L6219

LINEAR INTEGRATED CIRCUIT

UNISONICTECHNOLOGIESCO.,LTD

5 of 6

www.unisonic.com.tw

QW-R109-005,B

PWM CURRENT CONTROL

The L6219 dual bridge is designed to drive both windings of a bipolar stepper motor. Output current is sensed

and controlled independently in each bridge by an external sense resistor (Rs), internal comparator, and monostable

multivibrator.

When the bridge is turned on, current increases in the motor winding and it is sensed by the external sense

The comparator then triggers the monostable which turns off the source driver of the bridge. The actual load

current peak will be slightly higher than the trip point (especially for low-inductance loads) because of the internal

logic and switching delays. This delay (td)is typically 2µs.After turn-off, the motor current decays, circulating through

the ground-clamp diode and sink transistor. The source driver’s off time (and therefore the magnitude of the current

20kΩ to 100kΩ and 100pF to 1000pF

When the source driver is re-enabled, the winding current (the sense voltage) is again allowed to rise to the

comparator’s threshold. This cycle repeats itself, maintaining the average motor winding current at the desired level.

Loads with high distributed capacitances may result in high turn-on current peaks. This peak (appearing across

Rs) will attempt to trip the comparator, resulting in erroneous current control or high-frequency oscillations. An

many applications will not require these external components (SENSE connected to COMP IN).

PWM OUTPUT CURRENT WAVE FORM

+

-

0

LOAD CURRENT PATHS

BRIDGE ON

SOURCE OFF

ALL OFF