LM3658 Operation Description

(Continued)

TABLE 3. Status Pins Summary

STAT1

STAT2

Condition

OFF

OFF

Power-Down, charging is

suspended or interrupted

ON

OFF

Pre-qualification mode, CC and CV

charging, Top-off mode

OFF

ON

Charge is completed

ON

ON

Bad battery (Safety timer expired),

or LDO mode

SAFETY TIMERS

In order to prevent endless charging of the battery, which

can cause damage to the battery, there are three safety

timers that forcefully terminate charging if the charging mode

is not completed within the time allowed.

Pre-Qualification Timer (T

The pre-qualification timer starts with the initiation of the

pre-qualification mode and allows 30 minutes to transition

from pre-qualification to full rate charging. If the battery

voltage does not reach V

stops and status pins STAT1 and STAT2 both turn on to

indicate a bad battery status.

Charger Timer (T

The charge timer starts with the initiation of full-rate charging

and has a duration of 5 hours for the LM3658. If the charge

current does not reach EOC, charging stops and STAT1 and

STAT2 both turn on to indicate a bad battery status. Once

the charge control declares a bad battery, removing the input

source is the only means to clear the bad battery status.

Top-Off Timer (T

Once the charger successfully completes constant current

constant voltage charging, it enters top-off mode and starts

T

During top-off, charging stops when T

count or when I

current. There is no time-out condition in top-off mode.

When charging is interrupted either by battery temperature

out of range or disabling the LM3658, the applicable safety

timer will store its count value for the duration of the inter-

ruption and subsequently resumes counting from its stored

count value when charging continues, only if the charger

resumes to the same operation mode it was in before the

interrupt.

BATTERY TEMPERATURE MONITORING (Suspend

Mode)

The LM3658 is equipped with a battery thermistor interface

to continuously monitor the battery temperature by measur-

ing the voltage between the T

allowed only if the battery temperature is within the accept-

able temperature range set by a pair of internal comparators

inside the LM3658. If the battery temperature is out of range,

STAT1 and STAT2 both turn off and charging is suspended.

Timer holds its count value.

The TS pin is only active during charging and draws no

current from the battery when no external power source is

present.

If the TS pin is not used in the application, it should be

connected to GND through 10k

Ω pulldown resistor.

When the TS pin is left floating (battery removal), then the

charger will be disabled as the TS voltage exceeds the upper

temperature limit.

20128210

The LM3658 battery temperature feature is tailored to use

negative temperature coefficient (NTC) 103AT thermistors

with 10k

Ω impedance. If alternative thermistors need to be

used in the system, supplemental external resistors are

needed to create a circuit with equivalent impedance.

20128211

DISABLING CHARGER (Charge Interrupt Mode)

Charging can be safely interrupted by pulling the EN_b pin

high and charging can resume upon pulling the EN_b pin

low. The enable pin can be permanently tied to GND with no

extra current consumption penalty during power down mode.

When the charger is disabled, timer holds its count value,

and STAT1 and STAT2 are both off.

INPUT/OUTPUT BYPASS CAPACITORS

Care should be taken to support the stability of the charge

system by connectinga1µF capacitor as close as possible

to the BATT pin. An input capacitor ranging from 1.0 µF–

10.0 µF must be connected to the CHG_IN and USBpwr

input pins. Low cost ceramic capacitors can be selected.

THERMAL PERFORMANCE OF THE LLP PACKAGE

The LM3658 is a monolithic device with integrated power

FETs. For that reason, it is important to pay special attention

to the thermal impedance of the LLP package and to the

PCB layout rules in order to maximize power dissipation of

the LLP package.

The LLP package is designed for enhanced thermal perfor-

mance and features an exposed die attach pad at the bottom

center of the package that creates a direct path to the PCB

for maximum power dissipation. Compared to the traditional

leaded packages where the die attach pad is embedded

inside the molding compound, the LLP reduces one layer in

the thermal path.

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