DS2711(2008) 查看數據表（PDF） - Maxim Integrated

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DS2711
(Rev.:2008)

Loose Cell NiMH Chargers

Maxim Integrated 

DS2711/DS2712: Loose Cell NiMH Charger

Charge Timer

The charge timer monitors the duration of charge in fast and top-off charge phases, and is reset at the beginning of

each phase. The time-out period is set with an external resistor connected from the TMR pin to VSS. Resistors can

be selected to support fast-charge time-out periods of 0.5 to 10 hours and top-off charge time-out periods of 0.25 to

5 hours. If the timer expires in fast-charge, the timer count is reset and charging proceeds to the top-off charge

phase. The top-off time-out period is half of the fast charge time-out period. If the timer expires in top-off, charging

proceeds to the maintenance phase. The programmed charge time approximately follows the equation:

t = 1.5 x R / 1000

(time in minutes)

Suspend

Suspension of charge activity is possible by floating the TMR pin. The CC1 and CC2 outputs become high-Z and

the charge timer stops. The state machine and all timers are reset to their presence test conditions.

Temperature Sense

Connecting an external 10kΩ NTC thermistor between THM1 or THM2 (THMx) and VSS, and a 10kΩ bias resistor

between VDD and THMx allows the DS2711 to sense temperature. To sense the temperature of the battery cells,

locate the thermistor close to the body of the battery cell so THM1 monitors the temperature of cell-1 and THM2

monitors the temperature of cell-2. Alternatively, the thermistor can sense ambient temperature by locating it away

from the cells. THM1 and THM2 can be connected together to sense temperature using a single thermistor and

bias resistor. The temperature qualification function can be defeated by connecting THM1 and THM2 to a single

resistor-divider supplying a voltage between the Thermistor-Min and Thermistor-Max threshold voltages. Several

recommended 10kΩ thermistors are shown in Table 2.

Min, Max Temperature Compare

The voltage thresholds of the THMx inputs (VTHM-MIN, VTHM-MAX) are set to allow fast charging to start if 0°C <

TA < 45°C when using the recommended 10kΩ bias and 10kΩ thermistor. If fast charging is in progress, and the

voltage on THMx reaches VTHM-STOP, fast charging stops and the maintenance phase begins.

Table 2. THM1, THM2 THRESHOLDS

THM

THRESHOLD

MIN

MAX

STOP

RATIO

OF VDD

0.73

0.33

0.29

THERMISTOR

RESISTANCE

(Ω)

27.04k

4.925k

4.085k

Semitec

103AT-2

0°C

45°C

50°C

Figure 7. CELL VOLTAGE SENSE POINTS

TEMPERATURE (°C)

Fenwal

197-103LAG-A01

173-103LAF-301

4°C

42°C

47°C

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