4010CFE View Datasheet(PDF) - Linear Technology

Part Name

Description

Manufacturer

4010CFE

High Efficiency Standalone Nickel Battery Charger

Linear Technology 

LTC4010

Operation (Refer to Figure 1)

Charge Termination

Fast charge termination parameters are dependent upon

the battery chemistry selected with the CHEM pin. Volt-

age-based termination (–∆V) is always active after the

initial voltage stabilization period. If an external thermistor

network is present, chemistry-specific limits for ∆T/∆t (rate

of temperature rise) are also used in the termination algo-

rithm. Temperature-based termination, if enabled, becomes

active as soon as the fast charge state is entered.

Successful charge termination requires a charge rate

between C/2 and 2C. Lower rates may not produce the

battery voltage and temperature profile required for charge

termination.

Top-Off Charge State

If NiMH fast charge termination occurs because the

∆T/∆t limit is exceeded after an initial period of tMAX/12

has expired, the LTC4010 enters the top-off charge state.

Top-off charge is implemented by sourcing one-tenth the

programmed charge current for tMAX/3 minutes to ensure

that 100% charge has been delivered to the battery. The

CHRG status output is active during the top-off state. If

NiCd cells have been selected with the CHEM pin, the

LTC4010 never enters the top-off state.

Automatic Recharge State

Once charging is complete, the automatic recharge state

is entered to address the self-discharge characteristics of

nickel chemistry cells. The charge status output is inactive

during automatic recharge, but VCDIV remains switched

to GND to monitor the average cell voltage. If the VCELL

voltage drops below 1.325V without falling below 350mV,

the charge timer is reset and a new fast charge cycle is

initiated.

The internal termination algorithms of the LTC4010 are

adjusted when a fast charge cycle is initiated from auto-

matic recharge, because the battery should be almost fully

charged. Voltage-based termination is enabled immediately

and the NiMH ∆T/∆t limit is fixed at a battery temperature

rise of 1°C/minute.

Fault State

As discussed previously, the LTC4010 enters the fault state

based on detection of invalid battery voltages during vari-

ous charging phases. The IC also monitors the regulation

of the PWM control loop and will enter the fault state if

this is not within acceptable limits. Once in the fault state,

the battery must be removed or DC input power must be

cycled in order to initiate further charging. In the fault

state, the FAULT output is active, the READY output is

inactive, charging stops and the charge indicator output

is inactive. The VCDIV output remains connected to GND

to allow detection of battery removal.

Note that the LTC4010 also uses the FAULT output to indi-

cate that charging is suspended due to invalid battery or

internal die temperatures. However, the IC does not enter

the fault state in these cases and normal operation will

resume when all temperatures return to acceptable levels.

Refer to the Status Outputs section for more detail.

Insertion and Removal of Batteries

The LTC4010 automatically senses the insertion or removal

of a battery by monitoring the VCELL pin voltage. Should

this voltage fall below 350mV, the IC considers the bat-

tery to be absent. Removing and then inserting a battery

causes the LTC4010 to initiate a completely new charge

cycle beginning with charge qualification.

External Pause Control

After charging is initiated, the VTEMP pin may be used to

pause operation at any time. When the voltage between

VTEMP and GND drops below 200mV, the charge timer

pauses, fast charge termination algorithms are inhibited

and the PWM outputs are disabled. The status and VCDIV

outputs all remain active. Normal function is fully restored

from the previous state when pause ends.

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