DS2710G データシートの表示（PDF） - Maxim Integrated

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DS2710G

Single-Cell NiMH Charger

Maxim Integrated 

Single-Cell NiMH Charger

the MAINTENANCE state. If at any time during FAST-

CHARGE the cell voltage exceeds VMAX-CHARGE, the

DS2710 determines that the cell is either overcharged

or has been removed, and enters the FAULT state.

CELL TEST

CELL TEST is performed once every 31s during FAST-

CHARGE to determine if charging is complete. During

CELL TEST, the CS output is held high to prevent

charging. The cell’s voltage is measured and com-

pared against prior readings. The maximum cell volt-

age measurement during the charge is retained. If a

cell’s voltage falls more than 2mV (V-ΔV) from its peak

reading, the FAST-CHARGE terminates successfully

and moves to TOP-OFF. The DS2710 also moves to

TOP-OFF if the cell’s voltage reading does not exceed

the maximum over a 16min period (tFLAT). A hold-off

period for -ΔV and flat voltage detection begins at the

start of fast charging and prevents false termination in

the first 4min of the charge cycle (tTHO).

The impedance of the cell is also measured during

CELL TEST. The cell’s open-circuit voltage is compared

against the voltage of the cell under charge. The differ-

ence is compared against the impedance threshold set

by the CTEST pin. If the difference exceeds the thresh-

old set by CTEST, the cell’s impedance is considered

to be too high for charging and the DS2710 enters the

FAULT state. The DS2710 also enters FAULT state if

any voltage reading in CELL TEST exceeds the

VMAX-OPEN threshold.

TOP-OFF

In the TOP-OFF state, the DS2710 charges at 25% the

rate of FAST-CHARGE. The voltage across the sense

resistor is regulated to 113mV with a 25% duty cycle.

The STATUS output is held high to indicate the cell

pack is being charged. The charge timer is reset and

restarted with a timeout period of one-half the

FAST-CHARGE duration. When the charge timer

expires or if the measured temperature exceeds

+50°C, the charger enters the MAINTENANCE state. If

the cell voltage is greater than VMAX-CHARGE during

the 25% of time when charge current is applied or

VMAX-OPEN during the remaining time, TOP-OFF is exit-

ed early and the DS2710 goes to FAULT.

MAINTENANCE

The DS2710 enters the MAINTENANCE state whenever

the charge completes normally or if the measured cell

temperature exceeds +50°C during the charge. The

STATUS pin is driven low to indicate TOP-OFF has

completed. The cell’s state of charge is maintained

indefinitely by continuing a 1.56% duty-cycle charge of

the cell. The DS2710 remains in the MAINTENANCE

state until the cell is removed, the DS2710 is power

cycled, or the DS2710 is forced into SUSPEND state.

FAULT

The DS2710 can enter FAULT from any charge state if

the cell voltage exceeds VMAX-CHARGE any time when

charge current is applied (CS low) or VMAX-OPEN at any

time when no charge current is flowing (CS high). In

addition, FAULT can be entered during PRECHARGE if

the cell’s temperature exceeds +50°C or the

PRECHARGE timer expires, or during FAST-CHARGE if

impedance threshold is exceeded. In the FAULT state,

CS is forced high to prevent charging and the STATUS

output toggles at a 4Hz rate to indicate that an error

has occurred. The DS2710 remains in FAULT until a

cell voltage greater than 1.75V (VMAX-CHARGE) is

detected, indicating that the cell has been removed.

The DS2710 then enters the PRESENCE state and waits

for the next cell insertion.

SUSPEND

Suspension of charge activity is possible by floating the

TMR pin (RTMR > RSUSPEND). The CS output is pulled

to VDD to disable the charge control FET to prevent cur-

rent flow to the cell. When the TMR connection is

restored, charging begins from the PRESENCE state

with all timers reset. The SUSPEND state is useful as a

means to stop charging by the application circuit, such

as with a microcontroller signal.

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