LTC4001 Datasheet, PDF (6/20 Pages) Linear Technology – 2A Synchronous Buck Li-Ion Charger

LTC4001
PI FU CTIO S
FAULT (Pin 10): Battery Fault. This pin is a logic high if a
shorted battery is detected or if a temperature fault is
detected. A temperature fault occurs with the temperature
monitor circuit enabled and the thermistor temperature is
either below 0°C or above 50°C (typical).
NTC (Pin 11): Input to the NTC (Negative Temperature
Coefficient) 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 V_IN. When the voltage on this pin is above 0.74V_IN (Cold,
0°C) or below 0.29V_IN (Hot, 50°C), charging is disabled
and the CHRG pin blinks. When the voltage on NTC comes
back between 0.74V_IN and 0.29V_IN, the timer continues
where it left off and charging resumes. There is approxi-
mately 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
V_IN.
PROG (Pin 12): Charge Current Program. The R_PROG
resistor connects from this pin to GNDSENS, setting the
current:
R_PROG
=
1.110k
I_BAT(AMPS)
where I_BAT is the high rate battery charging current.
IDET (Pin 13): Charge Rate Detection Threshold. Connect-
ing a resistor, R_IDET to GNDSENS programs the charge
rate detection threshold. If R_IDET = R_PROG, CHRG provides
an I_BAT/10 indication. For other thresholds see the Appli-
cations Information section.
SS (Pin 14): Soft-Start/Compensation. Provides soft-start
function and compensation for the float 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, C_TIMER, to GNDSENS. Set C_TIMER
to:
C_TIMER = 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 I_BAT drops
below the IDET charge rate threshold.
BATSENS (Pin 16): Battery Sense Input. An internal resis-
tor divider sets the final float 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.
4001f
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