LM4897MM/NOPB [TI]
1.1W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO10, MSOP-10;
| 型号： | LM4897MM/NOPB |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 1.1W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO10, MSOP-10 放大器 光电二极管 商用集成电路 |
| 文件： | 总17页 (文件大小：635K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
OBSOLETE
LM4897
www.ti.com
SNAS183E –APRIL 2003–REVISED APRIL 2013
LM4897
1.1 Watt Audio Power Amplifier with Fade-In and
Fade-Out
Check for Samples: LM4897
1
FEATURES
DESCRIPTION
The LM4897 is an audio power amplifier primarily
designed for demanding applications in mobile
phones and other portable communication device
applications. It is capable of delivering 1.1W of
continuous average power to an 8Ω BTL load with
less than 1% distortion (THD+N) from a +5VDC power
supply.
2
•
No Output Coupling Capacitors, Snubber
Networks or Bootstrap Capacitors Required
•
•
•
•
Unity Gain Stable
Ultra Low Current Shutdown Mode
Fade-In/Fade-Out
BTL Output Can Drive Capacitive Loads up to
100pF
The LM4897 contains advanced pop and click
circuitry that eliminate noises which would otherwise
occur during turn-on and turn-off transitions. It also
contains a fade-in/fade-out feature that eliminates
unnatural sound generated by asserting/de-asserting
the SHUTDOWN pin. The LM4897 is unity-gain
stable and can be configured by external gain-setting
resistors.
•
Advanced Pop and Click Circuitry Eliminates
Noises During Turn-On and Turn-Off
Transitions
•
•
2.6V - 5.5V Operation
Available in a Space-Saving SOIC Package
KEY SPECIFICATIONS
The LM4897 features a low-power consumption
global shutdown mode, which is achieved by driving
the shutdown pin with logic low. Additionally, the
LM4897 features an internal thermal shutdown
protection mechanism.
•
•
•
•
Improved PSRR at 5V, 3V, & 217Hz: 62dB (typ)
Higher PO at 5V, THD+N = 1%: 1.1W (typ)
Higher PO at 3V, THD+N = 1%: 350mW (typ)
Shutdown Current: 0.1μA (typ)
Boomer audio power amplifiers were designed
specifically to provide high quality output power with a
minimal amount of external components. The
LM4897 does not require output coupling capacitors
or bootstrap capacitors, and therefore is ideally suited
for lower-power portable applications where minimal
space and power consumption are primary
requirements.
APPLICATIONS
•
•
•
Mobile Phones
PDAs
Portable Electronic Devices
Connection Diagrams
Mini Small Outline (VSSOP) Package
Figure 1. Top View
See package Number DGS0010A
1
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.
All trademarks are the property of their respective owners.
2
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 © 2003–2013, Texas Instruments Incorporated
OBSOLETE
LM4897
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Typical Application
Figure 2. Typical Audio Amplifier Application Circuit
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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)
Supply Voltage
6.0V
−65°C to +150°C
−0.3V to VDD +0.3V
Internally Limited
2000V
Storage Temperature
Input Voltage
Power Dissipation(3)
ESD Susceptibility(4)
ESD Susceptibility(5)
Junction Temperature
Thermal Resistance
θJC (DGS0010A)
200V
150°C
56°C/W
θJA (DGS0010A)
190°C/W
(1) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which specify performance limits. This assumes that the device is within the Operating
Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication of device
performance.
(2) If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
(3) 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. For the LM4897, see power derating curves (in the Typical Performance Characteristics section) for additional information.
(4) Human body model, 100pF discharged through a 1.5kΩ resistor.
(5) Machine Model, 220pF–240pF discharged through all pins.
Operating Ratings
Temperature Range
T
MIN ≤ TA ≤ TMAX
−40°C ≤ TA ≤ 85°C
2.6V ≤ VDD ≤ 5.5V
Supply Voltage
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Electrical Characteristics VDD = 5.0V(1)(2)
The following specifications apply for the circuit shown in Figure 2 unless otherwise specified. Limits apply for TA = 25°C.
LM4897
Units
(Limits)
Symbol
Parameter
Conditions
Typical(3)
Limit(4)(5)
IDD
Quiescent Power Supply Current
Shutdown Current
VIN = 0V, 8Ω BTL
5
9
2
mA (max)
µA (max)
mV (max)
W (min)
%
ISD
Vshutdown = GND
0.1
4
VOS
Po
Output Offset Voltage
Output Power
30
0.9
THD+N = 1% (max), f = 1kHz
Po = 0.4Wrms, f = 1kHz
1.1
0.1
THD+N
Total Harmonic Distortion+Noise
Vripple = 200mVpp sine wave,
CB = 1.0µF
63 (f = 1kHz)
62 (f = 217Hz)
55
55
PSRR
Power Supply Rejection Ratio
dB (min)
Input terminated with 10Ω to GND
VSDIH
VSDIL
Shutdown High Input Voltage
Shutdown Low Input Voltage
1.4
0.4
V (min)
V (max)
A-Weighted, Measured across 8Ω
BTL
Input terminated with 10Ω to ground
VON
TON
Output Noise
Turn-On Time
26
25
µVRMS
CBYPASS = 1µF
35
ms (max)
(1) All voltages are measured with respect to the ground pin, unless otherwise specified.
(2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which specify performance limits. This assumes that the device is within the Operating
Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication of device
performance.
(3) Typicals are measured at 25°C and represent the parametric norm.
(4) Limits are specified to AOQL (Average Outgoing Quality Level).
(5) Exposure to direct sunlight will increase ISD by a maximum of 2µA.
Electrical Characteristics VDD = 3.0V(1)(2)
The following specifications apply for the circuit shown in Figure 2 unless otherwise specified. Limits apply for TA = 25°C.
LM4897
Units
(Limits)
Symbol
Parameter
Conditions
Typical(3)
Limit(4)(5)
IDD
Quiescent Power Supply Current
Shutdown Current
VIN = 0V, 8Ω BTL
4
0.1
350
4
8
2
mA (max)
µA (max)
mW (min)
mV (max)
%
ISD
Vshutdown = GND
Po
Output Power
THD+N = 1% (max), f = 1kHz
320
30
VOS
THD+N
Output Offset Voltage
Total Harmonic Distortion+Noise
Po = 0.15Wrms, f = 1kHz
0.1
Vripple = 200mVpp sine wave,
CB = 1.0µF
63 (f = 1kHz)
62 (f = 217Hz)
55
55
PSRR
Power Supply Rejection Ratio
dB (min)
Input terminated with 10Ω to ground
VSDIH
VSDIL
Shutdown High Input Voltage
Shutdown Low Input Voltage
1.4
0.4
V (min)
V (max)
A-Weighted, Measured across 8Ω
BTL
VON
Output Voltage Noise
26
µVRMS
Input terminated with 10Ω to ground
(1) All voltages are measured with respect to the ground pin, unless otherwise specified.
(2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which specify performance limits. This assumes that the device is within the Operating
Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication of device
performance.
(3) Typicals are measured at 25°C and represent the parametric norm.
(4) Limits are specified to AOQL (Average Outgoing Quality Level).
(5) Exposure to direct sunlight will increase ISD by a maximum of 2µA.
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Electrical Characteristics VDD = 2.6V(1)(2)(3)(4)(5)
The following specifications apply for the circuit shown in Figure 2 unless otherwise specified. Limits apply for TA = 25°C.
LM4897
Units
(Limits)
Symbol
Parameter
Conditions
Typical(6)
Limit(7)(8)
IDD
Quiescent Power Supply Current
Shutdown Current
VIN = 0V, 8Ω BTL
3.5
0.1
4
7
2
mA (max)
µA (max)
mV (max)
ISD
Vshutdown = GND
VOS
Output Offset Voltage
30
THD+N = 1% (max), f = 1kHz
RL = 8Ω
Po
Output Power
mW (min)
%
250
0.1
THD+N
Total Harmonic Distortion+Noise
Po = 0.1Wrms, f = 1kHz
Vripple = 200mVpp sine wave,
CB = 1.0µF
55 (f = 1kHz)
55 (f = 217Hz)
PSRR
Power Supply Rejection Ratio
dB
Input terminated with 10Ω to GND
(1) All voltages are measured with respect to the ground pin, unless otherwise specified.
(2) Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for
which the device is functional, but do not ensure specific performance limits. Electrical Characteristics state DC and AC electrical
specifications under particular test conditions which specify performance limits. This assumes that the device is within the Operating
Ratings. Specifications are not ensured for parameters where no limit is given, however, the typical value is a good indication of device
performance.
(3) If the product is in shutdown mode, and VDD exceeds 6V (to a max of 8V VDD), then most of the excess current will flow through the
ESD protection circuits. If the source impedance limits the current to a max of 10ma, then the part will be protected. If the part is
enabled when VDD is above 6V, circuit performance will be curtailed or the part may be permanently damaged.
(4) All bumps have the same thermal resistance and contribute equally when used to lower thermal resistance.
(5) Maximum power dissipation (PDMAX) in the device occurs at an output power level significantly below full output power. PDMAX can be
calculated using APPLICATION INFORMATION shown in the APPLICATION INFORMATION section. It may also be obtained from the
power dissipation graphs.
(6) Typicals are measured at 25°C and represent the parametric norm.
(7) Limits are specified to AOQL (Average Outgoing Quality Level).
(8) Exposure to direct sunlight will increase ISD by a maximum of 2µA.
External Components Description
(See Figure 2)
Components
Functional Description
1.
Ri
Inverting input resistance which sets the closed-loop gain in conjunction with Rf. This resistor also forms a high pass
filter with Ci at fC= 1/(2πRiCi).
2.
Ci
Input coupling capacitor which blocks the DC voltage at the amplifiers input terminals. Also creates a highpass filter with
Ri at fC = 1/(2πRiCi). Refer to the section, Proper Selection of External Components, for an explanation of how to
determine the value of Ci.
3.
4.
Rf
Feedback resistance which sets the closed-loop gain in conjunction with Ri.
CS
Supply bypass capacitor which provides power supply filtering. Refer to the Power Supply Bypassing section for
information concerning proper placement and selection of the supply bypass capacitor.
5.
CB
Bypass pin capacitor which provides half-supply filtering. Refer to the section, Proper Selection of External
Components, for information concerning proper placement and selection of CB.
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TYPICAL PERFORMANCE CHARACTERISTICS
THD+N vs Frequency
THD+N vs Frequency
VDD = 3V, RL = 8Ω
PWR = 150mW
VDD = 5V, RL = 8Ω
PWR = 250mW
Figure 3.
Figure 4.
THD+N vs Frequency
VDD = 2.6V, RL = 8Ω
PWR = 100mW
THD+N vs Power Out
VDD = 5V
RL = 8Ω, f = 1kHz
Figure 5.
Figure 6.
Power Supply Rejection Ratio (PSRR), VDD = 5V
RL = 8Ω, f = 1kHz, CB = 1µF, AV = 2
Vripple = 200mVpp, Input terminated with 10Ω
Power Supply Rejection Ratio (PSRR), VDD = 3V
RL = 8Ω, f = 1kHz, CB = 1µF, AV = 2
Vripple = 200mVpp, Input terminated with 10Ω
Figure 7.
Figure 8.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Power Supply Rejection Ratio (PSRR), VDD = 2.6V
Power Dissipation vs Output Power
RL = 8Ω, f = 1kHz, CB = 1µF, AV = 2
VDD = 5V, RL = 8Ω, f = 1kHz
THD+N ≤ 1.0%, BW < 80kHz
Vripple = 200mVpp, Input terminated with 10Ω
Figure 9.
Figure 10.
Power Dissipation vs Output Power
VDD = 3V, RL = 8Ω, f = 1kHz
Power Dissipation vs Output Power
VDD = 2.6V, f = 1kHz
THD+N ≤ 1.0%, BW < 80kHz
THD+N ≤ 1.0%, BW < 80kHz
Figure 11.
Figure 12.
Power Derating - VSSOP PDMAX = 670mW
VDD = 5V, RL = 8Ω
Output Power vs Supply Voltage
Figure 13.
Figure 14.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Output Power vs Load Resistance
Clipping (Dropout) Voltage vs Supply Voltage
Figure 15.
Figure 16.
Supply Current vs Shutdown Voltage
Shutdown Hysterisis Voltage VDD = 5V
Figure 17.
Figure 18.
Shutdown Hysterisis Voltage VDD = 3V
Shutdown Hysterisis Voltage VDD = 2.6V
Figure 19.
Figure 20.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Open Loop Frequency Response
Frequency Response vs Input Capacitor Size
Figure 21.
Figure 22.
Fade-In VDD = 5V, RL = 8Ω, f = 1kHz
Ri = 100kΩ, Rf = 100kΩ
Fade-Out VDD = 5V, RL = 8Ω, f = 1kHz
Ri = 100kΩ, Rf = 100kΩ
Figure 23.
Figure 24.
Fade-In VDD = 5V, RL = 8Ω, f = 1kHz
Ri = 47kΩ, Rf = 47kΩ
Fade-Out VDD = 5V, RL = 8Ω, f = 1kHz
Ri = 47kΩ, Rf = 47kΩ
Figure 25.
Figure 26.
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TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Fade-In VDD = 5V, RL = 8Ω, f = 1kHz
Ri = 10kΩ, Rf = 10kΩ
Fade-Out VDD = 5V, RL = 8Ω, f = 1kHz
Ri = 10kΩ, Rf = 10kΩ
Figure 27.
Figure 28.
Fade-In VDD = 5V, RL = 8Ω, f = 1kHz
Ri = 9.4kΩ, Rf = 47kΩ
Fade-Out VDD = 5V, RL = 8Ω, f = 1kHz
Ri = 9.4kΩ, Rf = 47kΩ
Figure 29.
Figure 30.
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APPLICATION INFORMATION
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 2, the LM4897 has two operational amplifiers internally, allowing for a few different amplifier
configurations. The first amplifier's gain is externally configurable, while the second amplifier is internally fixed in
a unity-gain, inverting configuration. The closed-loop gain of the first amplifier is set by selecting the ratio of Rf to
Ri while the second amplifier's gain is fixed by the two internal 20kΩ resistors. Figure 2 shows that the output of
amplifier one serves as the input to amplifier two which results in both amplifiers producing signals identical in
magnitude, but out of phase by 180°. Consequently, the differential gain for the IC is:
AVD= 2 x (Rf/Ri)
(1)
By driving the load differentially through outputs Vo1 and Vo2, an amplifier configuration commonly referred to as
“bridged mode” is established. Bridged mode operation is different from the classical single-ended amplifier
configuration where one side of the load is connected to ground.
A bridge amplifier design has a few distinct advantages over the single-ended configuration, as it provides
differential drive to the load, thus doubling output swing for a specified supply voltage. Four times the output
power is possible as compared to a single-ended amplifier under the same conditions. This increase in attainable
output power assumes that the amplifier is not current limited or clipped. In order to choose an amplifier's closed-
loop gain without causing excessive clipping, please refer to the Audio Power Amplifier Design section.
A bridge configuration, such as the one used in LM4897, also creates a second advantage over single-ended
amplifiers. Since the differential outputs, Vo1 and Vo2, are biased at half-supply, no net DC voltage exists across
the load. This eliminates the need for an output coupling capacitor which is required in a single supply, single-
ended amplifier configuration. Without an output coupling capacitor, the half-supply bias across the load would
result in both increased internal IC power dissipation and also possible loudspeaker damage.
POWER DISSIPATION
Power dissipation is a major concern when designing a successful amplifier, whether the amplifier is bridged or
single-ended. A direct consequence of the increased power delivered to the load by a bridge amplifier is an
increase in internal power dissipation. Since the LM4897 has two operational amplifiers in one package, the
maximum internal power dissipation is 4 times that of a single-ended amplifier. The maximum power dissipation
for a given application can be derived from the power dissipation graphs or from Equation 2:
PDMAX = 4 x (VDD)2 / (2π2RL)
(2)
It is critical that the maximum junction temperature (TJMAX) of 150°C is not exceeded. TJMAX can be determined
from the power derating curves by using PDMAX and the PC board foil area. By adding additional copper foil, the
thermal resistance of the application can be reduced from a free air value of 150°C/W, resulting in higher PDMAX
Additional copper foil can be added to any of the leads connected to the LM4897. It is especially effective when
connected to VDD, GND, and the output pins. Refer to the application information on the LM4897 reference
design board for an example of good heat sinking. If TJMAX still exceeds 150°C, then additional changes must be
made. These changes can include reduced supply voltage, higher load impedance, or reduced ambient
temperature. Internal power dissipation is a function of output power. Refer to the Typical Performance
Characteristics curves for power dissipation information for different output powers and output loading.
.
POWER SUPPLY BYPASSING
As with any amplifier, proper supply bypassing is critical for low noise performance and high power supply
rejection. The capacitor location on both the bypass and power supply pins should be as close to the device as
possible. Typical applications employ a 5V regulator with 10µF tantalum or electrolytic capacitor and a ceramic
bypass capacitor which aid in supply stability. This does not eliminate the need for bypassing the supply nodes of
the LM4897. The selection of a bypass capacitor, especially CB, is dependent upon PSRR requirements, click
and pop performance (as explained in the section, Proper Selection of External Components), system cost, and
size constraints.
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SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the LM4897 contains a shutdown pin to externally turn off
the amplifier's bias circuitry. This shutdown feature turns the amplifier off when a logic low is placed on the
shutdown pin. By switching the shutdown pin to ground, the LM4897 supply current draw will be minimized in idle
mode. While the device will be disabled with shutdown pin voltages less than 0.4VDC, the idle current may be
greater than the typical value of 0.1µA. (Idle current is measured with the shutdown pin tied to ground).
In many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry to
provide a quick, smooth transition into shutdown. Another solution is to use a single-pole, single-throw switch in
conjunction with an external pull-up resistor. When the switch is closed, the shutdown pin is connected to ground
which disables the amplifier. If the switch is open, then the external pull-up resistor to VDD will enable the
LM4897. This scheme ensures that the shutdown pin will not float thus preventing unwanted state changes.
PROPER SELECTION OF EXTERNAL COMPONENTS
Proper selection of external components in applications using integrated power amplifiers is critical to optimize
device and system performance. While the LM4897 is tolerant of external component combinations,
consideration to component values must be used to maximize overall system quality.
The LM4897 is unity-gain stable which gives the designer maximum system flexibility. The LM4897 should be
used in low gain configurations to minimize THD+N values, and maximize the signal to noise ratio. Low gain
configurations require large input signals to obtain a given output power. Input signals equal to or greater than 1
Vrms are available from sources such as audio codecs. Please refer to the section, Audio Power Amplifier
Design, for a more complete explanation of proper gain selection.
Besides gain, one of the major considerations is the closed-loop bandwidth of the amplifier. To a large extent, the
bandwidth is dictated by the choice of external components shown in Figure 2. The input coupling capacitor, Ci,
forms a first order high pass filter which limits low frequency response. This value should be chosen based on
needed frequency response for a few distinct reasons.
Selection Of Input Capacitor Size
Large input capacitors are both expensive and space hungry for portable designs. Clearly, a certain sized
capacitor is needed to couple in low frequencies without severe attenuation. But in many cases the speakers
used in portable systems, whether internal or external, have little ability to reproduce signals below 100Hz to
150Hz. Thus, using a large input capacitor may not increase actual system performance.
In addition to system cost and size, click and pop performance is effected by the size of the input coupling
capacitor, Ci. A larger input coupling capacitor requires more charge to reach its quiescent DC voltage (nominally
1/2 VDD). This charge comes from the output via the feedback and is apt to create pops upon device enable.
Thus, by minimizing the capacitor size based on necessary low frequency response, turn-on pops can be
minimized.
Besides minimizing the input capacitor size, careful consideration should be paid to the bypass capacitor value.
Bypass capacitor, CB, is the most critical component to minimize turn-on pops since it determines how fast the
LM4897 turns on. The slower the LM4897's outputs ramp to their quiescent DC voltage (nominally 1/2 VDD), the
smaller the turn-on pop. Choosing CB equal to 1.0µF along with a small value of Ci (in the range of 0.1µF to
0.39µF), should produce a virtually clickless and popless shutdown function. While the device will function
properly, (no oscillations or motorboating), with CB equal to 0.1µF, the device will be much more susceptible to
turn-on clicks and pops. Thus, a value of CB equal to 1.0µF is recommended in all but the most cost sensitive
designs.
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AUDIO POWER AMPLIFIER DESIGN
A 1W/8Ω Audio Amplifier
Given:
Power Output
Load Impedance
Input Level
1 Wrms
8Ω
1 Vrms
Input Impedance
Bandwidth
20kΩ
100Hz – 20kHz ± 0.2 dB
A designer must first determine the minimum supply rail to obtain the specified output power. By extrapolating
from the Output Power vs Supply Voltage graphs in the Typical Performance Characteristics section, the supply
rail can be easily found. A second way to determine the minimum supply rail is to calculate the required Vopeak
using Equation 2 and add the output voltage. Using this method, the minimum supply voltage would be:
(Vopeak + (VOD + VODBOT))
TOP
where
•
VODBOT and VODTOP are extrapolated from the Dropout Voltage vs Supply Voltage curve (in the Typical
Performance Characteristics section), and
•
(3)
5V is a standard voltage, in most applications, chosen for the supply rail. Extra supply voltage creates headroom
that allows the LM4897 to reproduce peaks in excess of 1W without producing audible distortion. At this time, the
designer must make sure that the power supply choice along with the output impedance does not violate the
conditions explained in the Power Dissipation section.
Once the power dissipation equations have been addressed, the required differential gain can be determined
from Equation 4:
where
•
AVD = (Rf / Ri) 2
(4)
From Equation 4, the minimum AVD is 2.83; use AVD = 3.
Since the desired input impedance was 20kΩ, and with a AVD of 3, a ratio of 1.5:1 of Rf to Ri results in an
allocation of Ri = 20kΩ and Rf = 30kΩ. The final design step is to address the bandwidth requirements which
must be stated as a pair of −3dB frequency points. Five times away from a −3dB point is 0.17dB down from
passband response which is better than the required ±0.25dB specified:
fL = 100Hz / 5 = 20Hz
(5)
(6)
fH = 20kHz * 5 = 100kHz
As stated in the External Components section, Ri in conjunction with Ci create a highpass filter:
Ci ≥ 1 / (2π x 20kΩ*20Hz) = 0.397µF; use 0.39µF
(7)
The high frequency pole is determined by the product of the desired frequency pole, fH, and the differential gain,
AVD. With a AVD = 3 and fH = 100kHz, the resulting GBWP = 300kHz which is much smaller than the LM4897
GBWP of 10 MHz. This figure displays that if a designer has a need to design an amplifier with a higher
differential gain, the LM4897 can still be used without running into bandwidth limitations.
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LM4897 FADE-IN / FADE-OUT
Figure 31. Fade-In Behavior
Figure 32. Fade-Out Behavior
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LM4897 VSSOP DEMO BOARD ARTWORK
Figure 33. Top Overlay
Figure 34. Top Layer
Figure 35. Bottom Layer
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REVISION HISTORY
Changes from Revision D (April 2013) to Revision E
Page
•
Changed layout of National Data Sheet to TI format .......................................................................................................... 15
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