LX2207ILD データシートの表示（PDF） - Microsemi Corporation

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LX2207ILD

Three Level Lithium Ion Battery Charger

Microsemi Corporation 

LX2207

Three Level Lithium Ion Battery Charger

®

TM

PRODUCTION DATA SHEET

THEORY OF OPERATION

GENERAL DESCRIPTION

The LX2207 charges a single cell Lithium Ion battery

using two steps: a constant current mode followed by a

constant voltage mode. The maximum charging current

during the Constant Current Mode of the charging profile

can be logically set (using H/L) to two preprogrammed

levels set by resistors connected to HCP and LCP (High

and Low current). A 20% logic input selects either the full

current set by the LCP resistor or 20% of that value. The

charger will terminate constant voltage charging once the

current drops below the taper current setting, which is 10%

of the high charge current setting (determined by HCP

resistor value).

CONDITIONING CURRENT CHARGE MODE

A conditioning current is applied to batteries that are

deeply discharged and have a terminal voltage less than

60% of the constant voltage level. The conditioning current

is 5% of the HCP programmable constant current level.

Once the battery terminal voltage exceeds the conditioning

current threshold, the full constant current level is applied

(unless one of the other charger control loops limits

charging current).

CHARGE TERMINATION MODE

To increase system battery life and avoid float charging,

the LX2207 turns off the pass element once the battery is

fully charged. The charge termination state occurs at the

end of constant voltage mode. The value of the resistor

connected to the HCP programming pin sets the

termination current. The STAT pin changes state when

charge cycle has completed.

TOP OFF CHARGE MODE

Once the charger has completed a charge cycle, if power

remains applied, the LX2207 enters a Voltage Monitoring

mode. In this mode the LX2207 monitors the battery

terminal voltage and applies a top off charge if the battery

voltage drops below the top of threshold.

USB CHARGE MODE AND CURRENT LIMIT

The LX2207 is fully compliant with, and supports, the

USB specifications – the Low Power Peripheral (100mA)

and High Power Peripherals (500mA). USB current levels

can be set using the appropriate values for the LCP

programming resistor. 20% logic input selects USB

high/low charge currents. When the SD pin is pulled high,

the USB input enters Suspend mode and will not present a

load to the IN pin.

DCOK

The IN input is monitored and DCOK is set to a logic

low to report the presence of the power source with

sufficient voltage to charge the battery. The DCOK

threshold is the larger of the UVLO threshold or the battery

voltage.

PROTECTION FEATURES

Conditioning Current Mode – If the battery terminal

voltage is less than 2.7V, the battery charger will reduce the

charge current to 5%. This also protects the appliance from

overheating by trying to drive the full charging current into a

short circuited battery.

Under Voltage Lockout – The charge cycle will not start

until the IN voltage rises above 3.8V. Hysteresis helps

alleviate chattering on and off.

Thermal Control loop – If the power dissipation of the

charger becomes excessive, the charge current will be

reduced to prevent the die temperature from getting above

140°C. This does not cause the charge cycle to stop.

Reverse current blocking – If IN input is grounded,

current will not flow from the BAT pin through the charger.

No external blocking diode is required on the input.

Sleep Mode – If the SD pin is a logic high, the charger

enters a sleep mode where a very low quiescent current

prevents drain from the battery.

ADAPTER OR USB SELECTION

The LX2207 supports battery charging from a system that

provides adapter power or USB power using the same

external connector. Figure 1 shows one example of a

system using a special USB adapter cable to determine

whether the power source is USB or Wall Adapter.

Similarly, if the system processor senses the absence of

USB data, it can logically set the H/L logic level high for

the wall adapter.

Copyright © 2007

Rev. 1.0a, 2007-10-08

Microsemi

Analog Mixed Signal Group

11861 Western Avenue, Garden Grove, CA. 92841, 714-898-8121, Fax: 714-893-2570

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