BQ26150 Datasheet, PDF (12/16 Pages) Texas Instruments – BATTERY PACK SECURITY AND AUTHENTICATION IC FOR PORTABLE APPLICATIONS (bqSECURE)

bq26150
SLUS641A – JANUARY 2005 – REVISED JULY 2005
www.ti.com
A system using the bq26150 and a bq26200 or bq26220 communicates to the monitor during normal usage. This
means that the continuous pass-through mode is used. To put the bq262x0 to sleep, the host should exit
continuous pass through mode and put the bq26150 in one-time-pass-through mode. The host can then
communicate to the bq262x0 to issue the sleep command and communication control reverts to the bq26150.
The HDQP is not disturbed, allowing the bq262x0 to enter the low power mode. To wake the bq262x0, the
bq26150 can be put in either continuous or one-time-pass-through mode and a break can be issued from the
host.
Communicating With bq26150
The bq26150 includes a single-wire HDQ serial data interface. Host processors, configured for either polled or
interrupt processing, can use the interface to access various bq26150 registers. The HDQ pin is an open drain
device, which requires an external pull-up or pull-down resistor. The interface uses a command-based protocol,
where the host processor sends a command byte to the bq26150. The command directs the bq26150 either to
store the next eight bits of data received to a register specified by the command byte, or to output the eight bits
of data from a register specified by the command byte.
The communication protocol is asynchronous return-to-one and is referenced to V_SS. Command and data bytes
consist of a stream of eight bits that have a maximum transmission rate of 5 Kbits/s. The least-significant bit of a
command or data byte is transmitted first. Data input from the bq26150 may be sampled using the pulse-width
capture timers available on some microcontrollers. A UART can also be configured to communicate with the
bq26150.
If a communication time-out occurs, for example, if the host waits longer than t_(RSPS) for the bq26150 to respond
or if this is the first access command, then a BREAK should be sent by the host. The host may then re-send the
command. The bq26150 detects a BREAK when the HDQ pin is driven to a logic-low state for a time t_(B) or
greater. The bq26150 is ready for a command from the host processor t_(BR) seconds after the HDQ line is
released from the break.
The return-to-one data-bit frame consists of three distinct sections:
1. The first section starts the transmission by either the host or the bq26150 taking the HDQ pin to a logic-low
state for a period equal to t_(HW1) or t_(DW1).
2. The next section is the actual data transmission, where the data should be valid for t_(HW0)–t_(HW1) or
t_(DW0)–t_(DW1).
3. The final section stops the transmission by returning the HDQ pin to a logic-high state and holding it high
until the time from bit start to bit end is equal to t_(CYCH) or t_(CYCD).
The HDQ line may remain high for an indefinite period of time between each bit of address or between each bit
of data on a write cycle. After the last bit of address is sent on a read cycle, the bq26150 starts outputting the
data after t_(RSPS) with timing as specified. The serial communication timing specification and illustration sections
give the timings for data and break communication. Communication with the bq26150 always occurs with the
least-significant bit being transmitted first.
Plugging in the battery pack may be seen as the start of a communication due to contact bounce. It is
recommended that each communication or string of communications be proceeded by a break to reset the
bq26150s HDQ engine.
Command Byte
The Command byte of the bq26150 consists of eight contiguous valid command bits. The command byte
contains two fields: W/R Command and address. The Command byte values are shown in the following table:
7
6
5
4
3
2
1
0
W/R
AD6
AD5
AD4
AD3
AD2
AD1
AD0
W/R
Indicates whether the Command bytes is a read or write command. A 1 indicates a write command
and that the following eight bits should be written to the register specified by the address field of the
Command byte, while a 0 indicates that the command is a read. On a read command, the bq26150
outputs the requested register contents specified by the address field portion of the Command byte.
AD6–AD0 The seven bits labeled AD6–AD0 containing the address portion of the register to be accessed.
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