LM48557
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SNAS486D – JULY 2009 – REVISED MAY 2013
LM48557 Boomer™ Mono, Bridge-Tied Load, Ceramic Speaker Driver with I2C Volume
Control and Reset
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FEATURES
DESCRIPTION
•
•
•
•
•
•
•
•
•
•
•
The LM48557 is a single supply, mono, ceramic
speaker driver with an integrated charge-pump,
designed for portable devices, such as cell phones
and portable media players, where board space is at
a premium. The LM48557 charge pump allows the
device to deliver 5.8VRMS from a single 4.2V supply.
1
23
Integrated Charge Pump
Bridge-Tied Load Output
Differential Input
High PSRR
I2C Volume and Mode Control
Reset Input
Advanced Click-and-Pop Suppression
Low Supply Current
Minimum External Components
Micro-Power Shutdown
Available in Space-Saving 16-Bump DSBGA
Package
APPLICATIONS
•
•
•
•
Mobile Phones
PDAs
Notebook Electronic Devices
MP3 Players
The LM48557 features high power supply rejection
ratio (PSRR), 80dB at 217Hz, allowing the device to
operate in noisy environments without additional
power supply conditioning. Flexible power supply
requirements allow operation from 2.7V to 4.5V. The
LM48557 features an active low reset input that
reverts the device to its default state. Additionally, the
LM48557 features a 36-step I2C volume control and
mute function. The low power Shutdown mode
reduces supply current consumption to 0.01µA.
The LM48557’s superior click and pop suppression
eliminates audible transients on power-up/down and
during shutdown. The LM48557 is available in an
ultra-small 16-bump DSBGA package (1.965mm x
1.965mm).
KEY APPLICATIONS
•
Output Voltage at VDD = 4.2V
– RL = 1µF +22Ω, THD+N ≤ 1%: 5.8 VRMS (Typ)
1
2
3
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of
Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
Boomer is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2009–2013, Texas Instruments Incorporated
LM48557
SNAS486D – JULY 2009 – REVISED MAY 2013
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Typical Application
+2.7V to +4.5V
CS2
CS1
SVDD
PVDD
CIN
OUTIN+
VOLUME
CONTROL
AUDIO INPUT
IN-
OUT+
CIN
VCM
+1.7V to +4.5V
2
I CVDD
SDA
SCL
RESET
I2C
INTERFACE
CHARGE PUMP
SGND
C1P
C1N
C2
CPVSS
PGND
C1
Figure 1. Typical Audio Amplifier Application Circuit
Connection Diagram
2
IN-
IN+
I CVDD
PVDD
4
IN-
IN+
I CVDD
PVDD
3
VCM
RESET
SDA
C1P
3
VCM
RESET
SDA
C1P
2
SGND
OUT+
SCL
PGND
2
SGND
OUT+
SCL
PGND
1
VDD
OUT-
CPVSS
C1N
1
VDD
OUT-
CPVSS
C1N
A
B
C
D
A
B
C
D
Figure 2. YZR Package - Top View
See Package Number YZR001611A
2
2
4
Figure 3. YPD Package - Top View
See Package Number YPD001611A
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Table 1. Bump Descriptions
Bump
Name
A1
SVDD
Signal Power Supply
Description
A2
SGND
Signal Ground
A3
VCM
A4
IN-
B1
OUT-
Amplifier Inverting output
B2
OUT+
Amplifier Non-Inverting Output
B3
RESET
Common Mode Sense Input
Amplifier Inverting input
Active Low Reset Input. Connect to VDD for normal operation. Toggle
between VDD and GND to reset the device.
B4
IN+
C1
CPVSS
Charge Pump Output
C2
SCL
I2C Serial Clock Input
SDA
I2C Serial Data Input
C3
2
C4
I CVDD
D1
C1N
D2
PGND
Amplifier Non-Inverting Input
I2C Supply Voltage
Charge Pump Flying Capacitor Negative Terminal
Power Ground
D3
C1P
Charge Pump Flying Capacitor Positive Terminal
D4
PVDD
Power Supply
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
Absolute Maximum Ratings (1) (2) (3)
Supply Voltage (1)
5.25V
−65°C to +150°C
Storage Temperature
−0.3V to VDD +0.3V
Input Voltage
Power Dissipation
(4)
Internally Limited
ESD Rating-Human Body Model (5)
2kV
ESD Rating-Machine Model (6)
150V
Junction Temperature
Thermal Resistance
150°C
θJA (typ) - (YZR001611A)
63°C/W
Soldering Information: See AN-1112 "Micro SMD Wafer Level Chip Scale Package."
(1)
(2)
(3)
(4)
(5)
(6)
“Absolute Maximum Ratings indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or
other conditions beyond those indicated in the Operating Ratings is not implied. The Operating Ratings indicate conditions at which the
device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the
ground pin, unless otherwise specified.
The Electrical Characteristics tables list specified specifications under the listed Operating Ratings except as otherwise modified or
specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not ensured.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and
specifications.
The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature,
TA. The maximum allowable power dissipation is PDMAX = (TJMAX - TA) / θJA or the number given in Absolute Maximum Ratings,
whichever is lower.
Human body model, applicable std. JESD22-A114C.
Machine model, applicable std. JESD22-A115-A.
Operating Ratings
Temperature Range (TMIN ≤ TA ≤ TMAX)
Supply Voltage
−40°C ≤ TA ≤ +85°C
PVDD and SVDD
I2CVDD
2.7V ≤ VDD ≤ 4.5V
1.7V ≤ I2CVDD ≤ 4.5V
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Electrical Characteristics VDD = 4.2V (1) (2)
The following specifications apply for AV = 6dB, RL = 1µF + 22Ω, C1 = 2.2µF, C2 = 2.2µF, f = 1kHz, unless otherwise
specified. Limits apply for TA = 25°C.
Symbol
Parameter
Conditions
LM48557
Min (3)
Typ (4)
Max (3)
Units
VDD
Supply Voltage Range
2.7
4.5
I2CVDD
I2C Supply Voltage Range
1.7
4.5
V
IDD
Quiescent Power Supply Current VIN = 0V, RL = ∞
5
8
mA
ISD
Shutdown Current
0.01
1
µA
|VOS|
Differential Output Offset Voltage
VIH
Logic High Input Threshold
RESET, VDD = 2.7V to 4.5V
VIL
Logic Low Input Threshold
RESET, VDD = 2.7V to 4.5V
AV
Gain
Shutdown Enabled
V
VIN = 0V, AV = 0dB
3
12
mV
VIN = 0V, AV = 48dB
40
160
mV
1.4
Minimum Gain Setting
Volume Control = 000001
-25.5
Maximum Gain Setting
Volume Control = 111111
47
AV(MUTE)
Mute Attenuation
RIN
Input Resistance
Volume Control = 000000
1
VIN
Common Mode Input Voltage
Range
-1
V
0.4
V
-25
-24.5
dB
48
49
dB
–90
dB
3
MΩ
1
VP-P
RL = 1µF + 22Ω, THD+N = 1%
5.5
5.8
15.6
16.4
VP-P
4.0
VRMS
f = 1kHz
5.6
VRMS
f = 5kHz
2.9
VRMS
VO = 4VRMS, f = 1kHz, AV = 48dB
0.05
%
f = 1kHz
VO
Output Voltage
f = 5kHz
VRMS
RL = 2.2µF + 10Ω, THD+N = 1%
THD+N
Total Harmonic Distortion +
Noise
VDD = 4.2V + 200mVP-P (sine), Inputs AC GND, CIN = 0.1µF, AV = 0dB
PSRR
Power Supply Rejection Ratio
(Figure 4)
fRIPPLE = 217Hz
80
dB
fRIPPLE = 1kHz
80
dB
VDD = 4.2V + 200mVP-P (sine), Inputs AC GND, CIN = 0.1µF, AV = 48dB
f = 1kHz
15
f = 5kHZ
40
dB
40
dB
36
dB
37
dB
VCM = 200mVP-P (sine), CIN = 0.1µF, AV = 48dB
CMRR
Common Mode Rejection Ratio
(Figure 5)
fRIPPLE = 500Hz
16
fRIPPLE = 1kHz
fSW
Charge Pump Switching
Frequency
SNR
Signal To Noise Ratio
∈OS
(1)
(2)
(3)
(4)
4
Output Noise
230
300
VOUT = 5VRMS, f = 1kHz, AV = 48dB
74
AV = 0dB, A-Weighted Filter
20
AV = 48dB, A-weighted Filter
1
370
kHz
30
µV
dB
mV
“Absolute Maximum Ratings indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or
other conditions beyond those indicated in the Operating Ratings is not implied. The Operating Ratings indicate conditions at which the
device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the
ground pin, unless otherwise specified.
The Electrical Characteristics tables list specified specifications under the listed Operating Ratings except as otherwise modified or
specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not ensured.
Datasheet min/max specification limits are specified by test or statistical analysis.
Typical values represent most likely parametric norms at TA = +25ºC, and at theOperation Rating at the time of product characterization
and are not ensured.
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Electrical Characteristics VDD = 4.2V(1)(2) (continued)
The following specifications apply for AV = 6dB, RL = 1µF + 22Ω, C1 = 2.2µF, C2 = 2.2µF, f = 1kHz, unless otherwise
specified. Limits apply for TA = 25°C.
Symbol
TWU
Parameter
Wake Up Time
Conditions
From shutdown
LM48557
Min (3)
Typ (4)
Max (3)
Units
5
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I2C Interface Characteristics 1.7V ≤ I2CVDD ≤ 4.5V (1) (2)
The following specifications apply for RPU = 1kΩ to I2CVDD, unless otherwise specified. Limits apply for TA = 25°C.
Symbol
Parameter
Min
(3)
Typ (4)
Logic Input High Threshold
SDA, SCL
VIL
Logic Input Low Threshold
SDA, SCL
VOL
Logic Output Low Threshold
SDA, ISDA = 3.6mA
SDA, SCL, I CVDD = 4.5V
SCL Frequency
(1)
(2)
(3)
(4)
Units
V
2
Logic Output High Current
Max (3)
0.7 x I2CVDD
VIH
IOH
LM48557
Conditions
0.3 x I2CVDD
V
0.35
V
2
µA
400
kHz
6
SDA Setup Time
100
5
SDA Stable Time
1
Start Condition Time
100
ns
7
Stop Condition Time
100
ns
0
ns
250
900
ns
“Absolute Maximum Ratings indicate limits beyond which damage to the device may occur, including inoperability and degradation of
device reliability and/or performance. Functional operation of the device and/or non-degradation at the Absolute Maximum Ratings or
other conditions beyond those indicated in the Operating Ratings is not implied. The Operating Ratings indicate conditions at which the
device is functional and the device should not be operated beyond such conditions. All voltages are measured with respect to the
ground pin, unless otherwise specified.
The Electrical Characteristics tables list specified specifications under the listed Operating Ratings except as otherwise modified or
specified by the Electrical Characteristics Conditions and/or Notes. Typical specifications are estimations only and are not ensured.
Datasheet min/max specification limits are specified by test or statistical analysis.
Typical values represent most likely parametric norms at TA = +25ºC, and at theOperation Rating at the time of product characterization
and are not ensured.
200 mVp-p
AUDIO
ANALYZER
VDD
+
VDD
-
IN+
CIN
ZL
DUT
INVCM
Figure 4. PSRR Test Circuit
VDD
AUDIO
ANALYZER
-
+
VDD
CIN
IN+
IN200 mVp-p
DUT
ZL
VCM
Figure 5. CMRR Test Circuit
6
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Typical Performance Characteristics
THD+N vs Frequency
VDD = 4.2V, ZL = 1µF + 22Ω
AV = 48dB
10
10
1
1
THD + N (%)
THD + N (%)
THD+N vs Frequency
VDD = 3.6V, ZL = 1µF + 22Ω
AV = 48dB, VO = 2.5V
0.1
VO = 3VRMS
VO = 4VRMS
0.1
0.01
20
100 200
500 1k
2k
0.01
20
5k 10k 20k
100 200
FREQUENCY (Hz)
5k 10k 20k
Figure 6.
Figure 7.
THD+N vs Output Voltage
ZL = 1µF + 22Ω, AV = 0dB
Output Voltage vs Frequency
VDD = 4.2V, ZL = 1µF + 22Ω
THD+N = 1%
8
1
OUTPUT VOLTAGE (VRMS)
10
THD + N (%)
2k
FREQUENCY (Hz)
100
VDD = 4.2V
VDD = 3.6V
0.1
0.01
0.001
10m 20m
100m 200m
1
2
5
6
4
2
0
20
10
50 100 200 500 1k
OUTPUT VOLTAGE (VRMS)
2k
5k 10k 20k
FREQUENCY (Hz)
Figure 8.
Figure 9.
Power Consumption vs Output Voltage
VDD = 3.6V, ZL = 1µF + 22Ω
Power Consumption vs Output Voltage
VDD = 4.2V, ZL = 1µF + 22Ω
1400
1000
f = 10kHz
POWER CONSUMPTION (mW)
POWER CONSUMPTION (mW)
500 1k
800
600
400
f = 1kHz
200
1200
f = 10kHz
1000
800
600
f = 1kHz
400
200
0
0
0
1
2
3
4
5
6
0
1
2
3
4
5
6
7
OUTPUT VOLTAGE (VRMS)
OUTPUT VOLTAGE (VRMS)
Figure 10.
Figure 11.
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Typical Performance Characteristics (continued)
CMRR vs Frequency
VDD = 4.2V, VRIPPLE = 200mVP-P, AV = 48dB
PSRR vs Frequency
VDD = 4.2V, VRIPPLE = 200mVP-P
0
+0
-10
-20
AV = 48 dB
-40
PSRR (dB)
CMRR (dB)
-20
-30
-40
AV = 0 dB
-60
-80
-50
-100
-60
20
50 100 200 500 1k 2k
5k 10k 20k
-120
20
50 100 200 500 1k 2k
FREQUENCY (Hz)
Figure 12.
Figure 13.
Output Voltage vs Supply Voltage
ZL = 1µF + 22Ω, THD+N = 1%
Supply Current vs Supply Voltage
No Load
OUTPUT VOLTAGE (VRMS)
6
6
5.8
f = 1 kHz
5
SUPPLY CURRENT (mA)
7
5k 10k 20k
FREQUENCY (Hz)
f = 10 kHz
4
3
2
5.6
5.4
5.2
5
4.8
4.6
4.4
1
4.2
0
2.5
3
3.5
4
4.5
4
2.5
5
3
SUPPLY VOLTAGE (V)
3.5
4
4.5
5
SUPPLY VOLTAGE (V)
Figure 14.
Figure 15.
Charge Pump Output Voltage vs Load Current
VDD = 4.2V
CHARGE PUMP OUTPUT VOLTAGE (V)
0
-1
-2
-3
-4
-5
0
40
80
120
160
200
CHARGE PUMP LOAD CURRENT (mA)
Figure 16.
8
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APPLICATION INFORMATION
I2C COMPATIBLE INTERFACE
The LM48557 is controlled through an I2C compatible serial interface that consists of a serial data line (SDA) and
a serial clock (SCL). The clock line is uni-directional. The data line is bi-directional (open drain). The LM48557
and the master can communicate at clock rates up to 400kHz. Figure 17 shows the I2C interface timing diagram.
Data on the SDA line must be stable during the HIGH period of SCL. The LM48557 is a transmit/receive slaveonly device, reliant upon the master to generate the SCL signal. Each transmission sequence is framed by a
START condition and a STOP condition (Figure 18). Each data word, device address and data, transmitted over
the bus is 8 bits long and is always followed by an acknowledge pulse (Figure 19). The LM48557 device address
is 11011110.
I2C BUS FORMAT
The I2C bus format is shown in Figure 19. The START signal, the transition of SDA from HIGH to LOW while
SCL is HIGH, is generated, alerting all devices on the bus that a device address is being written to the bus.
The 7-bit device address is written to the bus, most significant bit (MSB) first, followed by the R/W bit. Set R/W =
0; the LM48557 is a WRITE-ONLY device and will not respond to R/W = 1. In other words, the LM48557 will not
issue an ACK when R/W = 1. Each address bit is latched in on the rising edge of the clock. Each address bit
must be stable while SCL is HIGH. After the last address bit is transmitted, the master device releases SDA,
during which time, an acknowledge clock pulse is generated by the LM48557. If the LM48557 receives the
correct address, the device pulls the SDA line low, generating an acknowledge bit (ACK).
Once the master device registers the ACK bit, the 8-bit register data word is sent. Each data bit should be stable
while SCL is HIGH. The LM48557 has two registers, Mode Control and Volume Control. The register address
and register data are combined into a single byte, the most significant bit (MSB) indicates which register is being
addressed. To address the Mode Control register, set the MSB of the data byte to 0, followed by seven bits of
register data. To address the Volume Control register, set the MSB of the data byte to 1, followed by seven bits
of register data. After the 8-bit register data word is sent, the LM48557 sends another ACK bit. The LM48557
supports single and multi-byte write operations, any number of data bytes can be transmitted to the device
between START and STOP conditions. Following the acknowledgement of the last register data word, the master
issues a STOP bit, allowing SDA to go high while SCL is high.
SDA
10
8
7
6
1
8
2
7
SCL
5
1
3
4
9
Figure 17. I2C Timing Diagram
SDA
SCL
S
P
START condition
STOP condition
Figure 18. Start and Stop Diagram
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SCL
START
SDA
MSB
DEVICE ADDRESS
LSB
R/W
ACK
MSB
REGISTER DATA
LSB
ACK
STOP
Figure 19. Example Write Sequence
Table 2. Device Address
Device Address
B7
B6
B5
B4
B3
B2
B1
B0 R/W
1
1
0
1
1
1
1
0
B2
B1
B0
Table 3. Control Registers
Register
Name
B7
B6
Mode Control
0
0
0
0
0
0
MUTE
SHDN
Volume Control
1
0
VOL5
VOL4
VOL3
VOL2
VOL1
VOL0
B5
B4
B3
Table 4. Mode Control Registers
(1)
BIT
NAME
B0
SHDN
B1
MUTE
B2
VALUE
DESCRIPTION
DEFAULT SETTING
0
Shutdown mode
1
Normal operation
0
Normal operation
1
Device mute, AV = -90dB.
RESERVED (1)
X
Unused, Set to 0
0
B3
RESERVED (1)
X
Unused, Set to 0
0
B4
TESTMODE
0
Set B4 to 0. B4 = 1 enables TESTMODE. See TEST MODE.
0
B5
RESERVED
(1)
X
Unused, Set to 0
0
B6
RESERVED (1)
X
Unused, Set to 0
0
B7
REGISTER
ADDRESS
0
Set to 0 to access Mode Control register
0
0
0
RESERVED bits are Don't Cares and are ignored by the device. The state of the RESERVED bits does not affect device operation.
Table 5. Volume Control Registers
BIT
NAME
VALUE
B0:B5
VOL0:VOL5
See Table 6
B6
B7
(1)
RESERVED
(1)
REGISTER
ADDRESS
DESCRIPTION
DEFAULT SETTING
Controls amplifier gain/attenuation
0
X
Unused, Set to 0
0
1
Set to 1 to access Volume Control register
1
RESERVED bits are Don't Cares and are ignored by the device. The state of the RESERVED bits does not affect device operation.
SINGLE AND MULTI-BYTE WRITE OPERATION
The LM48557 supports both single-byte and multi-byte write operations. A single-byte write operation begins with
the master device transmitting a START condition followed by the device address (Figure 20). After receiving the
correct device address, the LM48557 generates an ACK bit. The master device transmits the register data byte,
after which the LM48557 generates and ACK bit. Following the ACK, the master issues a STOP condition,
completing the singly-byte data transfer.
10
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A multi-byte write operation is similar to a single-byte operation, the master device issues a START condition and
device address, and the LM48557 responds with an ACK (Figure 21). The master device then transmits the first
data byte. Following the LM48557’s ACK, the master device does not issue a STOP condition, transmitting a
second data byte instead. The LM48557 responds with an ACK bit. The master device can continue to issue
data bytes, and the LM48557 will respond with an ACK, until a STOP condition is issued. Once a STOP
condition is issued, the LM48557 ignores the I2C bus until the master issues the LM48557’s device address.
START
MSB
DEVICE ADDRESS
LSB
R/W
ACK
MSB
REGISTER DATA
LSB
ACK
STOP
Figure 20. Single-Byte Write Example
START
MSB
DEVICE ADDRESS
LSB
R/W
ACK
MSB
FIRST REGISTER BYTE
LSB
ACK
MSB
LSB
SUCCESSIVE
REGISTER BYTES
ACK
MSB
LSB
ACK
STOP
LAST REGISTER
BYTE
Figure 21. Multi-Byte Write Example
GENERAL AMPLIFIER FUNCTION
The LM48557 is a fully differential ceramic speaker driver that utilizes Ti’s inverting charge pump technology to
deliver over 5.8VRMS to a 1µF ceramic speaker while operating from a single 4.2V supply. The low noise,
inverting charge pump generates a negative supply voltage (CPVSS) from the positive supply voltage (PVDD). The
LM48557 takes advantage of the increased head room created by the charge pump and the bridge-tied load
(BTL) architecture, delivering significantly more voltage than a single-ended, single-supply amplifier to the
speaker.
Table 6. Volume Control Table
VOLUME
STEP
VOL5
VOL4
VOL3
VOL2
VOL1
VOL0
GAIN (dB)
1 (MUTE)
0
0
0
0
0
0
-90
2
0
0
0
0
0
1
-25
3
0
0
0
0
1
0
-22
4
0
0
0
0
1
1
-19
5
0
0
0
1
0
0
-16
6
0
0
0
1
0
1
-13
7
0
0
0
1
1
0
-10
8
0
0
0
1
1
1
-8
9
0
0
1
0
0
0
-6
10
0
0
1
0
0
1
-4
11
0
0
1
0
1
0
-2
12
0
0
1
0
1
1
0
13
0
0
1
1
0
0
2
14
0
0
1
1
0
1
4
15
0
0
1
1
1
0
6
16
0
0
1
1
1
1
8
17
0
1
0
0
0
0
10
18
0
1
0
0
0
1
12
19
0
1
0
0
1
0
14
20
0
1
0
0
1
1
16
21
0
1
0
1
0
0
18
22
0
1
0
1
0
1
20
23
0
1
0
1
1
0
22
24
0
1
0
1
1
1
24
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Table 6. Volume Control Table (continued)
VOLUME
STEP
VOL5
VOL4
VOL3
VOL2
VOL1
VOL0
GAIN (dB)
25
0
1
1
0
0
0
26
26
0
1
1
0
0
1
28
27
0
1
1
0
1
0
30
28
0
1
1
0
1
1
32
29
0
1
1
1
0
0
34
30
0
1
1
1
0
1
36
31
0
1
1
1
1
0
38
32
0
1
1
1
1
1
40
Do Not Use Volume Steps 33-60 See Table 7
61
1
1
1
1
0
0
42
62
1
1
1
1
0
1
44
63
1
1
1
1
1
0
46
64
1
1
1
1
1
1
48
Table 7. Unused Volume Steps
12
VOLUME
STEP
VOL5
VOL4
VOL3
VOL2
VOL1
VOL0
GAIN (dB)
33
1
0
0
0
0
0
-90
34
1
0
0
0
0
1
-25
35
1
0
0
0
1
0
-22
36
1
0
0
0
1
1
-19
37
1
0
0
1
0
0
-16
38
1
0
0
1
0
1
-13
39
1
0
0
1
1
0
-10
40
1
0
0
1
1
1
-8
41
1
0
1
0
0
0
-6
42
1
0
1
0
0
1
-4
43
1
0
1
0
1
0
0
44
1
0
1
0
1
1
4
45
1
0
1
1
0
0
8
46
1
0
1
1
0
1
12
47
1
0
1
1
1
0
14
48
1
0
1
1
1
1
16
49
1
1
0
0
0
0
18
50
1
1
0
0
0
1
20
51
1
1
0
0
1
0
22
52
1
1
0
0
1
1
24
53
1
1
0
1
0
0
26
54
1
1
0
1
0
1
28
55
1
1
0
1
1
0
30
56
1
1
0
1
1
1
32
57
1
1
1
0
0
0
34
58
1
1
1
0
0
1
36
59
1
1
1
0
1
0
38
60
1
1
1
0
1
1
40
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VOLUME CONTROL
The LM48557 has a 64 step volume control, but only 36 steps are recommended for use. Use steps 1 through
32 and steps 61 through 64 to set the gain of the device. Accessing steps 33 through 60 results in the repeated
gain conditions shown in Table 7. Steps 33 through 60 are not tested and should not be used.
SHUTDOWN FUNCTION
The LM48557 features a low-power shutdown mode that disables the device lowers the quiescent current to
0.01µA. Set bit B0 (SHDN) of the Mode Control register to 0 to disable the amplifier and charge pump. Set
SHDN to 1 for normal operation. Shutdown mode does not clear the I2C register. When re-enabled, the device
returns to its previous volume setting. To clear the I2C register, either remove power from the device, or toggle
RESET (see RESET section).
RESET
The LM48557 features an active low reset input. Driving RESET low clears the I2C register. Volume control is set
to 000000 (-90dB) and SHDN is set to 0, disabling the device. While RESET is low, the LM48557 ignores any
I2C data. After the device is reset, and RESET is driven high, the LM48557 remains in shutdown mode with the
volume set to -90dB. Re-enable the device by writing to the I2C register.
MUTE
The LM48557 features a mute mode. Set bit B1 (MUTE) of the Mode Control register to 1 to mute the device. In
mute mode, the gain is set to -90dB, equivalent to the volume step 1. Set MUTE = 0 to unmute the device. Once
unmuted, the device returns to its previous volume step.
TEST MODE
If enabled, TESTMODE does not affect device performance under normal operating conditions. Operating above
the recommended supply voltage range with TESTMODE enabled can result in damage to the device.
PROPER SELECTION OF EXTERNAL COMPONENTS
Power Supply Bypassing/Filtering
Proper power supply bypassing is critical for low noise performance and high PSRR. Place the supply bypass
capacitors as close to the device as possible. Place a 1µF ceramic capacitor from VDD to GND. Additional bulk
capacitance may be added as required.
Charge Pump Capacitor Selection
Use low ESR ceramic capacitors (less than 100mΩ) for optimum performance.
Charge Pump Flying Capacitor (C1)
The flying capacitor (C1) affects the load regulation and output impedance of the charge pump. A C1 value that
is too low results in a loss of current drive, leading to a loss of amplifier headroom. A higher valued C1 improves
load regulation and lowers charge pump output impedance to an extent. Above 2.2µF, the RDS(ON) of the charge
pump switches and the ESR of C1 and C2 dominate the output impedance. A lower value capacitor can be used
in systems where low maximum output power requirements.
Charge Pump Hold Capacitor (C2)
The value and ESR of the hold capacitor (C2) directly affects the ripple on CPVSS. Increasing the value of C2
reduces output ripple. Decreasing the ESR of C2 reduces both output ripple and charge pump output impedance.
A lower value capacitor can be used in systems where low maximum output power requirements.
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Input Capacitor Selection
Input capacitors block the DC component of the audio signal, eliminating any conflict between the DC component
of the audio source and the bias voltage of the LM48557. The input capacitors create a high-pass filter with the
input resistors RIN. The -3dB point of the high pass filter is found using the equation below.
f = 1 / 2πRINCIN
(Hz)
(1)
Where the value of RIN is given in the Electrical Characteristics Table.
High pass filtering the audio signal helps protect the speakers. When the LM48557 is using a single-ended
source, power supply noise on the ground is seen as an input signal. Setting the high-pass filter point above the
power supply noise frequencies, 217Hz in a GSM phone, for example, filters out the noise such that it is not
amplified and heard on the output. Capacitors with a tolerance of 10% or better are recommended for impedance
matching and improved CMRR and PSRR.
COMMON MODE SENSE
The LM48557 features a common mode sense pin (VCM, pin A3) that includes additional common mode
cancelling circuitry that improves the CMRR. When the volume control is set at a high gain step such as 48dB,
any mismatch in the input capacitors would degrade CMRR performance significantly. With the VCM pin
connected to the ground of the input source, it takes the input capacitor mismatches out of the equation and
therefore improves the CMRR. Another advantage with this feature is that only one input capacitor is needed in
the single-ended configuration as opposed to two well matched capacitors. See next section for details of
different configurations of the LM48857.
SINGLE-ENDED INPUT CONFIGURATION
Ground-Referenced Audio Source
The LM48557 input stage is compatible with ground-referenced input sources, such as CODECs with an
integrated headphone amplifier. Connect either input, IN+ or IN- to the CODEC output, and connect the unused
input and VCM to the CODEC output ground (Figure 22). An input coupling capacitor in series with the source
and device input is recommended to block the CODEC output offset voltage, minimizing click and pop and zipper
noise during volume transitions.
IN+
IN-
IN-
IN+
VCM
VCM
LM48557
Non-Inverting Configuration
LM48557
Inverting Configuration
Figure 22. Single-Ended Input Configuration with a Ground-Referenced Source
NON-GROUND REFERENCED AUDIO SOURCE
Stereo-to-Mono Conversion
The LM48557 can convert a single-ended stereo signal to a mono BTL signal (Figure 23). Connect the left and
right CODEC outputs in parallel through two equal value resistors to either IN+ or IN-, and connect the unused
input and VCM to the CODEC ground. Select the value of the resistors based on the desired frequency response
created by the combination of the input resistor and the input coupling capacitor.
14
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LEFT
LEFT
IN+
RIGHT
IN-
RIGHT
IN-
IN+
VCM
VCM
LM48557
LM48557
Non-Inverting Configuration
Inverting Configuration
Figure 23. Single-Ended Stereo-to-Mono BTL Conversion
PCB Layout Guidelines
Minimize trace impedance of the power, ground and all output traces for optimum performance. Voltage loss due
to trace resistance between the LM48557 and the load results in decreased output power and efficiency. Trace
resistance between the power supply and ground has the same effect as a poorly regulated supply, increased
ripple and reduced peak output power. Use wide traces for power supply inputs and amplifier outputs to minimize
losses due to trace resistance, as well as route heat away from the device. Proper grounding improves audio
performance, minimizes crosstalk between channels and prevents switching noise from interfering with the audio
signal. Use of power and ground planes is recommended.
Place all digital components and route digital signal traces as far as possible from analog components and
traces. Do not run digital and analog traces in parallel on the same PCB layer. If digital and analog signal lines
must cross either over or under each other, ensure that they cross in a perpendicular fashion.
Table 8. LM48557TL Demoboard Bill of Materials
Designator
Quantity
U1
1
LM48557TL Differential, Mono, Ceramic Speaker Driver with I2C Volume Control, and Reset
C1, C2, C5, C6, C7
Description
5
CAP CERAMIC 2.2µF 10V X5R 10% 0603
C3, C4
2
CAP .1µF 16V CERAMIC X7R 10% 1206
C8
1
CAP TANT LOESR 10µF 16V 10% SMD
J2
1
CONN SOCKET PCB VERT 16POS .1"
12
CONN HEADER VERT .100 2POS 30Au
JU1, JU2, JU3, JU4,
VCM, VDD, GND,
I2CVDD, IN+, IN-,
OUT+, OUTJU5
1
CONN HEADER VERT .100 3POS 30Au
R1, R2
2
RES 5.1K OHM 1/10W 5% 0603 SMD
R3
1
RES 20K OHM 1/10W 5% 0603 SMD
4
Jumper Shunt w/handle, 30uin gold plated, 0.100" pitch
JU1_SH, JU2_SH,
JU3_SH, JU5_SH
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PC Board Layout
16
Figure 24. Silk Screen
Figure 25. Top Layer
Figure 26. Layer 2
Figure 27. Layer 3
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Figure 28. Bottom Layer
Figure 29. Bottom Silkscreen
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Demo Board Schematic
Figure 30. LM48557 Demo Board Schematic
18
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Revision History
Rev
Date
Description
1.0
07/08/09
Initial released.
1.01
07/15/09
Deleted the “Tru-GND...” trademark on the cover page.
1.02
08/05/09
Text edits.
1.03
08/06/09
Fixed a typo error.
1.04
01/11/10
Added the LM48557UR package drawing, top markings, and the marketing outline.
D
02/05/2013
Changed layout of National Data Sheet to TI format.
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
LM48557TL/NOPB
ACTIVE
DSBGA
YZR
16
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
GM2
LM48557TLX/NOPB
ACTIVE
DSBGA
YZR
16
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
GM2
LM48557UR/NOPB
ACTIVE
DSBGA
YPD
16
250
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
GN5
LM48557URX/NOPB
ACTIVE
DSBGA
YPD
16
3000
RoHS & Green
SNAGCU
Level-1-260C-UNLIM
GN5
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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