ISL12026_08 Datasheet, PDF (19/24 Pages) Intersil Corporation – Real Time Clock/Calendar with I2C Bus™ and EEPROM

ISL12026, ISL12026A
S
S
SIGNALS FROM
THE MASTER
T
A
SLAVE
R ADDRESS
T
WORD
ADDRESS 1
WORD
ADDRESS 0
T
A _SLAVE
R
T
ADDRESS
S
T
O
P
SDA BUS
SIGNALS FROM
THE SLAVE
1
1 11 0 0000000
A
A
C
C
K
K
1
A
C
K
1 1 11
A
C
K
DATA
FIGURE 21. RANDOM ADDRESS READ SEQUENCE
S
SIGNALS FROM
THE MASTER
SLAVE
ADDRESS
A
C
K
A
C
K
A
C
K
T
O
P
SDA BUS
SIGNALS FROM
THE SLAVE
1
A
C
DATA
K
(1)
DATA
(2)
DATA
(n-1)
DATA
(n)
(n is any integer greater than 1)
FIGURE 22. SEQUENTIAL READ SEQUENCE
Sequential Read
Sequential reads can be initiated as either a current address
read or random address read. The first data byte is
transmitted as with the other modes; however, the master
now responds with an acknowledge, indicating it requires
additional data. The device continues to output data for each
acknowledge received. The master terminates the read
operation by not responding with an acknowledge and then
issuing a stop condition.
The data output is sequential, with the data from address n
followed by the data from address n + 1. The address
counter for read operations increments through all page and
column addresses, allowing the entire memory contents to
be serially read during one operation. At the end of the
address space, the counter “rolls over” to the start of the
address space, and the ISL12026 continues to output data
for each acknowledge received. Refer to Figure 22 for the
acknowledge and data transfer sequence.
Application Section
Crystal Oscillator and Temperature Compensation
Intersil has now integrated the oscillator compensation
circuity on-chip, to eliminate the need for external
components and adjust for crystal drift over temperature and
enable very high accuracy time keeping (<5ppm drift).
The Intersil RTC family uses an oscillator circuit with on-chip
crystal compensation network, including adjustable
load-capacitance. The only external component required is
the crystal. The compensation network is optimized for
operation with certain crystal parameters which are common
in many of the surface mount or tuning-fork crystals available
today. Table 7 summarizes these parameters.
TABLE 7. CRYSTAL PARAMETERS REQUIRED FOR INTERSIL
RTCs
PARAMETER MIN TYP MAX UNITS
NOTES
Frequency
32.768
kHz
Frequency
Tolerance
±100 ppm Down to 20ppm
if desired
Turnover
Temperature
20 25 30 °C Typically the value
used for most
crystals
Operating Temp -40
Range
85 °C
Parallel Load
12.5
pF
Capacitance
Equivalent
Series
Resistance
50 kΩ For best oscillator
performance
Table 8 contains some crystal manufacturers and part numbers
that meet the requirements for the Intersil RTC products.
19
FN8231.8
October 28, 2008