6
LTC4060
4060f
UU
U
PI FU CTIO S
DRIVE (Pin 1): Base Drive Output for the External PNP
Pass Transistor. Provides a controlled sink current that
drives the base of the PNP. This pin has current limit
protection for the LTC4060.
BAT (Pin 2): Battery Voltage Sense Input Pin. The LTC4060
uses the voltage on this pin to monitor battery voltage and
control the battery current during charging. An internal
resistor divider is connected to this pin which is discon-
nected when in shutdown or when no power is applied to
V
CC
.
SENSE (Pin 3): Charge Current Sense Node Input. Current
from V
CC
passes through the internal current sense resis-
tor and reappears at the SENSE pin to supply current to the
external PNP emitter. The PNP collector provides charge
current directly to the battery.
TIMER (Pin 4): Charge Timer Input. A capacitor connected
between TIMER and GND along with a resistor connected
from PROG to GND programs the charge cycle timing
limits.
SHDN (Pin 5): Active Low Shutdown Control Logic Input.
When pulled low, charging stops and the LTC4060 supply
current is minimized.
PAUSE (Pin 6): Pause Enable Logic Input. The charger can
be paused, turning off the charge current, disabling termi-
nation and stopping the timer when this pin is high. A low
level will resume the charging process.
PROG (Pin 7): Charge Current Programming Input. Pro-
vides a virtual reference of 1.5V for an external resistor
(R
PROG
) tied between this pin and GND that programs the
battery charge current. The fast charge current will be 930
times the current through this resistor. This voltage is also
usable as system voltage reference.
ARCT (Pin 8): Autorecharge Threshold Programming
Input. When the average cell voltage falls below this
threshold, charging is reinitiated. The voltage on this pin
is conveniently derived by using two series PROG pin
resistors and connecting to their common. Connecting
ARCT to V
CC
invokes a default threshold of 1.3V. Connect-
ing ARCT to GND inhibits autorecharge.
SEL0, SEL1 (Pins 9, 10): Number of Cells Selection Logic
Input. For single cell, connect both pins to GND. For two
cells, connect SEL1 to GND and SEL0 to V
CC.
For three
cells, SEL1 connects to V
CC
and SEL0 to GND. For four
cells, connect both pins to V
CC
.
NTC (Pin 11): Battery Temperature Input. An external NTC
thermistor network may be connected to NTC to provide
temperature-based charge qualification. Connecting NTC
to GND inhibits this function.
CHEM (Pin 12): Battery Chemistry Selection Logic Input.
When connected to a high level NiCd fast charge –∆V
termination parameters are used. A low level selects NiMH
parameters.
ACP (Pin 13): Open-Drain Power Supply Status Output.
When V
CC
is greater than the undervoltage lockout thresh-
old, the ACP pin will pull to ground. Otherwise the pin is
high impedance. This output is capable of driving an LED.
V
CC
(Pin 14): Power Input. This pin can be bypassed to
ground with a capacitance of 1µF.
CHRG (Pin 15): Open-Drain Charge Indicator Status Out-
put. The LTC4060 indicates it is providing charge to the
battery by driving this pin to GND. If charging is paused or
suspended due to abnormal battery temperature, the pin
remains pulled to GND. Otherwise the pin is high imped-
ance. This output can drive an LED.
GND (Pin 16): Ground. This pin provides a ground for the
internal voltage reference and other circuits. All voltage
thresholds are referenced to this pin.
Exposed Pad (Pin 17): Thermal Connection. Internally
connected to GND. Solder to PCB ground for optimum
thermal performance.
