LTC4012IUF-1#TRPBF Linear Technology, LTC4012IUF-1#TRPBF Datasheet - Page 16

• Manufacturer Part Number: LTC4012IUF-1#TRPBF
• Description: IC CTLR BATT CHARGER CC/CV 20QFN
• Manufacturer: Linear Technology

Specifications of LTC4012IUF-1#TRPBF

• Function: Charge Management
• Battery Type: Multi-Chemistry
• Voltage - Supply: 6 V ~ 28 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 20-WFQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

LTC4012/
LTC4012-1/LTC4012-2
applications inForMation
Programming Charge Current
The formula for charge current is:
The LTC4012 operates best with 3.01k input resistors,
although other resistors near this value can be used to
accommodate standard sense resistor values. Refer to
the subsequent discussion on inductor selection for other
considerations that come into play when selecting input
resistors R
R
equation:
where I
The 100mV target can be adjusted to some degree to obtain
standard R
target voltages lower than 100mV will cause a proportional
reduction in current regulation accuracy.
The required minimum resistance between PROG and GND
can be determined by applying the suggested expression
for R
charge current with I
If R
this equation indicates a minimum value for R
26.9k. Table 6 gives some examples of recommended
charge current programming component values based
on these equations.
The resistance between PROG and GND can simply be
set with a single a resistor, if only maximum charge cur-
rent needs to be controlled during the desired charging
algorithm.

SENSE
I
R
R
IN
CHRG
PROG MIN
SENSE
SENSE
is chosen to be 3.01k with a sense voltage of 100mV,
MAX
should be chosen according to the following
=
(
SENSE
while solving the first equation given above for
IN
=
R
is the desired maximum charge current I
.
SENSE
100
R
)
I
=
IN
MAX
values and/or a desired R
mV
0 1
.
•
V
1 2085
CHRG

 
.
+
1 2085
R
.
11 67
PROG
= I
.
V R
MAX
V
•
µA R
–
:
IN
•
11 67
IN
.
µA
PROG

 
value, but
PROG
CHRG
of
.
However, some batteries require a low charge cur-
rent for initial conditioning when they are heav-
ily discharged. The charge current can then be safely
switched to a higher level after conditioning is complete.
Figure 3 illustrates one method of doing this with 2-level
control of the PROG pin resistance. Turning Q1 off reduces
the charge current to I
When Q1 is on, the LTC4012 is programmed to allow
full I
expanded through the use of additional digital control
inputs for an arbitrary number of pre-programmed cur-
rent values.
For a truly continuous range of maximum charge current
control, pulse width modulation can be used as shown
in Figure 4.
MAX
Figure 3. Programming 2-Level Charge Current
PRECHARGE
current for bulk charge. This technique can be
Figure 4. Programming PWM Current
5V
0V
CHARGE
BULK
LTC4012
PROG
13
MAX
LTC4012
Q1
2N7002
R
PROG
PROG
13
/10 for battery conditioning.
Q1
2N7002
R1
26.7k
C
PROG
R2
53.6k
4012 F04
4012 F03
R
511k
MAX
C
4.7nF
PROG
4012fa