Rainbow-electronics MAX1508 Bedienungsanleitung PDF herunterladen (Seite 7)

MAX1508

Li+ Linear Battery Charger with Integrated Pass FET,

Thermal Regulation, and

ACOK

in 3mm x 3mm TDFN

_______________________________________________________________________________________ 7

Applications Information

Charge-Current Selection

The maximum charging current is programmed by an

external R

ISET

resistor connected from ISET to GND.

Select the R

ISET

value based on the following formula:

FAST

= 1461V / R

ISET

Ω

where I

FAST

is in amps and R

ISET

is in ohms. ISET can

also be used to monitor the fast-charge current level.

The output current from the ISET pin is 0.958mA per

amp of charging current. The output voltage at ISET is

proportional to the charging current as follows:

ISET

= (I

CHG

x R

ISET

) / 1044

The voltage at ISET is nominally 1.4V at the selected

fast-charge current, and falls with charging current as

the cell becomes fully charged.

Thermal Regulation

The MAX1508 features a proprietary thermal-regulation

circuit to protect both the IC and the system from

excessive heat. When the MAX1508’s die temperature

reaches +100°C, the charge current is reduced to pre-

vent any additional increase in the die temperature. An

active thermal loop does not indicate a fault condition.

Thermal regulation allows the MAX1508 to provide con-

tinuous charge to the battery under adverse conditions

without causing excessive power dissipation.

SHUTDOWN

CHARGER = OFF

LED = OFF

PRECHARGE

100% CHARGE CURRENT

LED = ON

FAST CHARGE

100% CHARGER CURRENT

LED = ON

FULL BATT CONTINUES

TO REGULATE BATT

UP TO 4.2V

CHARGE

< 10%

OF ISET

BATT

> 2.5V

BATT

< 2.4V

BATT

< 2.5V

< 7V AND

> V

BATT

AND

EN = LOW

> 7V +

BATT

> V

EN = HIGH

ASYNCHRONOUS FROM

ANYWHERE

> 7V +

BATT

> VIN +

EN = HIGH

CHARGE

> 20%

OF ISET

FULL BATT

LED = OFF

Figure 2. Charge State Diagram

1 2 3 4 5 6 7 8 9 10 11

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