MIC5013 Micrel Semiconductor, MIC5013 Datasheet - Page 7

• Manufacturer Part Number: MIC5013
• Description: Protected High- or Low-Side MOSFET Driver
• Manufacturer: Micrel Semiconductor

MIC5013
Applications Information
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
MOSFET, and the load. Turn-off times are essentially the
same for all circuits (less than 10 s to V
of one topology over another is based on a combination of
considerations including speed, voltage, and desired sys-
tem characteristics. Each topology is described in this
section. Note that I
load current that just trips the over-current comparator.
Low-Side Driver with Current Shunt (Figure 2). The over-
July 2000
Control Input
L
Control Input
, as used in the design equations, is the
R
20k
TH
10k
R
TH
(Continued)
1
2
3
4
GS
1
2
3
4
Input
Thresh
Sense
Source
Figure 2. Low-Side Driver with
= 1V). The choice
Thresh
Source
Input
Sense
MIC5013
Figure 3. High-Side Driver
MIC5013
Fault
Gate
Gnd
with Current Shunt
V+
Fault
Gate
Gnd
Current Shunt
V+
24k
8
7
6
5
R1
8
7
6
5
10µF
V +
=7 to 15V
100
R2
7
+
10µF
V +
+
LOAD
current comparator monitors RS and trips if I
V
As a guideline, keep V
500mV (R
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 values
shown in Figure 2 are designed for a trip current of 20
amperes. It is important to ground pin 4 at the current shunt
R
A key advantage of the low-side topology is that the load
supply is limited only by the MOSFET BVDSS rating.
Clamping may be required to protect the MOSFET drain
terminal from inductive switching transients. The MIC5013
=24V
TRIP
S
, to eliminate the effects of ground resistance.
IRF541
R
18m
IRC 4LPW-5*
S
LOAD
. R is selected to produce the desired trip voltage.
V
LOAD
IRF540
TH
(International Resistive Company)
R
10m
IRC 4LPW-5
S
= 3.3k to 20k ). Thresholds at the high end
*International Resistive Company
R1=
R2=100
R =
R
For this example:
I =10A (trip current)
V
L
TRIP
TH
S
R
R =
For this example:
I =20A (trip current)
V
L
TRIP
TH
TRIP
S
=
=100mV
100mV+
=
1mA
2200
V
V
V
TRIP
= 200mV
TRIP
2200
V
I
within the limits of 100mV and
+
TRIP
L
I
–1000
L
V
–1000
TRIP
L
R
S
MIC5013
exceeds
Micrel