
Page 8
July 1999 TOKO, Inc.
TK11052
(6)
where I
SH
= 1.35
μ
A, T
C
= 6.1 mV and V
REF
= 1.597 V
Rb is calculated by Equations (3) and (6)
(7)
Example:
R
a
and R
b
when set temperature is 85
°
C and temperature
hysteresis is 5
°
C.
= 35.69 k
≈
36 k
= 61.57 k
≈
62 k
2. For Set Temperatures < 25
°
C
(8)
APPLICATION HINTS
EXTERNAL RESISTORS R
a
, R
b
, R
c
, and R
d
The temperature set point (T
SET
) and hysteresis (T
SH
) of
the TK11052 are easily set by external resistors R
a
, R
b
,
R
c
, and R
d
. See Figure 1 for clarification of T
SET
and T
SH
.
The set voltage (V
SET
) of the comparator at the set
temperature (T
SET
) is calculated as follows:
(1)
where T
C
= 6.1 mV/
°
C
1. For Set Temperatures
≥
25
°
C
The set voltage (V
SET
) of the comparator at the reference
voltage and external resistances is calculated as follows:
(2)
Rb is calculated by Equations (1) and (2), resulting in:
0.4925 + T
SET
x T
C
R
b
=
V
REF
- 0.4925 - T
SET
x T
C
(3)
The hysteresis voltage (V
SH
) of the comparator can be
calculated as follows:
R
a
x R
b
V
SH
=
(
)
(4)
where I
SH
= 1.35
μ
A
Rb is calculated by Equation (4)
(5)
Ra is calculated by Equations (3) and (5)
R
a
+ R
b
I
SH
x
R
b
=
R
a
x I
SH
- V
SH
R
a
x V
SH
V
SET
= 0.4925 + T
SET
x T
C
TSET
TSH
FIGURE 1
V
REF
V
SET
=
R
b
R
a
+ R
b
x
x R
a
≈
1183
x T
SH
80.74
+ T
SET
x 10
3
R
a
=
(0.4925 + T
SET
x T
C
) x
I
SH
V
ref
x T
SH
x T
C
(0.4925 + T
SET
x 6.1 m) x
1.35
μ
1.597
x T
SH
x 6.1 m
(1.597 - 0.4925 - T
SET
x 6.1 m) x
1.35
μ
1.597
x T
SH
x 6.1 m
≈
1183
x T
SH
181.07
- T
SET
x 10
3
R
b
=
(VREF - 0.4925 - T
SET
x T
C
) x
I
SH
V
ref
x T
SH
x T
C
3
80.74 + 85
80.74 + T
SET
x T
SH
1183
x 5
R
a
= 1183
3
=
3
181.07 - T
SET
x T
SH
1183
x 5
R
b
= 1183
3
=181.07 - 85
V
REF
x T
SH
x T
C
(0.4925 + T
SET
x T
C
- T
SH
x T
C
) x I
SH
R
a
=
80.74 + (T
SET
- T
SH
)
x T
SH
= 1183
3
=
=