LTC4015_15 Datasheet, PDF (13/76 Pages) Linear Technology – Multichemistry Buck Battery Charger Controller with Digital Telemetry System

LTC4015
Pin Functions
CELLS1 (Pin 1): Number of Cells Select Pin. Three-state
pin used in combination with CELLS0 and CELLS2 to set
the total number of battery cells.
CELLS2 (Pin 2): Number of Cells Select Pin. Three-state
pin used in combination with CELLS0 and CELLS1 to set
the total number of battery cells.
DV_CC (Pin 3): Logic Supply for the I²C Serial Port. DV_CC
sets the reference level of the SDA and SCL pins for I²C
compliance. It must be connected to the same power
supply used to power the I²C pull up resistors. If the I²C
port is unused connect this pin to INTV_CC, do not float.
SCL (Pin 4): Clock Input for the I²C Serial Port. The
I²C input levels are scaled with respect to DV_CC for I²C
compliance. If the I²C port is unused connect this pin to
INTV_CC, do not float.
SDA (Pin 5): Data Input/Output for the I²C serial port. The
I²C input levels are scaled with respect to DV_CC for I²C
compliance. If the I²C port is unused connect this pin to
INTV_CC, do not float.
SMBALERT (Pin 6): Open-Drain Interrupt Request. Pulls
low when something important needs to be reported back
to the system.
SGND (Pin 7): Signal Ground. All small signal components
and compensation should connect to this ground, which
should be connected to PGND at a single point.
UVCLFB (Pin 8): Undervoltage Current Limit Feedback
Pin. UVCLFB can be used to reduce charge current when
the V_IN pin reaches a level programmed by the user sup-
plied resistor divider. This feature can be used for power
sources with higher source impedance such as a solar
panel. Maximum charge current is tapered off when this
pin is below 1.2V, at 1.15V the charge current is zero.
UVCLFB is internally clamped to about 1.4V. Limit the
current into this pin to 200µA at maximum V_IN using
the thevenin resistance of the input divider. If the input
undervoltage current limit feature is not desired, connect
UVCLFB to 2P5V_CC through a 10k resistor.
VC (Pin 9): Current Control Threshold and Error Amplifier
Compensation Point. The current comparator threshold
increases with this control voltage. The voltage normally
ranges from 900mV to 2.4V.
RT (Pin 10): Connect a resistor from RT to GND to set
frequency of the switching power supply.
NTC (Pin 11): Thermistor Input. The NTC pin connects
to a negative temperature coefficient thermistor (Type_2)
to monitor the temperature of the battery. The voltage on
this pin is digitized by the analog to digital converter and
is available via the I²C port. The thermistor value is also
used to qualify battery charging. Connect a low drift bias
resistor is required from NTCBIAS to NTC and a thermistor
is required from NTC to ground. To disable NTC operation,
connect NTC to GND.
NTCBIAS (Pin 12): NTC Thermistor Bias Output. Connect
a bias resistor between NTCBIAS and NTC, and a thermis-
tor between NTC and GND. The bias resistor should be
equal in value to the nominal value of the thermistor. The
LTC4015 applies 1.2V to this pin during NTC measurement.
EQ (Pin 13): Equalize. Apply a logic signal between 1.5V
and INTV_CC (5V) to this pin to allow the 4015 to trigger
lead-acid equalize mode. GND this pin if unused, do not
float.
GND (Pin 14, Exposed Pad Pin 39): Ground. The exposed
pad should be connected by multiple vias directly under
the LTC4015 to a continuous ground plane on the second
layer of the printed circuit board.
CSPM5 (Pin 15): Internal Supply Pin. The V_CSPM5 pin
regulates at the higher of ground or approximately
V_CSP – 5V. A low impedance multilayer ceramic capacitor
should be connected from V_CSP to V_CSPM5.
CCREFM (Pin 16): Coulomb Counter Reference Resis-
tor Pin. Leakage on this pin will affect Coulomb counter
accuracy. Connect a 301k, 0.1%, 25ppm resistor from
CCREFM to CCREP.
CCREFP (Pin 17): Coulomb Counter Reference Resis-
tor Pin. CCREFP in conjunction with CCREFM provide a
reference for the Coulomb counter to make an accurate
measure of charge into and out of the battery. CCREFP is
connected internally to CSP with 50Ω. Connect a 301k,
0.1%, 25ppm resistor from CCREFP to CCREM.
BATSENS (Pin 18): Battery Voltage Sense Input. For proper
operation, this pin must be connected physically close to
the positive input terminal of the battery.
4015f
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