MIC5013 데이터 시트보기 (PDF) - Micrel

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MIC5013

Protected High- or Low-Side MOSFET Driver

Micrel 

MIC5013

Applications Information (Continued)

VL O A D

Control Input

V+=7 to 15V

RTH

10kΩ

MIC5013

1 Input Fault 8

2 Thresh V+ 7

3 Sense Gate 6

4 Source Gnd 5

10µF

+

LOAD

IRF540

RS=

VTR I P

IL

2200

RT H=

–1000

VTR I P

For this example:

I L =20A (trip current)

VTRI P = 200mV

RS

10mΩ

IRC 4LPW-5

(International Resistive Company)

Figure 2. Low-Side Driver

with Current Shunt

Micrel, Inc.

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

for all circuits (less than 10µs to VGS = 1V). The choice of

one topology over another is based on a combination of

considerations including speed, voltage, and desired system

characteristics. Each topology is described in this section.

Note that IL, as used in the design equations, is the load

current that just trips the over-current comparator.

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

current comparator monitors RS and trips if IL × RS exceeds

VTRIP. R is selected to produce the desired trip voltage.

As a guideline, keep VTRIP within the limits of 100mV and

500mV (RTH = 3.3kΩ to 20kΩ). Thresholds at the high end

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

RS, to eliminate the effects of ground resistance.

A key advantage of the low-side topology is that the load sup-

ply is limited only by the MOSFET BVDSS rating. Clamping

may be required to protect the MOSFET drain terminal from

Control Input

RTH

20kΩ

V+ =24V

MIC5013

10µF +

1 Input Fault 8

2 Thresh V+ 7

V+

R1=

1mA

R2=100Ω

3 Sense Gate 6

4 Source Gnd 5

RS

=

100mV+

IL

VT

R

I

P

IRF541

100Ω

2200

RT H=

–1000

VTR I P

R1

24kΩ

R2

RS

For this example:

18mΩ

IRC 4LPW-5*

IL =10A (trip current)

VTRI P =100mV

LOAD

*International Resistive Company

July 2005

Figure 3. High-Side Driver

with Current Shunt

7

MIC5013

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