DS2756E+ Datasheet DS2756E+ | P16-P18

DS2756: High-Accuracy Battery Fuel Gauge with Programmable Suspend Mode

MEMORY

The DS2756 has a 256-byte linear address space with registers for instrumentation, status, and control in the lower

32 bytes, with lockable EEPROM and SRAM memory occupying portions of the remaining address space. All

EEPROM and SRAM memory is general-purpose except addresses 31h, 33h, 34h and 35h, which should be

written with the default values for the Status Register, Accumulation Bias Register, Charge Suspend Threshold and

Discharge Suspend Threshold, respectively. If the Suspend interrupt is not used, addresses 34h and 35h can be

used as general-purpose EEPROM. When the MSB of any two-byte register is read, the MSB and LSB values are

latched and held for the duration of the Read Data command. This prevents updates during the read to ensure

synchronization between the two register bytes. For consistent results, always read the MSB and the LSB of a two-

byte register during the same Read Data command sequence. In describing register control and status bits, the

terms set and clear refer to internal operations which manipulate bit values. The terms read and write refer to 1-

Wire access to the bit values. Several bits are set internally but require the host system to write them to a 0 value.

EEPROM memory is shadowed by RAM to eliminate programming delays between writes and to allow the data to

be verified by the host system before being copied to EEPROM. The Read Data and Write Data protocols to/from

EEPROM memory addresses access the shadow RAM. The Recall Data function command transfers data from the

EEPROM to the shadow RAM. The Copy Data function command transfers data from the shadow RAM to the

EEPROM and requires t

EEC

to complete programming of the EEPROM cells. In unlocked EEPROM blocks, writing

data updates shadow RAM. In locked EEPROM blocks, the Write Data command is ignored. The Copy Data

function command copies the contents of shadow RAM to EEPROM in an unlocked block of EEPROM but has no

effect on locked blocks. The Recall Data function command copies the contents of a block of EEPROM to shadow

RAM regardless of whether the block is locked or not.

Figure 14. EEPROM Access via Shadow RAM

Serial

Interface

Write

Read

Shadow RAM

EEPROM

Copy

Recall

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DS2756: High-Accuracy Battery Fuel Gauge with Programmable Suspend Mode

Table 2. Memory Map

ADDRESS (HEX) DESCRIPTION READ/WRITE

00 Reserved

01 Status Register R

02 to 06 Reserved

07 EEPROM Register R/W

08 Special Feature Register R/W

09 to 0B Reserved

0C Voltage Register MSB R

0D Voltage Register LSB R

0E Current Register MSB R

0F Current Register LSB R

10 Accumulated Current Register MSB R/W

11 Accumulated Current Register LSB R/W

12 to 17 Reserved

18 Temperature Register MSB R

19 Temperature Register LSB R

1A Average Current Register MSB R

1B Average Current Register LSB R

1C to 1F Reserved

20 to 3F EEPROM, block 0 R/W*

40 to 5F EEPROM, block 1 R/W*

60 to 7F EEPROM, block 2 R/W*

80 to 8F SRAM R/W

90 to FF Reserved

*Each EEPROM block is read/write until locked by the LOCK command, after which it is read-only.

STATUS REGISTER

The default values for the Status Register bits are stored in lockable EEPROM in the corresponding bits of address

31h. A Recall Data command for EEPROM block 1 recalls the default values into the Status Register bits. The

format of the Status Register is shown in Figure 15. The function of each bit is described in detail in the following

paragraphs. Note that all bits are Read Only.

Figure 15. STATUS REGISTER FORMAT

Address 01h

bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

PIE1 PIE0 PMOD RNAOP UVEN IOS OBEN OVD

PIE1, PIE0—Programmable Suspend Interrupt Enable. A non zero value in these bits enables the DS2756 to enter

Suspend mode, and sets the Suspend Period (t

SUS

) for the low power oscillator timeout. A value of 00b disables the

DS2756 from entering Suspend mode and allows the DS2756 to enter Sleep mode.

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DS2756: High-Accuracy Battery Fuel Gauge with Programmable Suspend Mode

Table 3. SUMMARY OF SUSPEND MODES

PIE1 PIE0

SAMPLE RATE WHILE IN

SUSPEND MODE

AVERAGE IDD WHILE IN SUSPEND MODE

0 0 Suspend mode disabled Suspend mode disabled

0 1 2.0Hz

(500ms × I

SUSPEND

) + (90ms × I

ACTIVE

)

590ms

1 0 1.0Hz

(1000ms × I

SUSPEND

) + (90ms × I

ACTIVE

)

1090ms

1 1 0.5Hz

(2000ms × I

SUSPEND

) + (90ms × I

ACTIVE

)

2090ms

The desired default value should be set in bit 6 and bit 7 of address 31h. The factory default is 00b.

PMOD—Power Mode Enable. A value of 1 in this bit enables the DS2756 to enter Sleep mode or Suspend mode.

A value of 0 disables the DS2756 from entering the Sleep or Suspend mode. When PMOD is 0, only Active mode

operation is allowed. The desired default value must be set in bit 5 of address 31h. The factory default is 0.

RNAOP—Read Net Address Opcode. A value of 0 in this bit sets the opcode for the Read Net Address command

to 33h, while a 1 sets the opcode to 39h. This bit is read-only. The desired default value should be set in bit 4 of

address 31h. The factory default is 0.

UVEN—Undervoltage Sleep Enable. A value of 1 in UVEN along with a value of 1 in PMOD enables the DS2756 to

enter Sleep mode when the voltage on V

drops below undervoltage threshold V

for t

UVD

(cell depletion). A value

of 0 disables the DS2756 from entering the Sleep mode due to undervoltage events. The desired default value

must be set in bit 3 of address 31h. The factory default is 0.

IOS—Interrupt output select. IOS set to a 1 selects the DQ alarm interrupt signaling method for the Alarm

Comparator interrupt. IOS cleared to 0 selects the PIO alarm interrupt signaling method. The IE bit must be set and

PIE bits cleared to signal an Alarm Comparator interrupt using either method. The desired default value must be

set in bit 2 of address 31h. The factory default is 0.

OBEN—Offset Blanking Enable. A value of 1 in this bit location enables the offset blanking function described in

the Current Accumulation section. If set to 0, the offset blanking function is disabled. The desired default value

must be set in bit 1 of address 31h. The factory default is 0.

OVD—Overdrive Timing Enable. A value of 1 in this bit location enables the Overdrive 1-Wire timings. If set to 0,

the Regular mode timings are enabled. The desired bit value must be written to bit 1 of address 31h, (an EEPROM

block 0 location), then recalled before any change to the 1-Wire speed becomes effective. A power-on reset forces

a recall of settings from EEPROM block 0. The factory default in bit 1 of address 31h is 0 (Standard 1-Wire timing).

X—Reserved Bits.

EEPROM REGISTER

The format of the EEPROM Register is shown in Figure 16. The function of each bit is described in detail in the

following paragraphs.

Figure 16. EEPROM Register Format

Address 07h

bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0

EEC LOCK X X X BL2 BL1 BL0

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P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24 P25-P27

DS2756E+

Mfr. #:

Buy DS2756E+

Manufacturer:

Maxim Integrated

Description:

Battery Management High-Accuracy Bat Fuel Gauge

Lifecycle:

New from this manufacturer.

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DS2756E+