TDA5345HT 데이터 시트보기 (PDF) - Philips Electronics
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TDA5345HT Datasheet PDF : 44 Pages
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Philips Semiconductors
5 V spindle & VCM driver combo
Preliminary specification
TDA5345HT
Commutation control
DELAYS
The spindle block contains both the low-side and high-side drivers configured as a H bridge for a three phase DC
brushless, sensorless motor. In each of the six possible states, two outputs are active, one sourcing current and one
sinking current. The third output presents a high impedance to the motor which enables measurement of the BEMF in
the corresponding motor coil. The back-EMF comparator output (available on pin SpinDigOut) is processed by the
commutation logic circuit to calculate the correct time for the next commutation, which will change the output state.
The commutation block measures then the time between 2 consecutive zero-crossings and determines the actual
commutation time and the next motor coils state. All the following situations must be taken into account:
=> Start up, No start, Backwards spin, Run and Manual commutation.
The commutation logic keeps the motor spinning by commutating the motor each time a zero-crossing is detected. The
delay between the zero-crossing and the actual output driver change is either internally calculated or programmable via
the serial port (useful at start-up: no delay has been measured!).
The internal commutation clock can be monitored on pin SpinDigOut (44). The falling edges are the relevant
informations: they are caused by the zero-crossings. If preferred, SpinDigOut can be set to become the back-EMF
comparator output, to check if the spindle is already spinning at power up for instance. If the spindle outputs are floating,
don’t forget to bias them, using the “BiasCT” bit, before considering the BemfCompOut value.
Fig.6 and Fig.7 show typical motor commutation timing diagrams.
State Code
0
1
2
3
4
5
SpinMotA
SpinMotB
SpinMotC
L
L
H
F
F
H
F
H
L
L
H
F
H
F
F
H
L
L
Commutation
Clock
BemfCompOut
Zero-crossing
Fig.7 Input commutations to output drivers
1999 June 10
14
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