SD4054 datasheet(9/14 Pages) SHOUDING

9 / 14 page

SD4054 is ready to charge.

that the SD4054 is in undervolt

that the SD4054 is in a char

The SD4054 constantly monito

SD4054 terminates the char

SD4054 enters standby mode,

(4.2V), the SD4054 enters c

the SD4054 is capable of oper

In this mode, the SD4054

ote: The SD4054X does not

The SD4054 includes an internal

The SD4054 is a single cell lithium-ion battery charger

9-9

Operation

using a constant-current/constant-voltage algorithm. It

can deliver up to 800mA of charge current (using a

good thermal PCB layout) with a final float voltage

accuracy of ± 1%

P-channel power MOSFET and thermal regulation

circuitry. No blocking diode or external current sense

resistor is required; thus, the basic charger circuit

requires only two external components. Furthermore,

ating from a USB power

source.

Normal Charge Cycle

A charge cycle begins when the voltage at the VCC pin

rises above the UVLO threshold level and a 1%

program resistor is connected from the PROG pin to

ground or when a battery is connected to the charger

output. If the BAT pin is less than 2.9V, the charger

enters trickle charge mode.

supplies approximately 1/10 the programmed charge

current to bring the battery voltage up to a safe level for

full current charging. (N

include this trickle charge feature).

When the BAT pin voltage rises above 2.9V, the

charger enters constant-current mode, where the

programmed charge current is supplied to the battery.

When the BAT pin approaches the final float voltage

onstant-voltage mode and

the charge current begins to decrease. When the

charge current drops to 1/10 of the programmed value,

the charge cycle ends.

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:

The charge current out of the BAT pin can be

determined at any time by monitoring the PROG pin

voltage using the following equation:

Charge Termination

A charge cycle is terminated when the charge

current falls to 1/10th the programmed value after the

final float voltage is reached. This condition is detected

by using an internal, filtered comparator to monitor the

PROG pin. When the PROG pin voltage falls below

100mV for longer than tTERM (typically 1ms), charging

is terminated. The charge current is latched off and the

where the input supply

current drops to 200µA.

When charging, transient loads on the BAT pin can

cause the PROG pin to fall below 100mV for short

periods of time before the DC charge current has

dropped to 1/10th the programmed value. The 1ms filter

time (TTERM) on the termination comparator ensures that

transient loads of this nature do not result in premature

charge cycle termination. Once the average charge

current drops below 1/10th the programmed value, the

ge cycle and ceases to

provide any current through the BAT pin. In this state,

all loads on the BAT pin must be supplied by the

battery.

rs the BAT pin voltage in

standby mode. If this voltage drops below the 4.05V

recharge threshold (VRECHRG), another charge cycle

begins and current is once again supplied to the battery.

To manually restart a charge cycle when in standby

mode, the input voltage must be removed and reapplied,

or the charger must be shut down and restarted using

the PROG pin. Figure 7 shows the state diagram of a

typical charge cycle.

Charge Status Indicator(CHRG)

The charge status output has three different states:

strong pull-down(~10mA), weak pull-down (~12µA) and

high impedance. The strong pull-down state indicates

ge cycle. Once the charge

cycle has terminated , the pin state is determined by

undervoltage lockout conditions. A weak pull-down

indicates that VCC meets the UVLO conditions and the

High impedance indicates

age lockout mode: either

VCC is less than 100mV above the BAT pin voltage or

insufficient voltage is applied to the VCC pin. A

microprocessor can be used to distinguish between

SH OU D IN G

SD 4054

SD4054-datasheet V1.0

Sep.-2006

SD4054 Datasheet(PDF) 9 Page - SHOUDING Shouding Semiconductor

SD4054 Datasheet(HTML) 9 Page - SHOUDING Shouding Semiconductor

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