LTC4061 Datasheet, PDF (7/20 Pages) Linear Technology – Standalone Linear Li-lon Battery Charger with Thermistor Input

LTC4061
PI FU CTIO S
BAT (Pin 1): Charge Current Output. This pin provides
charge current to the battery and regulates the final float
voltage to 4.2V.
NTC (Pin 2): Input to the NTC (Negative Temperature Coef-
ficient) Thermistor Temperature Monitoring Circuit. Under
normal operation, connect a thermistor from the NTC pin
to ground and a resistor of equal value from the NTC pin
to V_CC. When the voltage at this pin drops below 0.35 •
V_CC at hot temperatures or rises above 0.76 • V_CC at cold,
charging is suspended, the internal timer is frozen and the
⎯C⎯H⎯R⎯G pin output will start to pulse at 1.5Hz. Pulling this
pin below 0.016 • V_CC disables the NTC feature. There is
approximately 2°C of temperature hysteresis associated
with each of the input comparators thresholds.
TIMER (Pin 3): Timer Program and Termination Select Pin.
This pin selects which method is used to terminate the
charge cycle. Connecting a capacitor, C_TIMER, to ground
selects charge time termination. The charge time is set
by the following formula:
TIME (HOURS) = 3 HOURS • ^{C TIMER} or
0.1µF
C
TIMER
=
0.1µF
•
TIME (HOURS)
3 (HOURS)
Connecting the TIMER pin to ground selects charge cur-
rent termination, while connecting the pin to V_CC selects
user termination. See Applications Information for more
information on current and user termination.
ACPR (Pin 4): Open-Drain Power Supply Present Status
Output. The power supply status indicator pin has two
states: pull-down and high impedance. This output can
be used as a logic interface or as a LED driver. In the
pull-down state, an NMOS transistor capable of sinking
10mA pulls down on the ^⎯A^⎯C^⎯P^⎯R pin. The state of this pin
is dependent on the value of V_CC and BAT: it requires that
V_CC is 190mV greater than V_BAT and greater than V_UVLO.
See Applications Information.
⎯C⎯H⎯R⎯G (Pin 5): Open-Drain Charge Status Output. The
charge status indicator pin has three states: pull-down,
pulse at 1.5Hz or 6Hz and high impedance. This output
can be used as a logic interface or as a LED driver. In the
pull-down state, an NMOS transistor capable of sinking
10mA pulls down on the ^⎯C^⎯H^⎯R^⎯G pin. The state of this pin
depends on the value of I_DETECT as well as the termina-
tion method being used and the state of the NTC pin. See
Applications Information.
⎯C⎯/⎯5 (Pin 6): ⎯C⎯/⎯5 Enable Input. Used to control the amount
of current drawn from the USB port. A logic high on the
⎯C⎯/⎯5 pin sets the current limit to 100% of the current
programmed by the PROG pin. A logic low on the ^⎯C^⎯/^⎯5 pin
sets the current limit to 20% of the current programmed
by the PROG pin. An internal 3MΩ pull-down resistor
defaults the ^⎯C^⎯/^⎯5 pin to its low current state.
E⎯ N⎯ (Pin 7): Charger Enable Input. A logic high on the E⎯ N⎯ pin
places the charger into shutdown mode, where the input
quiescent current is less than 50µA. A logic low on this
pin enables charging. An internal 3MΩ pull-down resistor
to ground defaults the charger to its enabled state.
I_DET (Pin 8): Current Detection Threshold Program Pin.
The current detection threshold, I_DETECT, is set by con-
necting a resistor, R_DETECT, to ground. I_DETECT is set by
the following formula:
I_DETECT
=
R_PROG
10R_DET
• I_CHG
=
100V
R_DET
or
R_DET
=
100V
I_DETECT
The ⎯C⎯H⎯R⎯G pin becomes high impedance when the charge
current drops below I_DETECT. I_DETECT can be set to 1/10th
the programmed charge current by connecting I_DET di-
rectly to PROG. If the I_DET pin is not connected, the ^⎯C^⎯H^⎯R^⎯G
output remains in its pull-down state until the charge time
elapses and terminates the charge cycle. See Applications
Information.
This pin is clamped to approximately 2.4V. Driving this pin to
voltages beyond the clamp voltage should be avoided.
PROG (Pin 9): Charge Current Program and Charge Cur-
rent Monitor. The charge current is set by connecting a
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