LTC4000-1 Datasheet, PDF (9/40 Pages) Linear Technology – High Voltage High Current Controller for Battery Charging with Maximum Power Point Control

LTC4000-1
Pin Functions (QFN/SSOP)
turns high impedance indicating that the CX threshold is
reached. When this occurs, the charge current is imme-
diately terminated if the TMR pin is shorted to the BIAS
pin, otherwise charging continues until the charge termi-
nation timer expires. The charge current termination value
is determined using the following formula:
( ) _{IC/X =}
0.25µA • R_CX
R_CS
− 0.5mV
Where R_CS is the sense resistor connected to the CSP
and the CSN pins. Note that if R_CX = R_CL ≤ 19.1kΩ, where
R_CL is the charge current programming resistor, then the
charge current termination value is one tenth the full charge
current, more familiarly known as C/10. Short this pin to
GND to disable CX termination.
CL (Pin 8/Pin 4): Charge Current Limit Programming. Con-
nect the charge current programming resistor (R_CL) to this
pin. This pin sources 50µA of current. The regulation loop
compares the voltage on this pin with the charge current
monitor voltage (V_IBMON), and drives the ITH pin accord-
ingly to ensure that the programmed charge current limit
is not exceeded. The charge current limit is determined
using the following formula:
I_CLIM
=
2.5µA
•



R_CL
R_CS



Where R_CS is the sense resistor connected to the CSP
and the CSN pins. Leave the pin open for the maximum
charge current limit of 50mV/R_CS.
TMR (Pin 9/Pin 5): Charge Timer. Attach 1nF of external
capacitance (C_TMR) to GND for each 104 seconds of charge
termination time and 26 seconds of bad battery indicator
time. Short to GND to prevent bad battery indicator time
and charge termination time from expiring – allowing a
continuous trickle charge and top off float voltage regula-
tion charge. Short to BIAS to disable bad battery detect
and enable C/X charging termination.
GND (Pins 10, 28, 29/Pins 6, 24): Device Ground Pins.
Connect the ground pins to a suitable PCB copper ground
plane for proper electrical operation. The QFN package
exposed pad must be soldered to PCB ground for rated
thermal performance.
FLT, CHRG (Pin 11, Pin 12/Pin 7, Pin 8): Charge Status
Indicator Pins. These pins are high voltage open drain pull
down pins. The FLT pin pulls down when there is an under
or over temperature condition during charging or when
the voltage on the BFB pin stays below the low battery
threshold during charging for a period longer than the bad
battery indicator time. The CHRG pin pulls down during
a charging cycle. Please refer to the application informa-
tion section for details on specific modes indicated by the
combination of the states of these two pins. Pull up each
of these pins with an LED in series with a resistor to a
voltage source to provide a visual status indicator. Short
these pins to GND when not used.
BIAS (Pin 13/Pin 9): 2.9V Regulator Output. Connect a
capacitor of at least 470nF to bypass this 2.9V regulated
voltage output. Use this pin to bias the resistor divider to
set up the voltage at the NTC pin.
40001f
9