Circuit description

L6207Q

12/27

DocID018993 Rev 3

5.3

PWM current control

The L6207Q device 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 Figure 9. As the current in the load

builds 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

MOSFET 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 deadtime, 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 deadtime.

Figure 9. PWM current controller simplified schematic

Table 6. Truth table

Inputs

Outputs

1. Valid only in case of load connected between OUT1 and OUT2.

EN

IN1

IN2

OUT1

OUT2

L

2. X = don’t care.

X

3. High Z = high impedance output.

High Z

Disable

H

L

L

GND

GND

Brake mode (lower path)

H

H

L

Forward

H

L

H

GND (Vs)

Reverse

H

H

H

Brake mode (upper path)