LTC2942-1C View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
LTC2942-1C
Linear Technology
'LTC2942-1C' PDF : 16 Pages View PDF
LTC2942-1
Applications Information
I2C/SMBus Interface
The LTC2942-1 communicates with a bus master using a
2-wire interface compatible with I2C and SMBus. The 7-bit
hard-coded I2C address of the LTC2942-1 is 1100100.
The LTC2942-1 is a slave-only device. Therefore the serial
clock line (SCL) is an input only while the serial data line
(SDA) is bidirectional. The device supports I2C standard
and fast mode. For more details refer to the I2C Protocol
section.
Internal Registers
The LTC2942-1 integrates current through a sense resistor,
measures battery voltage and temperature and stores the
results in internal 16-bit registers accessible via I2C. High
and low limits can be programmed for each measurement
quantity. The LTC2942-1 continuously monitors these
limits and sets a corresponding flag in its status register
when a limit is exceeded. If the alert mode is enabled, the
AL/CC pin pulls low.
The sixteen internal registers are organized as shown in
Table 1.
Table 1. Register Map
ADDRESS NAME REGISTER DESCRIPTION
00h
A Status
01h
B Control
02h
C Accumulated Charge MSB
03h
D Accumulated Charge LSB
04h
E Charge Threshold High MSB
05h
F Charge Threshold High LSB
06h
G Charge Threshold Low MSB
07h
H Charge Threshold Low LSB
08h
I Voltage MSB
09h
J Voltage LSB
0Ah
K Voltage Threshold High
0Bh
L Voltage Threshold Low
0Ch
M Temperature MSB
0Dh
N Temperature LSB
0Eh
O Temperature Threshold High
0Fh
P Temperature Threshold Low
R = Read, W = Write, XX = unknown
R/W DEFAULT
R See Below
R/W 3Ch
R/W 7Fh
R/W FFh
R/W FFh
R/W FFh
R/W 00h
R/W 00h
R
XXh
R
XXh
R/W FFh
R/W 00h
R
XXh
R
XXh
R/W FFh
R/W 00h
Status Register (A)
The status of the charge, voltage and temperature alerts
is reported in the status register shown in Table 2.
Table 2. Status Register A (Read only)
BIT NAME
OPERATION
DEFAULT
A[7] Chip Identification 0: LTC2942-1
0
1: LTC2941-1
A[6] Reserved
Not Used.
0
A[5] Accumulated Charge Indicates that the value of the
0
Overflow/Underflow accumulated charge hit either
top or bottom.
A[4] Temperature Alert Indicates one of the
0
temperature limits was
exceeded.
A[3] Charge Alert High Indicates that the accumulated 0
charge value exceeded the
charge threshold high limit.
A[2] Charge Alert Low Indicates that the accumulated 0
charge value dropped below
the charge threshold low limit.
A[1] Voltage Alert
Indicates one of the battery
0
voltage limits was exceeded.
A[0] Undervoltage
Indicates recovery from
X
Lockout Alert
undervoltage. If set to 1, a
UVLO has occurred and the
content of the registers is
uncertain.
All status register bits except A[7] are cleared after being
read by the host, if the conditions which set these bits
have been removed.
As soon as one of the three measured quantities exceeds
the programmed limits, the corresponding bit A[4], A[3],
A[2] or A[1] in the status register is set.
Bit A[5] is set if the LTC2942-1’s accumulated charge
registers (ACR) overflows or underflows. In these cases,
the ACR stays at FFFFh or 0000h and does not roll over.
The undervoltage lockout (UVLO) bit of the status register
A[0] is set if, during operation, the voltage on SENSE+
pin drops below 2.7V without reaching the POR level.
The analog parts of the coulomb counter are switched off
while the digital register values are retained. After recov-
ery 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+ < 2.7V.
29421f
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