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Diagnostic Output

The MAX13330/MAX13331 provides an analog diagnos-

tic output as a fraction of the analog supply voltage VDD.

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 condi-

tions occur on both headphone outputs, the diagnostic

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.

For both headphone outputs, short circuits to VBAT are

dynamic and VDIAG will be automatically cleared as soon

as the fault condition is removed. Short circuits to GND

occurring when a positive output voltage is present on

OUTL or OUTR, will result in VDIAG being latched until the

fault condition is cleared.

When VDIAG 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 amplifier 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 output-

coupling capacitor is a major contributor of audible clicks

and pops. Upon startup, the amplifier charges the cou-

pling capacitor to its bias voltage, typically half the sup-

ply. Likewise, on shutdown, the capacitor is discharged

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 extensive

click-and-pop suppression that eliminates any audible tran-

sient 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 tran-

sients at the output upon startup or shutdown.

In most applications, the output of the preamplifier driv-

ing the MAX13330/MAX13331 has a DC bias of typically

half the supply. At startup, the input-coupling capacitor is

charged to the preamplifier’s DC-bias voltage 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 RIN and CIN 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 shutdown 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 continuous

power dissipation or can be calculated by the following

equation:

(

)

J(MAX)

DISSPKG(MAX)

−

where TJ(MAX) is +145°C, TA is the ambient temperature,

and θJA is the reciprocal of the derating factor in °C/W as

specified in the Absolute Maximum Ratings section. The

thermal resistance θJA of the QSOP package 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 maximum

allowed for a particular package, either reduce VDD,

increase load impedance, decrease the ambient tem-

perature, or add heatsinking to the device. Large output,

supply, and ground traces improve the maximum power

dissipation in the package.

Table 1. MAX13330/MAX13331 Diagnostic

Priority

VDIAG

STATE

PRIORITY

VDD

OUTL Short to VBAT

3/4 VDD

OUTR Short to VBAT

1/2 VDD

OUTL Short to SGND

1/4 VDD

OUTR Short to SGND

No Fault

Three State

Shutdown

—

MAX13330/MAX13331

Automotive DirectDrive Headphone Amplifiers

with Output Protection and Diagnostics

www.maximintegrated.com

Maxim Integrated │ 10

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