1
dc1229bf
DEMO MANUAL DC1229B
Description
LT3650EDD-4.2/LT3650EDD-4.1
2A Monolithic Li-Ion
Battery Chargers
DC1229B is a 2A monolithic Li-Ion battery charger featur-
ing the LT
®
3650EDD-4.2/LT3650EDD-4.1. The LT3650 is a
complete mid-power Li-Ion battery charger that can operate
over a wide input voltage range. The circuit provides CC/CV
charging with a maximum charge current externally pro-
grammable up to 2A. A precondition feature trickle charges
a low-voltage battery and bad battery detection provides
L
, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
perForMAnce sUMMArY
operAting principles
a signal if the battery doesn’t respond to preconditioning.
The LT3650EDD is available in a 12-lead (3mm × 3mm)
DFN surface mount package with an exposed pad.
Design files for this circuit board are available at
http://www.linear.com/demo
(T
A
= 25°C)
PARAMETER
CONDITIONS
VALUE
Input Voltage Range
7.5V to 32V
V
OUT
3.7V to 4.24V
Output Float Voltage
Constant Voltage Mode
4.2V/4.1V
Output Current Limit I
LIM
R
RNG
= 20kΩ
2A
LT3650 is a complete monolithic mid-power Li-Ion battery
charger, addressing high input voltage applications with
solutions that require a minimum of external components.
The IC uses a 1MHz constant frequency, average-current
mode step-down architecture. Internal reverse voltage
protection allows direct connection to the input supply
without a blocking diode for single-cell applications
(LT3650-4.2/LT3650-4.1).
NOTE: A blocking diode on the input supply connection
is recommended to prevent the input from ringing below
ground with a battery on the output.
The LT3650 incorporates a 2A switch that is driven by a
bootstrapped supply to maximize efficiency during charg-
ing cycles. Wide input range allows operation to full charge
from 5V ±5% (single cell) to 36V. A precision-threshold
shutdown pin allows incorporation of UVLO functionality
using a simple resistor-divider. The IC can also be put into
a low-current shutdown mode, in which the input supply
bias is reduced to only 15µA.
The LT3650 incorporates several degrees of charge current
control freedom. The overall maximum charge current is
set using an external inductor current sense resistor. A
maximum charge current programming pin allows dynamic
manipulation of the battery charge current. The LT3650
also incorporates a system input-supply current limit
control feature that servos the battery charge current to
accommodate overall system load requirements.
The LT3650 automatically enters a battery precondition
mode if the sensed battery voltage is very low. In this mode,
the charging current is reduced to 15% of the programmed
maximum, as set by the inductor sense resistor, R
SENSE
.
Once the battery voltage climbs above an internally set
threshold of 2.9V/cell, the IC automatically increases
maximum charging current to the full programmed value.
