TDA1154 データシートの表示（PDF） - STMicroelectronics
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TDA1154 Datasheet PDF : 6 Pages
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TDA1154
If Eg and Rm are motor back electromotive force and
motor internal resistance respectively, then:
Eg + R m Im = Rt [ I (5) + V(ref) ] + V(ref) (b)
RS
From figure 2 it is seen that:
I (8)
=
Im
+
V(ref)
RS
(c)
Subsituting equations (a) and (c) into (b) yields:
Eg = Im [ Rt − Rm ] +
K
(1)
+ V(ref)
[
Rt
Rs
(
1
+
1
K
)
+
1
]
+
Rt IO (5)
(d)
The motor speed will be independent of the resist-
ing torque if Eg is also independentof Im. Therefore,
in order to determine the value of Rt term(1) in (d)
must be zero:
Rt = K R m (K = 20)
If Rt > KRm, an instability may occur as a result of
overcompensation.
The value of RS is determinated by term (2) in (d)
so as to obtain he back electromotive force (Eg)
corresponding to required motor speed:
RS
=
Rt
Eg
V(ref) (1 + 1 / K)
− V(ref) − Rt IO (5)
≅
≅ Rt
V(ref)
Eg − V(ref) − Rt IO (5)
Where V(ref) = 1.2V and IO (5) = 1.7 mA
(2)
Figure 4. Application circuit
4/6
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