LINEAR AN68-1 Data Handbook / Specifications

Application Note 68 December 1996

LT1510 Design Manual Applications Engineering Staff

INTRODUCTION

The ever-growing popularity of portable equipment in An important feature of the LT1510 is its constant-current recent years has pushed battery technologists to search output (see Figure 1). Although other switching regulators for battery types that store more energy in a smaller offer current limiting, the LT1510 offers constant current volume, weigh less and are safer. Also, the power source with 5% accuracy. In addition, the transition from con- selection for charging the batteries has diversified. For stant current to constant voltage and back is very smooth.

example, a notebook computer can be connected to a

Only a few basic calculations are required to design with

car battery, a power adapter, a docking station or even to

the LT1510. As the reader will see later, a voltage divider

solar cells.

(two resistors) and a current programming resistor need The variety of input voltages, coupled with the need for to be selected for the constant voltage and constant high efficiency and the need for accurate constant voltage current, respectively.

and constant current, as in the case of Li-Ion batteries (see

In constant-current/constant-voltage operation, the

below), have led to the introduction of a switching type

LT1510 can charge lithium-ion (Li-Ion) and sealed-lead-

constant-voltage, constant-current battery charger IC, the

acid (SLA) batteries. In constant-current only operation,

LT®1510.

the LT1510 can charge nickel-metal-hydride (Ni MH) and Being a switching regulator, the LT1510 can operate over nickel-cadmium (Ni Cd) batteries.

a large range of input voltages, up to 28V, with efficiency in the 90% range. Because the LT1510 operates in current mode, its output performance is not affected by input

voltage changes. , LTC and LT are registered trademarks of Linear Technology Corporation.

TABLE OF CONTENTS

ON BATTERIES AND CHARGERS AN68-2 LT1510 OPERATION/BLOCK DIAGRAM.................................................................................................................................... AN68-5 COMPONENT SELECTION AN68-8 INTEGRATING THE LT1510 INTO A SYSTEM AN68-13 CHARGING BATTERIES/TERMINATION METHODS AN68-16 APPENDIX A: TEST RESULTS AN68-28 APPENDIX B: AUXILIARY CIRCUITS FOR TESTING BATTERIES AND CHARGERS................................................................. AN68-35

AN68-1