LTC4069EDC Linear Technology, LTC4069EDC Datasheet - Page 11

• Manufacturer Part Number: LTC4069EDC
• Manufacturer: Linear Technology
• Type: Battery Chargerr

Specifications of LTC4069EDC

• Battery Type: Li-Ion
• Output Current: 500mA
• Output Voltage: 4.2V
• Operating Supply Voltage (min): 3.75V
• Operating Supply Voltage (max): 5.5V
• Operating Temp Range: -40C to 85C
• Package Type: DFN
• Mounting: Surface Mount
• Pin Count: 6
• Operating Temperature Classification: Industrial
• Lead Free Status / Rohs Status: Not Compliant

OPERATION
APPLICATIONS INFORMATION
Undervoltage Charge Current Limiting (UVCL)
The LTC4069 includes undervoltage charge (ΔV
current limiting that prevents full charge current until the
input supply voltage exceeds approximately 200mV above
the battery voltage. This feature is particularly useful if the
LTC4069 is powered from a supply with long leads (or any
relatively high output impedance).
For example, USB-powered systems tend to have highly
variable source impedances (due primarily to cable
quality and length). A transient load combined with such
impedance can easily trip the UVLO threshold and turn the
charger off unless undervoltage charge current limiting
is implemented.
Consider a situation where the LTC4069 is operating under
normal conditions and the input supply voltage begins to
droop (e.g., an external load drags the input supply down).
If the input voltage reaches V
220mV above the battery voltage), undervoltage charge
current limiting will begin to reduce the charge current
in an attempt to maintain ΔV
and the BAT output of the IC. The LTC4069 will continue
BAT
UVCL1
+ ΔV
between the V
UVCL1
R
NOM
R
NTC
(approximately
6
0.016 • V
0.76 • V
0.35 • V
NTC
Figure 3. NTC Circuit Information
CC
CC
CC
CC
V
UVCL1
CC
input
)
–
+
–
+
+
–
to operate at the reduced charge current until the input
supply voltage is increased or constant voltage mode
reduces the charge current further.
Operation from Current Limited Wall Adapter
By using a current limited wall adapter as the input supply,
the LTC4069 dissipates signifi cantly less power when
programmed for a current higher than the limit of the
supply as compared to using a non-current limited supply
at the same charge current.
Consider a situation where an application demands a
600mA charge current for an 800mAh Li-Ion battery. If a
typical 5V (non-current limited) input supply is used, the
charger’s peak power dissipation can exceed 1W.
Now consider the same scenario, but with a 5V input
supply with a 600mA current limit. To take advantage of
the current limited supply, it is necessary to program the
LTC4069 to charge at a current above 600mA. Assume
that the LTC4069 is programmed for 750mA (i.e.,
R
a programmed current higher than 600mA. Since the
PROG
= 1.33k) to ensure that part tolerances maintain
NTC_ENABLE
TOO COLD
TOO HOT
4069 F03
LTC4069
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4069fb