ZXBM1015ST20TC

As these threshold voltages are nominally set to V
THH
= 3V and V
THL
= 1V the equations can be simplified as
follows:
t
C
I
C
I
PWM
PWMC PWMD
=+
22
C
LCK
- Locked Rotor Timing Capacitor
Should the fan stop rotating for any reason, i.e. an
obstruction in the fan blade or a seized bearing, then
the device will enter a Rotor Locked condition. In this
condition after a predetermined time (t
lock
) the RD pin
will go high and the Phase outputs will be disabled.
After a further delay (t
off
) the controller will re-enable
the Phase drive for a defined period ((t
on
) in an attempt
to re-start the fan. This cycle of (t
off
) and (t
on
) will be
repeated indefinitely or until the fan re-starts.
The frequency at which this takes place is determined
by the value of the capacitor applied to this C
LCK
pin.
For a 12V supply a value of 1uF will typically provide an
'On' (drive) period of 0.56s and an 'Off' (wait) period of
6.8s, giving an On:Off ratio of 1:12.
The C
LCK
timing periods are determined by the
following equations:
t
VxC
I
lock
THH LCK
LCKC
=
t
VVxC
I
on
THH THL LCK
LCKC
=
()
t
VVxC
I
off
THH THL LCK
LCKD
=
()
Where: V
THH
and V
THL
are the C
LCK
pin
threshold voltages and
I
LCKC
and I
LCKD
are the charge and
discharge currents.
As these threshold voltages are nominally set to V
THH
= 3V and V
THL
= 1V the equations can be simplified as
follows:
t
xC
I
lock
LCK
LCKC
=
3
t
xC
I
on
LCK
LCKC
=
2
t
xC
I
off
LCK
LCKC
=
2
GND - Ground
This is the device supply ground return pin and will
generally be the most negative supply pin to the fan.
RD - Locked Rotor Error Output
This pin is the Locked Rotor output as referred to in the
C
LCK
timing section above. It is high when the rotor is
stopped and low when it is running.
This is an open collector drive giving an active pull
down with the high level being provided by an external
pull up resistor.
FG - Frequency Generator (speed)
This is the Frequency Generator output and is a
buffered signal from the Hall sensor.
This is an open collector drive giving an active pull
down with the high level being provided by an external
pull up resistor.
Ph1Lo & Ph2Lo - Low-side External H-bridge Driver
These pair of outputs drive the Low side of the external
high power H-bridge devices that in turn drives the
single phase winding. These outputs provide both the
commutation and PWM waveforms. The outputs are of
the Darlington emitter follower type with an active
pull-down to help faster switch off when using bipolar
devices or MOSFET devices with a high gate
capacitance. When in the high state the outputs will
provide up to 80mA of drive into the base or gates of
external transistors as shown in the Typical Application
circuit following.
When in the low state the active Phase drive is capable
of sinking up to 32mA when driving low to aid turn off
times during PWM operation. When the Phase is
inactive the output is held low by a 7.5k internal
pull-down resistor.
Ph1Hi & Ph2Hi - High-side External H-bridge Driver
These are the High side outputs to the external
H-bridge and are open collector outputs capable of
sinking 100mA. This signal provides commutation only
to the H-bridge.
V+OP- Phase Outputs supply voltage
This pin is the supply to the Phase outputs and will be
connected differently dependant upon external
transistor type.
For bipolar devices this pin will be connected via a
resistor to the VCC pin. The resistor is used to control
the current into the transistor base so its value is
chosen accordingly.
For MOSFET devices the pin will connect directly to the
VCC pin
ZXBM1015
ISSUE 3 - MAY 2007
7
V
CC
- Applied Voltage
This is the device internal circuitry supply voltage. For
5V to 12V fans this can be supplied directly from the Fan
Motor supply. For fans likely to run in excess of the 18V
maximum rating for the device this will be supplied
from an external regulator such as a Zener diode.
SetTh - Set Threshold Voltage
The ZXBM1015 contains a current monitor circuit used
to sense the current flowing in the motor winding and
this pin is used to control how the circuit responds to
that current.
The device works in a threshold feedback mode using a
potential divider to the Set Threshold pin. This
potential divider is used to set a voltage that will be
compared with the voltage generated by the current in
a Sense resistor attached in the Low-Side ground
return of the external H-Bridge driver. When the current
in the Sense resistor, and thus the voltage, rises above
the SetTh pin threshold the controller will back-off the
PWM drive to limit the maximum current taken by the
motor. To do this the current monitor will internally
apply a correction signal to the SPD pin. If the motor
current is below the set threshold the controller does
not influence the SPD voltage. A suitable voltage range
for the SetTh pin, and thus the sensed voltage on the
Sense pin, would be 50mV to 200mV.
It should be noted that the effectiveness of the control is
determined by the external network used to control the
SPD pin. It will not work where the fan is being
controlled by a low source impedance voltage. If the
fan is being controlled from an external voltage source
then a resistor >1k should be placed in series with the
SPD pin.
The minimum speed setting on the SMIN pin will
override the current limit feature. A current cannot be
set that is lower than the current taken when the motor
stalls at minimum speed.
Sense
This pin is used by the current sensing circuit, as
described above, to monitor the current taken by the
motor windings. The signal comes from a sense
resistor in the Low-Side ground return of the external
H-Bridge driver.
ZXBM1015
ISSUE 3 - MAY 2007
8
:
ZXBM1015
ISSUE 3 - MAY 2007
9
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ZXBM1015ST20TC

Mfr. #:
Manufacturer:
Diodes Incorporated
Description:
Motor / Motion / Ignition Controllers & Drivers Sngl Phase pre Drive
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
Payment:
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