OM9369SP IRF [International Rectifier], OM9369SP Datasheet - Page 10
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OM9369SP
Manufacturer Part Number
OM9369SP
Description
FULL-FEATURED POWER MODULE FOR HIGH VOLTAGE DIRECT DRIVE OF 3-PHASE BRUSHLESS DC MOTOR
Manufacturer
IRF [International Rectifier]
Datasheet
1.OM9369SP.pdf
(14 pages)
OM9369
QUAD SELECT INPUT (Pin 14) -- This input is used
to set the OM9369 in a half control or full control
chopping regime. When driven with a logic low level,
the OM9369 is in the half control mode, whereby only
the three lower (pull-down) power switches associated
with the Phase Outputs are allowed to chop. Alternately,
when driven with a logic high level, the OM9369 is
in the full control mode, where all six power switches
(pull-up and pull-down) associated with the Phase
Outputs are chopped by the PWM. During motor braking,
changing the logic state of the Quad Select Input
has no effect on the operation of the OM9369.
TACHOMETER OUTPUT (Pin 15) -- This output
provides a fixed width 5V pulse when any Hall-
effect Input (1, 2 or 3) changes state. The pulse width
of the Tachometer Output is set internally in the
OM9369 to 113µs (nominal). The average value of
the output voltage on pin 15 is directly proportional
to the motor's speed, so this output may be used
(with an external averaging filter) as a true tachometer
output, and fed back to the Speed Input (pin 23) to
sense the actual motor speed.
Note: Whenever pin 15 is high, the internal Hall-
effect position latches are inhibited (i.e. "latched"), to
reject noise during the chopping portion of the
commutation cycle, and this makes additional
commutations impossible. This means that in order
to prevent false commutation at a speed less than
the desired maximum speed, the highest speed as
observed at the Tachometer Output should be set
above the expected maximum value.
BRAKE / TACH TIMING INPUT (Pin 16) -- The
Brake/Tach Timing Input is a dual-purpose input.
Internal to the OM9369 are timing components tied
from pin 16 to Ground (a 51kΩ resistor and a
3300pF capacitor). These components set the minimum
pulse width of the Tachometer Output to 113µs, and
this time may be adjusted using external components,
according to the equation:
T(tach) = 0.67 x (C t + 3300pf) x
The recommended range of external resistance (to
Ground) is 15kΩ to ∞, and the range of external
capacitance (to Ground) is 0pF to 0.01uF. With each
Tachometer Output pulse, the capacitor tied to pin
16 is discharged from approximately 3.33V to
10
(
Rt + 51kΩ Ω Ω Ω Ω
Rt x 51kΩ Ω Ω Ω Ω
)
(µs)
approximately 1.67V by an internal timing resistor.
The Brake / Tach Timing Input has another function.
If this pin is pulled below the brake threshold
voltage, the OM9369 will enter the brake mode. The
brake mode is defined as the disabling of all three
high-side (pull-up) drivers associated with the Phase
Outputs, and the enabling of all three low-side (pull-
down) drivers.
OVERVOLTAGE / COAST INPUT (Pin 17) -- This
input may be used as a shutdown or an enable/
disable input to the OM9369.
switching inhibit threshold is so tightly defined, this
input can be directly interfaced with a resistive
divider which senses the voltage of the motor
supply, Vm, for overvoltage conditions. A high level
(greater than the inhibit threshold) on pin 17 causes
the coast condition to occur, whereby all Phase
Outputs revert to a Hi-Z state and any motor current
which flowed prior to the Overvoltage/ Coast command
is commutated via the power "catch" rectifiers
associated with each Phase Output.
SOFT-START INPUT (Pin 18) -- The Soft-Start input
is internally connected to a 10µA (nominal) current
source, the collector of an NPN clamp/discharge
transistor, and a voltage comparator whose soft-
start/restart threshold is 0.2Vdc (nominal). An external
capacitor is connected from this pin to Ground (pin
19). Whenever the Vcc supply input drops below the
turn-on threshold, approximately 9Vdc, or the sensed
current exceeds the over-current threshold,
approximately 0.3V at the current sense amplifier,
the soft-start latch is set. This drives the NPN clamp
transistor which discharges the external soft-start
capacitor. When the capacitor voltage drops below
the soft-start/restart threshold and a fault condition
does not exist, the soft-start latch is cleared; the soft-
start capacitor charges via the internal current
source.
In addition to discharging the soft-start capacitor, the
clamp transistor also clamps the output of the error
amplifier internal to the controller IC, not allowing
the voltage at the output of the error amplifier to
exceed the voltage at pin 18, regardless of the inputs
to the amplifier. This action provides for an orderly
motor start-up either at start-up or when recovering
from a fault condition.
Also, since the
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