LTM8062EVPBF LINER [Linear Technology], LTM8062EVPBF Datasheet - Page 11

• Manufacturer Part Number: LTM8062EVPBF
• Description: 32VIN, 2A ?Module Power Tracking Battery Charger
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
circuitry. For proper operation, it must be powered by at
least 2.8V and no more than the absolute maximum rat-
ing of 10V. In most applications, connect BIAS to BAT. If
there is no BIAS supply available or the battery voltage is
below 2.8V, the internal switch requires more headroom
from V
Performance Characteristics curves for minimum start and
running requirements under various battery conditions.
When charging a 2-cell battery using a relatively high input
voltage, the LTM8062 power dissipation can be reduced by
connecting BIAS to a voltage between 2.8V and 3.3V.
Output Capacitance
In many applications, the internal BAT capacitance of the
LTM8062 is sufficient for proper operation. There are cases,
however, where it may be necessary to add capacitance or
otherwise modify the output impedance of the LTM8062.
Case 1: the μModule is physically located far from the
battery and the added line impedance may interfere with
the control loop. Case 2: the battery ESR is very small or
very large; the LTM8062 controller is designed for a wide
range, but some battery packs have an ESR outside of this
range. Case 3: there is no battery at all. As the charger is
designed to work with the ESR of the battery, the output
may oscillate if no battery is present.
The optimum ESR is about 100mΩ, but ESR values both
higher and lower will work. Table 2 shows a sample of
parts successfully tested by Linear Technology:
Table 2
PART NUMBER
16TQC22M
35SVPD18M
TPSD226M025R0100
T495D226K025AS
TPSC686M006R0150
TPSB476M006R0250
APXE100ARA680ME61G
APS-150ELL680MHB5S
If system constraints preclude the use of electrolytic ca-
pacitors, a series R-C network may be used. Use a ceramic
capacitor of at least 22μF and an equivalent resistance of
100mΩ. An example of this is shown in the Typical Ap-
plications section.
IN
for proper operation. Please refer to the Typical
DESCRIPTION
22μF , 16V, POSCAP
18μF , 35V, OS-CON
22μF , 25V Tantalum
22μF , 25V, Tantalum
68μF , 6V, Tantalum
47μF , 6V, Tantalum
68μF , 10V Aluminum
68μF , 25V Aluminum
MANUFACTURER
Sanyo
Sanyo
AVX
Kemet
AVX
AVX
Nippon Chemicon
Nippon Chemicon
MPPT Temperature Compensation
A typical solar panel is comprised of a number of series-con-
nected cells, each cell being a forward-biased p-n junction.
As such, the open-circuit voltage (V
a temperature coefficient that is similar to a common p-n
diode, or about –2mV/°C. The peak power point voltage
(V
a fixed voltage below V
for the peak power point is similar to that of V
Panel manufacturers typically specify the 25°C values for
V
determination of the temperature coefficient for V
a typical panel straight forward. The LTM8062 employs
a feedback network to program the V
voltage. Manipulation of the network makes for efficient
implementation of various temperature compensation
schemes for a maximum peak power tracking (MPPT)
application. As the temperature characteristic for a typical
solar panel V
for tracking that characteristic can be implemented using a
Linear Technology LM234 3-terminal temperature sensor.
This creates an easily programmable, linear temperature
dependent characteristic.
In the circuit shown in Figure 4,
where TC = temperature coefficient (in V/°C), and
V
OC
MP
MP
R
R
, V
(25°C) = maximum power voltage at 25°C.
IN1
IN2
) for a crystalline solar panel can be approximated as
Figure 4. MPPT Temperature Compensation Network
MP
= –R
=
, and the temperature coefficient for V
V
V
IN
MP
MP
SET
(25°C) + R
R
R
voltage is highly linear, a simple solution
IN1
IN2
• (TC • 4405), and
V
V
+
–
OC
V
INREG
R
, so the temperature coefficient
IN1
R
LINEAR
TECHNOLOGY
LM234
IN1
• (0.0674 / R
R
SET
− 1
V
OC
INREG
LTM8062
) of a solar cell has
IN
V
LTM8062
IN
input regulation
SET
8062 F04
)
OC
OC
, making
.
11
MP
8062f
of