LTC1729CMS8-8.2 Linear Technology, LTC1729CMS8-8.2 Datasheet - Page 7

• Manufacturer Part Number: LTC1729CMS8-8.2
• Description: IC CTRLR BATT CHRGR LI-ION 8MSOP
• Manufacturer: Linear Technology

Specifications of LTC1729CMS8-8.2

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 8-TSSOP, 8-MSOP (0.118", 3.00mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIO S I FOR ATIO
Overview
The LTC1729 is a charge termination controller for the
LT1505/LT1510/LT1511/LT1512/LT1513/LT1769 con-
stant-voltage/constant-current battery charger family.
Table 1 details these chargers. The primary function of this
IC is to stop the charger after three hours of constant-
voltage/constant-current charging. The secondary func-
tion of this controller includes an indication when the
charge current (during constant-voltage mode) drops
below a user-selected threshold. A 500kHz Li-Ion cell
phone charger is shown in Figure 1. The LTC1729 requires
only six external components when combined with the
standard LT1510 application. The LTC1729 provides a
complete and tiny solution for cellular phones and other
portable applications.
Table 1. Battery Chargers
Block Diagram
Figure 2 shows the block diagram of the LTC1729. The IC
consists of six comparators, a resistive divider, a UVLO
block and a logic and timer block.
LT1505
LT1510
LT1510-5
LT1511
LT1512
LT1513
LT1769
20mV
4A Step-Down Charger with Input Current Limit
1.5A Step-Down Charger
1.5A 500kHz Step-Down Charger
3A Step-Down Charger with Input Current Limit
2A Switch SEPIC Charger
3A Switch SEPIC Charger
2A Step-Down Charger with Input Current Limit
+
–
U
R1
0.2
CHARGING
CURRENT
U
+
200
20mV
R2
–
W
C1
1 F
SENSE
BAT
Figure 3. C/10 Detection Circuit
U
–
+
I
COMP1
BIAS
Comparator COMP1 is used to indicate C/10 charge cur-
rent threshold. (“C” is a term used to indicate the Ampere-
hour capacity of a cell.) Figure 3 details the C/10 detection
circuit. The resistor and capacitor on the SENSE pin filter
the signal from the 0.2 current sense resistor R1. The
100 A current sink on the SENSE pin develops 20mV
across the 200 resistor R2. This sets a 20mV offset on
COMP1 that sense resistor R1 must equal before C/10
current is indicated. The C/10 is not recognized by the logic
until it passes through a 3-second digital filter.
For cases where there are multiple batteries to be charged,
the LTC1729 detects when a battery is removed and resets
the timers for the next charge cycle. The battery present
detection is the primary function of comparator COMP2.
When the battery is disconnected from the LTC1729, the
voltage at the BAT pin will begin ramping upward. This is
due to a current source inside the charger or an external
pull-up resistor. Once the voltage on the BAT pin exceeds
the 4.5V/cell limit, COMP2 signals a V
logic and turns on a transistor that clamps the voltage.
There is the possibility of an overvoltage transient at the
charging terminals. This occurs if the battery protection
circuit, which is often included in the battery pack, opens
the connection to the battery during high current charging
(constant-current mode). This is a result of energy storage
in the inductor. COMP2 senses the overvoltage and clamps
the V
battery protection circuit quickly returns battery connec-
tion to the charger (in less than one second), then the
LTC1729 continues charging without resetting the timers.
100 A
FILTER
3-SEC
C
pin, reducing the duty cycle of the charger. If the
TIMERS
LOGIC
AND
50 A
LTC1729
LTC1729 Series
STATUS
1729 F03
V
CC
CHARGE
LED
MAX
= true to the
7