LT3651EUHE-4.2-TRPBF データシートの表示（PDF） - Linear Technology

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LT3651EUHE-4.2-TRPBF

Monolithic 4A Wide Input 1 Cell Li-Ion Battery Charger

Linear Technology 

LT3651-4.1/LT3651-4.2

PIN FUNCTIONS

NTC (Pin 1): Battery Temperature Monitor Pin. This

pin is used to monitor battery temperature. Typically a

10kΩ NTC (negative temperature coefficient) thermistor

(B = 3380) is embedded with the battery and connected

from the NTC pin to ground. The pin sources 50µA into

the resistor and monitors the voltage across the therm-

istor, regulating charging based on the voltage. If this

function is not desired, leave the NTC pin unconnected.

ACPR (Pin 2): Open-Collector AC Present Status Pin.

This pin sinks current to indicate that VIN is valid and the

charger is on. Typically a resistor pull-up is used on this

pin. This pin can be pulled up to voltages as high as VIN

when disabled, and can sink currents up to 10mA when

enabled.

BAT (Pin 3): Battery Voltage Monitor Pin. This pin moni-

tors battery voltage. A Kelvin connection is made to the

battery from this pin and a decoupling capacitor (CBAT)

is placed from this pin to ground.

The charge function operates to achieve the final float

voltage at this pin. The auto-restart feature initiates a new

charging cycle when the voltage at the BAT pin falls 2.5%

below this float voltage. Once the charge cycle is termi-

nated, the input bias current of the BAT pin is reduced to

<0.1µA to minimize battery discharge while the charger

remains connected.

SENSE (Pin 4): Charge Current Sense Pin. The charge

current is monitored with a sense resistor (RSENSE) con-

nected between this pin and the BAT pin. The inductor

current flows through RSENSE to the battery. The voltage

across this resistor sets the average charge current. The

maximum average charge current (IMAX) corresponds to

95mV across the sense resistor.

BOOST (Pin 5): Bootstrapped Supply Rail for Switch

Drive. This pin facilitates saturation of the high side switch

transistor. Connect a 1µF or greater capacitor from the

BOOST pin to the SW pin. The operating range of this pin

is 2V to 4.5V, referenced to the SW pin when the switch is

high. The voltage on the decoupling capacitor is refreshed

through a rectifying diode, with the anode connected to

either the battery output voltage or an external source,

and the cathode connected to the BOOST pin.

GND (Pins 6, 23, 31, 37): Ground. These pins are the

ground pins for the part. Pins 31 and 37 must be connected

together. Pins 6 and 23 are connected via the leadframe to

the exposed backside Pin 37. Solder the exposed backside

to the PCB for good thermal and electrical connection.

SW (Pins 7, 11-18, 22, 38): Switch Output Pin. These

pins are the output of the charger switches. An inductor

is connected between this pin and the SENSE pin. When

the switcher is active, the inductor is charged by the high

side switch from VIN and discharged by the bottom side

switch to GND. Solder the exposed backside, Pin 38, to

the PCB for good thermal connection.

TIMER (Pin 24): End-Of-Cycle Timer Programming Pin.

A capacitor on this pin to ground determines the full

charge end-of-cycle time. Full charge end-of-cycle time is

programmed with this capacitor. A 3 hour charge cycle is

obtained with a 0.68µF capacitor. This timer also controls

the bad battery fault that is generated if the battery does not

reach the precondition threshold voltage within one-eighth

of a full cycle (22.5 minutes for a 3 hour charge cycle).

The timer based termination is disabled by connecting the

TIMER pin to ground. With the timer function disabled,

charging terminates when the charge current drops below a

C/10 rate, or approximately 10% of maximum charge rate.

FAULT (Pin 25): Open-Collector Fault Status Output. This

pin indicates charge cycle fault conditions during a battery

charging cycle. Typically a resistor pull-up is used on this

pin. This status pin can be pulled up to voltages as high

as VIN when disabled, and can sink currents up to 10mA

when enabled. A temperature fault causes this pin to be

pulled low. If the internal timer is used for termination,

a bad battery fault also causes this pin to be pulled low.

If no fault conditions exist, the FAULT pin remains high

impedance.

For more information www.linear.com/LT3651-4.1

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