DS2711/DS2712: Loose Cell NiMH Charger

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Table 4. PARALLEL CONFIGURATION, EACH CELL

MODE

CURRENT LIMIT 500mA

CURRENT LIMIT 1000mA

Cell Capacity

900mAH

1700mAH

2200mAH

900mAH

1700mAH

2200mAH

Fast

C/3.72

C/7.02

C/9.08

C/1.86

C/3.51

C/4.54

Precharge/Top-Off

C/14.4

C/27.2

C/35.2

C/7.20

C/13.6

C/17.6

Maintenance

C/115

C/218

C/282

C/57.6

C/109

C/141

Series and Single Cell Charging Example:

In the series and single-cell modes, the effective fast charge current is equal to 0.969 times the regulated current

limit and the top-off current is 0.25 times the regulated current. The maintenance mode is identical to the parallel

charging rate, that is, 1/64 times the regulated current. The C-rates for charging 3 different cell capacities using a

500mA and a 1000mA current source are shown in the following table.

Table 5. SERIES CONFIGURATION, EACH CELL

MODE

CURRENT LIMIT 500mA

CURRENT LIMIT 1000mA

Cell Capacity

900mAH

1700mAH

2200mAH

900mAH

1700mAH

2200mAH

Fast

C/1.86

C/3.51

C/4.54

C/0.93

C/1.75

C/2.27

Precharge/Top-Off

C/7.20

C/13.6

C/17.6

C/3.60

C/6.80

C/8.80

Maintenance

C/115

C/218

C/282

C/57.6

C/109

C/141

LED1 and LED2 Outputs, MODE-Select Input

Open-drain outputs LED1 and LED2 pull low to indicate charge status. When inactive, the outputs are high

impedance. LED1 displays the status for the cell monitored by VP1 and LED2 displays the status for the cell

monitored by VP2.

The LED pins drive low in three “blink” patterns to annunciate the charge status. Table 6 summarizes the LED

operation in each display mode (DM0, DM1, DM2) for each charge condition. In parallel mode, LED1 indicates the

status of the cell whose positive terminal is connected to VP1 and LED2 indicates the status of the cell whose

positive terminal is connected to VP2. In series mode, LED1 indicates the charge status for both cells since they

are charged in series.

Table 6. DISPLAY PATTERNS BY DISPLAY MODE AND CHARGE ACTIVITY

DISPLAY MODE

CHARGE ACTIVITY

DMSEL PIN

NO

BATTERY

PRE/FAST/TOP-

OFF

CHARGING

MAINTENANCE

FAULT

DM0

Low

High-Z

Low

0.80s Low

0.16s High-Z

0.48s Low

0.48s High-Z

DM1

Float

High-Z

Low

High-Z

0.16s Low

0.16s High-Z

DM2

High

High-Z

0.80s Low

0.16s High-Z

Low

0.16s Low

0.16s High-Z

High-Z = High Impedance

Package Information