July 2005

7

MIC5013

MIC5013

Micrel, Inc.

Fault

V+

Gate

1

2

3

4

8

MIC5013

Gnd

7

6

5

Thresh

Sense

Source

Input

IRF540

10µF

10kΩ

10mΩ

IRC 4LPW-5

LOAD

Control Input

=7 to 15V

V+

+

(International Resistive Company)

V

LOAD

I =20A (trip current)

L

V

For this example:

R =

2200

–1000

V

TRI P

TH

R =

S

R

S

Fault

V+

Gate

1

2

3

4

8

MIC5013

Gnd

7

6

5

Thresh

Sense

Source

Input

=24V

IRF541

10µF

100Ω

20kΩ

24kΩ

18mΩ

IRC 4LPW-5*

R1

LOAD

Control Input

V+

+

*International Resistive Company

R2

R1=

R2=100Ω

R =

R =

1mA

V

100mV+

2200

–1000

+

I

L

For this example:

I =10A (trip current)

L

V

=100mV

TRI P

V

TRI P

V

TRI P

S

R

S

TH

Circuit Topologies

The MIC5013 is suited for use in high- or low-side driver

applications with over-current protection for both current-

sensing and standard MOSFETs. In addition, the MIC5013

works well in applications where, for faster switching times,

the supply is bootstrapped from the MOSFET source out-

put. Low voltage, high-side drivers (such as shown in the

Test Circuit) are the slowest; their speed is reflected in the

gate turn-on time specifications. The fastest drivers are the

low-side and bootstrapped high-side types. Load current

switching times are often much faster than the time to full

gate enhancement, depending on the circuit type, the MOS-

FET, and the load. Turn-off times are essentially the same

one topology over another is based on a combination of

considerationsincludingspeed,voltage,anddesiredsystem

characteristics. Each topology is described in this section.

current that just trips the over-current comparator.

Low-Side Driver with Current Shunt (Figure 2). The over-

offer the best noise immunity, but also compromise switch

drop (especially in low voltage applications) and power

dissipation.

The trip current is set higher than the maximum expected

load current—typically twice that value. Trip point accuracy

is a function of resistor tolerances, comparator offset (only

a few millivolts), and threshold bias voltage (V2). The val-

ues shown in Figure 2 are designed for a trip current of 20

amperes. It is important to ground pin 4 at the current shunt

Akeyadvantageofthelow-sidetopologyisthattheloadsup-

ply is limited only by the MOSFET BVDSS rating. Clamping

may be required to protect the MOSFET drain terminal from

Figure 2. Low-Side Driver

with Current Shunt

Figure 3. High-Side Driver

with Current Shunt