DS2438 Dallas Semiconducotr, DS2438 Datasheet - Page 4

• Manufacturer Part Number: DS2438
• Description: Smart Battery Monitor
• Manufacturer: Dallas Semiconducotr

Temperature Register Format Table 1
OPERATION-MEASURING BATTERY VOLTAGE
The on-board analog-to-digital converter (ADC) has 10 bits of resolution and will perform a conversion
when the DS2438 receives a command protocol (Convert V) instructing it to do so. The result of this
measurement is placed in the 2-byte Voltage Register. The range for the DS2438 ADC is 0 volt to
10 volt; this range is suitable for NiCd or NiMH battery packs up to six cells, and for lithium ion battery
packs of two cells. The full-scale range of the ADC is scaled to 10.23 volt, resulting in a resolution of
10 mV.
While the ADC has a range that extends down to 0 volt, it is important to note that the battery voltage can
also be the supply voltage to the DS2438. As such, the accuracy of the ADC begins to degrade below
battery voltages of 2.4 volt, and the ability to make conversions is limited by the operating voltage range
of the DS2438.
Voltage is expressed in this register in scaled binary format, as outlined in Table 2. Note that while codes
exist for values below 2.4 volt, accuracy of the ADC and the limitation on the DS2438’s supply voltage
make it unlikely that these values would be used in actual practice. See “Memory Map” section for the
Voltage Register address location.
TEMPERATURE
+25.0625°C
-25.0625°C
+125°C
+0.5°C
-0.5°C
-55°C
0°C
MSb
2
S
-1
2
2
-2
6
2
2
-3
5
DIGITAL OUTPUT (Binary)
2
2
-4
4
01111101 00000000
00011001 00010000
00000000 10000000
00000000 00000000
11111111 10000000
11100110 11110000
11001001 00000000
(unit = °C)
2
2
-5
3
2
0
2
4 of 29
2
0
1
LSb
2
0
0
MSB
LSB
DIGITAL OUTPUT (Hex)
7D00h
FF80h
E6F0h
C900h
1910h
0080h
0000h
DS2438