LTC2943
9
2943fa
For more information www.linear.com/LTC2943
Internal Registers
The LTC2943 register map is shown in Table 1. The
LTC2943 integrates current through a sense resistor,
measures battery voltage, current and temperature and
stores the results in internal 16-bit registers accessible
via I
2
C. High and low limits can be programmed for each
measured quantity. The LTC2943 continuously monitors
these limits and sets a flag in the status register when a
limit is exceeded. If the alert mode is enabled, the ALCC
pin pulls low.
Table 1. Register Map
ADDRESS NAME REGISTER DESCRIPTION R/W DEFAULT
00h A Status R See Table 2
01h B Control R/W 3Ch
02h C Accumulated Charge MSB R/W 7Fh
03h D Accumulated Charge LSB R/W FFh
04h E Charge Threshold High MSB R/W FFh
05h F Charge Threshold High LSB R/W FFh
06h G Charge Threshold Low MSB R/W 00h
07h H Charge Threshold Low LSB R/W 00h
08h I Voltage MSB R 00h
09h J Voltage LSB R 00h
0Ah K Voltage Threshold High MSB R/W FFh
0Bh L Voltage Threshold High LSB R/W FFh
0Ch M Voltage Threshold Low MSB R/W 00h
0Dh N Voltage Threshold Low LSB R/W 00h
0Eh O Current MSB R 00h
0Fh P Current LSB R 00h
10h Q Current Threshold High MSB R/W FFh
11h R Current Threshold High LSB R/W FFh
12h S Current Threshold Low MSB R/W 00h
13h T Current Threshold Low LSB R/W 00h
14h U Temperature MSB R 00h
15h V Temperature LSB R 00h
16h W Temperature Threshold High R/W FFh
17h X Temperature Threshold Low R/W 00h
R = Read, W = Write
APPLICATIONS INFORMATION
The status of the charge, voltage, current and temperature
alerts is reported in the status register shown in Table 2.
Table 2. Status Register (A)
BIT NAME OPERATION DEFAULT
A[7] Reserved
A[6] Current Alert
Indicates one of the current
limits was exceeded
0
A[5]
Accumulated
Charge
Overflow/
Underflow
Indicates that the value of the
ACR hit either top or bottom
0
A[4]
Temperature
Alert
Indicates one of the
temperature limits was
exceeded
0
A[3]
Charge Alert
High
Indicates that the ACR value
exceeded the charge threshold
high limit
0
A[2]
Charge Alert
Low
Indicates that the ACR value
exceeded the charge threshold
low limit
0
A[1] Voltage Alert
Indicates one of the voltage
limits was exceeded
0
A[0]
Undervoltage
Lockout Alert
Indicates recovery from
undervoltage. If set to 1, a
UVLO has occurred and the
contents of the registers are
uncertain
1
After each voltage, current or temperature conversion, the
conversion result is compared to the respective threshold
registers. If a value in the threshold registers is exceeded,
the corresponding bit A[6], A[4] or A[1] is set.
The accumulated charge register (ACR) is compared to
the charge thresholds every time the analog integrator
increments or decrements the prescaler. If the ACR value
exceeds the threshold register values, the corresponding
bit A[3] or A[2] are set. Bit A[5] is set if the accumulated
charge registers (ACR) overflows or underflows. At each
overflow or underflow, the ACR rolls over and resumes
integration.
The
undervoltage lockout (UVLO) bit of the status register
A[0] is set if, during operation, the voltage on the SENSE
+
pin drops below 3.5V without reaching the POR level. The
analog parts of the coulomb counter are switched off while
the digital register values are retained. After recovery of the
supply voltage the coulomb counter resumes integrating
with the stored value in the accumulated charge registers
but it has missed any charge flowing while SENSE
+
< 3.5V.
