LM2678 [NSC]
SIMPLE SWITCHER High Efficiency 5A Step-Down Voltage Regulator; SIMPLE SWITCHER高效5A降压型稳压器
| 型号： | LM2678 |
| 厂家： | 
National Semiconductor |
| 描述： | SIMPLE SWITCHER High Efficiency 5A Step-Down Voltage Regulator |
| 文件： | 总27页 (文件大小：455K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
October 2003
LM2678
SIMPLE SWITCHER® High Efficiency 5A Step-Down
Voltage Regulator
General Description
Features
n Efficiency up to 92%
The LM2678 series of regulators are monolithic integrated
circuits which provide all of the active functions for a step-
down (buck) switching regulator capable of driving up to 5A
loads with excellent line and load regulation characteristics.
n Simple and easy to design with (using off-the-shelf
external components)
n 120 mΩ DMOS output switch
n 3.3V, 5V and 12V fixed output and adjustable (1.2V to
37V ) versions
n 50µA standby current when switched OFF
>
High efficiency ( 90%) is obtained through the use of a low
ON-resistance DMOS power switch. The series consists of
fixed output voltages of 3.3V, 5V and 12V and an adjustable
output version.
n
2%maximum output tolerance over full line and load
conditions
The SIMPLE SWITCHER concept provides for a complete
design using a minimum number of external components. A
high fixed frequency oscillator (260KHz) allows the use of
physically smaller sized components. A family of standard
inductors for use with the LM2678 are available from several
manufacturers to greatly simplify the design process.
n Wide input voltage range: 8V to 40V
n 260 KHz fixed frequency internal oscillator
n −40 to +125˚C operating junction temperature range
Applications
The LM2678 series also has built in thermal shutdown,
current limiting and an ON/OFF control input that can power
down the regulator to a low 50µA quiescent current standby
condition. The output voltage is guaranteed to a 2% toler-
ance. The clock frequency is controlled to within a 11%
tolerance.
>
n Simple to design, high efficiency ( 90%) step-down
switching regulators
n Efficient system pre-regulator for linear voltage
regulators
n Battery chargers
Typical Application
10088603
SIMPLE SWITCHER® is a registered trademark of National Semiconductor Corporation.
© 2003 National Semiconductor Corporation
DS100886
www.national.com
Connection Diagrams and Ordering Information
TO-263 Package
Top View
TO-220 Package
Top View
10088601
Order Number
10088602
Order Number
LM2678S-3.3, LM2678S-5.0,
LM2678S-12 or LM2678S-ADJ
LM2678T-3.3, LM2678T-5.0,
LM2678T-12 or LM2678T-ADJ
See NSC Package Number TS7B
See NSC Package Number TA07B
Top View
10088641
LLP-14
See NS package Number SRC14A
Ordering Information for LLP Package
Output Voltage
Order Information
Package Marking
Supplied As
250 Units on Tape and Reel
2500 Units on Tape and Reel
250 Units on Tape and Reel
2500 Units on Tape and Reel
250 Units on Tape and Reel
2500 Units on Tape and Reel
250 Units on Tape and Reel
2500 Units on Tape and Reel
12
12
LM2678SD-12
S0003BB
LM2678SDX-12
LM2678SD-3.3
LM2678SDX-3.3
LM2678SD-5.0
LM2678SDX-5.0
LM2678SD-ADJ
LM2678SDX-ADJ
S0003BB
3.3
3.3
5.0
5.0
ADJ
ADJ
S0003CB
S0003CB
S0003DB
S0003DB
S0003EB
S0003EB
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2
Absolute Maximum Ratings (Note 1)
Storage Temperature Range
Soldering Temperature
Wave
−65˚C to 150˚C
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
4 sec, 260˚C
10 sec, 240˚C
75 sec, 219˚C
Infrared
Input Supply Voltage
ON/OFF Pin Voltage
Switch Voltage to Ground
Boost Pin Voltage
45V
−0.1V to 6V
−1V to VIN
Vapor Phase
Operating Ratings
VSW + 8V
Supply Voltage
8V to 40V
Feedback Pin Voltage
Power Dissipation
ESD (Note 2)
−0.3V to 14V
Internally Limited
2 kV
Junction Temperature Range (TJ)
−40˚C to 125˚C
Electrical Characteristics Limits appearing in bold type face apply over the entire junction temperature
range of operation, −40˚C to 125˚C. Specifications appearing in normal type apply for TA = TJ = 25˚C.
LM2678-3.3
Symbol
Parameter
Conditions
Typical
(Note 3)
3.3
Min
Max
Units
(Note 4)
(Note 4)
VOUT
Output Voltage
Efficiency
VIN = 8V to 40V, 100mA ≤ IOUT ≤ 5A
3.234/3.201
3.366/3.399
V
η
VIN = 12V, ILOAD = 5A
82
%
LM2678-5.0
Symbol
Parameter
Conditions
Typical
(Note 3)
5.0
Min
Max
Units
(Note 4)
(Note 4)
VOUT
Output Voltage
Efficiency
VIN = 8V to 40V, 100mA ≤ IOUT ≤ 5A
4.900/4.850
5.100/5.150
V
η
VIN = 12V, ILOAD = 5A
84
%
LM2678-12
Symbol
Parameter
Conditions
Typical
(Note 3)
12
Min
Max
Units
(Note 4)
(Note 4)
VOUT
Output Voltage
Efficiency
VIN = 15V to 40V, 100mA ≤ IOUT ≤ 5A
11.76/11.64
12.24/12.36
V
η
VIN = 24V, ILOAD = 5A
92
%
LM2678-ADJ
Symbol
Parameter
Conditions
Typ
Min
Max
Units
(Note 3)
(Note 4)
(Note 4)
VFB
Feedback
VIN = 8V to 40V, 100mA ≤ IOUT ≤ 5A
VOUT Programmed for 5V
1.21
84
1.186/1.174
1.234/1.246
V
Voltage
η
Efficiency
VIN = 12V, ILOAD = 5A
%
3
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All Output Voltage Versions
Electrical Characteristics
Limits appearing in bold type face apply over the entire junction temperature range of operation, −40˚C to 125˚C. Specifica-
tions appearing in normal type apply for TA = TJ = 25˚C. Unless otherwise specified VIN=12V for the 3.3V, 5V and Adjustable
versions and VIN=24V for the 12V version.
Symbol
Parameter
Conditions
Typ
Min
Max
Units
DEVICE PARAMETERS
IQ
Quiescent
Current
VFEEDBACK = 8V
4.2
6
mA
For 3.3V, 5.0V, and ADJ Versions
VFEEDBACK = 15V
For 12V Versions
ISTBY
Standby
ON/OFF Pin = 0V
Quiescent
Current
50
7
100/150
8.3/8.75
µA
A
ICL
IL
Current Limit
Output Leakage
Current
6.1/5.75
VIN = 40V, ON/OFF Pin = 0V
VSWITCH = 0V
µA
200
15
mA
VSWITCH = −1V
16
RDS(ON) Switch
On-Resistance
ISWITCH = 5A
0.12
0.14/0.225
Ω
fO
Oscillator
Measured at Switch Pin
260
225
280
kHz
Frequency
Duty Cycle
D
Maximum Duty Cycle
Minimum Duty Cycle
VFEEDBACK = 1.3V
ADJ Version Only
91
0
%
%
IBIAS
Feedback Bias
Current
85
nA
VON/OFF ON/OFF
Threshold
1.4
0.8
2.0
45
V
Voltage
ION/OFF
θJA
ON/OFF Input
ON/OFF Input = 0V
20
65
µA
Current
Thermal
Resistance
T Package, Junction to Ambient
(Note 5)
θJA
T Package, Junction to Ambient
(Note 6)
45
θJC
θJA
T Package, Junction to Case
S Package, Junction to Ambient
(Note 7)
2
56
˚C/W
θJA
θJA
S Package, Junction to Ambient
(Note 8)
35
26
S Package, Junction to Ambient
(Note 9)
θJC
θJA
S Package, Junction to Case
SD Package, Junction to Ambient
(Note 10)
2
++
55
˚C/W
θJA
SD Package, Junction to Ambient
(Note 11)
29
Note 1: Absolute Maximum Ratings are limits beyond which damage to the device may occur. Operating Ratings indicate conditions under which of the device is
guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test condition, see the electrical
Characteristics tables.
Note 2: ESD was applied using the human-body model, a 100pF capacitor discharged through a 1.5 kΩ resistor into each pin.
Note 3: Typical values are determined with T = T = 25˚C and represent the most likely norm.
A
J
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4
All Output Voltage Versions
Electrical Characteristics (Continued)
Note 4: All limits are guaranteed at room temperature (standard type face) and at temperature extremes (bold type face). All room temperature limits are 100%
tested during production with T = T = 25˚C. All limits at temperature extremes are guaranteed via correlation using standard standard Quality Control (SQC)
A
J
methods. All limits are used to calculate Average Outgoing Quality Level (AOQL).
Note 5: Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with 1
board with minimum copper area.
⁄
2
inch leads in a socket, or on a PC
inch leads soldered to a PC board
Note 6: Junction to ambient thermal resistance (no external heat sink) for the 7 lead TO-220 package mounted vertically, with 1
⁄
2
containing approximately 4 square inches of (1 oz.) copper area surrounding the leads.
Note 7: Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board area of 0.136 square inches (the same size as the
TO-263 package) of 1 oz. (0.0014 in. thick) copper.
Note 8: Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board area of 0.4896 square inches (3.6 times the area
of the TO-263 package) of 1 oz. (0.0014 in. thick) copper.
Note 9: Junction to ambient thermal resistance for the 7 lead TO-263 mounted horizontally against a PC board copper area of 1.0064 square inches (7.4 times the
area of the TO-263 package) of 1 oz. (0.0014 in. thick) copper. Additional copper area will reduce thermal resistance further. See the thermal model in Switchers
Made Simple® software.
Note 10: Junction to ambient thermal resistance for the 14-lead LLP mounted on a PC board copper area equal to the die attach paddle.
Note 11: Junction to ambient thermal resistance for the 14-lead LLP mounted on a PC board copper area using 12 vias to a second layer of copper equal to die
attach paddle. Additional copper area will reduce thermal resistance further. For layout recommendations, refer to Application Note AN-1187.
5
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Typical Performance Characteristics
Normalized
Output Voltage
Line Regulation
10088609
10088610
Efficiency vs Input Voltage
Efficiency vs ILOAD
10088611
10088612
Switch Current Limit
Operating Quiescent Current
10088604
10088605
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Typical Performance Characteristics (Continued)
Standby Quiescent Current
ON/OFF Threshold Voltage
10088640
10088613
ON/OFF Pin Current (Sourcing)
Switching Frequency
10088614
10088615
Feedback Pin Bias Current
10088616
7
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Typical Performance Characteristics (Continued)
Continuous Mode Switching Waveforms
VIN = 20V, VOUT = 5V, ILOAD = 5A
Discontinuous Mode Switching Waveforms
VIN = 20V, VOUT = 5V, ILOAD = 500 mA
L = 10 µH, COUT = 400 µF, COUTESR = 13 mΩ
L = 10 µH, COUT = 400 µF, COUTESR = 13 mΩ
10088617
10088618
A: V
Pin Voltage, 10 V/div.
A: V
Pin Voltage, 10 V/div.
SW
SW
B: Inductor Current, 2 A/div
B: Inductor Current, 1 A/div
C: Output Ripple Voltage, 20 mV/div AC-Coupled
C: Output Ripple Voltage, 20 mV/div AC-Coupled
Horizontal Time Base: 1 µs/div
Horizontal Time Base: 1 µs//iv
Load Transient Response for Continuous Mode
VIN = 20V, VOUT = 5V
Load Transient Response for Discontinuous Mode
VIN = 20V, VOUT = 5V,
L = 10 µH, COUT = 400 µF, COUTESR = 13 mΩ
L = 10 µH, COUT = 400 µF, COUTESR = 13 mΩ
10088619
10088620
A: Output Voltage, 100 mV//div, AC-Coupled.
A: Output Voltage, 100 mV/div, AC-Coupled.
B: Load Current: 500 mA to 5A Load Pulse
B: Load Current: 200 mA to 3A Load Pulse
Horizontal Time Base: 100 µs/div
Horizontal Time Base: 200 µs/div
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Block Diagram
10088606
* Active Inductor Patent Number 5,514,947
†
Active Capacitor Patent Number 5,382,918
9
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GROUND
Application Hints
This is the ground reference connection for all components
in the power supply. In fast-switching, high-current applica-
tions such as those implemented with the LM2678, it is
recommended that a broad ground plane be used to mini-
mize signal coupling throughout the circuit
The LM2678 provides all of the active functions required for
a step-down (buck) switching regulator. The internal power
switch is a DMOS power MOSFET to provide power supply
designs with high current capability, up to 5A, and highly
efficient operation.
The LM2678 is part of the SIMPLE SWITCHER family of
power converters. A complete design uses a minimum num-
ber of external components, which have been pre-
determined from a variety of manufacturers. Using either this
data sheet or a design software program called LM267X
Made Simple (version 2.0) a complete switching power
supply can be designed quickly. The software is provided
free of charge and can be downloaded from National Semi-
conductor’s Internet site located at http://www.national.com.
FEEDBACK
This is the input to a two-stage high gain amplifier, which
drives the PWM controller. It is necessary to connect pin 6 to
the actual output of the power supply to set the dc output
voltage. For the fixed output devices (3.3V, 5V and 12V
outputs), a direct wire connection to the output is all that is
required as internal gain setting resistors are provided inside
the LM2678. For the adjustable output version two external
resistors are required to set the dc output voltage. For stable
operation of the power supply it is important to prevent
coupling of any inductor flux to the feedback input.
SWITCH OUTPUT
This is the output of a power MOSFET switch connected
directly to the input voltage. The switch provides energy to
an inductor, an output capacitor and the load circuitry under
control of an internal pulse-width-modulator (PWM). The
PWM controller is internally clocked by a fixed 260KHz
oscillator. In a standard step-down application the duty cycle
(Time ON/Time OFF) of the power switch is proportional to
the ratio of the power supply output voltage to the input
voltage. The voltage on pin 1 switches between Vin (switch
ON) and below ground by the voltage drop of the external
Schottky diode (switch OFF).
ON/OFF
This input provides an electrical ON/OFF control of the
power supply. Connecting this pin to ground or to any volt-
age less than 0.8V will completely turn OFF the regulator.
The current drain from the input supply when OFF is only
50µA. Pin 7 has an internal pull-up current source of approxi-
mately 20µA and a protection clamp zener diode of 7V to
ground. When electrically driving the ON/OFF pin the high
voltage level for the ON condition should not exceed the 6V
absolute maximum limit. When ON/OFF control is not re-
quired pin 7 should be left open circuited.
INPUT
The input voltage for the power supply is connected to pin 2.
In addition to providing energy to the load the input voltage
also provides bias for the internal circuitry of the LM2678.
For guaranteed performance the input voltage must be in the
range of 8V to 40V. For best performance of the power
supply the input pin should always be bypassed with an input
capacitor located close to pin 2.
DAP (LLP PACKAGE)
The Die Attach Pad (DAP) can and should be connected to
PCB Ground plane/island. For CAD and assembly guide-
lines refer to Application Note AN-1187 at http://
power.national.com.
C BOOST
A capacitor must be connected from pin 3 to the switch
output, pin 1. This capacitor boosts the gate drive to the
internal MOSFET above Vin to fully turn it ON. This mini-
mizes conduction losses in the power switch to maintain high
efficiency. The recommended value for C Boost is 0.01µF.
DESIGN CONSIDERATIONS
10088607
FIGURE 1. Basic circuit for fixed output voltage applications.
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Application Hints (Continued)
10088608
FIGURE 2. Basic circuit for adjustable output voltage applications
Power supply design using the LM2678 is greatly simplified
by using recommended external components. A wide range
of inductors, capacitors and Schottky diodes from several
manufacturers have been evaluated for use in designs that
cover the full range of capabilities (input voltage, output
voltage and load current) of the LM2678. A simple design
procedure using nomographs and component tables pro-
vided in this data sheet leads to a working design with very
little effort. Alternatively, the design software, LM267X Made
Simple (version 6.0), can also be used to provide instant
component selection, circuit performance calculations for
evaluation, a bill of materials component list and a circuit
schematic.
input and output voltage and load current. Several part types
are offered for a given amount of inductance. Both surface
mount and through-hole devices are available. The inductors
from each of the three manufacturers have unique charac-
teristics.
Renco: ferrite stick core inductors; benefits are typically
lowest cost and can withstand ripple and transient peak
currents above the rated value. These inductors have an
external magnetic field, which may generate EMI.
Pulse Engineering: powdered iron toroid core inductors;
these also can withstand higher than rated currents and,
being toroid inductors, will have low EMI.
Coilcraft: ferrite drum core inductors; these are the smallest
physical size inductors and are available only as surface
mount components. These inductors also generate EMI but
less than stick inductors.
The individual components from the various manufacturers
called out for use are still just a small sample of the vast
array of components available in the industry. While these
components are recommended, they are not exclusively the
only components for use in a design. After a close compari-
son of component specifications, equivalent devices from
other manufacturers could be substituted for use in an ap-
plication.
OUTPUT CAPACITOR
The output capacitor acts to smooth the dc output voltage
and also provides energy storage. Selection of an output
capacitor, with an associated equivalent series resistance
(ESR), impacts both the amount of output ripple voltage and
stability of the control loop.
Important considerations for each external component and
an explanation of how the nomographs and selection tables
were developed follows.
The output ripple voltage of the power supply is the product
of the capacitor ESR and the inductor ripple current. The
capacitor types recommended in the tables were selected
for having low ESR ratings.
INDUCTOR
The inductor is the key component in a switching regulator.
For efficiency the inductor stores energy during the switch
ON time and then transfers energy to the load while the
switch is OFF.
In addition, both surface mount tantalum capacitors and
through-hole aluminum electrolytic capacitors are offered as
solutions.
Nomographs are used to select the inductance value re-
quired for a given set of operating conditions. The nomo-
graphs assume that the circuit is operating in continuous
mode (the current flowing through the inductor never falls to
zero). The magnitude of inductance is selected to maintain a
maximum ripple current of 30% of the maximum load cur-
rent. If the ripple current exceeds this 30% limit the next
larger value is selected.
Impacting frequency stability of the overall control loop, the
output capacitance, in conjunction with the inductor, creates
a double pole inside the feedback loop. In addition the
capacitance and the ESR value create a zero. These fre-
quency response effects together with the internal frequency
compensation circuitry of the LM2678 modify the gain and
phase shift of the closed loop system.
As a general rule for stable switching regulator circuits it is
desired to have the unity gain bandwidth of the circuit to be
limited to no more than one-sixth of the controller switching
The inductors offered have been specifically manufactured
to provide proper operation under all operating conditions of
11
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The average current through the catch diode is dependent
on the switch duty cycle (D) and is equal to the load current
times (1-D). Use of a diode rated for much higher current
than is required by the actual application helps to minimize
the voltage drop and power loss in the diode.
Application Hints (Continued)
frequency. With the fixed 260KHz switching frequency of the
LM2678, the output capacitor is selected to provide a unity
gain bandwidth of 40KHz maximum. Each recommended
capacitor value has been chosen to achieve this result.
During the switch ON time the diode will be reversed biased
by the input voltage. The reverse voltage rating of the diode
should be at least 1.3 times greater than the maximum input
voltage.
In some cases multiple capacitors are required either to
reduce the ESR of the output capacitor, to minimize output
ripple (a ripple voltage of 1% of Vout or less is the assumed
performance condition), or to increase the output capaci-
tance to reduce the closed loop unity gain bandwidth (to less
than 40KHz). When parallel combinations of capacitors are
required it has been assumed that each capacitor is the
exact same part type.
BOOST CAPACITOR
The boost capacitor creates a voltage used to overdrive the
gate of the internal power MOSFET. This improves efficiency
by minimizing the on resistance of the switch and associated
power loss. For all applications it is recommended to use a
0.01µF/50V ceramic capacitor.
The RMS current and working voltage (WV) ratings of the
output capacitor are also important considerations. In a typi-
cal step-down switching regulator, the inductor ripple current
(set to be no more than 30% of the maximum load current by
the inductor selection) is the current that flows through the
output capacitor. The capacitor RMS current rating must be
greater than this ripple current. The voltage rating of the
output capacitor should be greater than 1.3 times the maxi-
mum output voltage of the power supply. If operation of the
system at elevated temperatures is required, the capacitor
voltage rating may be de-rated to less than the nominal room
temperature rating. Careful inspection of the manufacturer’s
specification for de-rating of working voltage with tempera-
ture is important.
ADDITIONAL APPLICATION INFORMATION
When the output voltage is greater than approximately 6V,
and the duty cycle at minimum input voltage is greater than
approximately 50%, the designer should exercise caution in
selection of the output filter components. When an applica-
tion designed to these specific operating conditions is sub-
jected to a current limit fault condition, it may be possible to
observe a large hysteresis in the current limit. This can affect
the output voltage of the device until the load current is
reduced sufficiently to allow the current limit protection circuit
to reset itself.
Under current limiting conditions, the LM267x is designed to
respond in the following manner:
INPUT CAPACITOR
1. At the moment when the inductor current reaches the
current limit threshold, the ON-pulse is immediately ter-
minated. This happens for any application condition.
Fast changing currents in high current switching regulators
place a significant dynamic load on the unregulated power
source. An input capacitor helps to provide additional current
to the power supply as well as smooth out input voltage
variations.
2. However, the current limit block is also designed to
momentarily reduce the duty cycle to below 50% to
avoid subharmonic oscillations, which could cause the
inductor to saturate.
Like the output capacitor, the key specifications for the input
capacitor are RMS current rating and working voltage. The
RMS current flowing through the input capacitor is equal to
one-half of the maximum dc load current so the capacitor
should be rated to handle this. Paralleling multiple capacitors
proportionally increases the current rating of the total capaci-
tance. The voltage rating should also be selected to be 1.3
times the maximum input voltage. Depending on the unregu-
lated input power source, under light load conditions the
maximum input voltage could be significantly higher than
normal operation and should be considered when selecting
an input capacitor.
3. Thereafter, once the inductor current falls below the
current limit threshold, there is a small relaxation time
during which the duty cycle progressively rises back
above 50% to the value required to achieve regulation.
If the output capacitance is sufficiently ‘large’, it may be
possible that as the output tries to recover, the output ca-
pacitor charging current is large enough to repeatedly re-
trigger the current limit circuit before the output has fully
settled. This condition is exacerbated with higher output
voltage settings because the energy requirement of the out-
put capacitor varies as the square of the output voltage
The input capacitor should be placed very close to the input
pin of the LM2678. Due to relative high current operation
with fast transient changes, the series inductance of input
connecting wires or PCB traces can create ringing signals at
the input terminal which could possibly propagate to the
output or other parts of the circuitry. It may be necessary in
some designs to add a small valued (0.1µF to 0.47µF)
ceramic type capacitor in parallel with the input capacitor to
prevent or minimize any ringing.
(1⁄ CV2), thus requiring an increased charging current.
2
A simple test to determine if this condition might exist for a
suspect application is to apply a short circuit across the
output of the converter, and then remove the shorted output
condition. In an application with properly selected external
components, the output will recover smoothly.
Practical values of external components that have been
experimentally found to work well under these specific oper-
ating conditions are COUT = 47µF, L = 22µH. It should be
noted that even with these components, for a device’s cur-
rent limit of ICLIM, the maximum load current under which the
possibility of the large current limit hysteresis can be mini-
mized is ICLIM/2. For example, if the input is 24V and the set
output voltage is 18V, then for a desired maximum current of
1.5A, the current limit of the chosen switcher must be con-
firmed to be at least 3A.
CATCH DIODE
When the power switch in the LM2678 turns OFF, the current
through the inductor continues to flow. The path for this
current is through the diode connected between the switch
output and ground. This forward biased diode clamps the
switch output to a voltage less than ground. This negative
voltage must be greater than −1V so a low voltage drop
(particularly at high current levels) Schottky diode is recom-
mended. Total efficiency of the entire power supply is signifi-
cantly impacted by the power lost in the output catch diode.
SIMPLE DESIGN PROCEDURE
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12
2 x 560µF/35V Panasonic HFQ (code C5)
Application Hints (Continued)
Step 5: Use Table 4 to select an input capacitor. With 3.3V
output and 15µH there are three through-hole solutions.
These capacitors provide a sufficient voltage rating and an
rms current rating greater than 2A (1/2 Iload max). Again
using Table 2 for specific component characteristics the
following choices are suitable:
Using the nomographs and tables in this data sheet (or use
the available design software at http://www.national.com) a
complete step-down regulator can be designed in a few
simple steps.
Step 1: Define the power supply operating conditions:
Required output voltage
2 x 680µF/63V Sanyo MV-GX (code C13)
1 x 1200µF/63V Nichicon PL (code C25)
1 x 1500µF/63V Panasonic HFQ (code C16)
Maximum DC input voltage
Maximum output load current
Step 2: Set the output voltage by selecting a fixed output
LM2678 (3.3V, 5V or 12V applications) or determine the
required feedback resistors for use with the adjustable
LM2678−ADJ
Step 6: From Table 5 a 5A or more Schottky diode must be
selected. For through-hole components only 40V rated di-
odes are indicated and 4 part types are suitable:
1N5825
Step 3: Determine the inductor required by using one of the
four nomographs, Figure 3 through Figure 6. Table 1 pro-
vides a specific manufacturer and part number for the induc-
tor.
MBR745
80SQ045
6TQ045
Step 7: A 0.01µF capacitor will be used for Cboost.
ADJUSTABLE OUTPUT DESIGN EXAMPLE
Step 4: Using Table 3 (fixed output voltage) or Table 6
(adjustable output voltage), determine the output capaci-
tance required for stable operation. Table 2 provides the
specific capacitor type from the manufacturer of choice.
In this example it is desired to convert the voltage from a two
battery automotive power supply (voltage range of 20V to
28V, typical in large truck applications) to the 14.8VDC alter-
nator supply typically used to power electronic equipment
from single battery 12V vehicle systems. The load current
required is 3.5A maximum. It is also desired to implement the
power supply with all surface mount components.
Step 5: Determine an input capacitor from Table 4 for fixed
output voltage applications. Use Table 2 to find the specific
capacitor type. For adjustable output circuits select a capaci-
tor from Table 2 with a sufficient working voltage (WV) rating
greater than Vin max, and an rms current rating greater than
one-half the maximum load current (2 or more capacitors in
parallel may be required).
Step 1: Operating conditions are:
Vout = 14.8V
Step 6: Select a diode from Table 5. The current rating of the
diode must be greater than I load max and the Reverse
Voltage rating must be greater than Vin max.
Vin max = 28V
Iload max = 3.5A
Step 2: Select an LM2678S-ADJ. To set the output voltage
to 14.9V two resistors need to be chosen (R1 and R2 in
Figure 2). For the adjustable device the output voltage is set
by the following relationship:
Step 7: Include a 0.01µF/50V capacitor for Cboost in the
design.
FIXED OUTPUT VOLTAGE DESIGN EXAMPLE
A system logic power supply bus of 3.3V is to be generated
from a wall adapter which provides an unregulated DC volt-
age of 13V to 16V. The maximum load current is 4A.
Through-hole components are preferred.
Step 1: Operating conditions are:
Vout = 3.3V
Where VFB is the feedback voltage of typically 1.21V.
A recommended value to use for R1 is 1K. In this example
then R2 is determined to be:
Vin max = 16V
Iload max = 4A
Step 2: Select an LM2678T-3.3. The output voltage will have
a tolerance of
2% at room temperature and 3% over the full operating
temperature range.
R2 = 11.23KΩ
Step 3: Use the nomograph for the 3.3V device ,Figure 3.
The intersection of the 16V horizontal line (Vin max) and the
4A vertical line (Iload max) indicates that L46, a 15µH induc-
tor, is required.
The closest standard 1% tolerance value to use is 11.3KΩ
This will set the nominal output voltage to 14.88V which is
within 0.5% of the target value.
Step 3: To use the nomograph for the adjustable device,
From Table 1, L46 in a through-hole component is available
from Renco with part number RL-1283-15-43.
Figure 6, requires
a
calculation of the inductor
Volt•microsecond constant (E•T expressed in V•µS) from
the following formula:
Step 4: Use Table 3 to determine an output capacitor. With a
3.3V output and a 15µH inductor there are four through-hole
output capacitor solutions with the number of same type
capacitors to be paralleled and an identifying capacitor code
given. Table 2 provides the actual capacitor characteristics.
Any of the following choices will work in the circuit:
where VSAT is the voltage drop across the internal power
switch which is Rds(ON) times Iload. In this example this would
be typically 0.12Ω x 3.5A or 0.42V and VD is the voltage drop
across the forward bisased Schottky diode, typically 0.5V.
2 x 220µF/10V Sanyo OS-CON (code C5)
2 x 820µF/16V Sanyo MV-GX (code C5)
1 x 3900µF/10V Nichicon PL (code C7)
13
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Step 4: Use Table 6 to determine an output capacitor. With a
14.8V output the 12.5 to 15V row is used and with a 47µH
inductor there are three surface mount output capacitor so-
lutions. Table 2 provides the actual capacitor characteristics
based on the C Code number. Any of the following choices
can be used:
Application Hints (Continued)
The switching frequency of 260KHz is the nominal value to
use to estimate the ON time of the switch during which
energy is stored in the inductor.
For this example E•T is found to be:
1 x 33µF/20V AVX TPS (code C6)
1 x 47µF/20V Sprague 594 (code C8)
1 x 47µF/20V Kemet T495 (code C8)
Important Note: When using the adjustable device in low
voltage applications (less than 3V output), if the nomograph,
Figure 6, selects an inductance of 22µH or less, Table 6 does
not provide an output capacitor solution. With these condi-
tions the number of output capacitors required for stable
operation becomes impractical. It is recommended to use
either a 33µH or 47µH inductor and the output capacitors
from Table 6.
Using Figure 6, the intersection of 27V•µS horizontally and
the 3.5A vertical line (Iload max) indicates that L48 , a 47µH
inductor, or L49, a 33µH inductor could be used. Either
inductor will be suitable, but for this example selecting the
larger inductance will result in lower ripple current.
From Table 1, L48 in a surface mount component is available
from Pulse Engineering with part number P0848.
www.national.com
14
MBRD1545CT
Application Hints (Continued)
6TQ045S
Step 5: An input capacitor for this example will require at
least a 35V WV rating with an rms current rating of 1.75A
(1/2 Iout max). From Table 2 it can be seen that C12, a
33µF/35V capacitor from Sprague, has the highest voltage/
current rating of the surface mount components and that two
of these capacitor in parallel will be adquate.
Step 7: A 0.01µF capacitor will be used for Cboost.
LLP PACKAGE DEVICES
The LM2678 is offered in the 14 lead LLP surface mount
package to allow for a significantly decreased footprint with
equivalent power dissipation compared to the TO-263. For
details on mounting and soldering specifications, refer to
Application Note AN-1187.
Step 6: From Table 5 a 5A or more Schottky diode must be
selected. For surface mount diodes with a margin of safety
on the voltage rating one of two diodes can be used:
15
www.national.com
Inductor Selection Guides For Continuous Mode Operation
10088621
10088622
FIGURE 3. LM2678-3.3
FIGURE 4. LM2678-5.0
10088624
10088623
FIGURE 6. LM2678-ADJ
FIGURE 5. LM2678-12
www.national.com
16
Inductor Selection Guides For Continuous Mode Operation (Continued)
TABLE 1. Inductor Manufacturer Part Numbers
Renco
Through Hole
Pulse Engineering
Coilcraft
Inductor
Reference
Number
Inductance Current
Surface
Mount
Through
Hole
Surface
Mount
Surface Mount
(µH)
(A)
L23
L24
L25
L29
L30
L31
L32
L33
L34
L38
L39
L40
L41
L44
L45
L46
L47
L48
L49
33
22
15
100
68
47
33
22
15
68
47
33
22
68
10
15
10
47
33
1.35
1.65
2.00
1.41
1.71
2.06
2.46
3.02
3.65
2.97
3.57
4.26
5.22
3.45
4.47
5.60
5.66
5.61
5.61
RL-5471-7
RL1500-33 PE-53823 PE-53823S DO3316-333
RL-1283-22-43 RL1500-22 PE-53824 PE-53824S DO3316-223
RL-1283-15-43 RL1500-15 PE-53825 PE-53825S DO3316-153
RL-5471-4
RL-5471-5
RL-5471-6
RL-5471-7
RL-6050-100 PE-53829 PE-53829S DO5022P-104
RL6050-68 PE-53830 PE-53830S DO5022P-683
RL6050-47 PE-53831 PE-53831S DO5022P-473
RL6050-33 PE-53932 PE-53932S DO5022P-333
RL-1283-22-43 RL6050-22 PE-53933 PE-53933S DO5022P-223
RL-1283-15-43
RL-5472-2
—
—
—
—
—
—
—
—
—
—
—
PE-53934 PE-53934S DO5022P-153
PE-54038 PE-54038S
PE-54039 PE-54039S
PE-54040 PE-54040S
PE-54041 P0841
—
RL-5472-3
—
RL-1283-33-43
RL-1283-22-43
RL-5473-3
—
—
PE-54044
—
—
DO5022P-103HC
DO5022P-153HC
DO5022P-103HC
—
RL-1283-10-43
RL-1283-15-43
RL-1283-10-43
RL-1282-47-43
RL-1282-33-43
—
—
—
—
—
P0845
P0846
P0847
P0848
P0849
—
Inductor Manufacturer Contact Numbers
Coilcraft
Phone (800) 322-2645
FAX (708) 639-1469
Phone +44 1236 730 595
FAX +44 1236 730 627
Phone (619) 674-8100
FAX (619) 674-8262
Phone +353 93 24 107
FAX +353 93 24 459
Phone (800) 645-5828
FAX (516) 586-5562
Coilcraft, Europe
Pulse Engineering
Pulse Engineering,
Europe
Renco Electronics
17
www.national.com
Capacitor Selection Guides
TABLE 2. Input and Output Capacitor Codes
Surface Mount
Sprague 594D Series
Irms
Capacitor
Reference
Code
AVX TPS Series
Irms
Kemet T495 Series
Irms
C (µF) WV (V) (A)
C (µF) WV (V)
(A)
C (µF) WV (V)
(A)
1.1
C1
C2
330
100
220
47
6.3
10
10
16
16
20
20
25
35
35
1.15
1.1
120
220
68
6.3
6.3
10
10
16
16
16
20
25
25
35
35
50
100
220
330
100
150
220
33
6.3
6.3
6.3
10
10
10
20
20
20
35
35
50
0.82
1.1
1.4
C3
1.15
0.89
1.15
0.77
0.94
0.77
0.63
0.66
1.05
1.35
1
1.1
C4
150
47
1.1
C5
100
33
1.1
C6
100
180
47
1.3
1.1
C7
68
1.95
1.15
1.05
1.6
0.78
0.94
0.94
0.63
0.63
0.66
C8
22
47
C9
10
33
68
C10
C11
C12
C13
22
68
10
15
0.75
1
22
33
4.7
15
0.9
www.national.com
18
Capacitor Selection Guides (Continued)
Input and Output Capacitor Codes (continued)
Through Hole
Sanyo OS-CON SA Series Sanyo MV-GX Series Nichicon PL Series
Capacitor
Reference
Code
Panasonic HFQ Series
Irms
Irms
(A)
Irms
(A)
Irms
(A)
C (µF) WV (V)
C (µF) WV (V)
C (µF) WV (V)
C (µF) WV (V)
(A)
0.4
C1
C2
47
150
330
100
220
33
6.3
6.3
6.3
10
10
16
16
16
20
25
1
1000
270
470
560
820
1000
150
470
680
1000
220
470
680
1000
6.3
16
16
16
16
16
35
35
35
35
63
63
63
63
0.8
680
820
10
10
10
10
10
10
10
10
16
16
16
16
16
16
25
35
35
35
50
50
50
63
63
63
63
0.8
82
120
220
330
560
820
1000
2200
56
35
35
35
35
35
35
35
35
50
50
50
50
50
50
63
63
1.95
2.45
1.87
2.36
0.96
1.92
2.28
2.25
2.09
0.6
0.98
1.06
1.28
1.71
2.18
2.36
2.68
0.41
0.55
0.77
1.02
1.22
1.88
0.63
0.79
1.43
2.68
0.82
1.04
1.3
0.44
0.76
1.01
1.4
C3
0.75
0.95
1.25
1.3
1000
1200
2200
3300
3900
6800
180
C4
C5
C6
1.62
1.73
2.8
C7
100
150
100
47
0.65
1.3
C8
C9
1.4
0.36
0.5
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
1.7
270
100
220
470
560
1200
330
1500
0.76
1.2
470
0.92
1.44
1.68
2.22
1.42
2.51
680
1.5
820
1.75
1800
220
220
560
2200
150
220
330
100
0.75
1.62
2.22
2.51
390
820
1200
Capacitor Manufacturer Contact Numbers
Nichicon
Panasonic
AVX
Phone
FAX
(847) 843-7500
(847) 843-2798
(714) 373-7857
(714) 373-7102
(845) 448-9411
(845) 448-1943
(207) 324-4140
(207) 324-7223
(619) 661-6322
(619) 661-1055
(864) 963-6300
(864) 963-6521
Phone
FAX
Phone
FAX
Sprague/Vishay
Sanyo
Phone
FAX
Phone
FAX
Kemet
Phone
FAX
19
www.national.com
Capacitor Selection Guides (Continued)
TABLE 3. Output Capacitors for Fixed Output Voltage Application
Surface Mount
Sprague 594D
Series
Output
Voltage (V)
Inductance
(µH)
AVX TPS Series
Kemet T495 Series
No.
5
C Code
C1
No.
5
C Code
No.
5
C Code
C2
10
15
22
33
10
15
22
33
47
10
15
22
33
47
68
100
C1
C1
C7
C7
C6
C7
C7
C3
C7
C6
C7
C6
C7
C6
C5
C5
4
C1
4
4
C3
3.3
5
3
C2
2
3
C4
1
C1
2
3
C4
4
C2
4
4
C4
3
C3
2
3
C5
3
C2
2
3
C4
2
C2
2
2
C4
2
C2
1
2
C4
4
C5
3
5
C9
3
C5
2
4
C9
2
C5
2
3
C8
12
2
C5
1
3
C8
2
C4
1
2
C8
1
C5
1
2
C7
1
C4
1
1
C8
Through Hole
Sanyo MV-GX Series Nichicon PL Series
Output
Voltage (V)
Inductance Sanyo OS-CON SA
Panasonic HFQ
Series
(µH)
Series
C Code
No.
2
No.
2
C Code
C6
No.
1
C Code
C8
No.
2
C Code
C6
10
15
22
33
10
15
22
33
47
10
15
22
33
47
68
100
C5
C5
C5
C5
C4
C5
C5
C4
C4
C7
C8
C7
C7
C7
C6
C6
2
2
C5
1
C7
2
C5
3.3
5
1
1
C10
C10
C5
1
C5
1
C7
1
1
1
C5
1
C7
2
2
1
C6
2
C5
1
1
C10
C9
1
C5
1
C7
1
1
1
C5
1
C5
1
1
C5
1
C4
1
C4
1
1
C4
1
C2
2
C4
2
1
C10
C6
1
C14
C17
C13
C12
C11
C10
C9
2
C4
1
1
1
1
C5
1
1
C5
1
1
C5
12
1
1
C4
1
1
C4
1
1
C3
1
1
C3
1
1
C2
1
1
C3
1
1
C2
1
1
C1
No. represents the number of identical capacitor types to be connected in parallel
C Code indicates the Capacitor Reference number in Table 2 for identifying the specific component from the manufacturer.
www.national.com
20
Capacitor Selection Guides (Continued)
TABLE 4. Input Capacitors for Fixed Output Voltage Application
(Assumes worst case maximum input voltage and load current for a given inductance value)
Surface Mount
Output
Voltage (V)
Inductance
(µH)
AVX TPS Series
Sprague 594D
Series
Kemet T495 Series
No.
3
*
C Code
No.
2
C Code
No.
3
C Code
C9
10
15
22
33
10
15
22
33
47
10
15
22
33
47
68
100
C7
*
C10
C13
C13
C13
C6
3
4
C12
C12
C12
C9
3.3
5
*
*
2
3
*
*
2
3
3
4
*
C4
C9
*
2
3
3
C12
C13
C13
C13
C10
C10
C12
C13
C13
C13
C13
4
C10
C12
C12
C12
C10
C10
C10
C12
C12
C12
C12
3
4
*
*
2
3
*
*
1
2
4
4
4
*
C9
C8
C9
*
2
4
2
4
3
4
12
3
4
*
*
2
3
*
*
2
2
*
*
1
2
Through Hole
Sanyo MV-GX Series Nichicon PL Series
Output
Voltage (V)
Inductance Sanyo OS-CON SA
Panasonic HFQ
Series
(µH)
Series
C Code
No.
2
*
No.
2
C Code
C8
No.
1
C Code
C18
C25
C24
C24
C25
C25
C25
C23
C19
C18
C18
C18
C24
C23
C21
C22
No.
1
C Code
C8
10
15
22
33
10
15
22
33
47
10
15
22
33
47
68
100
C9
*
2
C13
C14
C14
C8
1
1
C16
C16
C16
C8
3.3
5
*
*
*
1
1
1
*
1
1
1
2
*
C7
*
2
1
1
2
C8
1
1
C8
*
*
2
C13
C14
C12
C8
1
1
C16
C13
C11
C8
*
*
1
1
1
*
*
1
1
1
2
2
*
C10
C10
*
2
1
1
2
C8
1
1
C8
2
C8
1
1
C8
*
*
12
2
C12
C14
C13
C11
1
1
C14
C13
C15
C11
*
*
1
1
1
*
*
1
1
1
*
*
1
1
1
*
Check voltage rating of capacitors to be greater than application input voltage.
No. represents the number of identical capacitor types to be connected in parallel
C Code indicates the Capacitor Reference number in Table 2 for identifying the specific component from the manufacturer.
21
www.national.com
Capacitor Selection Guides (Continued)
TABLE 5. Schottky Diode Selection Table
Reverse
Voltage
(V)
Surface Mount Through Hole
3A
5A or More
3A
5A or
More
20V
30V
40V
SK32
1N5820
SR302
SK33
MBRD835L
1N5821
31DQ03
1N5822
MBR340
31DQ04
SR403
30WQ03F
SK34
MBRD1545CT
6TQ045S
1N5825
MBR745
80SQ045
6TQ045
30BQ040
30WQ04F
MBRS340
MBRD340
SK35
50V or
More
MBR350
31DQ05
SR305
30WQ05F
Diode Manufacturer Contact Numbers
International Rectifier Phone (310) 322-3331
(310) 322-3332
FAX
Motorola
Phone
FAX
(800) 521-6274
(602) 244-6609
(516) 847-3000
General
Phone
Semiconductor
FAX
(516) 847-3236
(805) 446-4800
(805) 446-4850
Diodes, Inc.
Phone
FAX
www.national.com
22
Capacitor Selection Guides (Continued)
TABLE 6. Output Capacitors for Adjustable Output Voltage Applications
Surface Mount
Sprague 594D
Series
Output Voltage Inductance
AVX TPS Series
Kemet T495 Series
(V)
(µH)
No.
7
5
4
3
4
3
2
3
2
2
1
3
2
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
C Code
C1
C1
C1
C1
C1
C1
C1
C2
C2
C2
C2
C2
C2
C3
C2
C5
C5
C5
C4
C5
C5
C5
C5
C6
C6
C6
C6
C8
C8
C8
C8
C9
C10
C9
C9
No.
6
4
3
2
3
2
2
3
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
2
1
1
1
4
3
2
1
1
1
C Code
No.
7
5
4
3
4
3
2
3
2
2
1
3
2
1
1
2
2
1
1
2
2
1
1
1
1
1
1
2
2
2
1
2
1
1
1
8
5
4
3
2
2
C Code
C3
*
*
*
*
33
47
33
47
C2
C2
1.21 to 2.50
2.5 to 3.75
C3
C2
C3
C2
C3
22
33
47
22
33
47
68
22
33
47
68
33
47
68
100
33
47
68
100
33
47
68
100
33
47
68
100
33
47
68
100
10
15
22
33
47
68
C2
C3
3.75 to 5
5 to 6.25
C2
C3
C2
C3
C3
C4
C3
C4
C3
C4
C3
C4
C4
C4
C3
C4
6.25 to 7.5
7.5 to 10
10 to 12.5
12.5 to 15
15 to 20
C4
C6
C3
C4
C6
C8
C6
C8
C6
C8
C5
C8
C6
C8
C6
C8
C6
C8
C6
C8
C8
C8
C8
C8
C8
C8
C8
C8
C10
C9
C10
C10
C10
C10
C11
C11
C11
C11
C12
C12
C12
C12
C12
C12
C9
C9
C11
C12
C12
C12
C13
C13
C13
C13
C13
C13
20 to 30
No Values Available
30 to 37
23
www.national.com
Capacitor Selection Guides (Continued)
Output Capacitors for Adjustable Output Voltage Applications (continued)
Through Hole
Output Voltage Inductance Sanyo OS-CON SA
Panasonic HFQ
Series
Sanyo MV-GX Series Nichicon PL Series
(V)
(µH)
Series
C Code
No.
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
No.
5
4
3
2
3
2
2
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
C Code
C1
No.
5
3
3
2
3
2
1
2
2
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
C Code
C3
No.
3
2
2
1
2
1
1
2
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
C Code
C
*
*
*
*
33
47
33
47
C3
C2
C3
C2
C3
C2
C2
C5
C4
C4
C4
C5
C4
C4
C4
C7
C7
C7
C7
C7
C7
C7
C7
C9
C9
C9
C9
C10
C10
C10
C10
1.21 to 2.50
2.5 to 3.75
C1
C3
C5
C5
C5
C5
C5
C5
C5
C5
C5
C5
C5
C5
C5
C5
C5
C5
C2
C2
C5
C5
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C2
C10
C11
C10
C10
C10
C10
C1
C1
C1
C3
22
33
47
22
33
47
68
22
33
47
68
33
47
68
100
33
47
68
100
33
47
68
100
33
47
68
100
33
47
68
100
10
15
22
33
47
68
C1
C1
3.75 to 5
5 to 6.25
C1
C1
C1
C3
C6
C3
C6
C1
C6
C3
C6
C1
C6
C1
C6
C3
6.25 to 7.5
7.5 to 10
10 to 12.5
12.5 to 15
15 to 20
C6
C1
C2
C1
C6
C14
C14
C14
C14
C14
C14
C9
C6
C2
C2
C6
C2
C2
C2
C9
C10
C10
C10
C10
C7
C15
C15
C15
C15
C15
C15
C15
C15
C16
C16
C16
C16
C20
C20
C20
C20
C20
C20
C7
C7
C7
C7
No Values
C7
20 to 30
Available
C7
C7
C12
C11
C11
C11
C11
C11
No Values
Available
30 to 37
* Set to a higher value for a practical design solution. See Applications Hints section
No. represents the number of identical capacitor types to be connected in parallel
C Code indicates the Capacitor Reference number in Table 2 for identifying the specific component from the manufacturer.
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24
Physical Dimensions inches (millimeters)
unless otherwise noted
TO-263 Surface Mount Power Package
Order Number LM2678S-3.3, LM2678S-5.0,
LM2678S-12 or LM2678S-ADJ
NS Package Number TS7B
25
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Physical Dimensions inches (millimeters) unless otherwise noted (Continued)
TO-220 Power Package
Order Number LM2678T-3.3, LM2678T-5.0,
LM2678T-12 or LM2678T-ADJ
NS Package Number TA07B
14-Lead LLP Package
NS Package Number SRC14A
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26
Notes
LIFE SUPPORT POLICY
NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT
DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL
COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:
1. Life support devices or systems are devices or
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
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Support Center
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Fax: +49 (0) 180-530 85 86
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www.national.com
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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