Datasheet

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General Description

The MAX4295 mono, switch-mode (Class D) audio

power amplifier operates from a single +2.7V to +5.5V

supply. The MAX4295 has >85% efficiency and is

capable of delivering 2W continuous power to a 4Ω

load, making it ideal for portable multimedia and gener-

al-purpose high-power audio applications.

The MAX4295 features a total harmonic distortion plus

noise (THD+N) of 0.4% (f

OSC

= 125kHz), low quiescent

current of 2.8mA, high efficiency, and clickless power-

up and shutdown. The SHDN input disables the device

and limits supply current to <1.5µA. Other features

include a 1A current limit, thermal protection, and

undervoltage lockout.

The MAX4295 reduces the number of required external

components. Internal high-speed power-MOS transis-

tors allow operation as a bridge-tied load (BTL) amplifi-

er. The BTL configuration eliminates the need for

isolation capacitors on the output. The frequency-selec-

table pulse-width modulator (PWM) allows the user to

optimize the size and cost of the output filter.

The MAX4295 is offered in a space-saving 16-pin

QSOP or narrow SO package.

Applications

Features

♦ +2.7V to +5.5V Single-Supply Operation

♦ 2W/Channel Output Power at 5V

0.7W/Channel Output Power at 3V

♦ 87% Efficiency (R

= 4Ω, P

OUT

= 2W)

♦ 0.4% THD+N (R

= 4Ω, f

OSC

= 125kHz)

♦ Logic-Programmable PWM Frequency Selection

(125kHz, 250kHz, 500kHz, 1MHz)

♦ Low-Power Shutdown Mode

♦ Clickless Transitions Into and Out of Shutdown

♦ 1A Current Limit and Thermal Protection

♦ Available in Space-Saving Packages

16-Pin QSOP or Narrow SO

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

MAX4295

Mono, 2W, Switch-Mode (Class D)

Audio Power Amplifier

________________________________________________________________ Maxim Integrated Products 1

AOUT

GND

VCM

OFF

SHDN

FS1

FS2

OUT+

OUT-

AUDIO

INPUT

2.7V TO 5.5V

GND

MAX4295

PGND

19-1746; Rev 3; 3/05

Ordering Information

Palmtop/Notebook

Computers

PDA Audio

Sound Cards

Game Cards

Boom Boxes

AC Amplifiers

Battery-Powered Speakers

Cordless Phones

Portable Equipment

Pin Configuration appears at end of data sheet.

Typical Operating Circuit

PART

TEMP RANGE

PIN-PACKAGE

MAX4295EEE

-40°C to +85°C

16 QSOP

MAX4295ESE

-40°C to +85°C

16 Narrow SO

Summary of content (15 pages)

PAGE 1
9-1746; Rev 3; 3/05 Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier Features ♦ +2.7V to +5.5V Single-Supply Operation ♦ 2W/Channel Output Power at 5V 0.7W/Channel Output Power at 3V ♦ 87% Efficiency (RL = 4Ω, POUT = 2W) ♦ 0.
PAGE 2
MAX4295 Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier ABSOLUTE MAXIMUM RATINGS VCC, PVCC to GND or PGND....................................-0.3V to +6V PGND to GND.....................................................................±0.3V PVCC to VCC .......................................................................±0.3V VCM, SS, AOUT, IN to GND .......................-0.3V to (VCC + 0.3V) SHDN, FS1, FS2 to GND ..........................................-0.3V to +6V OUT_ to PGND ................
PAGE 3
Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier (VCC = PVCC = +5V, SHDN = VCC, FS1 = GND, FS2 = VCC (fOSC = 250kHz), input amplifier gain = -1V/V, TA = TMIN to TMAX, unless otherwise noted. Typical values are TA = +25°C.) PARAMETER CONDITIONS MIN TYP MAX 0 to 0.6 x VCC Input Voltage Range VCC = +3V, fIN = 1kHz Maximum Output Power VCC = +5V, fIN = 1kHz RL = 8Ω 0.4 RL = 4Ω 0.7 RL = 8Ω 1.
PAGE 4
Typical Operating Characteristics (VCC = PVCC = +3V, input amplifier gain = -1, SHDN = VCC , TA = +25°C, unless otherwise noted.) TOTAL HARMONIC DISTORTION PLUS NOISE vs. INPUT FREQUENCY (VIN = 2.5VP-P) VCC = +5V RL = 4Ω VCC = +5V RL = 8Ω 1MHz 125kHz 1MHz 10 1MHz 1 0.1 500kHz 0.1 250kHz 500kHz 0.01 1k 10 100k 1k TOTAL HARMONIC DISTORTION PLUS NOISE vs.
PAGE 5
Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier TOTAL HARMONIC DISTORTION PLUS NOISE vs. INPUT FREQUENCY (VIN = 1.5VP-P) 125kHz 1MHz 10 VCC = +3V RL = 8Ω 1MHz 10 1MHz 1 THD+N (%) 500kHz 0.1 250kHz 0.1 250kHz 10 1k 0.01 10 100k 500kHz 250kHz 0.01 0.01 125kHz 1 THD+N (%) THD+N (%) 500kHz 0.1 VCC = +3V RL = 32Ω 125kHz 1 MAX4295 toc12 VCC = +3V RL = 4Ω MAX4295 toc10 10 TOTAL HARMONIC DISTORTION PLUS NOISE vs. INPUT FREQUENCY (VIN = 1.
PAGE 6
Typical Operating Characteristics (continued) (VCC = PVCC = +3V, input amplifier gain = -1, SHDN = VCC , TA = +25°C, unless otherwise noted.) EFFICIENCY vs. OUTPUT POWER (fIN = 1kHz) 80 50 125kHz 40 70 250kHz 60 1MHz 50 40 30 30 20 0 0.5 1.0 1.5 0 2.5 2.0 0.3 0.6 0.9 1.2 1.5 250kHz 1MHz 60 50 40 1.8 0.1 0.2 0.3 500kHz 90 80 70 250kHz 0.4 1MHz 60 50 40 125kHz 30 20 VCC = +3V 10 VCC = +3V 10 RL = 4Ω 0 RL = 8Ω 0 0 0.2 0.4 0.6 0.2 0.4 0.6 EFFICIENCY vs.
PAGE 7
Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier STARTUP/SHUTDOWN WAVEFORM OSCILLATOR FREQUENCY DEVIATION vs. SUPPLY VOLTAGE MAX4295 toc27 MAX4295 toc26 0.015 FREQUENCY DEVIATION (%) 0.010 125kHz 0.005 4V/div VOUT 0 -0.005 -0.010 250kHz 500kHz -0.015 -0.020 SHDN 1MHz RL = 4Ω fOSC = 250kHz fIN = 10kHz CSS = 560pF 2.5V/div -0.025 2.5 3.0 3.5 4.0 4.5 5.0 400µs/div 5.
PAGE 8
MAX4295 Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier AOUT PVCC MAX4295 IN OUT+ GATE DRIVE PGND 0.3 ✕ VCC (VCM) PVCC FS1 GATE DRIVE PWM OSC FS2 OUT- VCC SS PGND POWER MANAGEMENT AND PROTECTION GND CSS Figure 1. Functional Diagram Detailed Description The MAX4295 switch-mode, Class D audio power amplifier is intended for portable multimedia and general-purpose audio applications.
PAGE 9
Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier Undervoltage Lockout VIN VRAMP +5V VOUT 0V Figure 2. PWM Waveforms FS1 and FS2 program the oscillator to a frequency of 125kHz, 250kHz, 500kHz, and 1MHz. The sawtooth oscillator swings between GND and 0.6 ✕ VCC. The input signal is typically AC-coupled to the internal input op amp, whose gain can be controlled through external feedback components. The common-mode voltage of the input amplifier is 0.
PAGE 10
MAX4295 Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier Soft-Start (Clickless Startup) The H-bridge is disabled under any of the following conditions: • SHDN low • H-bridge current exceeds the 1A current limit • Thermal overload • Undervoltage lockout The circuit re-enters normal operation if none of the above conditions are present. A soft-start function prevents an audible pop on restart. An external capacitor connected to SS is charged by an internal 1.
PAGE 11
Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier where ωo = 2 ✕ π ✕ fo (fo = filter cutoff frequency); choosing fo = 30kHz and RL = 4Ω, C = 0.937µF, L = 30µH. A single-ended 2-pole filter uses the minimum number of external components, but the load (speaker) sees the large common-mode switching voltage, which can increase power dissipation and cause EMI problems. • Balanced 2-Pole (Figure 4b): A balanced 2-pole filter does not have the commonmode swing problem of the single-ended filter.
PAGE 12
MAX4295 Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier Filter Components The inductor current rating should be higher than the peak current for a given output power requirement and should have relatively constant inductance over temperature and frequency. Typically, an open-core inductor is desirable since these types of inductors are more linear. Toroidal inductors without an air gap are not recommended. Q-shielded inductors may be required if the amplifier is placed in an EMI-sensitive system.
PAGE 13
Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier Chip Information TRANSISTOR COUNT: 846 PROCESS: BiCMOS TOP VIEW GND 1 16 SS PVCC 2 15 PVCC OUT+ 3 14 OUT- PGND 4 MAX4295 13 PGND VCC 5 12 GND VCM 6 11 FS2 IN 7 10 FS1 AOUT 8 9 SHDN SO/QSOP ______________________________________________________________________________________ 13 MAX4295 Pin Configuration
PAGE 14
Package Information (The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information go to www.maxim-ic.com/packages.) QSOP.EPS MAX4295 Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier PACKAGE OUTLINE, QSOP .150", .
PAGE 15
Mono, 2W, Switch-Mode (Class D) Audio Power Amplifier N E H INCHES MILLIMETERS MAX MIN 0.053 0.069 0.004 0.010 0.014 0.019 0.007 0.010 0.050 BSC 0.150 0.157 0.228 0.244 0.016 0.050 MAX MIN 1.35 1.75 0.10 0.25 0.35 0.49 0.19 0.25 1.27 BSC 3.80 4.00 5.80 6.20 0.40 SOICN .EPS DIM A A1 B C e E H L 1.27 VARIATIONS: 1 INCHES TOP VIEW DIM D D D MIN 0.189 0.337 0.386 MAX 0.197 0.344 0.394 MILLIMETERS MIN 4.80 8.55 9.80 MAX 5.00 8.75 10.