wm8918 Wolfson Microelectronics plc, wm8918 Datasheet - Page 71

• Manufacturer Part Number: wm8918
• Description: Ultra Low Power Dac For Portable Audio Applications
• Manufacturer: Wolfson Microelectronics plc

Production Data
ANALOGUE OUTPUTS
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The WM8918 has four analogue output pins:
The output signal paths and associated control registers are illustrated in Figure 37.
HEADPHONE OUTPUTS – HPOUTL AND HPOUTR
The headphone outputs are designed to drive 16Ω or 32Ω headphones. These outputs are ground-
referenced, i.e. no series capacitor is required between the pins and the headphone load. They are
powered by an on-chip charge pump (see “Charge Pump” section). Signal volume at the headphone
outputs is controlled as shown in Table 43.
The ground-referenced outputs incorporates a common mode, or ground loop, feedback path which
provides rejection of system-related ground noise. The return path for the HPOUTL and HPOUTR
outputs is via HPOUTFB. This pin must be connected to ground for normal operation of the
headphone output. No register configuration is required.
LINE OUTPUTS – LINEOUTL AND LINEOUTR
The line outputs are identical to the headphone outputs in design. They are ground-referenced and
powered by the on-chip charge pump. Signal volume at the line outputs is controlled as shown in
Table 44.
Note that these outputs are intended for driving line loads, as the charge pump powering both the
Headphone and Line outputs can only provide sufficient power to drive one set of headphones at any
given time.
The ground-referenced outputs incorporates a common mode, or ground loop, feedback path which
provides rejection of system-related ground noise. The return path for the LINEOUTL and
LINEOUTR outputs is via LINEOUTFB. This pin must be connected to ground for normal operation of
the line output. No register configuration is required.
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Line outputs, LINEOUTL and LINEOUTR, with feedback LINEOUTFB
Headphone outputs, HPOUTL and HPOUTR, with feedback HPOUTFB
PD, Rev 4.0, September 2010
WM8918
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