LTC4015_15 Datasheet, PDF (48/76 Pages) Linear Technology – Multichemistry Buck Battery Charger Controller with Digital Telemetry System

LTC4015
Applications Information
D1
V_SYS
M_N1
C_SYS
HIGH
FREQUENCY
CIRCULATING
PATH
L1
R_SNSC
M_N2
D2
C_BAT
V_BAT
BAT1
BAT2
4015 F13
Figure 13. High Speed Switching Path
R_SNSC
OR
R_SNSI
TO CSP
OR
CLP
TO CSN
OR
CLN
4015 F14
Figure 14. Kelvin Current Sensing
R_SNSC
OR
R_SNSI
TO CSP
OR
CLP
TO CSN
OR
CLN
4015 F15
Figure 15. Kelvin Current Sensing
8. The input ideal diode senses the voltage between V_IN
and V_CLP. V_IN should be connected near the source of
the input ideal diode MOSFET. V_CLP is used for Kelvin
sensing the input current. Place the input current sense
resistor, R_SNSI, near the input ideal diode MOSFET with
a short, wide trace to minimize resistance between the
drain of the ideal diode MOSFET and R_SNSI.
9. The output ideal diode senses the voltage between V_SYS
and V_CSP. V_SYS should be connected near the source of
the output ideal diode MOSFET. V_CSP is used for Kelvin
sensing the charge current. Place the output ideal diode
near the charge current sense resistor, R_SNSB, with a
short, wide trace to minimize resistance between the
drain of the ideal diode MOSFET and R_SNSB.
LTC4015 Digital System
This section provides a detailed explanation of the func-
tions of the LTC4015 digital system available via the serial
port registers.
LTC4015 Digital System Usage Examples 1, 2
The following usage examples describe applications which
demonstrate a range of functionality available with the
LTC4015 system. Note that these examples represent only
a small fraction of the LTC4015’s full digital functionality.
LTC4015 Digital System Usage Example 1: Coulomb
counter and Low Limit Alert Only
Upon initial power up with an embedded battery in a known
state of charge, the serial port master writes the LTC4015
bit en_qcount=1, enabling the Coulomb counter. Register
QCOUNT is initialized to reflect the known state of charge,
QCOUNT_PRESCALE_FACTOR is written for optimum
range and resolution, QCOUNT_LO_ALERT_LIMIT is
written to a value known to correspond to a critical low
state of charge, and en_qcount_lo_alert is written to 1.
If the state of charge falls below the level defined by
QCOUNT_LO_ALERT_LIMIT, the LTC4015 pulls down
the SMBALERT pin. The serial port master performs an
alert response algorithm (ARA) which confirms that the
LTC4015 is the source of the alert and causes the LTC4015
to release the SMBALERT pin. The master then reads the
LIMIT_ALERTS register to confirm that qcount_lo_alert is
true. The master then initiates appropriate system action
(e.g. emergency power down, user warning, etc).
See the sections Coulomb Counter, Programmable Inter-
rupt Controller, and Detailed Register Descriptions for
more details.
LTC4015 Digital System Usage Example 2: Custom Bat-
tery Charger Settings for a Lead-Acid Battery Pack with
Battery Overtemperature Alert.
4015f
48
For more information www.linear.com/LTC4015