wm9010 Wolfson Microelectronics plc, wm9010 Datasheet - Page 8

• Manufacturer Part Number: wm9010
• Description: Low Power, Class G Stereo Headphone Driver
• Manufacturer: Wolfson Microelectronics plc

WM9010
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DEVICE DESCRIPTION
INTRODUCTION
HEADPHONE DRIVER
The WM9010 is a low power stereo headphone driver designed for mobile handset and portable
media player (PMP) applications. It is packaged in a 12-pin CSP.
The device comprises two analogue input pins, each accepting line signals up to 1Vrms. The signal
path gain is fixed at 0dB. The headphone output drivers deliver up to 28mW into a 32Ω load.
The WM9010 incorporates Class G technology to achieve high efficiency and low quiescent current.
An integrated charge pump circuit is used to generate the split (positive and negative) power rails
from a single VDD supply. The ground-referenced headphone driver design reduces the device
power consumption and also eliminates external DC-blocking capacitors on the audio output path.
The WM9010 is enabled when a logic high level is detected on ENA. Note that the ENA pin can
support digital logic levels up to 2.7V.
Wolfson’s Silent Switch™ technology is incorporated in order to minimise ‘pop’ noise whenever the
WM9010 is enabled or disabled.
A power on reset circuit ensures correct start-up and shut-down when VDD is switched on or off. The
WM9010 is held in reset when the ENA pin is held low, offering a low-power standby state.
Short circuit and thermal protection is also provided.
The WM9010 has two analogue input pins, INL and INR. The maximum analogue input signal level
varies with VDD, but is typically 0dBV (1Vrms) when VDD = 1.8V. This is suitable for single-ended
connection to line level input signals.
The headphone output drivers are capable of driving up to 28mW into a 32Ω load such as a stereo
headset or headphones. The outputs are ground-referenced, eliminating any requirement for AC
coupling capacitors. This is achieved by having separate positive and negative supply rails powered
by an on-chip charge pump.
A pop-suppression circuit ensures that DC offsets are minimised, suppressing ‘pop’ noise and
reducing power consumption.
The headphone output incorporates a common mode, or ground loop, feedback path which provides
rejection of system-related ground noise. The return path is via HPOUTFB. This pin should be
connected to the headphone as illustrated in Figure 2.
It is recommended to connect a zobel network to the headphone output pins HPOUTL and HPOUTR
for best audio performance in all applications. The components of the zobel network have the effect
of dampening high frequency oscillations or instabilities that can arise outside the audio band under
certain conditions. Possible sources of these instabilities include the inductive load of a headphone
coil or an active load in the form of an external line amplifier. The capacitance of lengthy cables or
PCB tracks can also lead to amplifier instability. The zobel network should comprise of a 20Ω resistor
and 100nF capacitor in series with each other, as illustrated in Figure 2.
PP, January 2010, Rev 1.0
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