DS2745 View Datasheet(PDF) - Maxim Integrated

Part Name

Description

Manufacturer

DS2745

Low-Cost I2C Battery Monitor

Maxim Integrated 

DS2745 Low-Cost I2C Battery Monitor

CURRENT ACCUMULATION

The Accumulated Current register (ACR) serves as an up/down counter holding a running count of charge stored in

the battery. Current measurement results, plus a programmable bias value are internally summed, or accumulated,

at the completion of each current measurement conversion period with the results displayed in the ACR. The ACR

has a range of 0mVh to +409.6mVh with an LSb of 6.25μVhAdditional registers hold fractional results of each

accumulation, however, these bits are not user accessible. The ACR count clamps at FFFFh when accumulating

charge values and at 0000h when accumulating discharge values.

Read and write access is allowed to the ACR. Whenever the ACR is written, fractional accumulation results are

cleared. A write to the ACR also forces the ADC to measure its offset and update the offset correction factor.

Current measurement and accumulation resume (using the new offset correction) with the second conversion

following the write to the ACR. Figure 7 describes the ACR address, format, and resolution.

Figure 7. ACCUMULATED CURRENT REGISTER FORMAT

MSB—Address 10

LSB—Address 11

215 214 213 212 211 210 29 28

MSb

LSb

“S”: sign bit

27 26 25 24 23 22 21 20

MSb

LSb

Units: 6.25Vh/Rsns

Table 4. ACCUMULATED CURRENT RANGE FOR VARIOUS RSNS VALUES

VSS - VSNS

409.6mVh

20m

20.48Ah

ACR RANGE

RSNS

15m

27.31Ah

10m

40.96Ah

5m

81.92Ah

CURRENT OFFSET BIAS

The Current Offset Bias register (COBR) allows a programmable offset value to be added to raw current

measurements. The result of the raw current measurement plus the COBR value is displayed as the current

measurement result in the CURRENT register, and is used for current accumulation. The COBR value can be used

to correct for a static offset error, or can be used to intentionally skew the current results and therefore the current

accumulation.

Read and write access is allowed to COBR. Whenever the COBR is written, the new value is applied to all

subsequent current measurements. COBR can be programmed in 1.56V steps to any value between +198.1V

and -199.7V. The COBR value is stored as a two’s complement value in volatile memory, and must be initialized

via the interface on power-up. Figure 8 describes the COBR address, format, and resolution.

Figure 8. CURRENT OFFSET BIAS REGISTER FORMAT

Address 61

S 26 25

MSb

“S”: sign bit

24 23 22 21 20

LSb

Units: 1.56V/Rsns

9 of 15

Share Link: