NSC LM2621MMX, LM2621MM Datasheet

LM2621
Low Input Voltage, Step-Up DC-DC Converter

LM2621 Low Input Voltage, Step-Up DC-DC Converter

February 2000

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 con­verts 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 capaci­tors. Because of the unique constant-duty-cycle gated oscil­lator 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 pack­age 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 Ω 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

DS100934-12

© 2000 National Semiconductor Corporation DS100934 www.national.com

Connection Diagram

LM2621

Ordering Information

Mini SO-8 (MM) Package

DS100934-18

Top View

Order Number Package Type

LM2621MMX Mini SO-8 MUA08A S06A 3000 Units on Tape and Reel

LM2621MM Mini SO-8 MUA08A S06A 1000 Units on Tape and Reel

NSC Package

Drawing

Package

Marking

Supplied As

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LM2621

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/

Power Dissipation (T

=25˚C)

A

500mW

(Note 2)
ESD Rating (Note 3) 2kV

Distributors for availability and specifications.

SW Pin Voltage −0.5 V to 14.5V
BOOT, V

, EN and FB Pins −0.5V to 10V

DD

FREQ Pin 100µA

θ

(Note 2) 240˚C/W

JA

T

(Note 2) 150˚C

Jmax

Storage Temperature Range −65˚C to +150˚C

Operating Conditions (Note 1)

V

Pin 2.5V to 5V

DD

FB, EN Pins 0 to V
BOOT Pin 0 to 10V
Ambient Temperature (T

) −40˚C to +85˚C

A

DD

Lead Temp. (Soldering, 5 sec) 260˚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=V

Symbol Parameter Condition Typ Min Max Units

V

IN_ST

Minimum Start-Up Supply

I

LOAD

Voltage (Note 4)

V

IN_OP

Minimum Operating Supply

I

LOAD

Voltage (once started)

V

FB

V

OUT_MAX

V

HYST

η Efficiency V

FB Pin Voltage 1.24 1.2028 1.2772 V
Maximum Output Voltage 14 V
Hysteresis Voltage (Note 7) 30 45 mV

IN

= 500mA
V

IN

= 200mA
D Switch Duty Cycle 70 60 80 %
I

DD

Operating Quiescent Current

FB Pin>1.3V; EN Pin at V

(Note 6)

I

SD

I

CL

R

DS_ON

Shutdown Quiescent Current
(Note 7)

VDD, BOOT and SW Pins at

5.0V; EN Pin
Switch Peak Current Limit 2.85 A
MOSFET Switch On

Resistance

Enable Section

V

EN_LO

V

EN_HI

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 T
bient thermal resistance), and T
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, V
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 V
Note 7: This is the total current into pins V
Note 8: When the EN pin is below V

EN Pin Voltage Low (Note 8) 0.15V
EN Pin Voltage High (Note 8) 0.7V

(ambient temperature). The maximum allowable power dissipation at any temperature is P

A

OUT=VOUT (NOMINAL

pin.

DD

EN_LO

)±5%

, BOOT, SW and FREQ.

DD

, the regulator is shut down; when it is above V

= 3.3V.

OUT

= 0mA 1.1 1.2 V

= 0mA 0.65 V

= 3.6V; V

= 2.5V; V

OUT

OUT

= 5V; I

= 3.3V; I

LOAD

LOAD

DD

87
87

80 110 µA

0.01 2.5 µA

<

200mV

0.17 Ω

DD

DD

(maximum junction temperature), θJA(junction to am-

jmax

, the regulator is operating.

EN_HI

dmax

=(T

)/ θJAor the number

jmax-TA

%

V
V

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