LT3652IDD-PBF Ver la hoja de datos (PDF) - Linear Technology

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LT3652IDD-PBF

Power Tracking 2A Battery Charger for Solar Power

Linear Technology 

LT3652

APPLICATIONS INFORMATION

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MAXIMUM OPERATIONAL VIN VOLTAGE (V)

3652 F03

Figure 3. 7.2V at 1.5A Switched Inductor Values

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+

ΔIMAX/2) • ICHG(MAX), and an RMS rating above ICHG(MAX).

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:

VBAT(FLT) • (1 – VBAT(FLT)/VIN(MAX)) (V • μS)

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

forward voltage yields the lowest power loss and highest

efficiency. The rectifier diode must be rated to withstand

reverse voltages greater than the maximum VIN voltage.

The minimum average diode current rating (IDIODE(MAX))

is calculated with maximum output current (ICHG(MAX)),

maximum operational VIN, and output at the precondition

threshold (VBAT(PRE), or 0.7 • VBAT(FLT)):

IDIODE(MAX) > ICHG(MAX) • (VIN(MAX) – VBAT(PRE)) / VIN(MAX)) (A)

For example, a rectifier diode for a 7.2V, 2A charger with

a 25V maximum input voltage would require:

IDIODE(MAX) > 2 • (25 – 0.7[7.2]) / 25), or

IDIODE(MAX) > 1.6A

Battery Float Voltage Programming

The output battery float voltage (VBAT(FLT)) is programmed

by connecting a resistor divider from the BAT pin to VFB.

VBAT(FLT) can be programmed up to 14.4V.

BAT

LT3652

VFB

3652 F04

+

RFB1

RFB2

Figure 4. Feedback Resistors from BAT to VFB

Program Float Voltage

3652fb

14

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