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| LTC4001-1_15 Datasheet, PDF (6/20 Pages) Linear Technology – 2A Synchronous Buck Li-Ion Charger | |||
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LTC4001-1
PIN FUNCTIONS
NTC (Pin 11): Input to the NTC (Negative Temperature
Coefï¬cient) Thermistor Temperature Monitoring Circuit.
Under normal operation, tie a thermistor from the NTC pin
to the GNDSENS pin and a resistor of equal value from
NTC to VIN. When the voltage on this pin is above 0.74VIN
(Cold, 0°C) or below 0.29VIN (Hot, 50°C), charging is
disabled and the CHRG pin blinks. When the voltage on
NTC comes back between 0.74VIN and 0.29VIN, the timer
continues where it left off and charging resumes. There is
approximately 3°C of temperature hysteresis associated
with each of the input comparators. If the NTC function
is not used connect the NTC pin to GNDSENS. This will
disable all of the NTC functions. NTC should never be
pulled above VIN.
PROG (Pin 12): Charge Current Program. The RPROG
resistor connects from this pin to GNDSENS, setting the
current:
RPROG
=
1.110k
IBAT(AMPS)
where IBAT is the high rate battery charging current.
IDET (Pin 13): Charge Rate Detection Threshold. Connect-
ing a resistor, RIDET to GNDSENS programs the charge rate
detection threshold. If RIDET = RPROG, CHRG provides an
IBAT/10 indication. For other thresholds see the Applica-
tions Information section.
SS (Pin 14): Soft-Start/Compensation. Provides soft-start
function and compensation for the ï¬oat voltage control
loop and compensation for the charge current control
loop. Tie a soft-start/compensation capacitor between
this pin and GNDSENS.
TIMER (Pin 15): Timer Capacitor. The timer period is set
by placing a capacitor, CTIMER, to GNDSENS. Set CTIMER
to:
CTIMER = Time (Hrs) ⢠0.0733 (μF)
where time is the desired charging time.
Connect this pin to IDET to disable the timer. Connect this
pin to GNDSENS to end battery charging when IBAT drops
below the IDET charge rate threshold.
BATSENS (Pin 16): Battery Sense Input. An internal resistor
divider sets the ï¬nal ï¬oat voltage at this pin. The resistor
divider is disconnected in sleep mode or when
EN = H to reduce the battery drain current. Connect this
pin to the positive battery terminal.
Exposed Pad (Pin 17): Ground. This pin must be soldered
to the PCB ground (PGND) for electrical contact and rated
thermal performance.
40011fa
6
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