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LTM8061

8061f

PIN FUNCTIONS

RNG/SS (Pin H7): Charge Current Programming/Soft-

Start Pin. This pin allows the maximum charge current

to be reduced from the default 2A level, and can be used

to employ a soft-start function. This pin has an effective

range from 0V to 1V, with the maximum BAT charge cur-

rent determined by IBAT.

50μA is sourced from this pin, so the maximum charge

current can be programmed by connecting a resistor

(RRNG/SS) from RNG/SS to ground, and the maximum

battery charge current is:

IBAT = 2A • VRNG/SS

IBAT = 2A • 50μA • RRNG/SS

where RRNG/SS is less than or equal to 20kΩ. With the

RNG/SS pin left open, the charge current is 2A.

Soft-start functionality can be implemented by connect-

ing a capacitor (CRNG/SS) from RNG/SS to ground, such

that the time required to charge the capacitor to 1V (full

charge current) is the desired soft-start interval (tSS). With

no RRNG/SS resistor applied, this capacitor value follows

the relation:

CRNG/SS = 50μA • tSS

The RNG/SS pin is pulled low during fault conditions,

allowing graceful recovery from faults should soft-start

functionality be implemented. Both the soft-start capaci-

tor and the programming resistor can be implemented in

parallel. All C/10 monitoring functions are disabled while

VRNG/SS is below 0.1V to accommodate long soft-start

intervals.

RNG/SS voltage can also be manipulated using an active

device, employing a pull-down transistor to disable charge

current or to dynamically servo maximum charge current.

Manipulation of the RNG/SS pin with active devices that

have low impedance pull-up capability is not allowed (see

the Applications Information section).

FAULT (Pin J7): Open-Collector Fault Status Output. Typi-

cally 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 charge 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 condi-

tions exist, the FAULT pin remains high impedance (see

the Applications Information section). If RUN is low, or

the LTM8061 is otherwise powered down, the state of the

FAULT pin is invalid.

TMR (Pin J6): End-Of-Cycle Timer Programming Pin.

If a timer-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 typically used, which generates a

timer EOC of three hours, and a precondition limit time of

22.5 minutes. If a timer-based termination is not desired,

the timer function is 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, or ICHG(MAX)/10.

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

threshold is 1.20V (rising), with 120mV of input hystere-

sis. 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 μModule enters a low current shutdown

mode where the VIN pin current is reduced to 15μA. Typical

RUN pin input bias current is 1μA. If the shutdown function

is not desired, connect the pin to the VIN pin.

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