AN720 データシートの表示（PDF） - Vishay Semiconductors

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AN720

Si9986 Buffered H-Bridge

Vishay Semiconductors 

Si9986 Buffered H-Bridge

AN720

Vishay Siliconix

INTRODUCTION

APPLICATIONS

The Si9986 is a buffered H-bridge that will eliminate all the

external discretes that are normally needed to prevent

shoot-through in low-voltage brushed motor, stepper motor,

and actuator applications. Key features include the following:

D The output FETs are complementary, thus requiring no

high-side drive power supply.

D Built-in shoot-through protection prevents both FETs on

the same side of the H from being on at the same time. This

protection ordinarily would require several external

components or additional logic.

D Operating range is 3.8 to 13.2 V, making the Si9986 ideal

for the common PC supply voltages of 5 and 12 V.

D Built-in logic provides four states controlled by CMOS level

commands.

— The two on-states where current flows through the

load from either terminal (OUTA to OUTB or OUTB to

OUTA).

— A brake state where terminals OUTA and OUTB of the

load are both connected to ground, resulting in a

dynamic braking action.

— A high impedance state where neither terminal OUTA

nor OUTB of the load is connected, except through the

internal flywheel diodes.

D The inputs may be switched at frequencies up to 200 kHz,

allowing PWM operation.

D No additional components are necessary, except for a

possible snubber circuit, depending on the load and

electrical noise requirements and any feedback signal

processors.

The examples and descriptions that follow refer to the truth

table below for the Si9986.

ÁÁÁÁÁÁÁÁÁÁÁÁÁÁSta0123ÁtÁÁÁÁÁÁe ÁÁÁÁÁÁÁÁIÁÁÁÁÁÁN0011AÁÁÁÁÁÁÁTÁÁÁÁÁÁÁRINU0101ÁÁÁÁÁÁÁBTHÁÁÁÁÁÁÁTOAÁÁÁÁÁÁÁHUB001iZTÁLÁÁÁÁÁÁAEÁÁÁÁÁÁÁOHUÁÁÁÁÁÁÁ010iZTBÁÁÁÁÁÁÁAÁÁÁÁÁÁÁBO–c+rDptDaiekiÁÁÁÁÁiorÁÁrne..n ÁÁÁÁÁÁÁ

Figure 1 shows a brushed dc motor operating in a full-on,

bi-directional mode. Open loop control could be implemented

by appropriate high-speed switching between states 1 and 2.

(Refer to the Truth Table.)

Figure 2 shows a brushed dc motor operating in a controlled

bi-directional, closed-loop mode. Speed control can be

implemented by feeding back the low-pass filtered voltage at

the load to control the duty cycle of the high-speed switching

between states 1 and 2. (Refer to the Truth Table.)

Torque control can be accomplished by using the current

feedback signal (Figure 3) to control the duty cycle of the high

speed switching between states 1 or 2 and 3. (Refer to the

Truth Table.)

INA

Shoot-

Through

Protection

Logic

INB

VDD

Motor

Document Number: 70590

25-Oct-95

= Si9986 Terminals

FIGURE 1. Basic Open Loop

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