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

Número de pieza

componentes Descripción

Fabricante

LT3652IDD-PBF

Power Tracking 2A Battery Charger for Solar Power

Linear Technology 

LT3652

APPLICATIONS INFORMATION

cleaning measures should be implemented to prevent

board contamination, and low-leakage solder flux is

recommended.

Input Supply Voltage Regulation

The LT3652 contains a voltage monitor pin that enables

programming a minimum operational voltage. Connect-

ing a resistor divider from VIN to the VIN_REG pin enables

programming of minimum input supply voltage, typically

used to program the peak power voltage for a solar panel.

Maximum charge current is reduced when the VIN_REG pin

is below the regulation threshold of 2.7V.

If an input supply cannot provide enough power to satisfy

the requirements of an LT3652 charger, the supply voltage

will collapse. A minimum operating supply voltage can

thus be programmed by monitoring the supply through

a resistor divider, such that the desired minimum volt-

age corresponds to 2.7V at the VIN_REG pin. The LT3652

servos the maximum output charge current to maintain

the voltage on VIN_REG at or above 2.7V.

Programming of the desired minimum voltage is ac-

complished by connecting a resistor divider as shown in

Figure 6. The ratio of RIN1/RIN2 for a desired minimum

voltage (VIN(MIN)) is:

RIN1/RIN2 = (VIN(MIN)/2.7) – 1

If the voltage regulation feature is not used, connect the

VIN_REG pin to VIN.

INPUT

SUPPLY

RIN1

RIN2

VIN

LT3652

VIN_REG

3652 F06

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 (VOC) of a solar cell has

a temperature coefficient that is similar to a common p-n

diode, or about –2mV/°C. The peak power point voltage

(VMP) for a crystalline solar panel can be approximated as

a fixed voltage below VOC, so the temperature coefficient

for the peak power point is similar to that of VOC.

Panel manufacturers typically specify the 25°C values for

VOC, VMP, and the temperature coefficient for VOC, making

determination of the temperature coefficient for VMP of a

typical panel straight forward.

The LT3652 employs a feedback network to program the

VIN input regulation voltage. Manipulation of the network

makes for efficient implementation of various temperature

compensation schemes for a maximum peak power track-

ing (MPPT) application. As the temperature characteristic

for a typical solar panel VMP voltage is highly linear, a

VOC(25°C)

VMP(25°C)

VOC TEMP CO.

VOC

VMP

VOC – VMP

5

15

25

35

45

55

TEMPERATURE (°C)

3652 F07

Figure 7. Temperature Characteristics for Solar Panel

Output Voltage

Figure 6. Resistor Divider Sets Minimum VIN

3652fb

16

Share Link: