TK11051 Просмотр технического описания (PDF) - Toko America Inc
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TK11051 Datasheet PDF : 8 Pages
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TK11051
APPLICATION HINTS
EXTERNAL RESISTORS R1 AND R2
The hysteresis voltage (VSH) of the comparator can be
The temperature set point (TSET) and hysteresis (TSDH)RoRfDRDcRaOlcPulated as follows:
the TK11051 are easily set by two external resistors R1 and
R2. See Figure 1 for clarification of TSET and TSH.
( ) VSH =
R1 x R2
R1 + R2
X (ISH - IIB)
(5)
TSH
TSET
FIGURE 1
The set voltage (VSET) of the comparator at the set
temperature (TSET) is calculated as follows:
where ISH = 1.25 µA
The hysteresis represented as temperature is:
( ) TSH =
R1 x R2
R1 + R2
(ISH - IIB)
x
TC
(6)
VSET = TSET x TC
(1)
Solving for temperature coefficient (TC):
where TSET is an absolute temperature (°K).
That is, TSET (°K) = °C + 273
and TC = 4 mV/°C.
( ) TC =
R1 x R2
R1 + R2
(ISH - IIB)
x
TSH
(7)
1. For Set Temperatures ≥ 25 °C
VSET =
R2 x Vref
R1 + R2
(2)
R1 x R2 x IIB
R1 + R2
=
R2
R1 + R2
x
(Vref - R1 x IIB)
Solving for R1 from Equations 3 and 7:
R1 =
Vref x TSH
TSET x ISH - ( TSET - TSH)
x IIB
(8)
where Vref = 1.6 V
IIB = 0.1 µA
The temperature coefficient (TC) is calculated by Equations
1 and 2, resulting in:
TC =
R2
R1 + R2
x
Vref -
R1 x
TSET
IIB
(3)
From Equation 3, R2 is calculated as follows:
R2 =
TSET x TC x R1
Vref - R1 x IIB - TSET x TC
(4)
R2 can now be calculated by substituting R1 into Equation 4:
Example:
R1 and R2 when set temperature is 80 °C (TSET = 353 °K)
and temperature hysteresis (TSH) is 5 °C.
R1 =
1.6 x 5
353 x1.25 µ - ( 353 - 5)
x 0.1 µ
R1 = 19.68 k = 20 kΩ
R2 =
353 x 4 m x 19.68 k
1.6 -19.68 k x 0.1 µ - 353 x 4 m
R2 = 149.39 k = 150 kΩ
Page 6
January 1999 TOKO, Inc.
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