MAX1660 Datasheet, PDF (9/20 Pages) Maxim Integrated Products – Digitally Controlled Fuel-Gauge Interface

Digitally Controlled
Fuel-Gauge Interface
Table 2. Read Word Commands
COMMAND
NAME
ReadCount01
ReadCount23
ReadStatus()
COMMAND
CODE
0x82
0x83
0x84
DESCRIPTION
Enables updating of the COUNT register; returns COUNT0 in the LSB and COUNT1 in the MSB of
the Read-Word protocol. COUNT updating remains enabled until the ReadCount23 command is
executed. See the Charge and Discharge Counters section.
Disables COUNT register updating; returns COUNT2 in the LSB and COUNT3 in the MSB of the
Read-Word protocol. See the Charge and Discharge Counters section.
Returns the status word’s contents in the Read-Word protocol’s LSB. The MSB’s contents are all 1s.
See Table 5 for a description of the status bits.
clocks in (Figure 4). COUNT0 returns in the least signifi-
cant byte (LSB), and COUNT1 returns in the most sig-
nificant byte (MSB) of the Read-Word protocol. After
the ReadCount01 command is executed (updating is
enabled), any command executed by the MAX1660
prior to execution of the ReadCount23 command
updates the COUNT contents, potentially corrupting the
data read by ReadCount23 (if a 16th-bit carry occurs).
ReadCount23 disables COUNT updating and then
returns COUNT2 and COUNT3 in the Read-Word proto-
col’s LSB and MSB. To ensure proper execution, issue
these commands in the correct order, with no com-
mands executed between them (ReadCount01 first, fol-
lowed by ReadCount23).
Digital Compare Function
The MAX1660’s digital compare function simplifies
implementation of end-of-charge and end-of-discharge
detection, relieving the host from having to constantly
monitor the counters. The host simply programs a value
into the COMP register, and the MAX1660 generates an
interrupt (INT goes low) when this condition is met.
Figure 5 shows the MAX1660’s digital compare section
functional diagram. When the digital compare function
is enabled, the MAX1660 continuously compares the
contents of the counter selected by the configuration
word’s SETCOUNT bit with the 32-bit word stored in the
COMP register (Table 1). The 32-bit COMP register is
divided into 4 bytes: COMP0 (the least significant)
through COMP3 (the most significant). When COMP is
equal to MUXOUT, the configuration word’s COMPSTA-
TUS bit is set, and the MAX1660 generates an interrupt
(INT goes low). The host defines any action taken as a
result of this interrupt. The COMP register contents
remain valid until either the host redefines the value
stored in COMP, or a power-on reset is executed.
Executing a power-on reset disables the digital com-
pare function. Enable the digital compare function by
setting the configuration word’s COMPENABLE bit.
ACKNOWLEDGE
BIT CLOCKED
INTO MASTER
COUNT
REGISTER
UPDATED
SCL
ANY
SDA ^COMMAND
BYTE
MAX1660
PULLING
SDA LOW
Figure 4. COUNT Register Updating
INT
CLRINT
POWER-ON RESET
OCSTATUS
ODSTATUS
Q
CLR
D
DIRCHANGE
COMPSTATUS
CHG _COULOMB
DIS ^COUNTER
32
COMP3 COMP2 COMP1 COMP0
DIGITAL
COMPARE
32
MUXOUT
8
8
8
8
SMB INTERFACE
DIRINTENABLE
Figure 5. Digital Compare Section Functional Diagram
*Patent pending
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