LTC4064 datasheet(9/16 Pages) LINER

9 / 16 page

LTC4064

sn4064 4064fs

For example, if 500mA charge current is required,

calculate:

RPROG = 1500V/0.5A = 3kΩ

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:

IBAT = (VPROG / RPROG) • 1000

USB and Wall Adapter Power

Although the LTC4064 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.

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 VCC

rises above the undervoltage lockout threshold. The UVLO

circuit has a built-in hysteresis of 200mV. Furthermore, to

protect against reverse current in the power MOSFET, the

UVLO circuit keeps the charger in shutdown mode if VCC

falls to within 35mV of the battery voltage. If the UVLO

comparator is tripped, the charger will not come out of

shutdown until VCC rises 70mV above the battery voltage.

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 VCC,

temporarily forcing the SHDN pin to 0V, or temporarily

forcing the BAT pin voltage above 2.48V.

Shutdown

The LTC4064 can be shut down (ICC = 25µA) by pulling the

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:

ICHG = (IPROG) • 1000

= (1.5V / RPROG) • 1000 or

RPROG = 1500V/ICHG

where RPROG is the total resistance from the PROG pin to

ground. Under trickle charge conditions, this current is

reduced to 10% of the full-scale value.

Figure 2. Combining Wall Adapter and USB Power

4064 F02

Li-Ion

BATTERY

5V WALL

ADAPTER

1A ICHG

LTC4064

BAT

VCC

ICHG

PROG

SYSTEM

LOAD

USB

POWER

500mA ICHG

MN1

MP1

LTC4064 bảng dữ liệu(PDF) 9 Page - Linear Technology

LTC4064 bảng dữ liệu(HTML) 9 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

bảng dữ liệu tải về

Link URL