RX
-
8581
SA
/
JE
/
NB
Page - 27
MQ372-02
10. Reference Data
[Finding the frequency stability]
1. Frequency and temperature characteristics can be
approximated using the following equations.
∆
f
T
=
α
(
θ
T
-
θ
X
)
2
∆
f
T
: Frequency deviation in any
temperature
α
(1
/
°
C
2
) : Coefficient of secondary temperature
(
−
0.035
±
0.005)
×
10
-6
/
°
C
2
θ
T
(
°
C)
: Ultimate temperature (+25
±
5
°
C)
θ
X
(
°
C)
: Any temperature
2. To determine overall clock accuracy, add the frequency
precision and voltage characteristics.
∆
f/f
=
∆
f/fo +
∆
f
T
+
∆
f
V
∆
f/f
: Clock accuracy (stable frequency) in any
temperature and voltage
∆
f/fo : Frequency precision
∆
f
T
: Frequency deviation in any temperature
∆
f
V
: 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
∆
f
T
×
10
-6
θ
T
= +25
°
C Typ.
α
= -0.035
×
10
-6
Typ.
(2) Example of frequency and voltage characteristics
- 3
2
Freque
ncy
∆
f
v
×
10
−
6
+ 3
0
3 4 5
Condition :
3 V as reference, Ta=+25
°
C
Supply Voltage V
DD
[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 [
µ
A]
Supply Voltage V
DD
[V]
1.0
0.5
3 4 5
Condition :
Ta = +25
°
C
f
SCL
= 0
Hz
FOE = GND,
/INT = V
DD
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 [
µ
A]
Condition :
Ta = +25
°
C
f
SCL
= 0
Hz
FOE, /INT = V
DD
FOUT ; 32.768 kHz output ON
Supply Voltage V
DD
[V]
CL=30 pF
