L6208QTR STMicroelectronics, L6208QTR Datasheet - Page 12

• Manufacturer Part Number: L6208QTR
• Description: Motor / Motion / Ignition Controllers & Drivers DMOS Dual Full Bridge Driver 5.6A
• Manufacturer: STMicroelectronics

Specifications of L6208QTR

• Product Category: Motor / Motion / Ignition Controllers & Drivers
• Rohs: yes

Circuit description
4.3
12/33
PWM current control
The L6208Q 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
MOSFET transistors and ground, as shown in
up, the 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
or VREF
off. The low-side MOSFET remains off for the time set by the monostable and the motor
current recirculates in the upper path. When the monostable times out, the bridge again
turns on. As the internal dead time, used to prevent cross conduction in the bridge, delays
the turn-on of the power MOSFET, 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
Section
Immediately after the low-side Power MOSFET turns on, a high peak current flows through
the sensing resistor due to the reverse recovery of the freewheeling diodes. The L6208Q
provides a 1 μs blanking time t
spike cannot prematurely re-trigger the monostable.
C
OFF
5V
5mA
(0)
TO GATE LOGIC
4.4.
B
R
RC A(or B)
), the sense comparator triggers the monostable switching the low-side MOSFET
OFF
shows the typical operating waveforms of the output current, the voltage drop
(1)
2.5V
Q
+
-
R
S
MONOSTABLE
BLANKING TIME
MONOSTABLE
SET
Doc ID 018710 Rev 2
BLANK
COMPARATOR
OUTPUT
BLANKER
that inhibits the comparator output so that this current
1μs
COMPARATOR
SENSE
DEAD TIME
DRIVERS
+
-
+
VREF A(or B)
Figure 12.
GATE DRIVERS
FROM THE
LOW-SIDE
2H
2L
R SENSE
As the current in the load builds
DEAD TIME
VS
DRIVERS
A
+
(or
SENSE A(or B)
B
)
1H
1L
OUT2 A(or B)
OUT1 A(or B)
D01IN1332
I OUT
STEPPER MOTOR
2 PHASE
L6208Q
A