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PDF LTC4121 Data sheet ( Hoja de datos )
| Número de pieza | LTC4121 | |
| Descripción | 40V 400mA Synchronous Step-Down Battery Charger | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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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
+–
VIN
VBAT + 200mV
TO 40V
IN INTVCC
RUN BOOST
MPPT
LTC4121
SW
CHGSNS
BAT
PROG
FB
RPROG
FREQ GND FBG
2.2µF
22nF
SLF6025T-470MR48
1.96M
787k +
Li-Ion
22µF
4121 TA01a
LTC4121 Efficiency vs VIN at VFLOAT = 8.4V
97
200mA, RPROG = 6.04k
400mA, RPROG = 3.01k
95
93
91
89
VBAT = 8.3V
87
5 10 15 20 25 30 35 40
VIN (V)
4121 TA01b
For more information www.linear.com/LTC4121
4121fa
1
1 page  
LTC4121/LTC4121-4.2
E lectrical Characteristics The l denotes the specifications which apply over the specified operating
junction temperature range, otherwise specifications
VFB = 2.29V (LTC4121), VBATSNS = 4V (LTC4121-4.2).
CaruerraetnTt Ain=to2a5°pCi.n
VisINp=osViRtiUvNe
=ou1t5oVf,aVpCHinGSisNSne=gVaBtiAvTe=.
(4NVo,teRP2R)OG
=
3.01k,
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX UNITS
RUN
VEN Enable Threshold
Hysteresis
Run Pin Input Current
VSD Shutdown Threshold
VRUN Rising
VRUN Falling
VRUN = 40V
VRUN Falling
l 2.35
l 0.4
2.45 2.55
200
0.01 0.1
1.2
V
mV
µA
V
Hysteresis
220 mV
FREQ
FREQ Pin Input Low
l 0.4
V
FREQ Pin Input High
l 3.6 V
MPPT
FREQ Pin Input Current
0 < VFREQ < VINTVCC
±1 µA
IMPPT
TMP
PWMP
KF
VMP(OS)
MPPT Pin Leakage Current
MPPT Sample Period
MPPT Sample Pulse Width
Internal Divider Gain
MPPT Error Amp Gain Offset
VMPPT = 4.2V
Period Between Charger Disabled Events
Charger Disabled Pulse Width
Internal DAC Voltage as a Ratio to VIN
VMPPT – VDAC, IBAT = 50%• ICHG
l
0.098
10
15 1000
28
36
0.1 0.102
–45 –100
nA
s
ms
V/V
mV
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTC4121 is tested under pulsed load conditions such that
TJ ≈ TA. The LTC4121E is guaranteed to meet performance specifications
for junction temperatures from 0°C to 85°C. Specifications over the
–40°C to 125°C operating junction temperature range are assured by
design, characterization and correlation with statistical process controls.
The LTC4121I is guaranteed over the full –40°C to 125°C operating
junction temperature range. Note that the maximum ambient temperature
consistent with these specifications is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
impedance, and other environmental factors.
Note 3: If a battery voltage greater than 11V can be hot plugged to the
LTC4121 a reverse blocking diode is required in series with the BAT pin to
prevent large inrush current into the low impedance BAT pin.
Note 4: Standby mode occurs when the LTC4121/LTC4121-4.2 stops
switching due to an NTC fault, MPPT pause, or when the charge current
has dropped low enough to enter Burst Mode operation. Disabled mode
occurs when VRUN is between VSD and VEN. Shutdown mode occurs
when VRUN is below VSD or when the differential undervoltage lockout
is engaged. Sleep mode occurs after a timeout while the battery voltage
remains above the VRCHG or VRCHG_42 threshold.
Note 5: The internal supply INTVCC should only be used for the NTC
divider, it should not be used for any other loads
Note 6: For the LTC4121, the FB pin is measured with a resistance of 588k
in series with the pin.
Note 7: hC/10 is expressed as a fraction of measured full charge current as
measured at the PROG pin voltage when the CHRG pin de-asserts.
Note 8: In an application circuit with an inductor connected from SW to
CHGSNS, the total battery leakage current when disabled is the sum of
IBATSNS and ISW (LTC4121-4.2) or IBAT and IFBG_LEAK and ISW (LTC4121).
Note 9: When no supply is present at IN, the SW powers IN through the
body diode of the top side switch. This may cause additional SW pin
current depending on the load present at IN.
Note 10: Guaranteed by design and/or correlation to static test.
For more information www.linear.com/LTC4121
4121fa
5
5 Page 
Block Diagram
LTC4121/LTC4121-4.2
VIN
KR • VIN
RMPPT1
RMPPT2
LTC4121-4.2
BATSNS
IN-80mV
+
–
ITH
DUVLO
MPPT
IN IMPPT
KF • VIN
9R
TMP
R
+
–
INTVCC
DAC
INTVCC
+ gm
–
KF • VIN
+VMP(OS)
LOWBAT
– BATSNS
+ 2.21V
INTVCC
+
–
C-EA
CHGSNS
RSNS
0.3Ω BAT
BATSNS
INTVCC
+
– 588k
V-EA
2.4V
ENABLE
PROG
DZ
4121 F02
CBAT
22µF
Li-Ion
Figure 2. LTC4121-4.2 BATSNS Connections
For more information www.linear.com/LTC4121
4121fa
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LTC4121.PDF ] | |
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