HA13568AT
External Components (cont)
Reccomended Reccomended
Parts No. Value
Range
Purpose
Note
Ct1
150 pF
≥ 120 pF
Time constant for CLK oscillation. Use a
3
capacitor with good temperature characteristics.
Ct2
0.033 µF
Time constant for start-up oscillation. Use a
4
capacitor with good temperature characteristics.
Ct3
470 pF
≥ 390 pF
PWM carrier oscillation time constant
5
Q1
Transistor for voltage regulator
Note:
1. The output current maximum value Iospnmax of SPN driver is controlled according to the
following equation. However, Vspncl is the current limiter reference voltage. (See the electrical
characteristics)
Iospnmax =
Vspncl
Rnf
2. The maximum duty Dmax of SLD driver output is controlled according to the following equation.
Dmax =
Vrt
Vhct3 − Vlct3
Rt2
Rt
−
Vlct3
Vrt
× 100 (%)
However,
Rt = Rt1 + Rt2,
Rt2
Rt
≥
Vlct3
Vrt
Where, Vrt : RT pin voltage (See the electrical characteristics)
Vlct3 : CT3 pin low voltage (≈ 1.3 V)
Vhct3 : CT3 pin high voltage (≈ 3.3 V)
Since Vrt ≈ Vhct3, Dmax is not limited at 100% when Rt1 = 0 Ω.
3. The CLK oscillation frequency is determined by the following equation.
fclk
=
8
Ct1
Vrt
Rt ∆Vct1
Where, Vrt : RT pin voltage (See the electrical characteristics)
∆Vct1 : CT1 pin voltage amplitude (≈ 1 V)
4. The Ct2 for start-up oscillation is determined by the following equation.
Tc2 = 1
6
J
P Kt Ispnmax
Ct2 =
Tc2 Vrt
8 Rt (Vhct2 − Vlct2)
Where, J
: Spindle motor inertia (kg · cm · S2)
P : Number of spindle motor poles (Total number of S poles and N poles)
Kt : Spindle motor torque constant (kg · cm / A)
Vhct2 : CT2 pin high voltage (≈ 3.3 V)
Vlct2 : CT2 pin low voltage (≈ 1.3 V)
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