MP230 Просмотр технического описания (PDF) - Cirrus Logic

Номер в каталоге

Компоненты Описание

производитель

MP230

Power Operational Amplifier

Cirrus Logic 

Product Innova tionFrom

MP230

TYPICAL APPLICATION

MOTOR POSITION CONTROL

The MOSFET output stage of the MP230 provides

superior SOA performance compared to bipolar

output stages where secondary breakdown is a

concern. The extended SOA is ideal in motor drive

applications where the back EMF of the motor may DAC OUTPUT

impose simultaneously both high voltage and high POSITION

current across the output stage transistors. In the COMMAND

figure above a mechanical to electrical feedback po-

sition converter allows the MP230 to drive the motor

in either direction to a set point determined by the

DAC voltage.

+Vs

12-14

18-20

1

42

+Vs

+Vb

2

GND

35

-ILIM

*

OUT

Cc1

Cc2

41

GND

6

4

-Vb

-Vs 40

38

Cc

21-23

27-29

Rs1

Rs2

Rs3

Rs4

36

+ILIM RLIM

*OUT

9-11

15-17

24-26

30-32

MOTOR

DRIVE

GENERAL

Please read Application Note 1 “General Operating

-Vs

POSITION

FEEDBACK

Considerations” which covers stability, power sup-

plies, heat sinking, mounting, current limit, SOA interpretation, and specification interpretation. Visit www.cirrus.

com for design tools that help automate tasks such as calculations for stability, internal power dissipation, current

limit, heat sink selection, Apex Precision Power’s complete Application Notes library, Technical Seminar Workbook

and Evaluation Kits.

GROUND PINS

The MP230 has two ground pins (pins 2, 40). These pins provide a return for the internal capacitive bypassing of

the small signal stages of the MP230. The two ground pins are not connected together on the substrate. Both of

these pins are required to be connected to the system signal ground.

BALANCING RESISTOR SELECTION (RS1-RS4)

The MP230 uses parallel sets of output transistors. To ensure that the load current is evenly shared among the

transistors external balancing resistors RS1-RS4 are required. To calculate the required value for each of the resistors

use: R = 4.5 / I2 ,where I is the maximum expected output current. For example, with a maximum output current of

10A each balancing resistor should be 0.045 ohms. Each resistor dissipates 1.125W at the maximum current. Use

a non-inductive 2W rated resistor. A ready source for such resistors is the IRC resistor series LR available from

Mouser Electronics.

SAFE OPERATING AREA

The MOSFET output stage of the MP230 is not limited by second breakdown considerations as in bipolar output

stages. Only thermal considerations and current handling capabilities limit the SOA (see Safe Operating Area graph

on previous page). The output stage is protected against transient flyback by the parasitic diodes of the output stage

MOSFET structure. However, for protection against sustained high energy flyback external fast-recovery diodes

must be used.

COMPENSATION

The external compensation capacitor CC is connected to pins 4 and 6. Unity gain stability can be achieved with

CC = 470pF for a minimum phase margin of 60 degrees. At higher gains more phase shift can usually be tolerated

and CC can be reduced resulting in higher bandwidth and slew rate. Use the typical operating curves as a guide to

select CC. A 100V NPO (COG) type capacitor is required. Boost operation requires more compensation or higher

gains than with normal operation due to the increased capacitance of the output transistors when the output signal

swings close to the supply rails.

OVERVOLTAGE PROTECTION

Although the MP230 can withstand differential input voltages up to ±25V, in some applications additional external

protection may be needed. 1N4148 signal diodes connected anti-parallel across the input pins is usually sufficient.

In more demanding applications where bias current is important diode connected JFETs such as 2N4416 will be

MP230U

5

Share Link: