Linear Technology DC299 User manual

DC299 Introduction
Description
Demo board DC299 features the LTC1729 Li-Ion charge-termination IC in combination with the
LT1769 battery charger IC. This board provides a complete solution for charging 1- or 2-cell Li-
Ion batteries with a 2A charging current. These ICs have end-of-charge termination that can be
configured to stop the charger when the charge current drops below 10% of its initial setting or
when the internal timer counts to 3 hours. A safety termination feature disables charging if the
temperature is below 0°C or above 50°C and resumes charging when the temperature returns to
the 0°C to 50°C range. The solution extends battery life by trickle charging when the battery is
depleted and by meeting the battery manufacturers’voltage requirement of 1% total accuracy.
Finally, the board adds convenience by automatically detecting when a battery or supply is
present.
This board is intended for designers who need the versatility of battery charger DC/DC
converters. The small size and efficiency of this circuit allow it to function in portable
applications as well as in wall operated chargers.
Quick Start Guide
It is simple to set up the DC299 demo board to charge a 1-cell or 2-cell Li-Ion battery. Follow the
procedure outlined below for proper operation. Note: Use the battery manufacturer’s
recommended safety procedures and protection circuits.
+
–
+
–
+
–
+
+
–
'SCOPE
BATTERY
TO BE
CHARGED
SYSTEM
LOAD
GND
UV OUT
PROGRAM
VBAT
GND
NTC
GND
+VIN
LT1769CGN/LTC1729CMS8
2A Li-Ion Battery Charger
With Termination Controller
Demo Circuit DC299A
U2
+
]
LED
]
C/10
]
3HR
JP1
Figure 1. DC299 Connection Diagram

1. The demo board comes in four versions, each with a different output voltage. It is very
important to determine the correct version for your battery. To verify the output voltage of the
board, compare the marking on the top of U2 (refer to Figure 1) with Table 1.
2. Before turning on power, connect the input power supply, battery, oscilloscope and meters as
shown in Figure 1. For best accuracy, it is important to connect voltmeters directly to the PCB
terminals when measuring input and output voltages.
3. Select the end-of-charge termination method desired. If 3-hour termination is preferred,
connect two jumpers on JP1, enabling LED and 3HR. To stop the charger after the current
drops below 10% of 2A or 200mA, connect the jumper on JP1 to enable C/10.
4. The charger can be stopped if the temperature is not in the 0°C to 50°C range using the NTC
terminal on the PCB board. An external 10k NTC thermistor, such as a Vishay
NTHS12106N02, must be connected between the NTC terminal and ground and R14 must be
removed from the PCB board.
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