LTC4053EMSE-4.2 Linear Technology, LTC4053EMSE-4.2 Datasheet - Page 9

• Manufacturer Part Number: LTC4053EMSE-4.2
• Description: IC CHARGER BATTERY USB 10-MSOP
• Manufacturer: Linear Technology

Specifications of LTC4053EMSE-4.2

• Function: Charge Management
• Battery Type: Lithium-Ion (Li-Ion)
• Voltage - Supply: 4.25 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
Undervoltage Lockout (UVLO)
An internal undervoltage lockout circuit monitors the input
voltage and keeps the charger in shutdown mode until V
rises above the undervoltage lockout threshold. The UVLO
circuit has a built-in hysteresis of 150mV. Furthermore, to
protect against reverse current in the power MOSFET, the
UVLO circuit keeps the charger in shutdown mode if V
falls to within 35mV of the battery voltage. If the UVLO
comparator is tripped, the charger will not come out of
shutdown until V
Trickle Charge And Defective Battery Detection
At the beginning of a charge cycle, if the battery voltage is
low (below 2.48V) 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 charge time, the battery is assumed to be
defective, the charge cycle is terminated, the CHRG pin
output assumes a high impedance state, and the FAULT
pin pulls low. The fault can be cleared by toggling V
temporarily forcing the SHDN pin to 0V, or temporarily
forcing the BAT pin voltage above 2.48V.
Shutdown
The LTC4053 can be shut down (I
SHDN pin to 0V. For normal operation, pull the SHDN pin
above the manual shutdown threshold voltage level. Do
not leave this pin open. In shutdown the internal linear
regulator is turned off, and the internal timer is reset.
Programming Charge Current
The formula for the battery charge current (see Figure 1)
is:
where R
ground. Under trickle charge conditions, this current is
reduced to 10% of the full-scale value.
I
R
CHG
PROG
= (I
= (1.5V / R
PROG
= 1500V/I
PROG
is the total resistance from the PROG pin to
) • 1000
CC
PROG
rises 70mV above the battery voltage.
U
CHG
) • 1000 or
U
CC
= 25µA) by pulling the
W
U
CC
CC
CC
,
For example, if 500mA charge current is required,
calculate:
For best stability over temperature and time, 1% metal-
film resistors are recommended.
If the charger is in constant-temperature or constant-
voltage mode, the battery current can be monitored by
measuring the PROG pin voltage as follows:
USB and Wall Adapter Power
Although the LTC4053 allows charging from a USB port,
a wall adapter can also be used to charge Li-Ion batteries.
Figure 2 shows an example of how to combine wall adapter
and USB power inputs. A P-channel MOSFET, MP1, is
used to prevent back conducting into the USB port when
a wall adapter is present and Schottky diode, D1, is used
to prevent USB power loss through the 1k pull-down
resistor.
Typically a wall adapter can supply significantly more
current than the 500mA-limited USB port. Therefore, an N-
channel MOSFET, MN1 and an extra 3k program resistor
can be used to increase the charge current to 1A when the
wall adapter is present.
R
I
CHG
500mA I
PROG
ADAPTER
5V WALL
Figure 2. Combining Wall Adapter and USB Power
POWER
1A I
= (V
USB
CHG
CHG
= 1500V/0.5A = 3kΩ
PROG
MP1
1k
/ R
PROG
D1
2
) • 1000
V
MN1
CC
LTC4053
LTC4053-4.2
3k
PROG
BAT
3k
9
7
4053 F02
I
CHG
+
Li-Ion
BATTERY
SYSTEM
LOAD
4053fa
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