DS2436Z Datasheet DS2436Z, DS2436B+ | P10-P12

DS2436

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MEMORY

The DS2436’s memory is divided into five pages, each page filling 32 bytes of address space. Not all of

the available addresses are used, however. Refer to the memory map of Figure 3 to see actual addresses

which are available.

The first three pages of memory consist of a scratchpad RAM and either EEPROM (pages 1 and 2) or

SRAM (page 3). The scratchpads help insure data integrity when communicating over the 1-Wire bus.

Data is first written to the scratchpad where it can be read back. After the data has been verified, a copy

scratchpad command will transfer the data to the EEPROM or SRAM. This process insures data integrity

when modifying the memory.

The fourth page of memory consists of registers which contain the Temperature, Voltage, and Status

registers. These registers are made from SRAM cells, except for the lock bit in the status register which is

implemented in EEPROM.

The fifth page of memory holds the Manufacturer ID, implemented in laser ROM, and the Cycle Counter,

implemented in EEPROM.

PAGE 1

The first page of memory has 24 bytes. It consists of scratchpad RAM and nonvolatile EEPROM

memory. These 24 bytes may be used to store any data, such as: battery chemistry descriptors,

manufacturing lot codes, etc.

This page may be locked to prevent data stored here from being changed inadvertently.

The nonvolatile and the scratchpad portions of this page are organized identically, as shown in Figure 3.

In this page, these two portions are referred to as NV1 and SP1, respectively.

PAGE 2

The second page of memory has 8 bytes. It consists of a scratchpad RAM and a nonvolatile EEPROM

memory. These 8 bytes may be used to store additional data. In contrast to Page 1 memory, the Lock

function is not available for Page 2.

PAGE 3

The third page of memory has 8 bytes. It consists of a scratchpad RAM and an SRAM memory. This

address space may be used to store additional data, provided that, should the battery discharge completely

and power to the DS2436 is lost, this data may also be lost without serious repercussions. Data which

must remain even if power to the DS2436 is lost should be placed in either Page 1 or Page 2.

Prefer this section of memory to store fuel gauge and self discharge information. If the battery dies and

this information is lost, no serious consequences will result since the user can easily determine that the

battery is dead.

PAGE 4

The fourth page of memory is used by the DS2436 to store the battery temperature and voltage. A 2-byte

Status Register informs of conversion progress and memory lock state.

DS2436

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TEMPERATURE REGISTERS (60h-61h)

The DS2436 can measure temperature without external components. The resulting temperature

measurement is placed in a two-byte Temperature Register. This register is implemented in SRAM, and

therefore will hold data until the battery voltage falls below minimum V

The temperature reading is provided in a 13-bit, two’s complement format, with 0.03125°C resolution.

Table 1 describes the exact relationship of output data to measured temperature. The data is transmitted

serially over the 1-Wire interface. The DS2436 can measure temperature over the range of -40°C to

+85°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 DS2436 in terms of a 0.03125°C LSB, yielding the following

13-bit format:

MSB LSB

S 2

-1

-2

-3

-4

-5

0 0 0

Unit =1°C

The MSB of the Temperature Register contains the integer portion of the temperature valve.

TEMPERATURE/DATA RELATIONSHIPS Table 1

TEMPERATURE DIGITAL OUTPUT (Binary) DIGITAL OUTPUT (Hex)

+125 °C

01111101 00000000 7B00

+25.0625°C

00011001 00010000 1910

+1/2°C

00000000 10000000 0080

0°C

00000000 00000000 0000

-1/2°C

11111111 10000000 FF80

-25.0625°C

11100110 11110000 E6F0

-55°C

11001001 00000000 C900

DS2436

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STATUS REGISTER (62h-63h)

The Status Register is a two-byte read only register at addresses 62h and 63h. Address 62h is the least

significant byte of the Status Register and is currently the only address with defined status bits; the other

byte at address 63h is reserved for future use. The Status Register is formatted as follows:

MSB LSB

0 0 0 0 ADB LOCK NVB TB 62h

1 1 1 1 1 1 1 1 63h

where

TB = Temperature Busy flag. “1” = temperature conversion in progress; “0” = temperature

conversion complete, valid data in temperature register.

NVB = Nonvolatile memory busy flag. “1” = Copy from scratchpad to EEPROM in progress, “0”

= nonvolatile memory is not busy. A copy to EEPROM may take from 2 ms to 10 ms

(taking longer at lower supply voltages).

LOCK = “1” indicates that NV1 is locked; “0” indicates that NV1 is unlocked. This status bit is

implemented in EEPROM in order to preserve its state even when the battery is

completely discharged.

ADB = A/D converter busy flag. “1” = analog-to-digital conversion in progress on battery voltage;

“0” = conversion complete, no measurement being made. An A/D conversion takes

approximately 10 ms.

VOLTAGE REGISTER (77h-78h)

The onboard analog-to-digital converter (ADC) has 10 bits of resolution and will perform a conversion

when the DS2436 receives the command protocol (Convert V) [B4h]. The result of this measurement is

placed in the 2-byte Voltage Register (see Memory Map). The range for the DS2436 ADC is 0V to 10V;

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 10.24V, resulting in a resolution of 10 mV.

While the ADC has a range that extends to 0V, it is important to note that the battery voltage is also the

supply voltage to the DS2436. As such, the accuracy of the ADC begins to degrade below battery

voltages of 2.4 volts, and the ability to make conversions is limited by the operating voltage range of the

DS2436.

Voltage is expressed in this register in straight binary format, as outlined in Table 2. Note that while

codes exits for values below 2.4 volts, accuracy of the ADC and the limitation on the DS2436’s supply

voltage make it unlikely that these values would be used in actual practice.

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DS2436Z

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DS2436Z

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