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National Semiconductor
National Semiconductor

LM2621 Datasheet

Low Input Voltage/ Step-Up DC-DC Converter


LM2621 Datasheet Preview


February 2000
LM2621
Low Input Voltage, Step-Up DC-DC Converter
General Description
The LM2621 is a high efficiency, step-up DC-DC switching
regulator for battery-powered and low input voltage systems.
It accepts an input voltage between 1.2V and 14V and con-
verts it into a regulated output voltage. The output voltage
can be adjusted between 1.24V and 14V. It has an internal
0.17N-Channel MOSFET power switch. Efficiencies up to
90% are achievable using the LM2621.
The high switching frequency (adjustable up to 2MHz) of the
LM2621 allows for tiny surface mount inductors and capaci-
tors. Because of the unique constant-duty-cycle gated oscil-
lator topology very high efficiencies are realized over a wide
load range. The supply current is reduced to 80µA because
of the BiCMOS process technology. In the shutdown mode,
the supply current is less than 2.5µA.
The LM2621 is available in a Mini-SO-8 package. This pack-
age uses half the board area of a standard 8-pin SO and has
a height of just 1.09 mm.
Features
n Small Mini-SO8 Package (Half the Footprint of Standard
8-Pin SO Package)
n 1.09 mm Package Height
n Up to 2 MHz Switching Frequency
n 1.2V to 14V Input Voltage
n 1.24V - 14V Adjustable Output Voltage
n Up to 1A Load Current
n 0.17 Internal MOSFET
n Up to 90% Regulator Efficiency
n 80 µA Typical Operating Current
n <2.5µA Guaranteed Supply Current In Shutdown
Applications
n PDAs, Cellular Phones
n 2-Cell and 3-Cell Battery-Operated Equipment
n PCMCIA Cards, Memory Cards
n Flash Memory Programming
n TFT/LCD Applications
n 3.3V to 5.0V Conversion
n GPS Devices
n Two-Way Pagers
n Palmtop Computers
n Hand-Held Instruments
Typical Application Circuit
© 2000 National Semiconductor Corporation DS100934
DS100934-12
www.national.com
Page 1

Connection Diagram
Mini SO-8 (MM) Package
Ordering Information
Top View
DS100934-18
Order Number
LM2621MMX
LM2621MM
Package Type
Mini SO-8
Mini SO-8
NSC Package
Drawing
MUA08A
MUA08A
Package
Marking
S06A
S06A
Supplied As
3000 Units on Tape and Reel
1000 Units on Tape and Reel
www.national.com
2
Page 2

Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
SW Pin Voltage
BOOT, VDD, EN and FB Pins
FREQ Pin
θJA (Note 2)
TJmax (Note 2)
Storage Temperature Range
Lead Temp. (Soldering, 5 sec)
−0.5 V to 14.5V
−0.5V to 10V
100µA
240˚C/W
150˚C
−65˚C to +150˚C
260˚C
Power Dissipation (TA=25˚C)
(Note 2)
ESD Rating (Note 3)
500mW
2kV
Operating Conditions (Note 1)
VDD Pin
FB, EN Pins
BOOT Pin
Ambient Temperature (TA)
2.5V to 5V
0 to VDD
0 to 10V
−40˚C to +85˚C
Electrical Characteristics
Limits in standard typeface are for TJ = 25˚C, and limits in boldface type apply over the full operating temperature range of
−40˚C to +85˚C. Unless otherwise specified: VDD= VOUT= 3.3V.
Symbol
Parameter
Condition
Typ Min Max Units
VIN_ST
Minimum Start-Up Supply
Voltage (Note 4)
ILOAD = 0mA
1.1 1.2 V
VIN_OP
Minimum Operating Supply
Voltage (once started)
ILOAD = 0mA
0.65
V
VFB
VOUT_MAX
VHYST
η
FB Pin Voltage
Maximum Output Voltage
Hysteresis Voltage (Note 7)
Efficiency
VIN = 3.6V; VOUT = 5V; ILOAD
= 500mA
VIN = 2.5V; VOUT = 3.3V; ILOAD
= 200mA
1.24
14
30
87
87
1.2028 1.2772
45
V
V
mV
%
D Switch Duty Cycle
70 60 80 %
IDD
Operating Quiescent Current FB Pin > 1.3V; EN Pin at VDD
80
(Note 6)
110 µA
ISD
Shutdown Quiescent Current VDD, BOOT and SW Pins at
0.01
(Note 7)
5.0V; EN Pin <200mV
2.5 µA
ICL
RDS_ON
Switch Peak Current Limit
MOSFET Switch On
Resistance
2.85 A
0.17
Enable Section
VEN_LO
EN Pin Voltage Low (Note 8)
0.15VDD
V
VEN_HI
EN Pin Voltage High (Note 8)
0.7VDD
V
Note 1: Absolute maximum ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when operating the device
outside of its rated operating conditions.
Note 2: The maximum power dissipation must be derated at elevated temperatures and is dictated by Tjmax (maximum junction temperature), θJA (junction to am-
bient thermal resistance), and TA (ambient temperature). The maximum allowable power dissipation at any temperature is Pdmax = (Tjmax - TA)/ θJA or the number
given in the Absolute Maximum Ratings, whichever is lower.
Note 3: The human body model is a 100 pF capacitor discharged through a 1.5 kresistor into each pin. For Pin 8 (SW) the ESD rating is 1.5 kV.
Note 4: Output in regulation, VOUT = VOUT (NOMINAL) ± 5%
Note 5: This is the hysteresis value of the internal comparator used for the gated-oscillator control scheme.
Note 6: This is the current into the VDD pin.
Note 7: This is the total current into pins VDD, BOOT, SW and FREQ.
Note 8: When the EN pin is below VEN_LO, the regulator is shut down; when it is above VEN_HI, the regulator is operating.
3 www.national.com
Page 3
Part Number LM2621
Manufactur National Semiconductor
Description Low Input Voltage/ Step-Up DC-DC Converter
Total Page 10 Pages
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