L6228QTR STMicroelectronics, L6228QTR Datasheet - Page 13

• Manufacturer Part Number: L6228QTR
• Description: IC DVR BIPO STEP MOTOR 32-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Bipolar Stepper Motor Driverr

Specifications of L6228QTR

• Applications: Stepper Motor Driver
• Number Of Outputs: 1
• Current - Output: 1.4A
• Voltage - Supply: 8 V ~ 52 V
• Operating Temperature: -25°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 32-VFQFN, 32-VFQFPN
• Product: Stepper Motor Controllers / Drivers
• Operating Supply Voltage: 48 V
• For Use With: 497-6818 - EVAL BOARD FOR L6228Q
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Load: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 497-6864-2; L6228QTR

L6228Q
4.3
PWM current control
The L6228Q includes a constant off time PWM current controller for each of the two bridges.
The current control circuit senses the bridge current by sensing the voltage drop across an
external sense resistor connected between the source of the two lower power MOS
transistors and ground, as shown in
voltage across the sense resistor increases proportionally. When the voltage drop across
the sense resistor becomes greater than the voltage at the reference input (VREF
VREF
MOS remain off for the time set by the monostable and the motor current recirculates as
defined by the selected decay mode, described in the next section. When the monostable
times out the bridge will again turn on. Since the internal dead time, used to prevent cross
conduction in the bridge, delays the turn on of the power MOS, the effective off time is the
sum of the monostable time plus the dead time.
Figure 12. PWM current controller simplified schematic
Figure 13
across the sensing resistor, the RC pin voltage and the status of the bridge. More details
regarding the Synchronous Rectification and the output stage configuration are included in
the next section.
Immediately after the power MOS turns on, a high peak current flows through the sensing
resistor due to the reverse recovery of the freewheeling diodes. The L6228Q provides a 1 μs
blanking time t
prematurely re-trigger the monostable.
C
OFF
5V
5mA
B
(0)
) the sense comparator triggers the monostable switching the bridge off. The power
TO GATE LOGIC
R
RC A(or B)
shows the typical operating waveforms of the output current, the voltage drop
OFF
(1)
2.5V
BLANK
Q
+
-
that inhibits the comparator output so that this current spike cannot
S
R
MONOSTABLE
BLANKING TIME
MONOSTABLE
SET
Doc ID 14321 Rev 4
COMPARATOR
OUTPUT
Figure
BLANKER
1μs
COMPARATOR
SENSE
DEAD TIME
12. As the current in the motor builds up the
DRIVERS
+
-
+
VREF A(or B)
GATE DRIVERS
FROM THE
LOW-SIDE
2H
2L
R SENSE
DEAD TIME
VS
DRIVERS
A
+
(or
SENSE A(or B)
B
)
1H
1L
Circuit description
OUT2 A(or B)
OUT1 A(or B)
D01IN1332
I OUT
STEPPER MOTOR
A
2 PHASE
or
13/32