MAX9725 1V, Low-Power, DirectDrive, Stereo Headphone Amplifier with Shutdown

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The MAX9725A–MAX9725D fixed-gain, stereo headphone amplifiers are ideal for portable equipment where board space is at a premium. The MAX9725E offers the flexibility to adjust the gain with external input and feedback resistors. The MAX9725A–MAX9725E use a unique, patented DirectDrive™ architecture to produce a ground-referenced output from a single supply, eliminating the need for large DC-blocking capacitors, saving cost, board space, and component height. Fixed gains of -2V/V (MAX9725A), -1.5V/V (MAX9725B), -1V/V (MAX9725C), and -4V/V (MAX9725D) further reduce external component count. The adjustable gain of the MAX9725E DirectDrive headphone amplifier allows for any gain down to -1V/V using external resistors.

The MAX9725 delivers up to 20mW per channel into a 32Ω load and achieves 0.006% THD+N. An 80dB at 1kHz power-supply rejection ratio (PSRR) allows the MAX9725 to operate from noisy digital supplies without an additional linear regulator. The MAX9725 includes ±8kV ESD protection on the headphone output. Comprehensive click-and-pop circuitry suppresses audible clicks and pops at startup and shutdown. A low-power shutdown mode reduces supply current to 0.6µA (typ).

The MAX9725 operates from a single 0.9V to 1.8V supply, allowing the device to be powered directly from a single AA or AAA battery. The MAX9725 consumes only 2.1mA of supply current, provides short-circuit protection, and is specified over the extended -40°C to +85°C temperature range. The MAX9725 is available in a tiny (1.54mm x 2.02mm x 0.6mm) 12-bump chip-scale package (UCSP™) and a 12-pin thin QFN package (4mm x 4mm x 0.8mm).

Key Features

Applications/Uses

Low Quiescent Current:
- 2.1mA (MAX9725A–MAX9725D)
- 2.3mA (MAX9725E)
Single-Cell, 0.9V to 1.8V Single-Supply Operation
Fixed Gain Eliminates External Feedback Network
- MAX9725A: -2V/V
- MAX9725B: -1.5V/V
- MAX9725C: -1V/V
- MAX9725D: -4V/V
Adjustable Gain with External Input and Feedback Resistors
- MAX9725E: Minimum Stable Gain of -1V/V
Ground-Referenced Outputs Eliminate DC Bias
No Degradation of Low-Frequency Response Due to Output Capacitors
20mW per Channel into 32Ω
Low 0.006% THD+N
High PSRR (80dB at 1kHz)
Integrated Click-and-Pop Suppression
Low-Power Shutdown Control
Short-Circuit Protection
±8kV ESD-Protected Amplifier Outputs
Available in Space-Saving Packages
- 12-Bump UCSP (1.54mm x 2.02mm x 0.6mm)
- 12-Pin Thin QFN (4mm x 4mm x 0.8mm)

	Cell Phones
	MP3 Players
	PDAs
	Portable Audio Equipment
	Smartphones

Key Specifications: Headphone Amplifiers

Part Number

Headphone Amp. V_CC (min) (V)

Headphone Amp. V_CC (max) (V)

Headphone Amp. I_CC (typ) (mA)

Headph. Amp. P_OUT into 32Ω @1% THD+N (W)

Headphone Amp. Half Pwr. THD+N (%)

SNR, A-weighted (dB)

PSRR (db)

Headphone Amp. External Gain

Headphone Amp. Fixed Gain (min) (|V/V|)

Headphone Amp. Fixed Gain (max) (|V/V|)

RoHS Available

Package

Smallest Available Package (max w/pins) (mm²)

Price^**

MAX9725

0.9

1.8

2.1

0.02

Yes

THIN QFN/12
UCSP/12

$0.63 @ 1k

See All Headphone Amplifiers (11)

Notes:
^**This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific prices and delivery, please see the price and availability page or contact an authorized distributor.