LT3652 LINER [Linear Technology], LT3652 Datasheet - Page 14

• Manufacturer Part Number: LT3652
• Description: Power Tracking 2A Battery Charger for Solar Power
• Manufacturer: LINER [Linear Technology]

LT3652
APPLICATIONS INFORMATION
Magnetics vendors typically specify inductors with
maximum RMS and saturation current ratings. Select an
inductor that has a saturation current rating at or above (1+
ΔI
Inductors must also meet a maximum volt-second product
requirement. If this specification is not in the data sheet of
an inductor, consult the vendor to make sure the maximum
volt-second product is not being exceeded by your design.
The minimum required volt-second product is:
Rectifier Selection
The rectifier diode from SW to GND, in a LT3652 battery
charger provides a current path for the inductor current
when the main power switch is disabled. The rectifier is
selected based upon forward voltage, reverse voltage, and
maximum current. A Schottky diode is required, as low
14
MAX
V
BAT(FLT)
/2) • I
Figure 3. 7.2V at 1.5A Switched Inductor Values
CHG(MAX)
• (1 – V
16
14
12
10
8
6
4
12
MAXIMUM OPERATIONAL V
16
BAT(FLT)
, and an RMS rating above I
20
/V
IN(MAX)
24
IN
VOLTAGE (V)
) (V • μS)
28
3652 F03
32
CHG(MAX)
.
forward voltage yields the lowest power loss and highest
efficiency. The rectifier diode must be rated to withstand
reverse voltages greater than the maximum V
The minimum average diode current rating (I
is calculated with maximum output current (I
maximum operational V
threshold (V
For example, a rectifier diode for a 7.2V, 2A charger with
a 25V maximum input voltage would require:
Battery Float Voltage Programming
The output battery float voltage (V
by connecting a resistor divider from the BAT pin to V
V
BAT(FLT)
I
I
I
DIODE(MAX)
DIODE(MAX)
DIODE(MAX)
Figure 4. Feedback Resistors from BAT to V
Program Float Voltage
can be programmed up to 14.4V.
BAT(PRE)
> I
> 2 • (25 – 0.7[7.2]) / 25), or
> 1.6A
CHG(MAX)
LT3652
, or 0.7 • V
3652 F04
BAT
V
FB
• (V
IN
, and output at the precondition
IN(MAX)
R
R
BAT(FLT)
FB1
FB2
BAT(FLT)
– V
BAT(PRE)
+
):
) is programmed
) / V
DIODE(MAX)
IN
FB
CHG(MAX)
IN(MAX)
voltage.
) (A)
3652fb
FB
),
)
.