MIC5021 datasheet(12/24 Pages) MICROCHIP

12 / 24 page

MIC5021

DS20005677B-page 12



2016 - 2021 Microchip Technology Inc. and its subsidiaries.

FIGURE 6-2:

12V to 36V Configuration.

FIGURE 6-3:

Preferred 20V to 36V

Configuration.

Do not use both boost capacitors between VBOOST and

the MOSFET source and VBOOST and VDD at the same

time.

6.7

Current-Sense Resistors

Lead length can be significant when using low value

(<1Ω) resistors for current sensing. Errors caused by

lead length can be avoided by using four-terminal cur-

rent-sensing resistors. Four-terminal resistors are

available from several manufacturers.

6.8

Circuits without Current Sensing

Current sensing may be omitted by connecting the

SENSE+ and SENSE– pins to the source of the MOS-

FET or to the supply. Connecting the sense pins to the

supply is preferred for inductive loads. Do not connect

the sense pins to ground.

FIGURE 6-4:

Connecting Sense to

Source.

FIGURE 6-5:

Connecting Sense to

Supply.

6.9

Inductive Load Precautions

Circuits controlling inductive loads, such as solenoids

(Figure 6-6) and motors, require precautions when

controlled by the MIC5021. Wire wound resistors,

which are sometimes used to simulate other loads, can

also show significant inductive properties.

An inductive load releases stored energy when its cur-

rent flow is interrupted (when the MOSFET is switched

off). The voltage across the inductor reverses and the

inductor attempts to force current flow. Since the circuit

appears open (the MOSFET appears as a very high

resistance) a very large negative voltage occurs across

the inductor.

V DD

Input

C T

Gnd

V BOOST

Gate

Sense-

Sense+

TTL Input

+20V to +36V

MIC5021

10μF

2.7

Load

V DD

Input

C T

Gnd

V BOOST

Gate

Sense-

Sense+

TTL Input

+20V to +36V

MIC5021

10μF

Load

0.01

μF

V DD

Input

C T

Gnd

V BOOST

Gate

Sense-

Sense+

TTL Input

Load

N-Channel

Power MOSFET

V+

MIC5021

10μF

0.01

μF

V DD

INPUT

C T

GND

V BOOST

GATE

SENSE-

SENSE+

TTL INPUT

LOAD

N-CHANNEL

POWER MOSFET

V+

MIC5021

10μF

0.01

μF

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