LTC1733EMSE#TR Linear Technology, LTC1733EMSE#TR Datasheet - Page 10

• Manufacturer Part Number: LTC1733EMSE#TR
• Description: IC CTRLR BATT CHRG LI-ION 10MSOP
• Manufacturer: Linear Technology

Specifications of LTC1733EMSE#TR

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 4.5 V ~ 6.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 10-TFSOP, 10-MSOP (0.118", 3.00mm Width) Exposed Pad
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

APPLICATIO S I FOR ATIO
LTC1733
Open-Drain Status Outputs
The LTC1733 has three open-drain status outputs: ACPR,
CHRG and FAULT. The ACPR pin pulls low when an input
voltage greater than the undervoltage lockout threshold is
applied and goes high impedance when power (V
is removed. CHRG and FAULT work together to indicate
the status of the charge cycle. Table 1 describes the status
of the charge cycle based on the CHRG and FAULT
outputs.
Table 1.
CHRG Status Output Pin
When the charge cycle starts, the CHRG pin is pulled to
ground by an internal N-channel MOSFET capable of
driving an LED. When the charge current drops to 10% of
the full-scale current (C/10), the N-channel MOSFET is
latched off and a weak 25 A current source to ground is
connected to the CHRG pin. After a time-out occurs, the
pin assumes a high impedance state. By using two differ-
ent value pull-up resistors a microprocessor can detect
three states from this pin (charging, C/10, and time-out).
See Figure 2.
10
FAULT
High
High
High
Low
Low
Low
pulldown
pulldown
CHRG
25 A
25 A
Low
High
High
Low
U
Description
Charge cycle has started, C/10 has not been
reached and charging is proceeding normally.
Charge cycle has started, C/10 has not been
reached, but the charge current and timer
have been paused due to an NTC out-of-
temperature condition.
C/10 has been reached and charging is
proceeding normally.
C/10 has been reached but the charge current
and timer have paused due to an
NTC out-of-temperature condition.
Normal timeout (charging has terminated).
If FAULT goes low and CHRG goes high
impedance simultaneously, then the LTC1733
has timed out due to a bad cell (V
after one-quarter the programmed charge time).
If CHRG goes high impedance first, then
the LTC1733 has timed out normally (charging
has terminated), but NTC is indicating an out-
of-temperature condition.
U
W
BAT
U
IN
<2.48V
< V
UV
)
When the LTC1733 is in charge mode, the CHRG pin is
pulled low by the internal N-channel MOSFET. To detect
this mode, force the digital output pin, OUT, high and
measure the voltage at the CHRG pin. The N-channel
MOSFET will pull the pin low even with the 2k pull-up
resistor. Once the charge current drops to 10% of the full-
scale current (C/10), the N-channel MOSFET is turned off
and a 25 A current source is connected to the CHRG pin.
The IN pin will then be pulled high by the 2k pull-up. By
forcing the OUT pin to a high impedance state, the current
source will pull the pin low through the 400k resistor.
When the internal timer has expired, the CHRG pin will
assume a high impedance state and the 400k resistor will
then pull the pin high to indicate that charging has termi-
nated.
NTC Thermistor
The battery temperature is measured by placing a negative
temperature coefficient (NTC) thermistor close to the
battery pack. The NTC circuitry is shown in Figure 3. To use
this feature, connect a 10k NTC thermistor between the
NTC pin and ground and a resistor (R
to V
the value of the chosen NTC thermistor at 50 C (this value
is 4.1k for a Vishay NTHS0603N02N1002J thermistor).
The LTC1733 goes into hold mode when the resistance of
the NTC thermistor drops below 4.1k which should be
at 50 C. The hold mode freezes the timer and stops
the charge cycle until the thermistor indicates a return
to a valid temperature. As the temperature drops, the
CC
. R
HOT
should be a 1% resistor with a value equal to
Figure 2. Microprocessor Interface
LTC1733
V
V
CC
+
8
CHRG
3
400k
2k
OUT
IN
PROCESSOR
HOT
V
DD
) from the NTC pin
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