Diodes PAM8902A User Manual

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Description

The PAM8902A is a mono, Class-D audio amplifier with integrated

boost convertor designed for piezo and ceramic speakers. The

PAM8902A is capable for driving a ceramic/piezo speaker with

(0.6Vrms) from a 3.6V power supply. The PAM8902A's boost

30V

converter operates at a fixed frequency of 1.5MHz and provides a

17.5V supply with a minimum number of external components. The

three gain mode of 18dB, 22dB and 26dB is easy for using. PAM

unique ant i -saturat ion technology which detects output signal clip

due to the over level input signal suppress the output signal clip

automatically. PAM8902A features an integrated audio low pass filter

that rejects high frequency noise, thus improving audio fidelity.

PAM8902A also provides thermal, over current, under and over

voltage protection.

The PAM8902A is available in a 16-ball 1.95mm x 1.95mm CSP

package and 16-pin QFN4x4 package.

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PAM8902A

30 VPP MONO CLASS-D AUDIO AMPLIFIER FOR

PIEZO/CERAMIC SPEAKERS WITH ANTI-SATURATION

Pin Assignments

Features

• Supply Voltage Range from 2.7V to 5.5V package.

• 30V

• Integrated Boost Converter Generates 17.5V Supply

• Programmable Soft-Start

• Unique Anti-Saturation Function

• Small Boost Converter Inductor

• Selectable Gain of 18dB, 22dB, and 26dB

• Selectable Boost output voltage of 8V, 12V, and 17.5V

• Low Shutdown Current: <1µA

• Build in Thermal, OCP, UVLO, OVP

• Available in Space Saving Packages:

Output Load Voltage from a 2.7V Supply

(Refer to “Application Notes”)

 16-ball 1.95mm x 1.95mm CSP package

 16-pin QFN4x4 package

Applications

• Wireless or Cellular Handsets

• Portable DVD Player

• Personal Digital Assistants (PDAs )

• Electronic Dictionaries

• Digital Still Cameras

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Typical Applications Circuit

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Pin Descriptions

Bump (CSP)

A1 13 PVCC Audio Amplifier Power Supply A2 1 VOUT Boost Convertor Output A3 2 SW Boost Convertor Switching Node A4 4 PGND1 Boost Convertor Power Ground B1 15 OUTP Positive Differential Audio Output B2 3 VSET Boost Convertor Output Voltage Setting(8V,12V,17.5V) B3 5 COMP Boost Convertor Compensation B4 6 AVDD Power Supply C1 14 OUTN Negative Differential Audio Output C2 11 GSET AmplifierGain Setting. (Refer to "Application Notes") C3 7 VCM Common Mode Bypass Cap C4 8 AGND Analog Ground D1 13 PGND2 Class D PowerGround D2 12 ENA Whole Chip Enable D3 10 INN Negative Differential Audio Input D4 9 INP Positive Differential Audio Input

Pin Number

(QFN)

Name

Function

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Functional Block Diagram

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PAM8902A

Absolute Maximum Ratings (@T

These are stress ratings only and functional operation is not implied. Exposure to absolute maximum ratings for prolonged time periods may affect device reliability. All voltages are with respect to ground.

Parameter Rating Unit

Supply Voltage 6.0

Input Voltage

Maximum Junction Temperature +150

Storage Temperature -65 to +150

Soldering Temperature 250, 10 sec

= +25°C, unless otherwise specified.)

-0.3 to V

+0.3

°C

Recommended Operating Conditions (@T

= +25°C, unless otherwise specified.)

Parameter Rating Unit

Supply Voltage Range 2.7 to 5.5 V

Ambient Temperature Range -40 to +85 °C

Junction Temperature Range -40 to +125 °C

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Thermal Information

Parameter Package Symbol Max Unit

Thermal Resistance (Junction to Ambient)

Thermal Resistance (Junction to Case)

CSP

QFN4x4-16 37

CSP

QFN4x4-16 2



90 – 220

°C/W

Electrical Characteristics

(@TA = +25°C, VDD = 3.6V, CL = 1µF, V

Parameter Symbol Test Conditions Min Typ Max Units

Input Voltage

Quiescent Current

Shutdown Current

Wake-Up Time

Chip Enable

Chip Disable

GSET/ VSET High

GSET/ VSET Floating

GSET/ VSET Low

Under Voltage Lockout Threshold UVLO

Under Voltage Lockout Hysteresis UVLO(H)

Thermal Shutdown Threshold OTP 150 °C

Thermal Shutdown Lockout Hysyeresis OTP(H) 30 °C

Boost Converter

Output Voltage

Current Limit

Lowside MOSFET R

RLS IO = 50mA

DS(ON)

Boost Switching Frequency

Over Voltage Protection Threshold

Class D

Class D Amplifier Switching Frequency

Common Mode Reject Ratio CMRR

Output Offset Voltage

DS(ON)

Closed-Loop Voltage Gain

Power Supply Reject Ratio PSRR

Total Harmonic Distortion Plus Noise THD+N

Signal to Noise Ratio SNR Input AC Ground, A-Weighting 90 dB

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floating, R

SET

LOAD

1 V

VO2 V

VO3 V

OSCB

OVP

OSCD

1 G

AV2 G

AV3 G

= 10, L

EN > 1.2V, V

= 22µh with external schottky diodes, unless otherwise specified.)

LOAD

2.7 5.5 V

= High

SET

= Floating

SET

= GND

SET

30 48

10 18

5 12

EN = 0V 0.1 1 µA

EN from Low to High 40 mS

1.2

0.4

VDD -0.5

VDD

VDD -1

0 0.5

from High to Low

from Low to High

= Low, No Load

SET

= Floating, No Load

SET

= High, No Load

SET

2.2

0.2

7.2 8.0 8.8 V

10.8 12.0 13.2 V

16.0 17.5 19.0 V

Average Input Current 0.8 A

0.5 

1.1 1.5 1.9 MHz

18 V

Input AC-GND 225 375 475 KHz

= ±100mV, VDD = 3.6V

60 dB

Output Offset Voltage 5 50 mV

High Side 1.5  Low Side 0.6 

= High, VO = 1V

SET

= Floating, VO = 1V

SET

= Low, VO = 1V

SET

200m V

Supply Ripple @ 217Hz

= 5VRMS

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RMS

25 26 27

21 22 23

17 18 19

70 dB

0.3 %

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Typical Performance Characteristics (@T

= 22µH, with external schottky diode, unless otherwise specified.)

LOAD

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= +25°C, VDD = 3.6V, CL = 1µF, L = 4.7µH, V

floating, R

SET

PAM8902A

= 10,

LOAD

PAM8902A

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Typical Performance Characteristics (cont.) (@T

= 22µH, with external schottky diode, unless otherwise specified.)

LOAD

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= +25°C, VDD = 3.6V, CL = 1µF, L = 4.7µH, V

floating, R

SET

PAM8902A

=10,

LOAD

PAM8902A

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Application Information

Select Boost Converter Output Voltage

The V

Gain Setting and Input Resistance (RI)

Gain setting function is only available in disable condition (ENA = low) and need to follow the sequence as pull ENA to low (disable the IC) first,

and change the GSET voltage between high, floating, low, then pull ENA to high (enable the IC). The input resistors (R

Where R

in fully differential amplifiers. The balance of the output on the reference voltage depends on matched ratios of the resistors. CMRR, PSRR, and

cancellation of the second harmonic distortion diminish if resistor mismatch occurs. Therefore, it is recommended to use 1% tolerance resistors

or better to keep the performance optimized. Matching is more important than overall tolerance. Resistor arrays with 1% matching can be used

with a tolerance greater than 1%.

Place the input resistors very close to the PAM8902A to limit noise injection on the high-impedance nodes. For optimal performance the gain

should be set to lower. Lower gain allows the PAM8902A to operate at its best, and keeps a high voltage at the input making the inputs less

susceptible to noise. In addition to these features, higher value of R

Anti-Saturation/Clipping Function

The anti-saturation circuitry detects the duty cycle of the PWM output. When the output starts to exhibit clipping, the gain is automatically

decreased with an attack time of 100µs per step a release time of 186ms per step. The following table describes the operation:

Attenuation Range The gain control range when anti-saturation is active.

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pin sets the boost converter output voltage to 8V, 12V or 17.5V. V

SET

Pin Configuration

SET

Min Max PVCC Voltage

High AVDD – 0.5 AVDD 17.5V

Floating 1V AVDD – 1V 12V

Low GND 0.5V 8V

= RIN + REX) set the gain of the amplifier according to Equation 1 when anti-saturation is inactive.

G = 20 Log [12.8*R

SET

pin configuration table as below:

SET

/ (RIN + REX)] (dB)

Audio Amplifier

Maximum Output Voltage

11 V

RMS

8 V

RMS

5 V

RMS

High 77.4k 122.6k

Floating 100k 100k

Low 122.6k 77.4k

is a 77.4K internal resistor, REX is the external input resistor, RF is a 122.6K internal resistor. Resistor matching is very important

minimizes pop noise.

Variable Description Value

= High)

SET

= Floating)

SET

= Low)

SET

= High)

SET

= Floating)

SET

= Low)

SET

Gain

The original gain of the device when the Anti-saturation is inactive.

26dB (G

22dB (G

18dB (G

-26dB (G

-22dB (G

-18dB (G

Step Size Gain adjust step size. 0.25dB/Step

Attack Time The minimum time between two gain decrements. 100µs

Release Time The minimum time between two gain increments. 186ms

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(VPP = 31.1V)

(VPP = 22.6V)

(VPP = 14.1V)

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Application Information (cont.)

Input Capacitors (CI)

In the typical application, an input capacitor, CI, is required to allow the amplifier to bias the input signal to the proper DC level for optimum

operation. In this case, C

equation:

It is important to consider the value of C

specification calls for a flat bass response are down to 150Hz.

Equation is reconfigured as followed:

When input resistance variation is considered, the C

capacitor is the leakage path from the input source through the input network (C

voltage at the input to the amplifier that reduces useful headroom, especially in high gain applications. For this reason, a low-leakage tantalum or

ceramic capacitor is the best choice. When polarized capacitors are used, the positive side of the capacitor should face the amplifier input in

most applications as the DC level is held at V

capacitor polarity in the application.

Decoupling Capacitor

The PAM8902 is a high-performance CMOS audio amplifier that requires adequate power supply decoupling to ensure the output total harmonic

distortion (THD) as low as possible.

The optimum decoupling is achieved by using two different types of capacitors that target on different types of noise on the power supply leads.

For higher frequency transients, spikes, or digital hash on the line, a good low equivalent series-resistance (ESR) ceramic capacitor, typically

1µF is placed as close as possible to the device AVDD pin for the best operation. For filtering lower frequency noise signals, a large ceramic

capacitor of 10µF or greater placed near the AVDD supply trace is recommended.

External Schottky Diode

Use external schottky diode can get the best driving capability and efficiency.

Since internal power diode has limited driving capability, only in following conditions customer can remove the external schottky diode to reduce

the cost.

= Low or Floating and CL less than 1µF.

1. V

SET

2. The signal frequency less than 4KHz.

3. Haptic application (50–500Hz).

Shutdown Operation

In order to reduce power consumption while not in use, the PAM8902A contains shutdown circuitry amplifier off when a logic low is placed on the

ENA pin. By switching the ENA pin connected to GND, the PAM8902A supply current draw will be minimized in idle mode.

Under-Voltage Lock-Out (UVLO)

The PAM8902A incorporates circuitry designed to detect supply voltage. When the supply voltage drops to 2.2V or below, the PAM8902A goes

into a state of shutdown, and the device comes out of its shutdown state and restore to normal function only when reset the power supply or

ENA pin.

Over-Temperature Protection (OTP)

Thermal protection on the PAM8902A prevents the device from damage when the internal die temperature exceeds +150°C. There is a 15°C

tolerance on this trip point from device to device. Once the die temperature exceeds the set point, the device will enter the shutdown state and

the outputs are disabled, in this condition both OUTP and OUTN will become high impedance. This is not a latched fault. The thermal fault is

cleared once the temperature of the die decreased by 30°C. This large hysteresis will prevent motor boating sound well and the device begins

normal operation at this point with no external system interaction.

and the minimum input impedance RI form is a high-pass filter with the corner frequency determined in the follow

ICΠ

as it directly affects the low frequency performance of the circuit. For example, when RI is 150k and the

IFC

is 7nF, so one would likely choose a value of 10nF. A further consideration for this

, RI + RF) to the load. This leakage current creates a DC offset

/2, which is likely higher than the source DC level. Please note that it is important to confirm the

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Ordering Information

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PAM8902A

Part Number Part Marking Package Type Standard Package

PAM8902AZER

PAM8902AKER

Marking Information

P8902A XXXYW

CSP-16L 3000Units/Tape&Reel

QFN4x4-16L 3000Units/Tape&Reel

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Package Outline Dimensions (All dimensions in mm.)

CSP-16

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PAM8902A

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Package Outline Dimensions (cont.) (All dimensions in mm.)

QFN4x4-16

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