MAX13331 datasheet(8/15 Pages) AD

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Detailed Description

The MAX13330/MAX13331 headphone amplifiers feature

Maxim’s DirectDrive architecture, eliminating the large

output-coupling capacitors required by conventional sin-

gle-supply headphone amplifiers. The devices consists of

two Class AB headphone amplifiers, under-voltage lock-

out (UVLO), low-power shutdown control, comprehensive

click-and-pop suppression, output short-circuit/ESD pro-

tection and output short-circuit diagnostics.

These devices can drive loads as low as 8Ω, and deliver

up to 120mW per channel into 16Ω and 135mW into 32Ω.

The MAX13330 features a fixed gain of -1.5V/V, and the

MAX13331 features a programmable gain configured with

external resistors. The headphone outputs feature ±15kV

Human Body Model ESD protection, and enhanced short-

circuit protection to ground or battery (VBAT up to +45V).

An integrated short-circuit diagnostic output provides the

status of the MAX13330/MAX13331 during operation as

a fraction of the analog supply voltage.

DirectDrive

Conventional single-supply headphone amplifiers have

their outputs biased about a nominal DC voltage (typi-

cally half the supply) for maximum dynamic range. Large

coupling capacitors are needed to block this DC bias from

the headphone. Without these capacitors, a significant

amount of DC current flows to the headphone, resulting

in unnecessary power dissipation and possible damage to

both the headphone and the headphone amplifier.

Maxim’s DirectDrive architecture uses a charge pump

to create an internal negative-supply voltage, allowing

the MAX13330/MAX13331 outputs to be biased about

SGND (Figure 1). With no DC component, there is no

need for the large DC-blocking capacitors. Instead of two

large (220μF, typ) tantalum capacitors, the MAX13330/

MAX13331 charge pump requires two small ceramic

capacitors, conserving board space, reducing cost, and

improving the frequency response of the headphone

amplifier. See the Output Power vs. Load Resistance

graph in the Typical Operating Characteristics for details

of the possible capacitor sizes. There is a low DC volt-

age on the amplifier outputs due to amplifier offset.

However, the output offset of the MAX13330 is typically

±2.5mV which, when combined with a 32Ω load, results

in less than ±78μA of DC current flow to the headphones.

Previous attempts to eliminate the output-coupling capac-

itors involved biasing the headphone return (sleeve) to

the DC-bias voltage of the headphone amplifiers.

This method raises some issues:

● The sleeve is typically grounded to the chassis.

Using this biasing approach, the sleeve must be

isolated from system ground, complicating product

design.

● During an ESD strike, the amplifier’s ESD structures

are the only path to system ground. Thus, the ampli-

fier must be able to withstand the full ESD strike.

● When using the headphone jack as a line out to

other equipment, the bias voltage on the sleeve may

conflict with the ground potential from other equip-

ment, resulting in possible damage to the amplifiers.

Figure 1. Conventional Driver Output Waveform vs. MAX13330/

MAX13331 Output Waveform

VDD

VSS

GND

VOUT

CONVENTIONAL DRIVER-BIASING SCHEME

DirectDrive BIASING SCHEME

VDD/2

VDD

GND

VOUT

MAX13330/MAX13331

Automotive DirectDrive Headphone Amplifiers

with Output Protection and Diagnostics

www.maximintegrated.com

Maxim Integrated │ 8

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