1
dc2069afb
DEMO MANUAL DC2069A
Description
LT8490
High Efficiency MPPT Battery
Charger Controller
Demonstration circuit 2069A features
LT
®
8490
, a high
performance buck-boost converter that implements an
MPPT function and flexible charging profiles suitable for
most battery types such as flooded and sealed lead acid
batteries and Lithium-Ion batteries, and can operate from
input voltages above, below or equal to the battery voltage.
The demo board is configured for a 17V to 54V input volt-
age range and the power source can be a solar panel with
36 to 72 cells (up to 200W) or a DC voltage source. Two
input connectors are provided. An LTC4359 ideal diode
controller protects the DC power supply output from being
back fed from the solar panel. This allows, for example,
that a 24VDC supply is plugged in while a solar panel with
higher voltage is being used to power the circuit.
On-chip logic provides automatic true power point tracking
for solar powered applications. The MPPT function not
only continuously tracks the maximum power point, it is
able to select the correct maximum on the power curve
to increase power harvested from the panel during partial
shade conditions, when multiple peaks occur on the power
curve. During periods of low light, a low power mode al-
lows the charger to deliver a small charge current even if
there is not enough light for the MPPT function to operate.
The demo board output is set up for charging a 12V SLA
battery with up to 16.6A charge current. Two charge
L
, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
performance summary
configuration headers are provided so the user can select
different charge algorithms.
There are two onboard LEDs that display information on
the charge stage, and they will blink fault messages if the
charger shuts down because of a fault. A simple serial
interface also sends out status bytes that can be interpreted
by external circuitry.
An RJ25 modular jack can be used to connect an external
NTC temperature sensor mounted at the battery. This
allows temperature compensation of the charge voltage,
which is important for lead acid batteries. The same con-
nector can be used for remote sensing of battery voltage,
to compensate for voltage drops in long battery cables.
The LT8490 data sheet gives a complete description of
the device, operation and application information. The data
sheet must be read in conjunction with this demo manual
for DC2069A. The LT8490EUKJ is assembled in a 64-lead
(7mm × 11mm) plastic QFN package with a thermal pad
underneath the chip. Proper board layout is essential for
maximum thermal performance.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2069A
Specifications are at T
A
= 25°C
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
IN
Input Supply Range
Note: Output Power Is Limited by Input Current Limit
When V
IN
< 24V (See Figure 2)
17
30
54
V
V
OUT
Charge Voltage
14.2
V
I
IN
Maximum Input Current
10
A
I
OUT
Maximum Output Current
V
IN
> 24V, V
OUT
= 12V
16.6
A
F
SW
Switching Frequency
200
kHz
EFF
Efficiency at DC input
V
IN
= 28V, V
OUT
= 14V, I
OUT
= 15A
V
IN
= 48V, V
OUT
= 14V, I
OUT
= 15A
V
IN
= 24V, V
OUT
= 14.2V, I
OUT
= 8A
96.3
95.6
97.3
%
%
%
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