A3988 查看數據表（PDF） - Allegro MicroSystems

零件编号

产品描述 (功能)

生产厂家

A3988

Quad DMOS Full Bridge PWM Motor Driver

Allegro MicroSystems 

A3988

Quad DMOS Full Bridge PWM Motor Driver

Synchronous Rectification When a PWM-off cycle is

triggered by an internal fixed off-time cycle, load current will

recirculate. The A3988 synchronous rectification feature will turn

on the appropriate MOSFETs during the current decay, and effec-

tively short out the body diodes with the low RDS(on) driver. This

significantly lowers power dissipation. When a zero current level

is detected, synchronous rectification is turned off to prevent

reversal of the load current.

Mixed Decay Operation The bridges operate in mixed

decay mode. Referring to figure 2, as the trip point is reached, the

device goes into fast decay mode for 30.1% of the fixed off-time

period. After this fast decay portion, tFD , the device switches

to slow decay mode for the remainder of the off-time. During

transitions from fast decay to slow decay, the drivers are forced

off for approximately 600 ns. This feature is added to prevent

shoot-through in the bridge. As shown in figure 2, during this

“dead time” portion, synchronous rectification is not active, and

the device operates in fast decay and slow decay only.

VPHASE

+

IOUT 0

–

See Enlargement A

Enlargement A

ITrip

Fixed Off-Time 30 μs

9 μs

21 μs

IOUT

FDDT

FDSR

SDDT

SDSR

SDDT

Figure 2. Mixed Decay Mode Operation

Allegro MicroSystems, Inc.

6

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Share Link: