National Semiconductor LM2698 Technical data
LM2698
SIMPLE SWITCHER
®
1.35A Boost Regulator
LM2698 SIMPLE SWITCHER
March 2005
General Description
The LM2698 is a general purpose PWM boost converter.
The 1.9A, 18V, 0.2ohm internal switch enables the LM2698
to provide efficient power conversion to outputs ranging from
2.2V to 17V. It can operate with input voltages as low as 2.2V
and as high as 12V. Current-mode architecture provides
superior line and load regulation and simple frequency compensation over the device’s 2.2V to 12V input voltage range.
The LM2698 sets the standard in power density and is
capable of supplying 12V at 400mA from a 5V input. The
LM2698 can also be used in flyback or SEPIC topologies.
®
The LM2698 SIMPLE SWITCHER
switching frequency of either 600kHz or 1.25MHz. This promotes flexibility in component selection and filtering techniques. A shutdown pin is available to suspend the device
and decrease the quiescent current to 5µA. An external
compensation pin gives the user flexibility in setting frequency compensation, which makes possible the use of
small, low ESR ceramic capacitors at the output. Switchers
Made Simple
and guaranteed design. The LM2698 is available in a low
profile 8-lead MSOP package.
®
software is available to insure a quick, easy
features a pin selectable
Typical Application Circuit
Features
n 1.9A, 0.2Ω, internal switch (typical)
n Operating voltage as low as 2.2V
n 600kHz/1.25MHz adjustable frequency operation
n Switchers Made Simple
n 8-Lead MSOP package
®
software
Applications
n 3.3V to 5V, 5V to 12V conversion
n Distributed Power
n Set-Top Boxes
n DSL Modems
n Diagnostic Medical Instrumentation
n Boost Converters
n Flyback Converters
n SEPIC Converters
®
1.35A Boost Regulator
20012658
SIMPLE SWITCHER®is a registered trademark of National Semiconductor Corporation.
© 2005 National Semiconductor Corporation DS200126 www.national.com
Connection Diagram
LM2698
Top View
8-Lead Plastic MSOP
20012604
NS Package Number MUA08A
Ordering Information
Order Number Package Type NSC Package
Drawing
LM2698MM-ADJ MSOP-8 MUA08A 1000 Units, Tape and Reel S22B
LM2698MMX-ADJ MSOP-8 MUA08A 3500 Units, Tape and Reel S22B
Supplied As Package ID
Pin Description
Pin Name Function
1V
C
2 FB Output voltage feedback input.
3 SHDN
4 GND Analog and power ground.
5V
6V
SW
IN
7 FSLCT Switching frequency select input. V
8 NC Connect to ground.
Compensation network connection. Connected to the output of the voltage error amplifier.
Shutdown control input, active low.
Power switch input. Switch connected between SW pin and GND pin.
Analog power input.
= 1.25MHz. Ground = 600kHz.
IN
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Block Diagram
LM2698
20012603
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Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
LM2698
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
IN
SW Voltage −0.3V ≤ V
FB Voltage −0.3V ≤ V
V
Voltage 0.965<V
C
SHDN Voltage
(Note 2) −0.3V ≤ V
FSLCT
(Note 2) −0.3V ≤ V
Maximum Junction
Temperature
Power Dissipation (Note 3) Internally Limited
Lead Temperature 300˚C
−0.3V ≤ VIN≤ 12V
C
SHDN
FSLCT
SW
FB
<
≤ 18V
≤ 7V
1.565
≤ 7V
≤ 12V
150˚C
Vapor Phase (60 sec.) 215˚C
Infrared (15 sec.) 220˚C
ESD Susceptibility
(Note 4)
Human Body Model
(Note 5) 2kV
Machine Model 200V
Operating Conditions
Operating Junction
Temperature Range
(Note 6) −40˚C to +125˚C
Storage Temperature −65˚C to +150˚C
Supply Voltage 2.2V to 12V
SW Voltage 0 ≤ V
Electrical Characteristics
Specifications in standard type face are for TJ= 25˚C and those with boldface type apply over the full Operating Temperature Range (T
Symbol Parameter Conditions
I
Q
V
FB
I
CL
%V
/∆VINFeedback Voltage Line
FB
I
B
V
IN
g
m
A
V
D
MAX
D
MIN
f
S
I
SHDN
I
L
R
DS(ON)
TH
SHDN
UVP On Threshold 1.95 2.05 2.2 V
= −40˚C to +125˚C)Unless otherwise specified. VIN=2.2V and IL= 0A, unless otherwise specified.
J
Min
(Note 6)
Typ
(Note 7)
Max
(Note 6)
Quiescent Current FB = 0V (Not Switching) 1.3 2.0 mA
V
=0V 5 10 µA
SHDN
Feedback Voltage 1.2285 1.26 1.2915 V
Switch Current Limit VIN= 2.7V (Note 8) 1.35 1.9 2.4 A
2.2V ≤ VIN≤ 12.0V 0.013 0.1 %/V
Regulation
FB Pin Bias Current
0.5 20 nA
(Note 9)
Input Voltage Range 2.2 12 V
Error Amp Transconductance ∆I = 5µA 40 135 290 µmho
Error Amp Voltage Gain 120 V/V
Maximum Duty Cycle FSLCT = Ground 78 85 %
Minimum Duty Cycle FSLCT = Ground 15 %
FSLCT = V
IN
30
Switching Frequency FSLCT = Ground 480 600 720 kHz
Shutdown Pin Current V
FSLCT = V
SHDN
V
SHDN
IN
=V
IN
=0V −0.5 -1
1 1.25 1.5 MHz
0.01 0.1 µA
Switch Leakage Current VSW= 18V 0.01 3 µA
Switch R
DS(ON)
VIN= 2.7V, ISW= 1A 0.2 0.4 Ω
SHDN Threshold Voltage Output High 0.6 0.9 V
Output Low 0.3 0.6 V
Off Threshold 1.85 1.95 2.1 V
SW
≤ 17.5V
Units
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Electrical Characteristics (Continued)
Specifications in standard type face are for TJ= 25˚C and those with boldface type apply over the full Operating Temperature Range (T
Symbol Parameter Conditions
θ
JA
Note 1: Absolute maximum ratings are limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is intended to
be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see the Electrical Characteristics.
Note 2: Shutdown and voltage frequency select should not exceed V
Note 3: The maximum allowable power dissipation is a function of the maximum junction temperature, T
and the ambient temperature, T
at any ambient temperature is calculated using: P
temperature, and the regulator will go into thermal shutdown.
Note 4: The human body model is a 100 pF capacitor discharged through a 1.5kΩ resistor into each pin. The machine model is a 200pF capacitor discharged
directly into each pin.
Note 5: ESD susceptibility using the human body model is 500V for V
Note 6: All limits guaranteed at room temperature (standard typeface) and at temperature extremes (bold typeface). All room temperature limits are 100% tested
or guaranteed through statistical analysis.All limits at temperature extremes are guaranteed via correlation using standard Statistical Quality Control (SQC) methods.
All limits are used to calculate Average Outgoing Quality Level (AOQL).
Note 7: Typical numbers are at 25˚C and represent the most likely norm.
Note 8: This is the switch current limit at 0% duty cycle. The switch current limit will change as a function of duty cycle. See Typical performance Characteristics
section for I
Note 9: Bias current flows into FB pin.
Note 10: Junction to ambient thermal resistance (no external heat sink) for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit.
See "Scenario ’A’" in the Power Dissipation section.
Note 11: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.0191 sq. in. of copper heat sinking. See "Scenario ’B’" in the Power Dissipation section.
Note 12: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.0465 sq. in. of copper heat sinking. See "Scenario ’C’" in the Power Dissipation section.
Note 13: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.2523 sq. in. of copper heat sinking. See "Scenario ’D’" in the Power Dissipation section.
Note 14: Junction to ambient thermal resistance for the MSO8 package with minimal trace widths (0.010 inches) from the pins to the circuit and approximately
0.0098 sq. in. of copper heat sinking on the top layer and 0.0760 sq. in. of copper heat sinking on the bottom layer, with three 0.020 in. vias connecting the planes.
See "Scenario ’E’" in the Power Dissipation section.
= −40˚C to +125˚C)Unless otherwise specified. VIN=2.2V and IL= 0A, unless otherwise specified.
J
Min
(Note 6)
Thermal Resistance Junction to Ambient
Typ
(Note 7)
235 ˚C/W
(Note 10)
Junction to Ambient
225
(Note 11)
Junction to Ambient
220
(Note 12)
Junction to Ambient
200
(Note 13)
Junction to Ambient
195
(Note 14)
.
IN
. See the Electrical Characteristics table for the thermal resistance of various layouts. The maximum allowable power dissipation
A
vs. V
CL
IN
(MAX) = (T
D
J(MAX)−TA
.
C
)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die
(MAX), the junction-to-ambient thermal resistance, θJA,
J
Max
(Note 6)
Units
LM2698
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