米6体育平台手机版

ZHCSCY4B November 2013 – October 2014

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机械数据 (封装 | 引脚)

DRZ|12
- MPDS289B

散热焊盘机械数据 (封装 | 引脚)

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9 Detailed Description

9.1 Overview

The fuel gauge accurately predicts the battery capacity and other operational characteristics of a single Li-based rechargeable cell. It can be interrogated by a system processor to provide cell information, such as state-of-charge (SoC).

NOTE

The following formatting conventions are used in this document:

Commands: italics with parenthesesSRP – SRN) and no breaking spaces, for example, ControlSRP – SRN).

Data Flash: italics, bold, and breaking spaces, for example, Design Capacity.

Register bits and flags: italics with brackets [ ], for example, [TDA]

Data flash bits: italics, bold, and brackets [ ], for example, [LED1]

Modes and states: ALL CAPITALS, for example, UNSEALED mode.

9.2 Functional Block Diagram

9.3 Feature Description

Information is accessed through a series of commands, called Standard Commands. Further capabilities are provided by the additional Extended Commands set. Both sets of commands, indicated by the general format CommandSRP – SRN), are used to read and write information contained within the control and status registers, as well as its data locations. Commands are sent from system to gauge using the I²C serial communications engine, and can be executed during application development, system manufacture, or end-equipment operation.

The key to the high-accuracy gas gauging prediction is Texas Instruments proprietary Impedance Track™ algorithm. This algorithm uses cell measurements, characteristics, and properties to create state-of-charge predictions that can achieve high accuracy across a wide variety of operating conditions and over the lifetime of the battery.

The fuel gauge measures the charging and discharging of the battery by monitoring the voltage across a small-value sense resistor. When a cell is attached to the fuel gauge, cell impedance is computed based on cell current, cell open-circuit voltage (OCV), and cell voltage under loading conditions.

The fuel gauge uses an integrated temperature sensor for estimating cell temperature. Alternatively, the host processor can provide temperature data for the fuel gauge.

More details are found in the bq27441-G1 Technical Reference Manual (SLUUAC9).

9.4 Device Functional Modes

To minimize power consumption, the fuel gauge has several power modes: INITIALIZATION, NORMAL, SLEEP, and HIBERNATE. The fuel gauge passes automatically between these modes, depending upon the occurrence of specific events, though a system processor can initiate some of these modes directly. More details are found in the bq27441-G1 Technical Reference Manual (SLUUAC9).

9.5 Programming

9.5.1 Standard Data Commands

The fuel gauge uses a series of 2-byte standard commands to enable system reading and writing of battery information. Each standard command has an associated command-code pair, as indicated in Table 1. Because each command consists of two bytes of data, two consecutive I²C transmissions must be executed both to initiate the command function, and to read or write the corresponding two bytes of data. Additional details are found in the bq27441-G1 Technical Reference Manual (SLUUAC9).

Table 1. Standard Commands

NAME		COMMAND CODE	UNIT	SEALED ACCESS
ControlSRP – SRN)	CNTL	0x00 and 0x01	NA	RW
TemperatureSRP – SRN)	TEMP	0x02 and 0x03	0.1°K	RW
VoltageSRP – SRN)	VOLT	0x04 and 0x05	mV	R
FlagsSRP – SRN)	FLAGS	0x06 and 0x07	NA	R
NominalAvailableCapacitySRP – SRN)		0x08 and 0x09	mAh	R
FullAvailableCapacitySRP – SRN)		0x0A and 0x0B	mAh	R
RemainingCapacitySRP – SRN)	RM	0x0C and 0x0D	mAh	R
FullChargeCapacitySRP – SRN)	FCC	0x0E and 0x0F	mAh	R
AverageCurrentSRP – SRN)		0x10 and 0x11	mA	R
StandbyCurrentSRP – SRN)		0x12 and 0x13	mA	R
MaxLoadCurrentSRP – SRN)		0x14 and 0x15	mA	R
AveragePowerSRP – SRN)		0x18 and 0x19	mW	R
StateOfChargeSRP – SRN)	SOC	0x1C and 0x1D	%	R
InternalTemperatureSRP – SRN)		0x1E and 0x1F	0.1°K	R
StateOfHealthSRP – SRN)	SOH	0x20 and 0x21	num / %	R
RemainingCapacityUnfilteredSRP – SRN)		0x28 and 0x29	mAh	R
RemainingCapacityFilteredSRP – SRN)		0x2A and 0x2B	mAh	R
FullChargeCapacityUnfilteredSRP – SRN)		0x2C and 0x2D	mAh	R
FullChargeCapacityFilteredSRP – SRN)		0x2E and 0x2F	mAh	R
StateOfChargeUnfilteredSRP – SRN)		0x30 and 0x31	%	R
TrueRemainingCapacitySRP – SRN)		0x6A and 0x6B	mAh	R

9.5.2 ControlSRP – SRN): 0x00 and 0x01

Issuing a ControlSRP – SRN) command requires a subsequent 2-byte subcommand. These additional bytes specify the particular control function desired. The ControlSRP – SRN) command allows the system to control specific features of the fuel gauge during normal operation and additional features when the device is in different access modes, as described in Table 2. Additional details are found in the bq27441-G1 Technical Reference Manual (SLUUAC9).

Table 2. ControlSRP – SRN) Subcommands

CNTL FUNCTION	CNTL DATA	SEALED ACCESS	DESCRIPTION
CONTROL_STATUS	0x0000	Yes	Reports the status of device.
FW_VERSION	0x0002	Yes	Reports the firmware version of the device.
DM_CODE	0x0004	Yes	Reports the Data Memory Code number stored in NVM.
PREV_MACWRITE	0x0007	Yes	Returns previous MAC command code.
CHEM_ID	0x0008	Yes	Reports the chemical identifier of the battery profile used by the fuel gauge.
BAT_INSERT	0x000C	Yes	Forces the Flags() [BAT_DET] bit set when the OpConfig [BIE] bit is 0.
BAT_REMOVE	0x000D	Yes	Forces the Flags() [BAT_DET] bit clear when the OpConfig [BIE] bit is 0.
SET_HIBERNATE	0x0011	Yes	Forces CONTROL_STATUS [HIBERNATE] to 1.
CLEAR_HIBERNATE	0x0012	Yes	Forces CONTROL_STATUS [HIBERNATE] to 0.
SET_CFGUPDATE	0x0013	No	Force CONTROL_STATUS [CFGUPMODE] to 1 and gauge enters CONFIG UPDATE mode.
SHUTDOWN_ENABLE	0x001B	No	Enables device SHUTDOWN mode.
SHUTDOWN	0x001C	No	Commands the device to enter SHUTDOWN mode.
SEALED	0x0020	No	Places the device in SEALED access mode.
TOGGLE_GPOUT	0x0023	Yes	Commands the device to toggle the GPOUT pin for 1 ms.
RESET	0x0041	No	Performs a full device reset.
SOFT_RESET	0x0042	No	Gauge exits CONFIG UPDATE mode.
EXIT_CFGUPDATE	0x0043	No	Exits CONFIG UPDATE mode without an OCV measurement and without resimulating to update StateOfChargeSRP – SRN).
EXIT_RESIM	0x0044	No	Exits CONFIG UPDATE mode without an OCV measurement and resimulates with updated configuration data to update StateOfChargeSRP – SRN).

9.5.3 Extended Data Commands

Extended data commands offer additional functionality beyond the standard set of commands. They are used in the same manner; however, unlike standard commands, extended commands are not limited to 2-byte words. The number of command bytes for a given extended command ranges in size from single to multiple bytes, as specified in Table 3.

Table 3. Extended Commands

NAME	COMMAND CODE	UNIT	SEALED ACCESS⁽¹⁾⁽²⁾	UNSEALED ACCESS⁽¹⁾⁽²⁾
OpConfigSRP – SRN)	0x3A and 0x3B	NA	R	R
DesignCapacitySRP – SRN)	0x3C and 0x3D	mAh	R	R
DataClassSRP – SRN)⁽²⁾	0x3E	NA	NA	RW
DataBlockSRP – SRN)⁽²⁾	0x3F	NA	RW	RW
BlockDataSRP – SRN)	0x40 through 0x5F	NA	R	RW
BlockDataCheckSumSRP – SRN)	0x60	NA	RW	RW
BlockDataControlSRP – SRN)	0x61	NA	NA	RW
Reserved	0x62 through 0x7F	NA	R	R

(1) SEALED and UNSEALED states are entered via commands to ControlSRP – SRN) 0x00 and 0x01.

(2) In SEALED mode, data cannot be accessed through commands 0x3E and 0x3F.

9.5.4 Communications

9.5.4.1 I²C Interface

The fuel gauge supports the standard I²C read, incremental read, quick read, one-byte write, and incremental write functions. The 7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as 1010101. The first 8 bits of the I²C protocol are, therefore, 0xAA or 0xAB for write or read, respectively.

The quick read returns data at the address indicated by the address pointer. The address pointer, a register internal to the I²C communication engine, increments whenever data is acknowledged by the fuel gauge or the I²C master. “Quick writes” function in the same manner and are a convenient means of sending multiple bytes to consecutive command locations (such as two-byte commands that require two bytes of data).

The following command sequences are not supported:

Attempt to write a read-only address (NACK after data sent by master):

Attempt to read an address above 0x6B (NACK command):

9.5.4.2 I²C Time Out

The I²C engine releases both SDA and SCL if the I²C bus is held low for 2 seconds. If the fuel gauge is holding the lines, releasing them frees them for the master to drive the lines. If an external condition is holding either of the lines low, the I²C engine enters the low-power SLEEP mode.

9.5.4.3 I²C Command Waiting Time

To ensure proper operation at 400 kHz, a t_(BUF) ≥ 66 μs bus-free waiting time must be inserted between all packets addressed to the fuel gauge. In addition, if the SCL clock frequency (f_SCL) is > 100 kHz, use individual 1-byte write commands for proper data flow control. The following diagram shows the standard waiting time required between issuing the control subcommand the reading the status result. For read-write standard command, a minimum of 2 seconds is required to get the result updated. For read-only standard commands, there is no waiting time required, but the host must not issue any standard command more than two times per second. Otherwise, the gauge could result in a reset issue due to the expiration of the watchdog timer.

9.5.4.4 I²C Clock Stretching

A clock stretch can occur during all modes of fuel gauge operation. In SLEEP and HIBERNATE modes, a short ≤ 100-µs clock stretch occurs on all I²C traffic as the device must wake-up to process the packet. In the other modes (INITIALIZATION, NORMAL), a ≤ 4-ms clock stretching period may occur within packets addressed for the fuel gauge as the I²C interface performs normal data flow control.