DS2438Z View Datasheet(PDF) - Dallas Semiconductor -> Maxim Integrated

Part Name

Description

Manufacturer

DS2438Z

Smart Battery Monitor

Dallas Semiconductor -> Maxim Integrated 

DS2438

PARASITE POWER

The block diagram (Figure 1) shows the parasite-powered circuitry. This circuitry “steals” power

whenever the DQ pin is high. DQ will provide sufficient power as long as the specified timing and

voltage requirements are met (see the section titled “1-Wire Bus System”). The advantage of parasite

power is that the ROM may be read in absence of normal power, i.e., if the battery pack is completely

discharged.

DS2438 BLOCK DIAGRAM Figure 1

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.

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