MAX4410 查看數據表（PDF） - Maxim Integrated

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MAX4410

80mW, DirectDrive Stereo Headphone Driver with Shutdown

Maxim Integrated 

80mW, DirectDrive Stereo Headphone Driver

with Shutdown

Detailed Description

The MAX4410 stereo headphone driver features Maxim’s

patented DirectDrive architecture, eliminating the large

output-coupling capacitors required by traditional single-

supply headphone drivers. The device consists of two

80mW Class AB headphone drivers, undervoltage lock-

out (UVLO)/shutdown control, charge-pump, and com-

prehensive click-and-pop suppression circuitry (see

Typical Application Circuit). The charge pump inverts the

positive supply (PVDD), creating a negative supply

(PVSS). The headphone drivers operate from these bipo-

lar supplies with their outputs biased about GND (Figure

1). The drivers have almost twice the supply range com-

pared to other 3V single-supply drivers, increasing the

available output power. The benefit of this GND bias is

that the driver outputs do not have a DC component typi-

cally VDD/2. Thus, the large DC-blocking capacitors are

unnecessary, improving frequency response while con-

serving board space and system cost.

Each channel has independent left/right, active-low

shutdown controls, making it possible to optimize

power savings in mixed-mode, mono/stereo operation.

The device features an undervoltage lockout that pre-

vents operation from an insufficient power supply and

click-and-pop suppression that eliminates audible tran-

sients on startup and shutdown. Additionally, the

MAX4410 features thermal overload and short-circuit

protection and can withstand ±8kV ESD strikes on the

output pins.

DirectDrive

Traditional single-supply headphone drivers have their

outputs biased about a nominal DC voltage (typically

half the supply) for maximum dynamic range. Large

coupling capacitors are needed to block this DC bias

from the headphone. Without these capacitors, a signif-

icant amount of DC current flows to the headphone,

resulting in unnecessary power dissipation and possi-

ble damage to both headphone and headphone driver.

Maxim’s patented DirectDrive architecture uses a

charge pump to create an internal negative supply volt-

age. This allows the outputs of the MAX4410 to be

biased about GND, almost doubling dynamic range

while operating from a single supply. With no DC com-

ponent, there is no need for the large DC-blocking

capacitors. Instead of two large (220µF, typ) tantalum

capacitors, the MAX4410 charge pump requires two

small ceramic capacitors, conserving board space,

reducing cost, and improving the frequency response

of the headphone driver. See the Output Power vs.

Charge-Pump Capacitance and Load Resistance

graph in the Typical Operating Characteristics for

VDD

VOUT

VDD/2

GND

CONVENTIONAL DRIVER-BIASING SCHEME

+VDD

VOUT

GND

-VDD

DirectDrive BIASING SCHEME

Figure 1. Traditional Driver Output Waveform vs. MAX4410

Output Waveform

details of the possible capacitor sizes. There is a low

DC voltage on the driver outputs due to amplifier offset.

However, the offset of the MAX4410 is typically 0.5mV,

which, when combined with a 32Ω load, results in less

than 16µA 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:

1) When combining a microphone and headphone on

a single connector, the microphone bias scheme

typically requires a 0V reference.

2) The sleeve is typically grounded to the chassis.

Using this biasing approach, the sleeve must be

isolated from system ground, complicating product

design.

3) During an ESD strike, the driver’s ESD structures

are the only path to system ground. Thus, the driver

must be able to withstand the full ESD strike.

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