QUICK START GUIDE FOR DEMONSTRATION CIRCUIT 920
STAND ALONE LI-ION CHARGER WITH SYNCHRONOUS BUCK REGULATOR
1
LTC4080
Demonstration circuit 920 is a complete single
cell Lithium-Ion battery charger and adjustable
output voltage buck switching regulator. Operat-
ing at a frequency of 2.25MHz, the 300mA syn-
chronous regulator is powered from the Li-Ion
battery.
This demonstration circuit allows the user to
quickly evaluate the LTC4080 performance. In-
dividual jumpers are provided for shutting down
the charger and/or the switching regulator, for
selecting several regulated output voltages and
the mode of operation (fixed frequency or
Burst). LEDs indicate charger status (input
power and charge) and pins on the board allow
easy hookup to an input supply and battery or
battery simulator.
The high switching frequency of the voltage
regulator allow tiny LC components to be used
and the 10-Pin 3mm x 3mm DFN thermally en-
hanced package with the metal backside allow
the linear charger to provide up to 500mA of
charge current in addition to the regulator out-
put current.
Design files for this circuit board are available.
Call the LTC factory.
LTC and Burst Mode are trademarks of Linear Technol-
ogy Corporation
Table 1. Typical Specifications (25°C)
Input Voltage Range VIN
3.75V to 5.5V
Output Charger Float Voltage VBAT (constant voltage mode)
4.2V ±0.5%
Output Current IBAT (constant current mode)
500mA ± 5%
Current Monitor Output
1V ±1.5% @ Full Current
Charge Termination Timer
4.5 Hours ±25%
C/10 Output Indication Level (CHRG)
50mA ± 10%
1.2V Regulator VOUT (100ma)
1.2V ± 2.5%
1.5V Regulator VOUT (100ma)
1.5V ± 2.5%
1.8V Regulator VOUT (100ma)
1.8V ± 2.5%
2.5V Regulator VOUT (100ma)
2.5V ± 2.5%
Regulator Output Ripple Voltage (fixed frequency)
5mV p-p
Regulator Output Ripple Voltage (burst mode)
50mV p-p
Buck Regulator Maximum Output Current (fixed frequency) 350mA
The battery charger portion of demonstration
circuit 920 uses a constant-current/constant
voltage charge algorithm with timer charge
termination. The battery float voltage is fixed at
4.2V and the charge current is programmed for
500mA, although a lower charge current can
be programmed by replacing the program re-
sistor (R5) with a suitable value. Either a
leaded resistor, from PROG to GND, or a 0402
surface mount resistor can be used.
