BQ27546-G1 Datasheet, PDF (13/38 Pages) Texas Instruments – nullSingle-Cell Li-Ion Battery Fuel Gauge

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bq27546-G1
SLUSC53A – MAY 2015 – REVISED DECEMBER 2015
HDQ serial communication is normally initiated by the host processor sending a break command to the bq27546-
G1 device. A break is detected when the DATA pin is driven to a logic-low state for a time t_(B) or greater. The
DATA pin should then be returned to its normal ready high logic state for a time t_(BR). The bq27546-G1 fuel
gauge is now ready to receive information from the host processor.
The bq27546-G1 device is shipped in I²C mode. TI provides tools to enable the HDQ peripheral. The HDQ
Communication Basics Application Report (SLUA408A) provides details of HDQ communication.
9.3.5.6 HDQ Host Interruption Feature
The default bq27546-G1 gauge behaves as an HDQ slave-only device when HDQ mode is enabled. If the HDQ
interrupt function is enabled, the bq27546-G1 is capable of mastering and also communicating to an HDQ
device. There is no mechanism for negotiating what is to function as the HDQ master and care must be taken to
avoid message collisions. The interrupt is signaled to the host processor with the bq27546-G1 mastering an HDQ
message. This message is a fixed message that will be used to signal the interrupt condition. The message itself
is 0x80 (slave write to register 0x00) with no data byte being sent as the command, and is not intended to
convey any status of the interrupt condition. The HDQ interrupt function is disabled by default and needs to be
enabled by command.
When the SET_HDQINTEN subcommand is received, the bq27546-G1 device detects any of the interrupt
conditions and asserts the interrupt at 1-s intervals until the CLEAR_HDQINTEN command is received or the
count of HDQHostIntrTries has lapsed.
The number of tries for interrupting the host is determined by the data flash parameter named
HDQHostIntrTries.
9.3.5.6.1 Low Battery Capacity
This feature works identically to SOC1. It uses the same data flash entries as SOC1 and triggers interrupts as
long as SOC1 = 1 and HDQIntEN = 1.
9.3.5.6.2 Temperature
This feature triggers an interrupt based on the OTC (Overtemperature in Charge) or OTD (Overtemperature in
Discharge) condition being met. It uses the same data flash entries as OTC or OTD and triggers interrupts as
long as either the OTD or OTC condition is met and HDQIntEN = 1.
9.3.5.7 I²C Interface
The fuel gauge supports the standard I²C read, incremental read, one-byte write quick read, and functions. The
7-bit device address (ADDR) is the most significant 7 bits of the hex address and is fixed as 1010101. The 8-bit
device address is therefore 0xAA or 0xAB for a write or read, respectively.
Host Generated
Fuel Gauge Generated
S ADDR[6:0] 0 A
CMD[7:0]
(a)
A DATA[7:0]
AP
S ADDR[6:0] 1 A DATA[7:0] N P
(b)
S ADDR[6:0] 0 A CMD[7:0]
A Sr ADDR[6:0]
(c)
1A
DATA[7:0]
NP
S ADDR[6:0] 0 A CMD[7:0]
A Sr
ADDR[6:0]
(d)
1A
DATA[7:0]
A . . . DATA[7:0] N P
Figure 7. Supported I²C formats: (a) 1-byte write, (b) quick read, (c) 1 byte-read, and (d) incremental read
(S = Start, Sr = Repeated Start, A = Acknowledge, N = No Acknowledge, and P = Stop).
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 bq27546-G1 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).
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