TDA5345HT Datasheet, PDF (23/44 Pages) NXP Semiconductors – 5 V spindle & VCM driver combo

Philips Semiconductors
5 V spindle & VCM driver combo
Preliminary specification
TDA5345HT
63
(ext.)
VDD=5V
62
Isolation switch, used in reverse mode
(ext.)
1
SpinRectBemf
2
10
PA
PB
MotA
PC
MotB
NA
NB
NC
Retract PMOS
4
Off
MotC
P-
Off
Vcm-
Vcm+
14
Off
P+
On
5
(ext.)
N-
N+
15
GND=0V 9
(ext.)
(ext.)
VCM
Rsense
The back-EMF is synchronously rectified
by the spindle power transistors:
PA (resp. PB, PC) is switched On
when MotA (resp. MotB, MotC) is above SpinRectBemf
NA (resp. NB, NC) is switched On
when MotA (resp. MotB, MotC) is below GND
Fig.15 Power transistors structure during a retract phase
During the VCM brake, VCM power transistors N- & N+ are switched fully On while transistors P- & P+ are switched off.
During the soft retract step, N- transistor is switched off while the retract PMOS brings some current to the VCM. The
control loop is drawn in figure 14 (the voltage on VcmMinus is regulated).
VcmMinus
(6)
Fig.16 VCM retract circuitry
Rsense
(ext.)
RetPmosDrain
VCM
(11)
(62)
Programmable
voltage divider
On
VcmPlus
SpinRectBemf ₍₂₎
Retract PMOS
retract amplifier
Internal voltage reference
=> 125 mV in slow retract
=> 250mV in full power.
1999 June 10
23