Dialog UM-DA7202 Manuale d'uso - Pagina 7

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DA7202 10 W mono class D amplifier for 2S systems
UM-DA7202 evaluation board
4.1

Power supply

The DA7202 has high power supply rejection ration (PSRR) and may be run directly from a 2S
lithium-ion battery or, for evaluation purposes, a bench supply.
4.2

Analogue input

The analogue input connection contains DC block capacitors (C1 and C9) which allow an input signal
with any DC level within the recommended operating conditions to be connected.
4.2.1

Lower gain configuration

DA7202 has a fixed +18 dB gain in the signal path. The input signal amplitude can be reduced with
an external resistor creating a divider with the internal device impedance. This can be achieved by
replacing resistor sites R1 and R2 (shorted by default) with resistor values using the following
formula:
Where:
●
30 kΩ = the input impedance for DA7202
●
Rext = the resistor value required at both R1 and R2
4.2.2

Single-ended input

In normal operation, the input to the EVB is differential. To use a single-ended input, connect the
input signal to J4 pin 2 and the 0 V/GND to J4 pin 3, see schematic diagram in Figure 3.
J4 can be accessed from the rear of the board. Alternatively, J3 can be removed for top access to J4.
4.3

Speaker output

An inductive 4 Ω or 8 Ω speaker load can be connected directly to J5. The length of the speaker
cable must be kept as short as possible to minimise electromagnetic interference (EMI).
4.3.1

Additional filtering

There is no EMI filtering on the EVB as default. As can be seen from the schematic diagram in Figure
3, provision has been made to allow a filter to be added to sites FB1, FB2, C10, C11, C2 and C3, as
well as L1, L2, C12 and C13. Examples of when the filtering options can be useful are if the speaker
load is non-inductive or if the speaker cable is long.
As default, the shorting points at SP1 and SP2 are short via a solder connection to bypass the filter
but allow the output signal to reach J5.
User Manual
CFR0012
Ω
240
k
A
=
20Log(
)
V
R
X
Ω
+
R
=
30
k
Rext
X
Revision 2.0
7 of 12
28-Mar-16
© 2016 Dialog Semiconductor