LTC4065LEDC#TRMPBF Linear Technology, LTC4065LEDC#TRMPBF Datasheet - Page 10

• Manufacturer Part Number: LTC4065LEDC#TRMPBF
• Description: IC CHARGER LI-ION 6-DFN
• Manufacturer: Linear Technology

Specifications of LTC4065LEDC#TRMPBF

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 3.75 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 6-WFDFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

OPERATIO
Charge Current Soft-Start and Soft-Stop
The LTC4065L 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 cur-
rent 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 LTC4065L use a unique architecture to charge a
battery in a constant-current, constant-voltage and con-
stant-temperature fashion. Figure 1 shows a simplified
block diagram of the LTC4065L. Three of the amplifier
feedback loops shown control the constant-current, CA,
constant-voltage, VA, and constant-temperature, TA
modes. A fourth amplifier 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
205 times greater than the drain current of M2.
Amplifiers 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
LTC4065L/LTC4065LX
10
U
loop, whichever is trying to reduce the charge current the
most. The output of the other amplifier 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 4.2V.
The PROG pin voltage gives an indication of the charge
current during constant-voltage mode as discussed in
“Programming Charge Current”.
The transconductance amplifier, TA, limits the die tem-
perature to approximately 115°C when in constant-tem-
perature 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 205V/R
LTC4065L results in the junction temperature approach-
ing 115°C, the amplifier (TA) will begin decreasing the
charge current to limit the die temperature to approxi-
mately 115°C. As the battery voltage rises, the LTC4065L
either returns to constant-current mode or enters con-
stant-voltage mode straight from constant-temperature
mode. Regardless of mode, the voltage at the PROG pin is
proportional to the current delivered to the battery.
PROG
. If the power dissipation of the
4065lxfa