2770EAR 查看數據表（PDF） - Dallas Semiconductor -> Maxim Integrated

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2770EAR

Battery Monitor and Charge Controller

Dallas Semiconductor -> Maxim Integrated 

RECHARGEABLE LITHIUM PULSE CHARGING Figure 3

DS2770

VCV

VIN

VLB

UV

CC

Trickle Bulk

Charge Region

Pulse

Region

t VCV

Pulse Charge

t CD

Charge

Complete

NiMH CHARGER OPERATION

During NiMH charging, charge current from a constant current or current-limited supply is gated to the

battery under control of UV and CC pins. Since the transition from trickle charge to fast charge occurs

when the battery reaches 3.0V, a three-cell NiMH battery will begin fast charge at 1.0V per cell. A

voltage divider can be used to adjust the transition point to a higher per cell voltage, though values in the

Voltage Measurement Register would be affected by the divider ratio.

At the start of fast charge, the DS2770 uses the most recent temperature measurement to determine the

appropriate dT/dt termination rate for the ambient conditions from Table 2 below. During the first 5

minutes, temperature rate termination is blanked to avoid false dT/dt detection due to I2R heating. After

the blanking period, dT/dt detection begins using one of the initial rates from Table 2 and requires that the

rate of temperature rise continue at or above the selected rate for 2.8 minutes. Internally, values from the

Temperature Measurement Register are averaged in determining the sustained rate of temperature rise.

The effective rate shown in Table 2 is based on NiMH charge data and represents the predicted

instantaneous dT/dt rate at termination.

NiMH CHARGE TERMINATION THRESHOLDS Table 2

AMBIENT

TEMPERATURE (°C)

0 to +5

+5 to +15

+15 to +40

dT/dt THRESHOLD

INITIAL

EFFECTIVE

(°C/MIN)

(°C/MIN)

0.30

1.0

0.45

1.0

0.60

1.0

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