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LTC4069EDC-4.4#TRMPBF

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16
LTC4069-4.4
7
406944fa
SIMPLIFIED BLOCK DIAGRAM
–
+
–
+
–+
–+
2
+
MP
M2
1s
M1
1000s
V
CC
V
CC
R1
R2
ENABLE
R3
R4
R5
2.9V
CHRG
6
PROG
1
GND
4069 F01
R
PROG
BAT
1V
PROG
C/10
C1
–
+
TA
T
DIE
115°C
0.1V
1.2V
SUSPEND
D3
TOO
HOT
TOO
COLD
NTC_EN
0.1V
D2
3.6V
D1
1.2V
–+
REF
CA
MA
LOBAT
5
R7
NTC
R8
R9
R10
V
CC
V
CC
–
+
UVLO
3
4
BAT
LOGIC COUNTER
OSCILLATOR
CHARGE CONTROL
–+
–
+
C3
–
+
C2
C5
VA
4V
–
+
SHUTDOWN
SUSPEND
OR
AND
R
NOM
R
NTC
C4
OPERATION
Figure 1. LTC4069-4.4 Block Diagram
The LTC4069-4.4 is a linear battery charger designed
primarily for charging single-cell lithium-ion batteries.
Featuring an internal P-channel power MOSFET, the
charger uses a constant-current/constant-voltage charge
algorithm with programmable current. Charge current can
be programmed up to 750mA with a fi nal fl oat voltage
accuracy of ±0.6%. The CHRG open-drain status output
indicates if C/10 has been reached. No blocking diode
or external sense resistor is required; thus, the basic
charger circuit requires only two external components.
An internal termination timer and trickle charge low-
battery conditioning adhere to battery manufacturer safety
guidelines.
Furthermore, the LTC4069-4.4 is capable of operating
from a USB power source.
An internal thermal limit reduces the programmed charge
current if the die temperature attempts to rise above a
preset value of approximately 115°C. This feature protects
the LTC4069-4.4 from excessive temperature and allows
the user to push the limits of the power handling capability
of a given circuit board without risk of damaging the
LTC4069-4.4 or external components. Another benefi t
of the LTC4069-4.4 thermal limit is that charge current
can be set according to typical, not worst-case, ambient
LTC4069-4.4
8
406944fa
OPERATION
temperatures for a given application with the assurance
that the charger will automatically reduce the current in
worst-case conditions.
The charge cycle begins when the voltage at the V
CC
pin
rises above 3.5V and approximately 80mV above the BAT
pin voltage, a 1% program resistor is connected from the
PROG pin to ground and the NTC pin voltage stays between
0.76 • V
CC
and 0.35 • V
CC
or below 0.016 • V
CC
.
If the BAT pin voltage is below 2.9V, the charger goes into
trickle charge mode, charging the battery at one-tenth the
programmed charge current to bring the cell voltage up to
a safe level for charging. If the BAT pin voltage is above
4.3V, the charger will not charge the battery as the cell
is near full capacity. Otherwise, the charger goes into the
fast charge constant-current mode.
When the BAT pin approaches the fi nal fl oat voltage (4.4V),
the LTC4069-4.4 enters constant-voltage mode and the
charge current begins to decrease. When the current
drops to 10% of the full-scale charge current, an internal
comparator turns off the N-channel MOSFET on the CHRG
pin and the pin assumes a high impedance state.
An internal timer sets the total charge time, t
TIMER
(typically
4.5 hours). When this time elapses, the charge cycle
terminates and the CHRG pin assumes a high impedance
state. The charge cycle will automatically restart if the
BAT pin voltage falls below V
RECHRG
(typically 4.3V).
To manually restart the charge cycle, remove the input
voltage and reapply it, or momentarily fl oat the PROG pin
and reconnect it.
Programming Charge Current
The charge current is programmed using a single resistor
from the PROG pin to ground. The battery charge current is
1000 times the current out of the PROG pin. The program
resistor and the charge current are calculated using the
following equations:
R
V
I
I
V
R
PROG
CHG
CHG
PROG
==1000
1 1000
•,
The charge current out of the BAT pin can be determined
at any time by monitoring the PROG pin voltage and using
the following equation:
I
V
R
BAT
PROG
PROG
= • 1000
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the
input voltage and keeps the charger in undervoltage
lockout until V
CC
rises above 3.6V
and
approximately
80mV above the BAT pin voltage. The 3.6V UVLO circuit
has a built-in hysteresis of approximately 0.6V and the
automatic shutdown threshold has a built-in hysteresis
of approximately 50mV. During undervoltage lockout
conditions, maximum battery drain current is 4μA and
maximum supply current is 11μA.
Shutdown Mode
The LTC4069-4.4 can be disabled by fl oating the PROG pin.
In shutdown mode, the battery drain current is reduced to
less than 1μA and the supply current to about 20μA.
Timer and Recharge
The LTC4069-4.4 has an internal termination timer that
starts when an input voltage greater than the undervoltage
lockout threshold is applied to V
CC
, or when leaving
shutdown and the battery voltage is less than the recharge
threshold.
At power-up or when exiting shutdown, if the battery voltage
is less than the recharge threshold, the charge time is set
to 4.5 hours. If the battery temperature is either too high
or too low, the timer will pause until the battery returns
to normal temperature. If the battery is greater than the
recharge threshold at power-up or when exiting shutdown,
the timer will not start and charging is prevented since the
battery is at or near full capacity.
Once the charge cycle terminates, the LTC4069-4.4
continuously monitors the BAT pin voltage using a
comparator with a 2ms fi lter time. When the battery
voltage falls below 4.3V (which corresponds to 80% to
90% battery capacity), a new charge cycle is initiated and
a 2.25 hour timer begins. This ensures that the battery is
kept at, or near, a fully charged condition and eliminates
the need for periodic charge cycle initiations. Also, if the
LTC4069-4.4
9
406944fa
OPERATION
battery voltage does not exceed the recharge threshold
voltage when the timer ends, the timer resets and a 2.25
hour recharge cycle begins. The CHRG output assumes a
strong pull-down state during recharge cycles until C/10 is
reached when it transitions to a high impendance state.
Trickle Charge and Defective Battery Detection
At the beginning of a charge cycle, if the battery voltage
is low (below 2.9V), the charger goes into trickle charge,
reducing the charge current to 10% of the full-scale
current. If the low-battery voltage persists for one quarter
of the total time (1.125 hour), the battery is assumed to
be defective, the charge cycle is terminated and the CHRG
pin output pulses at a frequency of 2Hz with a 75% duty
cycle. If for any reason the battery voltage rises above
2.9V, the charge cycle will be restarted. To restart the
charge cycle (i.e., when the defective battery is replaced
with a discharged battery less than 2.9V), simply remove
the input voltage and reapply it or momentarily fl oat the
PROG pin and reconnect it.
CHRG Status Output Pin
The charge status indicator pin has three states: pull-
down, pulse at 2Hz (see Trickle Charge and Defective
Battery Detection and Battery Temperature Monitoring)
and high impedance. The pull-down state indicates that the
LTC4069-4.4 is in a charge cycle. A high impedance state
indicates that the charge current has dropped below 10%
of the full-scale current, the timer has ended the charge
cycle, or the LTC4069-4.4 is disabled. Figure 2 shows the
CHRG status under various conditions.
Charge Current Soft-Start and Soft-Stop
The LTC4069-4.4 includes a soft-start circuit to minimize
the inrush current at the start of a charge cycle. When a
charge cycle is initiated, the charge current ramps from
zero to the full-scale current over a period of approximately
170μs. Likewise, internal circuitry slowly ramps the charge
current from full-scale to zero when the charger is shut off
or self terminates. This has the effect of minimizing the
transient current load on the power supply during start-up
and charge termination.
Constant-Current/Constant-Voltage/
Constant-Temperature
The LTC4069-4.4 uses a unique architecture to charge
a battery in a constant-current, constant-voltage and
constant-temperature fashion. Figure 1 shows a Simplifi ed
Block Diagram of the LTC4069-4.4. Three of the amplifi er
feedback loops shown control the constant-current (CA),
constant-voltage (VA), and constant-temperature (TA)
modes. A fourth amplifi er feedback loop (MA) is used to
increase the output impedance of the current source pair,
M1 and M2 (note that M1 is the internal P-channel power
MOSFET). It ensures that the drain current of M1 is exactly
1000 times greater than the drain current of M2.
Amplifi ers CA and VA are used in separate feedback loops
to force the charger into constant-current or constant-
voltage mode, respectively. Diodes D1 and D2 provide
priority to either the constant-current or constant-voltage
loop, whichever is trying to reduce the charge current
the most. The output of the other amplifi er saturates low
which effectively removes its loop from the system. When
in constant-current mode, CA servos the voltage at the
PROG pin to be precisely 1V. VA servos its inverting input
to an internal reference voltage when in constant-voltage
mode and the internal resistor divider, made up of R1 and
R2, ensures that the battery voltage is maintained at 4.4V.
The PROG pin voltage gives an indication of the charge
current during constant-voltage mode as discussed in
“Programming Charge Current”.
Transconductance amplifi er, TA, limits the die temperature
to approximately 115°C when in constant-temperature
mode. Diode D3 ensures that TA does not affect the charge
current when the die temperature is below approximately
115°C. The PROG pin voltage continues to give an indication
of the charge current.
In typical operation, the charge cycle begins in constant-
current mode with the current delivered to the battery equal
to 1000V/R
PROG
. If the power dissipation of the LTC4069-4.4
results in the junction temperature approaching 115°C, the
amplifi er (TA) will begin decreasing the charge current to
limit the die temperature to approximately 115°C. As the
battery voltage rises, the LTC4069-4.4 either returns to
constant-current mode or enters constant-voltage mode
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P16

LTC4069EDC-4.4#TRMPBF

Mfr. #:
Buy LTC4069EDC-4.4#TRMPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Battery Management Standalone Li-Ion Battery Charger w/ Thermistor Input, New 4.4V Batteries
Lifecycle:
New from this manufacturer.
Delivery:
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