ML4425IS Ver la hoja de datos (PDF) - Fairchild Semiconductor
Número de pieza
componentes Descripción
Fabricante
ML4425IS Datasheet PDF : 16 Pages
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ML4425
PRODUCT SPECIFICATION
State
R
A
B
C
D
E
F
LA
OFF
OFF
OFF
ON
ON
OFF
OFF
LB
ON
OFF
OFF
OFF
OFF
ON
ON
Outputs
LC
OFF
ON
ON
OFF
OFF
OFF
OFF
HA
ON
ON
OFF
OFF
OFF
OFF
ON
HB
OFF
OFF
ON
ON
OFF
OFF
OFF
Table 1. Commutation State Functions
HC
ON
OFF
OFF
OFF
ON
ON
OFF
Input
Sampling
N/A
FB B
FB A
FB C
FB B
FB A
FB C
A
B
C
D
E
F
A
B
C
D
E
F
HA
HIGH
SIDE
DRIVE
HB
OUTPUTS
HC
LA
LOW
SIDE
DRIVE
LB
OUTPUTS
LC
Figure 4. Output Commutation Sequence Timing Diagram
Cycle 1 – Full Commutation, Cycle 2 – Commutation with 50% PWM Duty Cycle
Voltage Controlled Oscillator (VCO)
The VCO provides a TTL compatible clock output on the
VCO/TACH pin proportional to the VCO input voltage at the
SPEED FB pin. The proportion of frequency to voltage
(VCO constant, Kv) is set by an 80.6kΩ resistor on RVCO
and a capacitor on CVCO as shown in Figure 5. RVCO sets up
a current proportional the VCO input voltage at SPEED FB.
This current is used to charge and discharge CVCO between
the threshold voltages of 2.3V and 4.3V. The resulting trian-
gle wave on CVCO corresponds to the clock on VCO. Kv
should be set so that the VCO output frequency corresponds
to the maximum commutation frequency or maximum motor
speed when the VCO input is equal to or slightly less than
VREF. CVCO is calculated using the following equation:
CVCO
=
6----.--5---V------×-----3---.--1---0---1-----×-----1---0----–--6----H----------z---------•---------VF--------a-------r-----a--------d-
0.05R----H-P---z--M--- × N × SPEEDMAX
(2)
The closest standard value that is equal to or less than the
calculated CVCO should be used.
8
REV. 1.0.2 7/2/01
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