RX - 8581 SA / JE / NB
Page - 27
ETM13E-02
10. Reference Data
[Finding the frequency stability]
1. Frequency and temperature characteristics can be
approximated using the following equations.
fT = α (θT - θX)2
fT
: Frequency deviation in any
temperature
α
(1 /
°C2) : Coefficient of secondary temperature
(
0.035±0.005) × 10-6 / °C2
θT (°C)
: Ultimate temperature (+25
±5 °C)
θX (°C)
: Any temperature
2. To determine overall clock accuracy, add the frequency
precision and voltage characteristics.
f/f = f/fo + fT + fV
f/f
: Clock accuracy (stable frequency) in any
temperature and voltage
f/fo : Frequency precision
fT
: Frequency deviation in any temperature
fV
: Frequency deviation in any voltage
3. How to find the date difference
Date difference =
f/f × 86400 (seconds)
* For example:
f/f = 11.574 × 10-6 is an error of
approximately 1 second/day.
(1) Example of frequency and temperature characteristics
-150
-100
-50
0
-50
0
+50
+100
Temperature [
°C]
F
re
que
nc
y
fT
× 10-6
θT = +25 °C Typ.
α = -0.035 × 10-6 Typ.
(2) Example of frequency and voltage characteristics
- 3
2
Freque
n
cy
fv
×10
6
+ 3
0
3
4
5
Condition :
3 V as reference, Ta=+25
°C
Supply Voltage VDD[V]
(3) Current and voltage consumption characteristics
(3-1) Current consumption when non-accessed (i)
when FOUT=OFF
2
Cu
rre
nt
c
ons
um
p
ti
o
n
[
A]
Supply Voltage VDD[V]
1.0
0.5
3
4
5
Condition :
Ta = +25
°C
fSCL = 0 Hz
FOE = GND, /INT = VDD
FOUT ; Output OFF
(3-2) Current consumption when non-accessed (ii)
when FOUT=32.768 kHz
2
10
5
3
4
5
CL=0 pF
Cu
rre
nt
c
ons
um
p
ti
o
n
[
A]
Condition :
Ta = +25
°C
fSCL = 0 Hz
FOE, /INT = VDD
FOUT ; 32.768 kHz output ON
Supply Voltage VDD[V]
CL=30 pF