Low Input Voltage, Step-Up DC-DC Converter
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
0.17Ω N-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.
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 Ω Internal MOSFET
n Up to 90% Regulator Efficiency
n 80 µA Typical Operating Current
n <2.5µA Guaranteed Supply Current In Shutdown
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
Mini SO-8 (MM) Package
3000 Units on Tape and Reel
1000 Units on Tape and Reel
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
θJA (Note 2)
TJmax (Note 2)
Storage Temperature Range
Lead Temp. (Soldering, 5 sec)
−0.5 V to 14.5V
−0.5V to 10V
−65˚C to +150˚C
Power Dissipation (TA=25˚C)
ESD Rating (Note 3)
Operating Conditions (Note 1)
FB, EN Pins
Ambient Temperature (TA)
2.5V to 5V
0 to VDD
0 to 10V
−40˚C to +85˚C
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.
Typ Min Max Units
Minimum Start-Up Supply
Voltage (Note 4)
ILOAD = 0mA
1.1 1.2 V
Minimum Operating Supply
Voltage (once started)
ILOAD = 0mA
FB Pin Voltage
Maximum Output Voltage
Hysteresis Voltage (Note 7)
VIN = 3.6V; VOUT = 5V; ILOAD
VIN = 2.5V; VOUT = 3.3V; ILOAD
D Switch Duty Cycle
70 60 80 %
Operating Quiescent Current FB Pin > 1.3V; EN Pin at VDD
Shutdown Quiescent Current VDD, BOOT and SW Pins at
5.0V; EN Pin <200mV
Switch Peak Current Limit
MOSFET Switch On
EN Pin Voltage Low (Note 8)
EN Pin Voltage High (Note 8)
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 kΩ resistor 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.
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