MAX13330_09 Datasheet, PDF (10/15 Pages) Maxim Integrated Products – Automotive DirectDrive Headphone Amplifiers with Output Protection and Diagnostics

Automotive DirectDrive Headphone Amplifiers
with Output Protection and Diagnostics
Diagnostic Output
The MAX13330/MAX13331 provides an analog diag-
nostic output as a fraction of the analog supply voltage
V_DD. The voltage at DIAG will correspond to the fault
condition with the highest priority that is present in the
system, as shown in Table 1. When simultaneous fault
conditions occur on both headphone outputs, the diag-
nostic output will only report the fault condition at OUTR
until it is cleared or removed. Only then will the fault
condition at OUTL be reported at DIAG. Connect DIAG
to a high-impedance input.
Table 1. MAX13330/MAX13331 Diagnostic
Priority
V_DIAG
V_DD
3/4 V_DD
1/2 V_DD
1/4 V_DD
0
Three State
STATE
OUTL Short to V_BAT
OUTR Short to V_BAT
OUTL Short to SGND
OUTR Short to SGND
No Fault
Shutdown
PRIORITY
3
1
4
2
5
—
For both headphone outputs, short circuits to V_BAT are
dynamic and V_DIAG will be automatically cleared as
soon as the fault condition is removed. Short circuits to
GND occurring when a positive output voltage is pre-
sent on OUTL or OUTR, will result in V_DIAG being
latched until the fault condition is cleared.
When V_DIAG is latched, it can be cleared by either tog-
gling SHDN low for less than 5µs or initiating a full reset
of the MAX13330/MAX13331. Toggling SHDN low for
less than 5µs will cause the fault to ground to be
cleared without shutting down the device or interrupting
the output state of the amplifiers. A full reset requires
SHDN to be pulled low for more than 50µs. The amplifi-
er outputs will enter high impedance and remain in that
state until the device exits shutdown.
Click-and-Pop Suppression
In conventional single-supply audio amplifiers, the out-
put-coupling capacitor is a major contributor of audible
clicks and pops. Upon startup, the amplifier charges
the coupling capacitor to its bias voltage, typically half
the supply. Likewise, on shutdown, the capacitor is dis-
charged to SGND. This results in a DC shift across the
capacitor which appears as an audible transient at the
speaker. Since the MAX13330/MAX13331 does not
require output-coupling capacitors, this problem does
not arise.
Additionally, the MAX13330/MAX13331 feature exten-
sive click-and-pop suppression that eliminates any
audible transient sources internal to the device. The
power-up/-down transient graph in the Typical
Operating Characteristics shows that there is minimal
DC shift and no spurious transients at the output upon
startup or shutdown.
In most applications, the output of the preamplifier dri-
ving the MAX13330/MAX13331 has a DC bias of typi-
cally half the supply. At startup, the input-coupling
capacitor is charged to the preamplifier’s DC-bias volt-
age through the feedback resistor of the MAX13330/
MAX13331, resulting in a DC shift across the capacitor
and an audible click/pop. Delaying the rise of SHDN 4
to 5 time constants (80ms to 100ms) based on R_IN and
C_IN relative to the startup of the preamplifier, eliminates
this click/pop caused by the input filter.
Shutdown
The MAX13330/MAX13331 feature shutdown control
allowing audio signals to be shut down or muted.
Driving SHDN low disables the amplifiers and the
charge pump, sets the amplifier output impedance to
14kΩ (typ), and reduces the supply current. In shut-
down mode, the supply current is reduced to 2µA. The
charge pump is enabled once SHDN is driven high.
Applications Information
Power Dissipation
Under normal operating conditions, linear power ampli-
fiers can dissipate a significant amount of power. The
maximum power dissipation for each package is given
in the Absolute Maximum Ratings section under contin-
uous power dissipation or can be calculated by the
following equation:
P_DISSPKG(MAX)
=
(T_J(MAX) −
θ_JA
T_A )
where T_J(MAX) is +145°C, T_A is the ambient tempera-
ture, and θ_JA is the reciprocal of the derating factor in
°C/W as specified in the Absolute Maximum Ratings
section. The thermal resistance θ_JA of the QSOP pack-
age is 120°C/W.
The MAX13330/MAX13331 have two power dissipation
sources: the charge pump and two amplifiers. If power
dissipation for a given application exceeds the maxi-
mum allowed for a particular package, either reduce
V_DD, increase load impedance, decrease the ambient
temperature, or add heatsinking to the device. Large
output, supply, and ground traces improve the maxi-
mum power dissipation in the package.
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