LM621 National Semiconductor, LM621 Datasheet - Page 4

• Manufacturer Part Number: LM621
• Description: LM621 Brushless Motor Commutator
• Manufacturer: National Semiconductor

Typical Performance Characteristics
Description of Inputs and Outputs
Pin 1 V
Pin 2 DIRECTION This input determines the direction of
rotation of the motor ie clockwise vs counterclockwise
See truth table
Pin 3 DEAD-TIME ENABLE This input enables or disables
the dead-time feature Connecting
dead-time and grounding pin 3 disables it Pin 3 should not
be allowed to float
Pin 4 CLOCK TIMING An RC network connected between
this pin and ground sets the period of the clock oscillator
which determines the amount of dead-time See Figure 2
and text
Pins 5 thru 7 HS1 HS2 and HS3 (Hall-sensor inputs)
These inputs receive the rotor-position sensor inputs from
the motor Three-phase motors provide all three signals
four phase motors provide only two one of which is con-
nected to both HS2 and HS3
Pin 8 30 60 SELECT This input is used to select the re-
quired decoding for three-phase motors ie either ‘‘30-de-
gree’’ (
Pin 9 LOGIC GROUND Ground for the logic power supply
a
5V when using a four-phase motor
a
CC1
5V) or ‘‘60-degree’’ (ground) Connect pin 8 to
Selection Graph
for R and C
V
(
sat
a
5V) The logic and clock power supply pin
vs Temperature
a
5V to pin 3 enables
Supply Currents
vs Temperature
V
drop
vs Temperature
4
Pin 10 POWER GROUND Ground for the output buffer
supply
Pins 11 thru 13 SOURCE OUTPUTS The three current-
sourcing outputs which drive the external power devices
that drive the motor
Pins 14 thru 16 SINK OUTPUTS The three current-sinking
outputs which drive the external power devices that drive
the motor
Pin 17 OUTPUT INHIBIT This input disables the LM621
outputs It is typically driven by the magnitude signal from an
external sign magnitude PWM generator Pin 17
outputs off
Pin 18 V
collectors of the three current-sourcing outputs (pins 11 thru
13) When driving MOSFET power devices pin 18 may be
connected to a voltage source of up to
sufficient output swing for the gate When driving bipolar
power devices pin 18 should be connected to
mize on-chip power dissipation Undervoltage lockout auto-
matically shuts down all outputs if the V
low All outputs will be off if V
tage lockout voltage
CC2
(
a
5 to
a
40V) This is the supply for the
Supply Currents
vs Temperature
Typ V
Typ V
(
CC1
T
A
falls below the undervol-
sat
drop
e
25 C)
vs I
vs I
CC1
a
out sink
40V to achieve
out source
supply is too
a
e a
5V to mini-
TL H 8679 – 2
5V
e