TDA5147CH Datasheet, PDF (12/32 Pages) NXP Semiconductors – 12 V Voice Coil Motor VCM driver and spindle motor drive combination chip

Philips Semiconductors
12 V Voice Coil Motor (VCM) driver and
spindle motor drive combination chip
Preliminary specification
TDA5147CH
Power-on reset
The Power-on reset circuit monitors the voltage levels of
both the +5 V and the +12 V supply voltages as shown in
Fig.6. The PORN (active LOW) logic line is set HIGH
following a supply voltage rise above a specified voltage
threshold plus a hysteresis, and delayed by a time t_C that
is controlled by an external capacitor. This PORN signal
should remain HIGH until either the +5 or +12 V supplies
drop below the voltage threshold, at which point the PORN
line should be asserted LOW.
The t_C timing is set by the following equation:
t_C = ^C------×---I--V----^t--^h-
Where V_th = 2.5 V and I is 12 µA (typ.).
A negative going pulse width of 5 µs on either the
+5 or +12 V rail will provide a full output pulse. If another
trigger pulse occurs before the output is completed a new
output pulse will be originated. This implies the Power-on
reset circuit is a retriggerable one-shot with a maximum
trigger pulse of 5 µs (see Fig.7).
During a power-down situation the Power-on reset circuit
must not only generate a PORN output signal, but must
also activate the VCM retract circuitry. In doing so, the
VCM driver draws power from SHPWR2 and SHPWR3
during spin-down, and uses this power to bias the VCM
against one of the hard stops of the actuator. This prevents
the heads from landing on data zones. This BEMF supply
is isolated from the supply voltage for the drive, and is
half-wave rectified. An external retract capacitor is used to
provide the supply voltage for the retract circuit
(SHPWR1).
It should be noted that in both power-down retract and
command retract situations, the voltage across the VCM
can be adjusted (RET_ADJ pin) to limit the velocity of the
actuator.
The status of both the VCM driver blocks and the spindle
driver blocks is shown in Tables 5 and 6.
handbook, full pagewidth
VCC
Vhys
0.8 V
PORN
tC
tC
1997 Jul 09
Fig.6 Power-on reset timing.
12
MGG848
threshold
t
t