LTC4015_15 Datasheet, PDF (35/76 Pages) Linear Technology – Multichemistry Buck Battery Charger Controller with Digital Telemetry System

LTC4015
Operation
lead-acid programmable mode only. All voltages are per
cell at 25°C.
PROGRAMMABLE MODE
PARAMETER
RANGE
BITS RESOLUTION
ICHARGE_TARGET
VCHARGE_SETTING
1mV to 32mV/ 5
R_SNSB
2V to 2.6V/Cell 6
1mV/R_SNSB
9.523mV
VABSORB_DELTA
0V to 0.6V/Cell 6
9.523mV
VEQUALIZE_DELTA
0V to 0.6V/Cell 6
9.523mV
MAX_ABSORB_TIME
0 to 65535
16
1 Second
EQUALIZE_TIME
0 to 65535
16
1 Second
en_lead_acid_temp_comp
C_OVER_X_THRESHOLD¹
Notes
0, 1
1
0mV to 32mV/ 16
R_SNSB
1 = Enable
1.465µV/
R_SNSB
1: In lead-acid mode C_OVER_XTHRESHOLD is used only to terminate
the absorb charge phase.
Lead-Acid Battery Charger Operation
The LTC4015 provides full featured, inherently safe,
constant-current/constant-voltage lead-acid battery
charging with battery presence detection, equalization,
absorb, bad battery detection, thermistor based charge
voltage temperature compensation, programmable charge
voltage, programmable charge current, battery series
resistance measurement, detailed status reporting, and
programmable interrupt generation.
LTC4015 Charge Algorithm Overview
The LTC4015 charge algorithms are based on a constant-
current constant-voltage charging (CC-CV) technique. The
battery is charged at a constant-current (CC) until the
battery reaches its charge voltage (V_CHARGE) whereupon
the delivered charge current is automatically reduced to
maintain the battery at a constant V_CHARGE (CV).
Under voltage current limiting (UVCL) is used to automati-
cally reduce charge current to help keep V_IN from falling
below a minimum voltage. Input current limiting (ICL) is
used to automatically limit charge current to help keep
input current below a maximum level. However, UVCL
and ICL can only reduce charge current. The total load
current from V_IN cannot be limited by the LTC4015 if the
load on SYS exceeds the ICL setpoint.
CHARGER_
SUSPENDED*
BATTERY
DETECTION
NO BATTERY
BATTERY
VOLTAGE
STABLE
SHORTED
BATTERY
BAT_MISSING_
FAULT
BAT_SHORT_
FAULT
30 SECOND
TIMEOUT
ABSORB_CHARGE
ABSORB_TIME PASSED
WITH BATTERY AT
ABSORB VOLTAGE
—OR—
(BATTERY AT ABSORB VOLTAGE
AND I_CHG <
C_OVER_X_THRESHOLD)
CC_CV_CHARGE
BATTERY AT CHARGE
VOLTAGE
—AND—
EQ PIN RISING
EDGE DETECTED
EQUALIZE_TIME
PASSED
—OR—
EQ PIN FALLING
EDGE DETECTED
EQUALIZE_
CHARGE
4015 F08
* NOTE: ALL STATES RETURN TO CHARGER SUSPENDED IF ANY OF THE FOLLOWING OCCUR:
A. THE INPUT VOLTAGE V_IN FALLS TO WITHIN 100mV OF THE BATSENS PIN VOLTAGE.
B. SUSPEND_CHARGER IS WRITTEN TO 1 VIA THE SERIAL PORT.
C. A SYSTEM FAULT OCCURS (V_IN OVERVOLTAGE LOCKOUT, 2P5V_CC UNDERVOLTAGE LOCKOUT, INTV_CC
UNDERVOLTAGE LOCKOUT, DRV_CC UNDERVOLTAGE LOCKOUT. THERMAL SHUTDOWN, MISSING R_T
RESISTOR, OR INVALID COMBINATION OF CELLS PINS).
Figure 8. Lead-Acid Battery Charging State Diagram
Lead Acid Charge Algorithm Overview
(See Figure 8 for lead-acid battery charging state diagram)
The charge algorithm begins with a battery detection test,
then proceeds to CC-CV charging with a charge voltage
of V_ABSORB, which is an absorb delta added to V_CHARGE.
Following constant-current bulk charging, constant-voltage
absorption charging continues until V_ABSORB is reached
CHARGING
ALGORITHM
ICHARGE_
TARGET
Lead-Acid Standard
Lead-Acid
Programmable
32mV/R_SNSB
32mV/R_SNSB
ABSORB
C_OVER_X_
THRESHOLD
3.2mV/R_SNSB
3.2mV/R_SNSB
V_EQUALIZE,
EQUALIZE TIME
(MINUTES)
2.60, 60
2.60,60
V_ABSORB, MAX
ABSORB TIME
(MINUTES)
2.40, 90
2.40, 90
END
ABSORB
ON C/x
Yes
Yes
V_CHARGE
2.20
2.20
For more information www.linear.com/LTC4015
mV/C
TEMPCO
–3.65
–3.65
TEMPCO
ENABLED
Yes
Yes
4015f
35