A2919SB 데이터 시트보기 (PDF) - Allegro MicroSystems

부품명

상세내역

일치하는 목록

A2919SB

DUAL FULL-BRIDGE PWM MOTOR DRIVER

Allegro MicroSystems 

2919

DUAL FULL-BRIDGE

MOTOR DRIVER

APPLICATIONS INFORMATION

PWM CURRENT CONTROL

The A2919SB/SLB dual bridges are 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 flows through the external sense

resistor until the sense voltage (VS) reaches the level set

at the comparator’s input:

ITRIP = VREF/10 RS

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 2 µs. 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 decrease) is determined by

the monostable’s external RC timing components, where

toff = RTCT within the range of 20 kΩ to 100 kΩ and

100 pF to 1000 pF.

The fixed-off time should be short enough to keep

the current chopping above the audible range (< 46 µs)

and long enough to properly regulate the current. Be-

cause only slow-decay current control is available, short

off times (< 10 µs) require additional efforts to ensure

proper current regulation. Factors that can negatively

affect the ability to properly regulate the current when

using short off times include: higher motor-supply

voltage, light load, and longer than necessary blank time.

PWM OUTPUT CURRENT WAVE FORM

V PHAS E

+

I OUT 0

–

ITR IP

td

toff

Dwg. WM-003-1A

LOAD CURRENT PATHS

VB B

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, main-

taining the average motor winding current at the desired

level.

Loads with high distributed capacitances may cause

current spikes capable of tripping the comparator,

resulting in erroneous current control.

time delay should be used to delay the

AancteioxnteorfntahleRCCC

comparator. Depending on load type, many applications

will not require these external components (SENSE

connected to E).

BR IDGE ON

RS

S OUR CE OFF

ALL OFF

Dwg. E P -006-1

115 Northeast Cutoff, Box 15036

Worcester, Massachusetts 01615-0036 (508) 853-5000

Share Link: