DS2437 データシートの表示（PDF） - Dallas Semiconductor -> Maxim Integrated

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DS2437

Smart Battery Monitor

Dallas Semiconductor -> Maxim Integrated 

DS2437

The current is measured by the ADC with a signed 10-bit (0.004883C) resolution, and the last completed

measurement is placed in the CURRENT REGISTER in a sign-extended 2’s-complement format. This

register is scaled such that a count of 20510 corresponds to a current level of 1C. Thus, the range of

current flow that can be measured is from -2.5C (discharging) to +2.5C (charging). The sign (S) of the

current measurement, indicating charge or discharge, resides in the seven most significant bits of the

CURRENT REGISTER, as shown in Table 3. See “Memory Map” section for the CURRENT

REGISTER address location.

Current/Data Relationships Table 3

BATTERY

CURRENT

+2.495C

+2.002C

+1.25C

+1.001C

0C

-1.001C

-1.25C

-2.002C

-2.500C

DIGITAL OUTPUT (Binary)

0000 0001 1111 1111

0000 0001 1001 1010

0000 0001 0000 0000

0000 0000 1100 1101

0000 0000 0000 0000

1111 1111 0011 0011

1111 1111 0000 0000

1111 1110 0110 0110

1111 1110 0000 0000

DIGITAL OUTPUT (Hex)

01FFh

019Ah

0100h

00CDh

0000h

FF33h

FF00h

FE66h

FE00h

For the DS2437 to output current data scaled as in Table 3, the user is responsible for selecting an RSENS

that will provide a 100 mV drop across it at a 2C rate. However, this value could be changed to

correspond to a different rate as long as this is comprehended by the user’s software in interpreting the

results from the DS2437.

OPERATION – CURRENT ACCUMULATORS

The DS2437 keeps track of the remaining capacity of a battery through the Integrated Current

Accumulator (ICA). The ICA maintains a net accumulated total of current flowing into and out of the

battery; therefore, the reading in this register is an indication of the remaining capacity in a battery and

may be used in performing gas gauge functions. In addition, the DS2437 has a register that accumulates

battery charging (positive) current (CCA) and one that accumulates discharging (negative) current

(DCA). This gives the smart battery system information needed to determine the end of life of a

rechargeable battery, based on total charge/discharge current over its lifetime.

The current measurement described above yields a result of the instantaneous current measured at the

31.25 ms measurement times. This value is then used to increment or decrement the ICA register,

increment the CCA (if current is positive), or increment the DCA (if current is negative).

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