
LT3652EDD
1
DESCRIPTION
Demonstration Circuit 1568A is a 2A Monolithic Multi-
Chemistry battery charger for solar power applications
featuring the LT3652EDD. The LT3652 is a complete
mid-power Li-Ion battery charger that can operate
over a wide input voltage range. The charger employs
a 3.3V float voltage feedback reference that allows the
battery float voltage to be adjusted up to 14.4V. R10
and R11, in the demonstration circuit, set the float
voltage and are 0603 resistors to accommodate the
use of 0.1% resistors if desired. The circuit is con-
structed with 1% resistors which could introduce as
much as a 1.56% error in the float voltage. Replacing
these resistors with 0.1% resistors would introduce
less than a 0.154% error. The LT3652 has an input
voltage regulation loop which reduces charge current
if the input falls below a programmed level, set with a
resistor divider. The charger is a CC/CV charger with a
maximum charge current of 2A. A precondition fea-
ture trickle charges a low-voltage battery, and bad bat-
tery detection provides a signal if the battery doesn’t
respond to preconditioning.
The LT3652EDD is available in a 12-lead (3mm ×
3mm) DFN surface mount package with an exposed
pad.
Design files for this circuit board are available. Call
the LTC factory.
L, LTC, LTM, LT, Burst Mode, OPTI-LOOP, Over-The-Top and PolyPhase are registered
trademarks of Linear Technology Corporation. Adaptive Power, C-Load, DirectSense, Easy
Drive, FilterCAD, Hot Swap, LinearView, μModule, Micropower SwitcherCAD, Multimode
Dimming, No Latency ΔΣ, No Latency Delta-Sigma, No R
SENSE
, Operational Filter, PanelProtect,
PowerPath, PowerSOT, SmartStart, SoftSpan, Stage Shedding, SwitcherCAD, ThinSOT,
UltraFast and VLDO are trademarks of Linear Technology Corporation. Other product names
may be trademarks of the companies that manufacture the products.
Table 1: Typical Specifications (25°C)
HV Input Voltage Range 11.5V to 32V
VOUT 8.04V to 8.36V
Output Float Voltage (constant voltage mode) 8.2V
Output Current Limit ILIM 2A
OPERATING PRINCIPLE
LT3652 is a complete monolithic mid-power Li-Ion bat-
tery charger, addressing high input voltage applications
with solutions that require a minimum of external com-
ponents. The IC uses a 1MHz constant frequency, aver-
age-current mode step-down architecture.
The LT3652 incorporates a 2A switch that is driven by a
bootstrapped supply to maximize efficiency during
charging cycles. A wide input range allows operation to
fully charge from 11.5V (single cell) to 32V. A precision-
threshold shutdown pin allows the 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 15uA.
The LT3652 incorporates several degrees of charge cur-
rent control freedom. The overall maximum charge cur-
rent is set using an external inductor current sense resis-
tor. A maximum charge current programming pin allows
DEMO CIRCUI
1568
QUICK START GUID
LT3652ED
2A Monolithic Multi
Chemistry Battery Charge