LTC4121_15 Datasheet, PDF (1/30 Pages) Linear Technology – 40V 400mA Synchronous Step-Down Battery Charger

LTC4121/LTC4121-4.2
40V 400mA Synchronous
Step-Down Battery Charger
Features
nn _{Wide Input Voltage Range: 4.4V to 40V}
nn _{Temperature Compensated Input Voltage}
Regulation for Maximum Power Point Tracking
(MPPT)
nn _{Adjustable Float Voltage 3.5V to 18V (LTC4121)}
nn _{Fixed 4.2V Float Voltage Option (LTC4121-4.2)}
nn _{High Efficiency: Up to 95%}
nn _{50mA to 400mA Programmable Charge Current}
nn _{±1% Feedback Voltage Accuracy}
nn _{Programmable 5% Accurate Charge Current}
nn _{Thermally Enhanced, Low Profile (0.75mm)}
16-Lead (3mm × 3mm) QFN Package
Applications
nn _{Handheld Instruments}
nn _{Solar Powered Devices}
nn _{Industrial/Military Sensors and Devices}
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode are registered trademarks
of Linear Technology Corporation. All other trademarks are the property of their respective
owners.
Description
The LTC^®4121 is a 400mA constant-current/constant-
voltage (CC/CV) synchronous step-down battery charger.
In addition to CC/CV operation, the LTC4121 regulates its
input voltage to a programmable percentage of the input
open-circuit voltage. This technique maintains maximum
power transfer with high impedance input sources such
as solar panels.
An external resistor programs the charge current up to
400mA. The LTC4121-4.2 is suitable for charging Li-Ion/
Polymer batteries, while the programmable float voltage
of the LTC4121 is suitable for several battery chemistries.
The LTC4121 and LTC4121-4.2 include an accurate RUN
pin threshold, low voltage battery preconditioning and bad
battery fault detection, timer termination, auto-recharge,
and NTC temperature qualified charging. The FAULT pin
provides an indication of bad battery or temperature faults.
Once charging is terminated, the LTC4121 signals end-of-
charge via the CHRG pin, and enters a low current SLEEP
mode. An auto-restart feature starts a new charging cycle
if the battery voltage drops by 2.2%.
Typical Application
High Efficiency, Wide Input Voltage Range Charging with LTC4121
10µF _10k
+–
V_IN
V_BAT + 200mV
TO 40V
IN
INTV_CC
RUN
BOOST
MPPT
LTC4121 SW
CHGSNS
BAT
PROG
FB
R_PROG
FREQ GND FBG
2.2µF
22nF
SLF6025T-470MR48
1.96M
22µF
787k ₊
Li-Ion
4121 TA01a
LTC4121 Efficiency vs V_IN at V_FLOAT = 8.4V
97
200mA, R_PROG = 6.04k
400mA, R_PROG = 3.01k
95
93
91
89
V_BAT = 8.3V
87
5 10 15 20 25 30 35 40
V_IN (V)
4121 TA01b
For more information www.linear.com/LTC4121
4121fa
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