LTC4015_15 Datasheet, PDF (33/76 Pages) Linear Technology – Multichemistry Buck Battery Charger Controller with Digital Telemetry System

LTC4015
Operation
profile can be programmed into the LTC4015 to ensure
that optimum charging parameters as a function of
temperature are always used. Figure 6 illustrates an
example of the JEITA system available in the LTC4015.
There are seven distinct temperature regions programmed
by the six temperature set points JEITA_T1-JEITA_T6. For
each of the temperature regions, the charge current and
charge voltage can be programmed within the limits set
by V_CSP–CSN/R_SNSB (I_CHARGE) and battery charge voltage
(V_CHARGE) for a selected chemistry code.
When JEITA is enabled, charge current is controlled by
ICHARGE_DAC, which in turn is set by icharge_jeita_n of
the applicable JEITA region. Writing ICHARGE_TARGET
has no effect, as it will be overwritten by JEITA. Likewise
V_CHARGE is controlled by VCHARGE_DAC which in turn
is set by vcharge_jeita_n of the applicable JEITA region.
The LTC4015 provides temperature controlled charging if
a grounded thermistor and a bias resistor are connected
to the NTCBIAS and NTC pins. Charging is paused if the
temperature rises above a programmable upper limit or
falls below a programmable lower limit.
If the application does not require temperature controlled
charging then the thermistor should be replaced with
a resistor of equal value to bias resistor R_NTCBIAS, for
example, 10kΩ.
The values for the JEITA registers are shown in the tables
below. The bold values in the tables are programmable
when using Li-Ion programmable or LiFePO₄ program-
mable chemistry selections.
The JEITA_Tn registers determine the NTC_RATIO values
for the breakpoints between regions. The corresponding
temperature values assume a thermistor β value of 3490k,
such as provided by a Vishay NTCS0402E3103FLT or
NTHS0402N02N1002JE. For other thermistors, one or
two inexpensive low temperature coefficient resistors can
generally be added to the circuit to adjust the thermistor’s
biasing (see the section NTC Resistor in Applications
Information for details).
T1 T2
T3 T4 T5 T6
4.5
45
4.0
40
3.5
35
3.0
30
CHARGE VOLTAGE
2.5
25
CHARGE CURRENT
2.0
20
1.5
15
1.0
10
0.5
0
0
05
0
10 20 30 40 50 60
TEMPERATURE (°C)
4015 F06
Figure 6. Default JEITA Temperature Profile, Showing
Values for Li-Ion Fixed 4.2V
Table Illustrates the JEITA Values That Can Be Programmed Via the Serial Port.
REGION 1
REGION 2
REGION 3
REGION 4
REGION 5
REGION 6
REGION 7
JEITA_T1
JEITA_T2
JEITA_T3
JEITA_T4
JEITA_T5
JEITA_T6
CHARGER
OFF
icharge_jeita_2
vcharge_jeita_2
icharge_jeita_3
vcharge_jeita_3
icharge_jeita_4
vcharge_jeita_4
icharge_jeita_5
vcharge_jeita_5
icharge_jeita_6
vcharge_jeita_6
CHARGER
OFF
For more information www.linear.com/LTC4015
4015f
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