LTC3789 LINER [Linear Technology], LTC3789 Datasheet - Page 9

• Manufacturer Part Number: LTC3789
• Description: High Voltage High Current Controller for Battery Charging and Power Management
• Manufacturer: LINER [Linear Technology]

pin FuncTions
CL (Pin 8/Pin 4): Charge Current Limit Programming. Con-
nect the charge current programming resistor (R
pin. This pin sources 50µA of current. The regulation loop
compares the voltage on this pin with the charge current
monitor voltage (V
ingly to ensure that the programmed charge current limit
is not exceeded. The charge current limit is determined
using the following formula:
Where R
and the CSN pins. Leave the pin open for the maximum
charge current limit of 50mV/R
TMR (Pin 9/Pin 5): Charge Timer. Attach 1nF of external
capacitance (C
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
I
CLIM
= 2.5µA •
CS
is the sense resistor connected to the CSP
TMR
) to GND for each 104 seconds of charge
IBMON
⎛
⎜
⎝
R
R
CL
CS
), and drives the ITH pin accord-
⎞
⎟
⎠
(QFN/SSOP)
CS
.
CL
) to this
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.
NTC (Pin 14/Pin 10): Thermistor Input. Connect a ther-
mistor from NTC to GND, and a corresponding resistor
from BIAS to NTC. The voltage level on this pin determines
if the battery temperature is safe for charging. The charge
current and charge timer are suspended if the thermistor
indicates a temperature that is unsafe for charging. Once the
temperature returns to the safe region, charging resumes.
Leave the pin open or connected to a capacitor to disable
the temperature qualified charging function.
FBG (Pin 15/Pin 11): Feedback Ground Pin. This is the
ground return pin for the resistor dividers connected to
the BFB and OFB pins. As soon as the voltage at IN is valid
(>3V typical), this pin has a 100Ω resistance to GND. When
the voltage at IN is not valid, this pin is disconnected from
GND to ensure that the resistor dividers connected to the
BFB and OFB pins do not continue to drain the battery
when the battery is the only available power source.
BFB (Pin 16/Pin 12): Battery Feedback Voltage Pin. This
pin is a high impedance input pin used to sense the battery
voltage level. In regulation, the battery float voltage loop
sets the voltage on this pin to 1.136V (typical). Connect
this pin to the center node of a resistor divider between
the BAT pin and the FBG pin to set the battery float voltage.
The battery float voltage can then be obtained as follows:
BAT (Pin 17/Pin 13): Battery Pack Connection. Connect
the battery to this pin. This pin is the anode of the battery
ideal diode driver (the cathode is the CSN pin).
V
FLOAT
=
R
BFB2
R
BFB2
+ R
BFB1
• 1.136V
LTC4000
9
4000f