Preliminary Technical Data
WM3100
DEVICE DESCRIPTION
INTRODUCTION
The WM3100 is a high-performance stereo line driver designed for Digital televisions, DVD, Blu-ray,
set-top box and gaming applications. It is packaged in a 14-pin SOIC.
The device comprises two fixed gain analogue channels. Input signals up to 1VRMS are supported, in
single-ended or differential configurations. The output driver drives up to 2.1VRMS, assuming a 3.3V
supply.
The inputs and outputs to the WM3100 are ground-referenced; an integrated charge pump circuit
generates the required negative supply rail from the single VDD supply.
The analogue outputs can be muted under control of a digital logic input. The outputs can also be set
to a high impedance state, supporting applications where a common external connector is used as
an input and an output.
INPUT SIGNAL PATH
The WM3100 supports two line input channels, which can each be used in single-ended or
differential circuit configurations, as illustrated in Figure 1, Figure 2 and Figure 3. The signal gain is
6.4dB in each case.
The input capacitor must be correctly selected as it affects the low cut-off frequency of the input
circuit. A low cut-off frequency is desirable as it means that there is no significant filtering of the 20Hz
to 20kHz audio frequency bandwidth.
Typically, the 3dB cut-off frequency for the line input should be around 10Hz. The WM3100 input
impedance is 24kΩ (see “Electrical Characteristics”). Using the equations below, it follows that the
AC coupling capacitors should be approximately 1μF (which gives a 3dB cut-off frequency around
7Hz).
Figure 1 Single-Ended Line Input (Inverting)
Figure 2 Single-Ended Line Input (Non-Inverting)
PTD, October 2010, Rev 2.0
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
