LM4902LD/NOPB [TI]
0.675W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8, LLP-8;
| 型号： | LM4902LD/NOPB |
| 厂家： | 
TEXAS INSTRUMENTS |
| 描述： | 0.675W, 1 CHANNEL, AUDIO AMPLIFIER, PDSO8, LLP-8 放大器 光电二极管 商用集成电路 |
| 文件： | 总19页 (文件大小：794K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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information and details on our current products and services.
February 2002
LM4902
265mW at 3.3V Supply Audio Power Amplifier with
Shutdown Mode
j
General Description
The LM4902 is a bridged audio power amplifier capable of
delivering 265mW of continuous average power into an 8Ω
load with 1% THD+N from a 3.3V power supply.
THD+N at 1kHz for 675mW continuous
average output power into 8Ω,
VDD = 5V
1.0% (max)
0.1µA (typ)
j
Shutdown current
Boomer® audio power amplifiers were designed specifically
to provide high quality output power from a low supply volt-
age while requiring a minimal amount of external compo-
nents. Since the LM4902 does not require output coupling
capacitors, bootstrap capacitors or snubber networks, it is
optimally suited for low-power portable applications.
Features
n MSOP and LLP packaging
n No output coupling capacitors, bootstrap capacitors, or
snubber circuits are necessary
The LM4902 features an externally controlled, low power
consumption shutdown mode, and thermal shutdown protec-
tion.
n Thermal shutdown protection circuitry
n Unity-gain stable
n External gain configuration capability
n Latest generation ’click and pop’ suppression circuitry
The closed loop response of the unity-gain stable LM4902
can be configured by external gain-setting resistors.
Applications
n Cellular phones
Key Specifications
n PDA’s
n Any portable audio application
j
THD+N at 1kHz for 265mW continuous
average output power into 8Ω,
VDD = 3.3V
1.0% (max)
Typical Application
20029801
FIGURE 1. Typical Audio Amplifier Application Circuit
Boomer® is a registered trademark of National Semiconductor Corporation.
© 2002 National Semiconductor Corporation
DS200298
www.national.com
Connection Diagrams
MSOP
MSOP Marking
20029878
Top View
20029802
G - Boomer Family
C3 - LM4902MM
Top View
Order Number LM4902MM
See NS Package Number MUA08A
LLP
LLP Marking
20029877
Top View
XY - Date Code
TT - Die Traceability
G - Boomer Family
A3 - LM4902LD
20029875
Top View
Order Number LM4902LD
See NS Package Number LDA08B
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2
Absolute Maximum Ratings (Note 2)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Infrared (15 sec.)
220˚C
See AN-450 “Surface Mounting and their Effects on
Product Reliability” for other methods of soldering surface
mount devices.
Supply Voltage
6.0V
−65˚C to +150˚C
−0.3V to VDD + 0.3V
Internally limited
2000V
Thermal Resistance
Storage Temperature
Input Voltage
θJC (MSOP)
θJA (MSOP)
θJA (LLP)
56˚C/W
190˚C/W
67˚C/W
Power Dissipation (Note 3)
ESD Susceptibility (Note 4)
ESD Susceptibility (Note 5)
Junction Temperature
Soldering Information
Small Outline Package
Vapor Phase (60 sec.)
200V
Operating Ratings
Temperature Range
TMIN ≤ TA ≤ TMAX
Supply Voltage
150˚C
−40˚C ≤ TA ≤ +85˚C
2.0V ≤ VDD ≤ 5.5V
215˚C
Electrical Characteristics (Note 1) (Note 2)
The following specifications apply for VDD = 5V, for all available packages, unless otherwise specified. Limits apply for TA
25˚C
=
LM4902
Units
Limit
Symbol
Parameter
Conditions
Typical
(Limits)
(Notes 7,
(Note 6)
9)
6.0
5
IDD
Quiescent Power Supply Current
Shutdown Current
VIN = 0V, IO = 0A (Note 8)
VPIN1 =GND
4
0.1
5
mA (max)
µA (max)
mV (max)
mW (min)
ISD
VOS
PO
Output Offset Voltage
Output Power
VIN = 0V
50
300
THD = 1% (max); f = 1kHz; RL = 8Ω;
PO = 400 mWrms; AVD = 2; RL = 8Ω;
675
THD+N
Total Harmonic Distortion+Noise
0.4
%
<
20Hz ≤ f ≤ 20kHz, BW 80kHz
PSRR
Power Supply Rejection Ratio
VRIPPLE = 200mV sine p-p
f = 217Hz (Note 10)
f = 1KHz (Note 10)
70
67
55
55
dB
f = 217Hz (Note 11)
f = 1KHz (Note 11)
Electrical Characteristics (Notes 1, 2)
The following specifications apply for VDD = 3.3V, for all available packages, unless otherwise specified. Limits apply for TA
25˚C
=
LM4902
Units
Limit
Symbol
Parameter
Conditions
Typical
(Limits)
(Notes 7,
(Note 6)
9)
5
IDD
Quiescent Power Supply Current
Shutdown Current
VIN = 0V, IO = 0A (Note 8)
VPIN1 = GND
3
0.1
5
mA (max)
µA (max)
mV (max)
mW
ISD
3
VOS
PO
Output Offset Voltage
Output Power
VIN = 0V
50
THD = 1% (max); f = 1kHz; RL = 8Ω;
PO = 250 mWrms; AVD = 2; RL = 8Ω;
265
THD+N
Total Harmonic Distortion+Noise
0.4
%
<
20Hz ≤ f ≤ 20kHz, BW 80kHz
PSRR
Power Supply Rejection Ratio
VRIPPLE = 200mV sine p-p
f = 217Hz (Note 10)
f = 1KHz (Note 10)
73
70
60
68
dB
f = 217Hz (Note 11)
f = 1KHz (Note 11)
3
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Electrical Characteristics (Notes 1, 2)
The following specifications apply for VDD = 2.6V, for all available packages, unless otherwise specified. Limits apply for TA
25˚C
=
LM4902
Units
Limit
Symbol
Parameter
Conditions
Typical
(Limits)
(Notes 7,
(Note 6)
9)
4
IDD
Quiescent Power Supply Current
Shutdown Current
VIN = 0V, IO = 0A (Note 8)
VPIN1 = VDD
2.6
0.1
5
mA (max)
µA (max)
mV
ISD
2.0
VOS
PO
Output Offset Voltage
Output Power
VIN = 0V
THD = 1% (max); f = 1kHz; RL = 8Ω
PO = 100 mWrms; AVD = 2; RL = 8Ω;
130
mW
THD+N
Total Harmonic Distortion+Noise
0.4
%
<
20Hz ≤ f ≤ 20kHz, BW 80kHz
PSRR
Power Supply Rejection Ratio
VRIPPLE = 200mV sine p-p
f = 217Hz (Note 11)
f = 1KHz (Note 11)
58
63
dB
Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 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 guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which
guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit
is given, however, the typical value is a good indication of device performance.
Note 3: The maximum power dissipation must be derated at elevated temperatures and is dictated by T
, θ , and the ambient temperature T . The maximum
A
JMAX JA
allowable power dissipation is P
= (T
− T )/θ or the number given in the Absolute Maximum Ratings, whichever is lower. For the LM4902, T
=
JMAX
DMAX
JMAX
A
JA
150˚C. The typical junction-to-ambient thermal resistance, when board mounted, is 190˚C/W for package number MUA08A.
Note 4: Human body model, 100pF discharged through a 1.5kΩ resistor.
Note 5: Machine Model, 220pF–240pF discharged through all pins.
Note 6: Typicals are measured at 25˚C and represent the parametric norm.
Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 8: The quiescent power supply current depends on the offset voltage when a practical load is connected to the amplifier.
Note 9: Datasheet min/max specification limits are guaranteed by design, test, or statistical analysis.
Note 10: Unterminated input.
Note 11: 10Ω terminated input.
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4
External Components Description
(Figure 1)
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/(2π RiCI).
2.
Ci
Input coupling capacitor which blocks the DC voltage at the amplifier’s input terminals. Also creates a
highpass filter with Ri at fc = 1/(2π RiCi). Refer to the section, Proper Selection of External Components,
for an explanation of how to determine the value of Ci.
3.
4.
RF
CS
Feedback resistance which sets the closed-loop gain in conjunction with Ri.
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.
Bypass pin capacitor which provides half-supply filtering. Refer to the Proper Selection of External
Components for information concerning proper placement and selection of CB.
5.
CB
Typical Performance
Characteristics
THD+N vs Frequency
THD+N vs Frequency
20029830
20029831
THD+N vs Frequency
THD+N vs Frequency
20029832
20029833
5
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Typical Performance Characteristics (Continued)
THD+N vs Frequency
THD+N vs Frequency
THD+N vs Frequency
THD+N vs Frequency
20029834
20029835
20029837
20029839
THD+N vs Frequency
20029836
THD+N vs Frequency
20029838
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6
Typical Performance Characteristics (Continued)
THD+N vs Frequency
THD+N vs Output Power
20029840
20029841
THD+N vs
THD+N vs
Output Power
Output Power
20029842
20029843
THD+N vs
THD+N vs
Output Power
Output Power
20029844
20029845
7
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Typical Performance Characteristics (Continued)
THD+N vs
THD+N vs
Output Power
Output Power
20029846
20029847
20029849
20029851
THD+N vs
Output Power
THD+N vs
Output Power
20029848
THD+N vs
Output Power
THD+N vs
Output Power
20029850
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8
Typical Performance Characteristics (Continued)
Output Power vs
Supply Voltage
Output Power vs
Supply Voltage
20029852
20029853
Output Power vs
Supply Voltage
Output Power vs
Supply Voltage
20029854
20029855
Output Power vs
Load Resistance
Power Dissipation vs
Output Power
20029856
20029857
9
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Typical Performance Characteristics (Continued)
Power Dissipation vs
Output Power
Power Dissipation vs
Output Power
20029858
20029859
20029861
20029871
Clipping Voltage vs
Supply Voltage
Noise Floor
20029860
Noise Floor
Frequency Response vs
Input Capacitor Size
20029862
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10
Typical Performance Characteristics (Continued)
Power Supply
Rejection Ratio
Power Supply
Rejection Ratio
20029863
20029864
Power Supply
Rejection Ratio
Power Supply
Rejection Ratio
20029865
20029866
Power Supply Rejection Ratio
vs Supply Voltage
Power Supply Rejection Ratio
vs Supply Voltage
20029867
20029868
11
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Typical Performance Characteristics (Continued)
Power Derating Curve
Supply Current vs
Supply Voltage
20029870
20029873
Open Loop Frequency Response
LM4902LD Power Derating Curve (Note 12)
20029876
20029872
Note 12: This curve shows the LM4902LD’s thermal dissipation ability at different ambient temperatures given the exposed-DAP of the part is soldered to a plane
of 1oz. Cu with an area given in the label of each curve.
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12
choose an amplifier’s closed-loop gain without causing ex-
cessive clipping, please refer to the Audio Power Amplifier
Design section.
Application Information
EXPOSED-DAP PACKAGE PCB MOUNTING
CONSIDERATION
A bridge configuration, such as the one used in LM4902,
also creates a second advantage over single-ended amplifi-
ers. 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 configura-
tion. If an output coupling capacitor is not used in a
single-ended configuration, the half-supply bias across the
load would result in both increased internal lC power dissi-
pation as well as permanent loudspeaker damage.
The LM4902’s exposed-DAP (die-attach paddle) package
(LD) provides a low thermal resistance between the die and
the PCB to which the part is mounted and soldered. This
allows rapid heat from the die to the surrounding PCB cop-
per traces, ground plane, and surrounding air. This allows
the LM4902LD to operate at higher output power levels in
higher ambient temperatures than the MM package. Failing
to optimize thermal design may compromise the high power
performance and activate unwanted, though necessary,
thermal shutdown protection.
POWER DISSIPATION
Power dissipation is a major concern when designing a
successful amplifier, whether the amplifier is bridged or
single-ended. Equation 1 states the maximum power dissi-
pation point for a bridge amplifier operating at a given supply
voltage and driving a specified output load.
The LD package must have its DAP soldered to a copper
pad on the PCB. The DAP’s PCB copper pad is connected to
a large plane of continuous unbroken copper. This plane
forms a thermal mass, heat sink, and radiation area. Place
the heat sink area on either outside plane in the case of a
two-sided PCB, or on an inner layer of a board with more
than two layers. Connect the DAP copper pad to the inner
layer or backside copper heat sink area with 2 vias. The via
diameter should be 0.012in - 0.013in with a 1.27mm pitch.
Ensure efficient thermal conductivity by plating through the
vias.
PDMAX = (VDD)2/(2π2RL)
Single-Ended (1)
However, a direct consequence of the increased power de-
livered to the load by a bridge amplifier is an increase in
internal power dissipation point for a bridge amplifier oper-
ating at the same conditions.
PDMAX = 4(VDD)2/(2π2RL)
Bridge Mode (2)
Since the LM4902 has two operational amplifiers in one
package, the maximum internal power dissipation is 4 times
that of a single-ended amplifier. Even with this substantial
increase in power dissipation, the LM4902 does not require
heatsinking. From Equation 1, assuming a 5V power supply
and an 8Ω load, the maximum power dissipation point is
625 mW. The maximum power dissipation point obtained
from Equation 2 must not be greater than the power dissi-
pation that results from Equation 3:
Best thermal performance is achieved with the largest prac-
tical heat sink area. The power derating curve in the Typical
Performance Characteristics shows the maximum power
dissipation versus temperature for several different areas of
heat sink area. Placing the majority of the heat sink area on
another plane is preferred as heat is best dissipated through
the bottom of the chip. Further detailed and specific informa-
tion concerning PCB layout, fabrication, and mounting an LD
(LLP) package is available from National Semiconductor’s
Package Engineering Group under application note AN1187.
PDMAX = (TJMAX − TA)/θJA
(3)
For package MUA08A, θJA = 190˚C/W. TJMAX = 150˚C for
the LM4902. Depending on the ambient temperature, TA, of
the system surroundings, Equation 3 can be used to find the
maximum internal power dissipation supported by the IC
packaging. If the result of Equation 2 is greater than that of
Equation 3, then either the supply voltage must be de-
creased, the load impedance increased, the ambient tem-
perature reduced, or the θJA reduced with heatsinking. In
many cases larger traces near the output, VDD, and Gnd
pins can be used to lower the θJA. The larger areas of copper
provide a form of heatsinking allowing a higher power dissi-
pation. For the typical application of a 5V power supply, with
an 8Ω load, the maximum ambient temperature possible
without violating the maximum junction temperature is ap-
proximately 30˚C provided that device operation is around
the maximum power dissipation point. Internal power dissi-
pation is a function of output power. If typical operation is not
around the maximum power dissipation point, the ambient
temperature can be increased. Refer to the Typical Perfor-
mance Characteristics curves for power dissipation infor-
mation for lower output powers.
BRIDGE CONFIGURATION EXPLANATION
As shown in Figure 1, the LM4902 has two operational
amplifiers internally, allowing for a few different amplifier
configurations. The first amplifier’s gain is externally config-
urable, 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 10 kΩ
resistors. Figure 1 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 180˚. Consequently, the differential gain for the IC
is
*
AVD = 2 (RF/Ri)
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 its 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 con-
ditions. This increase in attainable output power assumes
that the amplifier is not current limited or clipped. In order to
POWER SUPPLY BYPASSING
As with any power 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. The effect of a larger half supply bypass capacitor
is improved PSRR due to increased half-supply stability.
13
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systems, whether internal or external, have little ability to
reproduce signals below 150Hz. In this case using a large
input capacitor may not increase system performance.
Application Information (Continued)
Typical applications employ a 5V regulator with 10µF and a
0.1µF bypass capacitors which aid in supply stability, but do
not eliminate the need for bypassing the supply nodes of the
LM4902. The selection of bypass capacitors, especially CB,
is thus dependent upon desired PSRR requirements, click
and pop performance as explained in the section, Proper
Selection of External Components, system cost, and size
constraints.
In addition to system cost and size, click and pop perfor-
mance is effected by the size of the input coupling capacitor,
Ci. A larger input coupling capacitor requires more charge to
1
reach its quiescent DC voltage (nominally
⁄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.
SHUTDOWN FUNCTION
Besides minimizing the input capacitor size, careful consid-
eration 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 LM4902 turns
In order to reduce power consumption while not in use, the
LM4902 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.
The trigger point between a logic low and logic high level is
typically half supply. It is best to switch between ground and
supply to provide maximum device performance. By switch-
ing the shutdown pin to GND, the LM4902 supply current
draw will be minimized in idle mode. While the device will be
disabled with shutdown pin voltages greater than GND, the
idle current may be greater than the typical value of 0.1µA. In
either case, the shutdown pin should be tied to a definite
voltage to avoid unwanted state changes.
on. The slower the LM4902’s outputs ramp to their quiescent
1
DC voltage (nominally ⁄
2
VDD), the smaller the turn-on pop.
Choosing CB equal to 1.0 µF along with a small value of Ci
(in the range of 0.1µF to 0.39µF), should produce a clickless
and popless shutdown function. While the device will func-
tion 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 or larger
is recommended in all but the most cost sensitive designs.
In many applications, a microcontroller or microprocessor
output is used to control the shutdown circuitry which pro-
vides a quick, smooth transition into shutdown. Another so-
lution is to use a single-pole, single-throw switch in conjunc-
tion with an external pull-up resistor. When the switch is
closed, the shutdown pin is connected to ground and dis-
ables the amplifier. If the switch is open, then the external
pull-up resistor will enable the LM4902. This scheme guar-
antees that the shutdown pin will not float, thus preventing
unwanted state changes.
AUDIO POWER AMPLIFIER DESIGN
Design a 300 mW/8Ω Audio Amplifier
Given:
Power Output
Load Impedance
Input Level
300mWrms
8Ω
1Vrms
20kΩ
Input Impedance
Bandwidth
±
100Hz–20 kHz 0.25dB
PROPER SELECTION OF EXTERNAL COMPONENTS
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 Per-
formance Characteristics section, the supply rail can be
easily found. A second way to determine the minimum sup-
ply rail is to calculate the required Vopeak using Equation 4
and add the dropout voltage. Using this method, the mini-
Proper selection of external components in applications us-
ing integrated power amplifiers is critical to optimize device
and system performance. While the LM4902 is tolerant to a
variety of external component combinations, consideration
to component values must be used to maximize overall
system quality.
The LM4902 is unity-gain stable, giving a designer maximum
system flexibility. The LM4902 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.
*
mum supply voltage would be (Vopeak + (2 VOD)), where
VOD is extrapolated from the Dropout Voltage vs Supply
Voltage curve in the Typical Performance Characteristics
section.
(4)
Using the Output Power vs Supply Voltage graph for an 8Ω
load, the minimum supply rail is 3.5V. But since 5V is a
standard supply voltage in most applications, it is chosen for
the supply rail. Extra supply voltage creates headroom that
allows the LM4902 to reproduce peaks in excess of 700 mW
without producing audible distortion. At this time, the de-
signer must make sure that the power supply choice along
with the output impedance does not violate the conditions
explained in the Power Dissipation section.
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 1. The input coupling capacitor, Ci, forms a
first order high pass filter which limits low frequency re-
sponse. This value should be chosen based on needed
frequency response for a few distinct reasons.
Once the power dissipation equations have been addressed,
the required differential gain can be determined from Equa-
tion 5.
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 attenu-
ation. But in many cases the speakers used in portable
(5)
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14
Application Information (Continued)
RF/Ri = AVD/2
(6)
From Equation 5, the minimum AVD is 1.55; use AVD = 2.
*
*
Ci ≥ 1/(2π 20 kΩ 20 Hz) = 0.397µF; use 0.39µF
Since the desired input impedance was 20 kΩ, and with a
AVD of 2, a ratio of 1:1 of RF to Ri results in an allocation of
Ri = RF = 20 kΩ. The final design step is to address the
bandwidth requirements which must be stated as a pair of
−3 dB frequency points. Five times away from a pole gives
0.17 dB down from passband response which is better than
The high frequency pole is determined by the product of the
desired high frequency pole, fH, and the differential gain,
VD. With a AVD = 2 and fH = 100kHz, the resulting GBWP
= 100kHz which is much smaller than the LM4902 GBWP of
25MHz. This figure displays that if a designer has a need to
design an amplifier with a higher differential gain, the
LM4902 can still be used without running into bandwidth
problems.
A
±
the required 0.25 dB specified.
fL = 100Hz/5 = 20Hz
fH = 20kHz x 5 = 100kHz
As stated in the External Components section, Ri in con-
junction with Ci create a highpass filter.
15
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Application Information (Continued)
DIFFERENTIAL AMPLIFIER CONFIGURATION FOR
LM4902
20029874
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16
Physical Dimensions inches (millimeters)
unless otherwise noted
8-Lead (0.118" Wide) Molded Mini Small Outline Package
Order Number LM4902MM
NS Package Number MUA08A
17
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
Order Number LM4902LD
NS Package Number LDA08B
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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
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systems which, (a) are intended for surgical implant
into the body, or (b) support or sustain life, and
whose failure to perform when properly used in
accordance with instructions for use provided in the
labeling, can be reasonably expected to result in a
significant injury to the user.
2. A critical component is any component of a life
support device or system whose failure to perform
can be reasonably expected to cause the failure of
the life support device or system, or to affect its
safety or effectiveness.
National Semiconductor
Corporation
Americas
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Response Group
Tel: 65-2544466
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National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.
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