PAM8902A Description Features Applications Pin Assignments

A Product Line of
Diodes Incorporated
PAM8902A
30 VPP MONO CLASS-D AUDIO AMPLIFIER FOR
PIEZO/CERAMIC SPEAKERS WITH ANTI-SATURATION
Description
Pin Assignments
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
30VPP(0.6Vrms) from a 3.6V power supply. The PAM8902A's boost
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.
Features
•
•
Supply Voltage Range from 2.7V to 5.5V package.
30VPP Output Load Voltage from a 2.7V Supply
•
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
(Refer to “Application Notes”)
•
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:
ƒ
16-ball 1.95mm x 1.95mm CSP package
ƒ
16-pin QFN4x4 package
Applications
•
Wireless or Cellular Handsets
•
Portable DVD Player
•
Personal Digital Assistants (PDAs )
•
Electronic Dictionaries
•
Digital Still Cameras
PAM8902A
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PAM8902A
Typical Applications Circuit
Pin Descriptions
Bump
(CSP)
A1
A2
A3
A4
B1
B2
B3
B4
C1
C2
C3
C4
D1
D2
D3
D4
Pin Number
(QFN)
13
1
2
4
15
3
5
6
14
11
7
8
13
12
10
9
PAM8902A
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Pin
Name
PVCC
VOUT
SW
PGND1
OUTP
VSET
COMP
AVDD
OUTN
GSET
VCM
AGND
PGND2
ENA
INN
INP
Function
Audio Amplifier Power Supply
Boost Convertor Output
Boost Convertor Switching Node
Boost Convertor Power Ground
Positive Differential Audio Output
Boost Convertor Output Voltage Setting(8V,12V,17.5V)
Boost Convertor Compensation
Power Supply
Negative Differential Audio Output
AmplifierGain Setting. (Refer to "Application Notes")
Common Mode Bypass Cap
Analog Ground
Class D PowerGround
Whole Chip Enable
Negative Differential Audio Input
Positive Differential Audio Input
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Functional Block Diagram
Absolute Maximum Ratings (@TA = +25°C, unless otherwise specified.)
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
Supply Voltage
Input Voltage
Maximum Junction Temperature
Storage Temperature
Soldering Temperature
Rating
6.0
-0.3 to VDD +0.3
+150
-65 to +150
250, 10 sec
Unit
V
°C
Recommended Operating Conditions (@TA = +25°C, unless otherwise specified.)
Parameter
Supply Voltage Range
Ambient Temperature Range
Junction Temperature Range
PAM8902A
Document number: DSxxxxx Rev. 1 - 3
Rating
2.7 to 5.5
-40 to +85
-40 to +125
Unit
V
°C
°C
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PAM8902A
Thermal Information
Parameter
Thermal Resistance (Junction to Ambient)
Thermal Resistance (Junction to Case)
Package
CSP
QFN4x4-16
CSP
QFN4x4-16
Symbol
θJA
θJC
Max
90 – 220
37
75
2
Unit
°C/W
Electrical Characteristics
(@TA = +25°C, VDD = 3.6V, CL = 1µF, VSET floating, RLOAD = 10Ω, LLOAD = 22µh with external schottky diodes, unless otherwise specified.)
Parameter
Input Voltage
Symbol
Test Conditions
Min
Typ
2.7
VDD
Max
Units
5.5
V
EN > 1.2V, VSET = High
30
48
10
18
mA
Quiescent Current
IQ
EN > 1.2V, VSET = Floating
5
12
Shutdown Current
ISD
EN = 0V
0.1
1
Wake-Up Time
TWU
EN from Low to High
40
Chip Enable
VEH
Chip Disable
VEL
GSET/ VSET High
VH
VDD -0.5
VDD
GSET/ VSET Floating
VF
1
VDD -1
GSET/ VSET Low
VL
0
0.5
EN > 1.2V, VSET = GND
1.2
V
0.4
Under Voltage Lockout Threshold
UVLO
VDD from High to Low
2.2
Under Voltage Lockout Hysteresis
UVLO(H)
VDD from Low to High
0.2
Thermal Shutdown Threshold
Thermal Shutdown Lockout Hysyeresis
Boost Converter
µA
mS
OTP
OTP(H)
V
V
150
30
°C
°C
V O1
VSET = Low, No Load
7.2
8.0
8.8
V
V O2
VSET = Floating, No Load
10.8
12.0
13.2
V
V O3
VSET = High, No Load
16.0
17.5
19.0
Current Limit
CL
Average Input Current
0.8
A
Lowside MOSFET RDS(ON)
RLS
IO = 50mA
0.5
Ω
Boost Switching Frequency
fOSCB
Over Voltage Protection Threshold
VOVP
Output Voltage
1.1
1.5
1.9
18
V
MHz
V
Class D
Class D Amplifier Switching Frequency
fOSCD
Input AC-GND
Common Mode Reject Ratio
CMRR
VIN = ±100mV, VDD = 3.6V
60
5
225
375
475
KHz
50
mV
dB
Output Offset Voltage
VOS
Output Offset Voltage
RDS(ON)
RP
High Side
Low Side
AV1
GSET = High, VO = 1VRMS
AV2
GSET = Floating, VO = 1VRMS
21
22
23
AV3
GSET = Low, VO = 1VRMS
17
18
19
Closed-Loop Voltage Gain
1.5
0.6
25
26
Ω
Ω
27
dB
Power Supply Reject Ratio
PSRR
200m VPP Supply Ripple @ 217Hz
70
Total Harmonic Distortion Plus Noise
THD+N
VO = 5VRMS
Input AC Ground, A-Weighting
0.3
%
90
dB
Signal to Noise Ratio
PAM8902A
Document number: DSxxxxx Rev. 1 - 3
SNR
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PAM8902A
Typical Performance Characteristics (@TA = +25°C, VDD = 3.6V, CL = 1µF, L = 4.7µH, VSET floating, RLOAD = 10Ω,
LLOAD = 22µH, with external schottky diode, unless otherwise specified.)
PAM8902A
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PAM8902A
Typical Performance Characteristics (cont.) (@TA = +25°C, VDD = 3.6V, CL = 1µF, L = 4.7µH, VSET floating, RLOAD =10Ω,
LLOAD = 22µH, with external schottky diode, unless otherwise specified.)
PAM8902A
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Application Information
Select Boost Converter Output Voltage
The VSET pin sets the boost converter output voltage to 8V, 12V or 17.5V. VSET pin configuration table as below:
VSET Pin Configuration
Min
Max
PVCC Voltage
Audio Amplifier
Maximum Output Voltage
11 VRMS (VPP = 31.1V)
High
AVDD – 0.5
AVDD
17.5V
Floating
1V
AVDD – 1V
12V
8 VRMS (VPP = 22.6V)
Low
GND
0.5V
8V
5 VRMS (VPP = 14.1V)
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 (RI = RIN + REX) set the gain of the amplifier according to Equation 1 when anti-saturation is inactive.
G = 20 Log [12.8*RF/ (RIN + REX)] (dB)
GSET
RIN
RFB
High
77.4kΩ
122.6kΩ
Floating
100kΩ
100kΩ
Low
122.6kΩ
77.4kΩ
Where RIN is a 77.4KΩ internal resistor, REX is the external input resistor, RF is a 122.6KΩ internal resistor. Resistor matching is very important
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 RI minimizes pop noise.
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:
Variable
Gain
Description
Value
The original gain of the device when the Anti-saturation is
inactive.
Attenuation Range The gain control range when anti-saturation is active.
Step Size
Attack Time
Release Time
Gain adjust step size.
The minimum time between two gain decrements.
The minimum time between two gain increments.
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26dB (GSET = High)
22dB (GSET = Floating)
18dB (GSET = Low)
-26dB (GSET = High)
-22dB (GSET = Floating)
-18dB (GSET = Low)
0.25dB/Step
100µs
186ms
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PAM8902A
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, CI and the minimum input impedance RI form is a high-pass filter with the corner frequency determined in the follow
equation:
fC =
1
2Π RI CI
It is important to consider the value of CI as it directly affects the low frequency performance of the circuit. For example, when RI is 150k and the
specification calls for a flat bass response are down to 150Hz.
Equation is reconfigured as followed:
CI =
1
2Π RIFC
When input resistance variation is considered, the CI is 7nF, so one would likely choose a value of 10nF. A further consideration for this
capacitor is the leakage path from the input source through the input network (CI, RI + RF) to the load. This leakage current creates a DC offset
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 VDD /2, which is likely higher than the source DC level. Please note that it is important to confirm the
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.
1. VSET = Low or Floating and CL less than 1µF.
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.
PAM8902A
Document number: DSxxxxx Rev. 1 - 3
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PAM8902A
Ordering Information
Part Number
PAM8902AZER
PAM8902AKER
Part Marking
BN
YW
P8902A
XXXYW
Package Type
Standard Package
CSP-16L
3000Units/Tape&Reel
QFN4x4-16L
3000Units/Tape&Reel
Marking Information
PAM8902A
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PAM8902A
Package Outline Dimensions (All dimensions in mm.)
CSP-16
PAM8902A
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Package Outline Dimensions (cont.) (All dimensions in mm.)
QFN4x4-16
PAM8902A
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