National LM2611AMF, LM2611BMF Schematic [ru]
LM2611
1.4MHz Cuk Converter
LM2611 1.4MHz Cuk Converter
January 2005
General Description
The LM2611 is a current mode, PWM inverting switching
regulator. Operating from a 2.7 - 14V supply, it is capable of
producing a regulated negative output voltage of up to −(36V
which enables low voltage ripple and RMS current on both
the input and the output. With a switching frequency of
1.4MHz, the inductors and output capacitor can be physically small and low cost. High efficiency is achieved through
the use of a low R
The LM2611 features a shutdown pin, which can be activated when the part is not needed to lower the Iq and save
battery life. A negative feedback (NFB) pin provides a simple
method of setting the output voltage, using just two resistors.
Cycle-by-cycle current limiting and internal compensation
further simplify the use of the LM2611.
The LM2611 is available is a small SOT23-5 package. It
comes in two grades:
). The LM2611 utilizes an input and output inductor,
IN(MAX)
FET.
DS(ON)
Grade A Grade B
Current Limit 1.2A 0.9A
R
DS(ON)
0.5Ω 0.7Ω
Typical Application Circuit
Features
n 1.4MHz switching frequency
n Low R
n 1mVp-p output ripple
n −5V at 300mA from 5V input
n Better regulation than a charge pump
n Uses tiny capacitors and inductors
n Wide input range: 2.7V to 14V
n Low shutdown current:
n 5-lead SOT-23 package
DS(ON)
DMOS FET
<
1uA
Applications
n MR Head Bias
n Digital camera CCD bias
n LCD bias
n GaAs FET bias
n Positive to negative conversion
20018117
© 2005 National Semiconductor Corporation DS200181 www.national.com
Connection Diagram
LM2611
Top View
5-lead SOT-23 Package
NS Package Number MF05A
20018115
Ordering Information
Order Number Package Type NSC Package
Drawing
LM2611AMF
LM2611AMFX 3K Tape and Reel S40A
LM2611BMF 1K Tape and Reel S40B
LM2611BMFX 3K Tape and Reel S40B
SOT23-5 MF05A
Supplied As Package ID
1K Tape and Reel S40A
Pin Description
Pin Name Function
1 SW Drain of internal switch. Connect at the node of the input inductor and Cuk capacitor.
2 GND Analog and power ground.
3 NFB Negative feedback. Connect to output via external resistor divider to set output voltage.
4 SHDN
5V
IN
Shutdown control input. VIN= Device on. Ground = Device in shutdown.
Analog and power input. Filter out high frequency noise with a 0.1 µF ceramic capacitor
placed close to the pin.
Block Diagram
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20018101
LM2611
Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
V
IN
14.5V
ESD Susceptibility (Note 3)
Human Body Model 2kV
Machine Model 200V
Operating Conditions
SW Voltage −0. 4V to 36V
NFB Voltage +0. 4V to −6V
SHDN Voltage
Maximum Junction
−0. 4V to 14.5V
125˚C
Temperature
Power Dissipation (Note 2) Internally Limited
Operating Junction
Temperature Range −40˚C to +125˚C
Storage Temperature −65˚C to +150˚C
Supply Voltage 2.7V to 14V
θ
JA
256˚C/W
Lead Temperature 300˚C
Electrical Characteristics
Specifications in standard type face are for TJ= 25˚C and those with boldface type apply over the Temperature Range TJ=
−40˚C to +85˚C, unless otherwise specified. V
Symbol Parameter Conditions
V
IN
I
SW
R
DSON
SHDN
I
SHDN
Input Voltage 2.7 14 V
Switch Current Limit Grade A 1 1.2 2 A
Switch ON Resistance Grade A 0.5 0.65
Shutdown Threshold Device enabled 1.5 V
TH
Shutdown Pin Bias Current V
NFB Negative Feedback
Reference
I
NFB
I
q
%V
OUT
∆V
IN
f
S
D
MAX
I
L
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: 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 3: 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 4: 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 5: Typical numbers are at 25˚C and represent the expected value of the parameter.
NFB Pin Bias Current V
Quiescent Current V
/
Reference Line Regulation 2.7V ≤ VIN≤ 14V 0.02 %/V
Switching Frequency 1.0 1.4 1.8 MHz
Maximum Duty Cycle 82 88 %
Switch Leakage Not Switching
. See the Electrical Characteristics table for the thermal resistance of various layouts. The maximum allowable power dissipation
A
D
= 5.0V and IL= 0A, unless otherwise specified.
IN
Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Grade B 0.7 0.9
Grade B 0.7 0.9
Device disabled 0.50
= 0V 0.0 µA
SHDN
V
= 5V 0.0 1.0
SHDN
V
=3V −1.205 −1.23 −1.255 V
IN
=−1.23V −2.7 −4.7 −6.7 µA
NFB
= 5V, Switching 1.8 3.5 mA
SHDN
V
= 5V, Not Switching 270 500 µA
SHDN
V
= 0V 0.024 1 µA
SHDN
1µA
=5V
V
SW
(MAX), the junction-to-ambient thermal resistance, θJA,
J
(MAX) = (T
J(MAX)−TA
)/θJA. Exceeding the maximum allowable power dissipation will cause excessive die
Units
Ω
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Typical Performance Characteristics
LM2611
R
Switch Current Limit vs. V
DS(ON)
vs V
IN
IN
R
20018112 20018145
Vs. Ambient Temperature
DS(ON)
=5V
V
IN
Switch Current Limit vs Ambient Temperature
=5V
V
IN
20018111
Oscillator Frequency vs V
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IN
20018119
20018143
Oscillator Frequency vs Ambient Temperature
=5V
V
IN
20018116
Typical Performance Characteristics (Continued)
LM2611
V
NFB
TA= 25˚C, V
I
NFB
TA= 25˚C, V
vs V
OUT
vs V
OUT
IN
= −5V
IN
= −5V
V
vs Ambient Temperature
NFB
20018107 20018124
I
vs Ambient Temperature
NFB
V
IN
V
IN
= 3.5V, V
=5V
OUT
= −5V
Iqvs Ambient Temperature (No Load)
20018108 20018109
V
SHUTDOWN
20018144 20018110
vs Ambient Temperature
=5V
V
IN
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