DS2438Z Maxim Integrated Products, DS2438Z Datasheet - Page 4

IC MONITOR SMART BATTERY 8-SOIC

DS2438Z

Manufacturer Part Number
DS2438Z
Description
IC MONITOR SMART BATTERY 8-SOIC
Manufacturer
Maxim Integrated Products
Datasheet

Specifications of DS2438Z

Function
Fuel, Gas Gauge/Monitor
Battery Type
Smart Batteries
Voltage - Supply
2.4 V ~ 10 V
Operating Temperature
-40°C ~ 85°C
Mounting Type
Surface Mount
Package / Case
8-SOIC (0.154", 3.90mm Width)
Lead Free Status / RoHS Status
Contains lead / RoHS non-compliant

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OPERATION-MEASURING TEMPERATURE
The DS2438 measures temperatures through the use of an on-board temperature measurement technique.
The temperature reading is provided in a 13-bit, two’s complement format, which provides 0.03125°C of
resolution. Table 1 describes the exact relationship of output data to measured temperature. The data is
transmitted serially over the 1-Wire interface. The DS2438 can measure temperature over the range of
-55°C to +125°C in 0.03125°C increments. For Fahrenheit usage, a lookup table or conversion factor
must be used.
Note that temperature is represented in the DS2438 in terms of a 0.03125°C LSb, yielding the following
13-bit format. The 3 least significant bits of the Temperature Register will always be 0. The remaining
13 bits contain the two’s complement representation of the temperature in °C, with the MSb holding the
sign (S) bit. See “Memory Map” section for the Temperature Register address location.
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
4 of 29
2
0
2
2
0
1
LSb
2
0
0
MSB
LSB
DIGITAL OUTPUT (Hex)
7D00h
E6F0h
C900h
FF80h
1910h
0080h
0000h

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