPA3251D2EVM uses the NE5532 to buffer the differential input signal to the differential inputs of the
TPA3251D2. The input RCA jack, J3, is used to provide INA, RCA jack J14 provides INB, RCA jack J18
provides INC, and RCA jack J15 provides IND with differential inputs.
NOTE: Single-ended input settings on the TPA3251D2EVM should only be used for channels with
output configuration BTL or PBTL, not SE. For SE output configuration J4 and/or J19
jumpers for that channel must be set to the DIFF position, so the input signal INx is mapped
directly to OUTx.
SLVUAG8A – September 2015 – Revised October 2015
Submit Documentation Feedback
Table 1. Frequency Adjust Master Mode Selection
Master Mode
Nominal
AM1
AM2
Copyright © 2015, Texas Instruments Incorporated
Table
Resistor to GND
10 kΩ
20 kΩ
30 kΩ
Hardware Overview
1.
3
TPA3251D2EVM
Advertisement
Table of Contents
