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LTM8062

8062f

PIN FUNCTIONS

the CHRG pin becomes high impedance. If the internal timer

is used for termination, the pin stays low during the charg-

ing cycle until the charge current drops below a C/10 rate,

approximately 200mA, even though the charger will continue

to top off the battery until the end-of-charge timer terminates

the charge cycle. A temperature fault also causes this pin to

be pulled low (see the Applications Information section).

NTC (Pin H6): Battery Temperature Monitor Pin. This pin

is the input to the NTC (negative temperature coefficient)

thermistor temperature monitoring circuit. This function is

enabled by connecting a 10kΩ, B = 3380 NTC thermistor

from the NTC pin to ground. The pin sources 50μA, and

monitors the voltage across the 10kΩ thermistor. When the

voltage on this pin is above 1.36V (T < 0°C) or below 0.29V

(T > 40°C), charging is disabled and the CHRG and FAULT

pins are both pulled low. If the internal timer termination is

being used, the timer is paused, suspending the charging

cycle. Charging resumes when the voltage on NTC returns to

within the 0.29V to 1.36V active region. There is approximately

5°C of temperature hysteresis associated with each of the

temperature thresholds. The temperature monitoring func-

tion remains enabled while thermistor resistance to ground

is less than 250kΩ. If this function is not desired, leave the

NTC pin unconnected.

ADJ (Pin H7): Battery Float Voltage Feedback Input. The charge

function operates to achieve a final float voltage of 3.3V on this

pin. The output battery float voltage (VBAT(FLT))isprogrammed

using a resistor divider. VBAT(FLT) can be programmed up to

14.4V. The auto-restart feature initiates a new charging cycle

when the voltage at the ADJ pin falls 2.5% below the float

voltage reference. The ADJ pin input bias current is 110nA.

Using a resistor divider with an equivalent input resistance

at the ADJ pin of 250k compensates for input bias current

error. Required resistor values to program desired VBAT(FLT)

follow the equations:

R1=

VBAT(FLT) • 2.5 •10

3.3

(Ω)

R2 =

R1• 2.5 • 105

R1− (2.5 • 105)

(Ω)

R1 is connected from BAT to ADJ, and R2 is connected from

ADJ to ground.

FAULT (Pin J7): Open-Collector Fault Status Output; typically

pulled up through a resistor to a reference voltage. This status

pin can be pulled up to voltages as high as VIN and can sink

currents up to 10mA. This pin indicates charge cycle fault

conditions during a battery charging cycle. 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 (see the Applications Information

section).

TMR(PinJ6):End-Of-CycleTimerProgrammingPin.Ifatimer-

based charge termination is desired, connect a capacitor from

this pin to ground. Full charge end-of cycle time (in hours) is

programmed with this capacitor following the equation:

tEOC = CTIMER • 4.4 • 106

A bad battery fault is generated if the battery does not reach

the precondition threshold voltage within one-eighth of tEOC,

or:

tPRE = CTIMER • 5.5 • 105

A 0.68μF capacitor is often used, which generates a timer EOC

at three hours, and a precondition limit time of 22.5 minutes.

If a timer-based termination is not desired, the timer function

can be disabled by connecting the TMR pin to ground. With the

timer function disabled, charging terminates when the charge

current drops below a C/10 rate, approximately 200mA.

VINREG (Pin L6): Input Voltage Regulation Reference. The

maximum charge current is reduced when this pin is below

2.7V. Connecting a resistor divider from VIN to this sets the

minimum operational VIN voltage. This is typically used to

programthepeakpowervoltageforasolarpanel.TheLTM8062

servos the maximum charge current required to maintain the

programmed operational VINvoltage,throughmaintainingthe

voltage on VINREG at or above 2.7V. If the voltage regulation

feature is not used, connect the pin to VIN.

RUN (Pin K6): Precision Threshold Enable Input Pin. The

RUN threshold is 1.25V (rising), with 120mV of input hys-

teresis. When in shutdown mode, all charging functions are

disabled. The precision threshold allows use of the RUN pin

to incorporate UVLO functions. If the RUN pin is pulled below

0.4V, the IC enters a low current shutdown mode where the

VIN pin current is reduced to 15μA. Typical RUN pin input

bias current is 10nA. If the shutdown function is not desired,

connect the pin to the VIN pin.

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