LTC4015 datasheet(13/76 Pages) LINER

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LTC4015

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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.

DVCC (Pin 3): Logic Supply for the I2C Serial Port. DVCC

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 INTVCC, do not float.

SCL (Pin 4): Clock Input for the I2C Serial Port. The

I2C input levels are scaled with respect to DVCC for I2C

compliance. If the I2C port is unused connect this pin to

INTVCC, do not float.

SDA (Pin 5): Data Input/Output for the I2C serial port. The

I2C input levels are scaled with respect to DVCC for I2C

compliance. If the I2C port is unused connect this pin to

INTVCC, do not float.

SMBALERT (Pin 6): Open-Drain Interrupt Request. Pulls

low when something important needs to be reported back

to the system.

SGND(Pin7):SignalGround.Allsmallsignalcomponents

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 VIN 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 2.5V with 200µA

in this pin. Limit the current into this pin to 200µA at

maximum VIN using the thevenin resistance of the input

divider. If the input undervoltage current limit feature is

not desired, connect UVCLFB to 2P5VCC through a 10k

resistor or to VIN through an appropriately sized 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 from NTCBIAS to NTC and a thermistor from NTC

to ground. If NTC functions are unwanted, use a resistor

equal in value to RNTCBIAS instead of a thermistor.

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

LTC4015applies1.2VtothispinduringNTCmeasurement.

EQ (Pin 13): Equalize. Apply a logic signal between 1.5V

and INTVCC (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 VCSPM5 pin

regulates at the higher of ground or approximately

VCSP – 5V. A low impedance multilayer ceramic capacitor

should be connected from VCSP to VCSPM5.

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.

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