MAX9759 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

MAX9759

3.2W, High-Efficiency, Low-EMI, Filterless, Class D Audio Amplifier

Maxim Integrated 

3.2W, High-Efficiency, Low-EMI, Filterless,

Class D Audio Amplifier

TQFN

1

2

3

4

PIN

TSSOP

7

8

9

10

5

11

6, 14

4, 12

7

13

8

9, 12

10

11

13

15

16

EP

14

2, 15

16

1

3

5

6

EP

Pin Description

NAME

FUNCTION

VDD

Analog Power Supply. Bypass to GND with a 1µF ceramic capacitor.

IN+

Noninverting Audio Input

IN-

Inverting Audio Input

GND Analog Ground

SHDN

PGND

Active-Low Shutdown Input. Drive SHDN low to shut down the MAX9759. Connect to

VDD for normal operation.

Power Ground

SYNC

MUTE

PVDD

OUT-

Frequency Select and External Clock Input:

SYNC = GND: Fixed-frequency mode with fS = 1100kHz.

SYNC = FLOAT: Fixed-frequency mode with fS = 1500kHz.

SYNC = VDD: Spread-spectrum mode with fS = 1200kHz ±70kHz.

SYNC = Clocked: Fixed-frequency mode with fS = external clock frequency.

Active-Low Mute Function. Drive MUTE low to disable the H-bridge outputs. Connect to

VDD for normal operation.

H-Bridge Power Supply. Bypass to PGND with a 10µF ceramic capacitor.

Negative Speaker Output

OUT+ Positive Speaker Output

SYNC_OUT

Internal Clock Output. Connect SYNC_OUT to the clock input of cascaded Maxim class

D amplifiers. Float SYNC_OUT if unused.

G2

Gain Control 2 (See the Gain Selection Section)

G1

Gain Control 1 (See the Gain Selection Section)

EP

Exposed Paddle. Can be left floating or tied to GND.

Detailed Description

Operating Modes

The MAX9759 filterless, Class D audio power amplifier

features several improvements to switch-mode amplifier

technology. The MAX9759 offers Class AB performance

with Class D efficiency, while occupying minimal board

space. A unique modulation scheme, synchronizable

switching frequency, and SSM mode create a compact,

flexible, low-noise, efficient audio power amplifier. The

differential input architecture reduces common-mode

noise pickup, and can be used without input-coupling

capacitors. The device can also be configured as a sin-

gle-ended input amplifier.

Comparators monitor the MAX9759 inputs and com-

pare the complementary input voltages to the sawtooth

waveform. The comparators trip when the input magni-

tude of the sawtooth exceeds their corresponding input

voltage. Both comparators reset at a fixed time after the

rising edge of the second comparator trip point, gener-

ating a minimum-width pulse tON(MIN) at the output of

the second comparator (Figure 1). As the input voltage

increases or decreases, the duration of the pulse at

one output increases (the first comparator to trip) while

the other output pulse duration remains at tON(MIN).

This causes the net voltage across the speaker (VOUT+

- VOUT-) to change.

Fixed-Frequency Modulation (FFM) Mode

The MAX9759 features two FFM modes. The FFM

modes are selected by setting SYNC = GND for a

1.1MHz switching frequency, and SYNC = FLOAT for a

1.5MHz switching frequency. In FFM mode, the fre-

quency spectrum of the class D output consists of the

fundamental switching frequency and its associated

harmonics (see the Wideband FFT graph in the Typical

Operating Characteristics). The MAX9759 allows the

switching frequency to be changed, should the fre-

quency of one or more of the harmonics fall in a sensi-

tive band. This can be done at any time and does not

affect audio reproduction.

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