Philips Semiconductors
Product specification
Low power clock/calendar
PCF8593
Procedure:
14 APPLICATION INFORMATION
14.1 Quartz frequency adjustment
14.1.1 METHOD 1: FIXED OSCI CAPACITOR
• Power-on
• Apply RESET
• Initialization (alarm functions).
Routine:
By evaluating the average capacitance necessary for the
application layout a fixed capacitor can be used. The
frequency is best measured via the 1 Hz signal which can
be programmed to occur at the interrupt output (pin 7). The
frequency tolerance depends on the quartz crystal
tolerance, the capacitor tolerance and the
device-to-device tolerance (on average ±5 × 10−6).
Average deviations of ±5 minutes per year can be
achieved.
• Set clock to time T and set alarm to time T + ∆T
• At time T + ∆T (interrupt) repeat routine.
14.1.3 METHOD 3: DIRECT OUTPUT
Direct measurement of oscillator output (accounting for
test probe capacitance).
14.1.2 METHOD 2: OSCI TRIMMER
Using the alarm function (via the I2C-bus) a signal faster
than 1 Hz can be generated at the interrupt output for fast
setting of a trimmer.
V
handbook, full pagewidth
RESET
DD
SDA
SCL
MASTER
TRANSMITTER/
RECEIVER
(1)
1 F
RESET
SCL
CLOCK CALENDAR
PCF8593
OSCI
V
DD
SDA
OSCO
V
SS
R
R
R: pull-up resistor
t
r
R =
C
BUS
MBD825
SDA SCL
2
(I C-bus)
(1) Example Philips DLC 196 Double-Layer Capacitor family.
Fig.23 Application diagram.
1997 Mar 25
23
NXP [ NXP ]
