LTM8061
8
8061fa
For more information www.linear.com/LTM8601
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 I
BAT
.
50μA is sourced from this pin, so the maximum charge
current can be programmed by connecting a resistor
(R
RNG/SS
) from RNG/SS to ground, and the maximum
battery charge current is:
I
BAT
= 2A • V
RNG/SS
I
BAT
= 2A • 50μA • R
RNG/SS
where R
RNG/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 (C
RNG/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 (t
SS
). With
no R
RNG/SS
resistor applied, this capacitor value follows
the relation:
C
RNG/SS
= 50μA • t
SS
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
V
RNG/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
V
IN
, 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:
t
EOC
= C
TIMER
• 4.4 • 10
6
A bad battery fault is generated if the battery does not
reach the precondition threshold voltage within one-eighth
of t
EOC
, or:
t
PRE
= C
TIMER
• 5.5 • 10
5
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 I
CHG(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
V
IN
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 V
IN
pin.
