DS2740U+ Maxim Integrated Products, DS2740U+ Datasheet - Page 6

• Manufacturer Part Number: DS2740U+
• Description: IC CURRENT GAUGE(15BIT) 8UMAX
• Manufacturer: Maxim Integrated Products

Specifications of DS2740U+

• Function: Current Gauge (15 Bit)
• Voltage - Input: 2.7 ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-MSOP, Micro8™, 8-uMAX, 8-uSOP,
• Battery Type: Li-Ion, NiMH
• Operating Supply Voltage: 2.7 V to 5.5 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Charge Safety Timers: No
• Mounting Style: SMD/SMT
• Temperature Monitoring: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Accuracy: -
• Sensing Method: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Every 1024th conversion, the ADC measures its input offset to facilitate offset correction. Offset
correction occurs approximately once per hour in the DS2740U and four times per hour in the
DS2740BU. The resulting correction factor is applied to the subsequent 1023 measurements. During the
offset correction conversion, the ADC does not measure the IS1 to IS2 signal. A maximum error of
1/1024 in the accumulated current register (ACR) is possible, however, to reduce the error, the current
measurement just prior to the offset conversion is displayed in the current register and is substituted for
the dropped current measurement in the current accumulation process. The typical error due to offset
correction is much less than 1/1024.
CURRENT ACCUMULATOR
Current measurements are internally summed, or accumulated, at the completion of each conversion
period with the results displayed in the ACR. The accuracy of the ACR is dependent on both the current
measurement and the conversion timebase. The ACR has a range of ±204.8mVh with a LSb of
6.25μVh . Additional registers hold fractional results of each accumulation, however, these bits are not
user accessible.
Read and write access is allowed to the ACR. Whenever the ACR is written, fractional accumulation
results are cleared. Also, a write forces the ADC to measure its offset and update the offset correction
factor. The current measurement and accumulation begin with the second conversion following a write to
the ACR. Figure 4 describes the ACR address, format, and resolution.
Figure 4. CURRENT ACCUMULATOR FORMAT
DS2740U
DS2740BU
PART
DS2740U
DS2740BU
MSb
PART
S
2
INTERVAL
14
UPDATE
3.515s
0.878s
MSB—Address 10h
2
CONVERSION
13
3.515s
0.878s
TIME
2
12
V
6.25 μ Vh
2
IS1
11
- V
2
IS2
10
V
1.5625 μ V
6.250 μ V
IS1
2
312.5 μ Ah
9
- V
20m Ω
LSb
IS2
2
8
CURRENT RESOLUTION (1 LSB)
6 of 16
78.13 μ A
312.5 μ A
20m Ω
MSb
ACR LSB
416.7 μ Ah
2
15m Ω
7
2
104.2 μ A
416.7 μ A
6
15m Ω
R
LSB—Address 11h
SNS
2
5
625 μ Ah
10m Ω
R
2
Units: 6.25 μ Vh/R
SNS
4
156.3 μ A
625 μ A
10m Ω
2
3
1.250mAh
2
2
5m Ω
1.250mA
312.5 μ A
2
5m Ω
1
LSb
SNS
2
0