April 1998
5-87
MIC5010
Micrel
5
=24V
IRCZ44
(S=2590,
R=11m
)
10F
43
20k
4.3k
R
R1
Figure 1. High-Side Driver with
Current-Sensing MOSFET
LOAD
Control Input
V
+
+
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
NC
NC
S
R1=
100mV
SRR
(SR+R )
V
+
SR( +100mV)
R I
( +100mV)
R =
R =
1000
2200
V
TRIP
S
For this example:
=30A (trip current)
I
L
=100mV
V
TRIP
S
S
TH
V
TRIP
V
TRIP
L
R
TH
SENSE
SOURCE
KELVIN
Ordering Information
Part Number
Temperature Range
Package
MIC5010BN
40
C to +85
C
14-pin Plastic DIP
MIC5010BM
40
C to +85
C
14-pin SOIC
MIC5010
Full-Featured High- or Low-Side MOSFET Driver
Not Recommended for New Designs
General Description
The MIC5010 is the full-featured member of the Micrel
MIC501X driver family. These ICs are designed to drive the
gate of an N-channel power MOSFET above the supply rail
in high-side power switch applications. The MIC5010 is
compatible with standard or current-sensing power FETs in
both high- and low-side driver topologies.
The MIC5010 charges a 1nF load in 60
s typical and
protects the MOSFET from over-current conditions. Faster
switching is achieved by adding two 1nF charge pump
capacitors. The current sense trip point is fully program-
mable and a dynamic threshold allows high in-rush current
loads to be started. A fault pin indicates when the MIC5010
has turned off the FET due to excessive current.
Other members of the Micrel driver family include the
MIC5011 minimum parts count 8 pin driver, MIC5012 dual
driver, and MIC5013 protected 8 pin driver.
Features
7V to 32V operation
Less than 1
A standby current in the "OFF" state
Internal charge pump to drive the gate of an N-channel
power FET above supply
Available in small outline SOIC packages
Internal zener clamp for gate protection
25
s typical turn-on time to 50% gate overdrive
Programmable over-current sensing
Dynamic current threshold for high in-rush loads
Fault output pin indicates current faults
Implements high- or low-side switches
Applications
Lamp drivers
Relay and solenoid drivers
Heater switching
Power bus switching
Motion control
Half or full H-bridge drivers
Typical Application
Protected under one or more of the following Micrel patents:
patent #4,951,101; patent #4,914,546
Note: The MIC5010 is ESD sensitive.
MIC5010
Micrel
5-88
April 1998
Pin Description
(Refer to Figures 1 and 2)
Pin Number
Pin Name
Pin Function
1
Inhibit
Inhibits current sense function when connected to supply. Normally
grounded.
3
Input
Resets current sense latch and turns on power MOSFET when taken above
threshold (3.5V typical). Pin 3 requires <1
A to switch.
4
Threshold
Sets current sense trip voltage according to:
2200
R +1000
TRIP
V
=
TH
where R
TH
to ground is 3.3k to 20k
. Adding capacitor C
TH
increases the
trip voltage at turn-on to 2V. Use C
TH
=10
F for a 10mS turn-on time
constant.
5
Sense
The sense pin causes the current sense to trip when V
SENSE
is V
TRIP
above
V
SOURCE
. Pin 5 is used in conjunction with a current shunt in the source of
a 3 lead FET or a resistor R
S
in the sense lead of a current sensing FET.
6
Source
Reference for the current sense voltage on pin 5 and return for the gate
clamp zener. Connect to the load side of current shunt or kelvin lead of
current sensing FET. Pins 5 and 6 can safely swing to 10V when turning
off inductive loads.
7
Ground
8
Gate
Drives and clamps the gate of the power FET. Pin 8 will be clamped to
approximately 0.7V by an internal diode when turning off inductive loads.
9, 10, 11
C2, Com, C1
Optional 1nF capacitors reduce gate turn-on time; C2 has dominant effect.
13
V
+
Supply pin; must be decoupled to isolate from large transients caused by
the power FET drain. 10
F is recommended close to pins 13 and 7.
14
Fault
Outputs status of protection circuit when pin 3 is high. Fault low indicates
normal operation; fault high indicates current sense tripped.
Absolute Maximum Ratings
(Note 1, 2)
Inhibit Voltage, Pin 1
1V to V+
Input Voltage, Pin 3
10V to V+
Threshold Voltage, Pin 4
0.5 to +5V
Sense Voltage, Pin 5
10V to V+
Source Voltage, Pin 6
10V to V+
Current into Pin 6
50 mA
Gate Voltage, Pin 8
1V to 50V
Supply Voltage (V
+
), Pin 13
0.5V to 36V
Fault Output Current, Pin 14
1mA to +1mA
Junction Temperature
150
C
Operating Ratings
(Notes 1, 2)
Power Dissipation
1.56W
JA
(Plastic DIP)
80
C/W
JA
(SOIC)
115
C/W
Ambient Temperature: B version
40
C to +85
C
Storage Temperature
65
C to +150
C
Lead Temperature
260
C
(Soldering, 10 seconds)
Supply Voltage (V
+
), Pin 13
7V to 32V high side
7V to 15V low side
Pin Configuration
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
NC
NC
April 1998
5-89
MIC5010
Micrel
5
Electrical Characteristics
(Note 3) Test circuit. T
A
= 55
C to +125
C, V
+
= 15V, V
1
= 0 V, I
4
=
I
5
= I
14
= 0, all
switches open, unless otherwise specified.
Parameter
Conditions
Min
Typical
Max
Units
Supply Current, I
13
V
+
= 32V
V
IN
= 0V, S4 closed
0.1
10
A
V
IN
= V
S
= 32V, I
4
= 200
A
8
20
mA
Logic Input Voltage, V
IN
V
+
= 4.75V
Adjust V
IN
for V
GATE
low
2
V
Adjust V
IN
for V
GATE
high
4.5
V
V
+
= 15V
Adjust V
IN
for V
GATE
high
5.0
V
Logic Input Current, I
3
V+ = 32V
V
IN
= 0V
1
A
V
IN
= 32V
1
A
Input Capacitance
Pin 3
5
pF
Gate Drive, V
GATE
S1, S2 closed,
V
+
= 7V, I
8
= 0
13
15
V
V
S
= V+, V
IN
= 5V
V
+
= 15V, I
8
= 100
A
24
27
V
Zener Clamp,
S2 closed, V
IN
= 5V
V+ = 15V, V
S
= 15V
11
12.5
15
V
V
GATE
V
SOURCE
V
+
= 32V, V
S
= 32V
11
13
16
V
Gate Turn-on Time, t
ON
V
IN
switched from 0 to 5V; measure time
25
50
s
(Note 4)
for V
GATE
to reach 20V
Gate Turn-off Time, t
OFF
V
IN
switched from 5 to 0V; measure time
4
10
s
for V
GATE
to reach 1V
Threshold Bias Voltage, V
4
I
4
= 200
A
1.7
2
2.2
V
Current Sense Trip Voltage,
S2 closed, V
IN
= 5V,
V
+
= 7V,
S4 closed
75
105
135
mV
V
SENSE
V
SOURCE
Increase I
5
I
4
= 100
A
V
S
= 4.9V
70
100
130
mV
V
+
= 15V
S4 closed
150
210
270
mV
I
4
= 200
A
V
S
= 11.8V
140
200
260
mV
V
+
= 32V
V
S
= 0V
360
520
680
mV
I
4
= 500
A
V
S
= 25.5V
350
500
650
mV
Peak Current Trip Voltage,
S3, S4 closed,
1.6
2.1
V
V
SENSE
V
SOURCE
V
+
= 15V, V
IN
= 5V
Fault Output Voltage, V
14
V
IN
= 0V, I
14
= 100
A
0.4
1
V
V
IN
= 5V, I
14
= 100
A, current sense tripped
14
14.6
V
Current Sense Inhibit, V
1
V
1
above which current sense is disabled
7.5
13
V
Minimum possible V
1
1
V
Note 1
Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Electrical specifications do not apply when
operating the device beyond its specified Operating Ratings.
Note 2
The MIC5010 is ESD sensitive.
Note 3
Minimum and maximum Electrical Characteristics are 100% tested at T
A
= 25
C and T
A
= 85
C, and 100% guaranteed over the entire
range. Typicals are characterized at 25
C and represent the most likely parametric norm.
Note 4
Test conditions reflect worst case high-side driver performance. Low-side and bootstrapped topologies are significantly faster--see
Applications Information.
MIC5010
Micrel
5-90
April 1998
V+
50
S2
3.5k
VS
1nF
1nF
1nF
I14
I8
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
V3
S3 I4
S1
+ 1
F
I5
V1
500
1W
S4
NC
NC
Test Circuit
0
5
10
15
20
25
30
35
0
2
4
6
8
10
12
Supply Current
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (mA)
0
3
6
9
12
15
SUPPLY VOLTAGE (V)
0
2
4
6
8
10
12
14
VGATE V+ (V)
DC Gate Voltage
above Supply
Typical Characteristics
April 1998
5-91
MIC5010
Micrel
5
0
3
6
9
12
15
0
50
100
150
200
250
300
350
TURN-ON TIME (
S)
SUPPLY VOLTAGE (V)
High-side Turn-on Time*
GATE
C =1 nF
0
3
6
9
12
15
0
20
40
60
80
100
120
140
TURN-ON TIME (
S)
SUPPLY VOLTAGE (V)
C2=1 nF
High-side Turn-on Time*
GATE
C =1 nF
0
3
6
9
12
15
TURN-ON TIME (mS)
SUPPLY VOLTAGE (V)
High-side Turn-on Time*
GATE
C =10 nF
0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
0
3
6
9
12
15
TURN-ON TIME (mS)
SUPPLY VOLTAGE (V)
C2=1 nF
High-side Turn-on Time*
GATE
C =10 nF
0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
CHARGE-PUMP CURRENT (
A)
0
50
100
150
200
250
0
5
10
15
20
25
30
SUPPLY VOLTAGE (V)
Charge Pump
Output Current
V =V
GATE
+
V =V +5V
GATE
+
VS=V 5V
+
CHARGE-PUMP CURRENT (mA)
0
5
10
15
20
25
30
SUPPLY VOLTAGE (V)
Charge Pump
Output Current
V =V
GATE
+
0
0.2
0.4
0.6
0.8
1.0
V =V +5V
GATE
+
VS=V 5V
+
C2=1 nF
Typical Characteristics
(Continued)
* Time for gate to reach V
+
+ 5V in test circuit with VS = V
+
5V (prevents gate clamp from interfering with measurement).
MIC5010
Micrel
5-92
April 1998
0
3
6
9
12
15
SUPPLY VOLTAGE (V)
GATE
C =10 nF
TURN-OFF TIME (
S)
GATE
C =1 nF
0
10
20
30
40
50
Turn-off Time
0.5
0.75
1.0
1.25
1.5
1.75
2.0
25
0
25
50
75
100 125
DIE TEMPERATURE (
C)
NORMALIZED TURN-ON TIME
Turn-on Time
0
3
6
9
12
15
SUPPLY VOLTAGE (V)
GATE
C =10 nF
1
3
10
30
100
300
1000
TURN-ON TIME (
S)
GATE
C =1 nF
Low-side Turn-on Time
for Gate = 5V
0
3
6
9
12
15
SUPPLY VOLTAGE (V)
C2=1 nF
GATE
C =10 nF
1
3
10
30
100
300
1000
TURN-ON TIME (
S)
GATE
C =1 nF
Low-side Turn-on Time
for Gate = 5V
0
3
6
9
12
15
SUPPLY VOLTAGE (V)
GATE
C =10 nF
TURN-ON TIME (
S)
GATE
C =1 nF
Low-side Turn-on Time
for Gate = 10V
3
10
30
100
300
1000
3000
0
3
6
9
12
15
SUPPLY VOLTAGE (V)
GATE
C =10 nF
TURN-ON TIME (
S)
GATE
C =1 nF
Low-side Turn-on Time
for Gate = 10V
3
10
30
100
300
1000
3000
C2=1 nF
Typical Characteristics
(Continued)
April 1998
5-93
MIC5010
Micrel
5
Applications Information
Functional Description (Refer to Block Diagram)
The various MIC5010 functions are controlled via a logic
block connected to the input pin 3. When the input is low all
functions are turned off for low standby current, and the gate
of the power MOSFET is also held low through 500
to an
N-channel switch. When the input is taken above the turn-
on threshold (3.5V typical), the N-channel switch turns off
and the charge pump is turned on to charge the gate of the
power FET. A bandgap type voltage regulator is also turned
on which biases the current sense circuitry.
The charge pump incorporates a 100kHz oscillator and on-
chip pump capacitors capable of charging 1 nF to 5V above
supply in 60
S typical. With the addition of 1nF capacitors
at C1 and C2, the turn-on time is reduced to 25
S typical.
The charge pump is capable of pumping thegate up to over
twice the supply voltage. For this reason a zener clamp
(12.5V typical) is provided between the gate pin 8 and the
source pin 6 to prevent exceeding the V
GS
rating of the
MOSFET at high supplies.
The current sense operates by comparing the sense volt-
age at pin 5 to an offset version of the source voltage at pin
6. Current I4 flowing in threshold pin 4 is mirrored and
returned to the source via a 1k
resistor to set the offset or
trip voltage. When (V
SENSE
V
SOURCE
) exceeds V
TRIP
, the
current sense trips and sets the current sense latch to turn
off the power FET. An integrating comparator is used to
reduce sensitivity to spikes on pin 5. The latch is reset to turn
the FET back on by "recycling" the input pin 3 low and then
high again.
A resistor R
TH
from pin 4 to ground sets I4, and hence V
TRIP
.
An additional capacitor C
TH
from pin 4 to ground creates a
higher trip voltage at turn-on, which is necessary to prevent
high in-rush current loads such as lamps or capacitors from
false-tripping the current sense.
When the current sense has tripped, the fault pin 14 will be
high as long as the input pin 3 remains high. However, when
the input is low the fault pin will also be low.
Construction Hints
High current pulse circuits demand equipment and assem-
bly techniques that are more stringent than normal, low
current lab practices. The following are the sources of
common pitfalls encountered while prototyping:Supplies:
many bench power supplies have poor transient response.
Circuits that are being pulse tested, or those that operate by
pulse-width modulation will produce strange results when
used with a supply that has poor ripple rejection, or a
peaked transient response. Monitor the power supply volt-
age that appears at the drain of a high-side driver (or the
supply side of the load in a low-side driver) with an oscillo-
scope. It is not uncommon to find bench power supplies in
the 1kW class that overshoot or undershoot by as much as
50% when pulse loaded. Not only will the load current and
voltage measurements be affected, but it is possible to
over-stress various components--especially electrolytic
capacitors--with possibly catastrophic results. A 10
F sup-
ply bypass capacitor at the chip is recommended.
+
-
V+
CHARGE
PUMP
TEMP
SENSE
V. REG
R
S
Q
LOGIC
MIC5010
3
14
7
1
4
6
5
8
9
10
11
13
500
1k
C1 Com C2
V+
Gate
Sense
Source
Ground
Inhibit
Threshold
Input
Fault
1k
+
-
I4
CURRENT
SENSE
LATCH
V
TRIP
12.5V
Block Diagram
MIC5010
Micrel
5-94
April 1998
Applications Information
(Continued)
Residual Resistances: Resistances in circuit connections
may also cause confusing results. For example, a circuit
may employ a 50m
power MOSFET for low drop, but
careless construction techniques could easily add 50 to 100
m
resistance. Do not use a socket for the MOSFET. If the
MOSFET is a TO-220 type package, make high-current
drain connections to the tab. Wiring losses have a profound
effect on high-current circuits. A floating millivoltmeter can
identify connections that are contributing excess drop un-
der load.
Circuit Topologies
The MIC5010 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 MIC5010
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
GS
= 1V). The choice
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
L
, 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 R
S
and trips if I
L
R
S
exceeds
V
TRIP
. R
TH
is selected to produce the desired trip voltage.
As a guideline, keep V
TRIP
within the limits of 100mV and
500mV (R
TH
= 3.3k
to 20k
). 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 (V
4
). The values
shown in Figure 2 are designed for a trip current of 20
amperes. It is important to ground pin 6 at the current shunt
R
S
, to eliminate the effects of ground resistance.
A key advantage of the low-side topology is that the load
supply is limited only by the MOSFET BV
DSS
rating. Clamp-
ing may be required to protect the MOSFET drain terminal
from inductive switching transients. The MIC5010 supply
should be limited to 15V in low-side topologies; otherwise,
a large current will be forced through the gate clamp zener.
Low-side drivers constructed with the MIC501X family are
also fast; the MOSFET gate is driven to near supply
immediately when commanded ON. Typical circuits achieve
10V enhancement in 10
s or less on a 12 to 15V supply.
High-Side Driver with Current Shunt (Figure 3). The
comparator input pins (source and sense) float with the
current sensing resistor (R
S
) on top of the load. R1 and R2
add a small, additional potential to V
TRIP
to prevent false-
triggering of the over-current shutdown circuit with open or
inductive loads. R1 is sized for a current flow of 1mA, while
R2 contributes a drop of 100mV. The shunt voltage should
be 200 to 500mV at the trip point. The example of Figure 3
gives a 10A trip current when the output is near supply. The
trip point is somewhat reduced when the output is at ground
as the voltage drop across R1 (and therefore R2) is zero.
High-side drivers implemented with MIC501X drivers are
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
IRF540
10F
10k
10m
IRC 4LPW-5
Figure 2. Low-Side Driver with
Current Shunt
LOAD
Control Input
=7 to 15V
V
+
+
NC
NC
(International Resistive Company)
V
LOAD
I =20A (trip current)
L
V
TRIP
I
L
V
TRIP
= 200mV
For this example:
R =
2200
1000
V
TRIP
TH
R =
S
R
S
R
TH
April 1998
5-95
MIC5010
Micrel
5
Applications Information
(Continued)
self-protected against inductive switching transients. Dur-
ing turn-off an inductive load will force the MOSFET source
5V or more below ground, while the driver holds the gate at
ground potential. The MOSFET is forced into conduction,
and it dissipates the energy stored in the load inductance.
The MIC5010 source and sense pins (5 and 6) are designed
to withstand this negative excursion without damage. Exter-
nal clamp diodes are unnecessary, but may be added to
reduce power dissipation in the MOSFET.
Current Shunts (R
S
). Low-valued resistors are necessary
for use at R
S
.Values for R
S
range from 5 to 50m
, at 2 to
10W. Worthy of special mention are Kelvin-sensed, "four-
terminal" units supplied by a number of manufacturers
.
Kelvin-sensed resistors eliminate errors that are caused by
lead and terminal resistances, and simplify product assem-
bly. 10% tolerance is normally adequate, and with shunt
potentials of 200mV thermocouple effects are insignificant.
Temperature coefficient is important; a linear, 500ppm/
C
change will contribute as much as 10% shift in the over-
current trip point. Most power resistors designed for current
shunt service drift less than 100ppm/
C.
Low-Side Driver with Current Sensing MOSFET (Figure
4). Several manufacturers now supply power MOSFETs in
which a small sampling of the total load current is diverted
to a "sense" pin. One additional pin, called "Kelvin source,"
is included to eliminate the effects of resistance in the
source bond wires. Current-sensing MOSFETs are speci-
fied with a sensing ratio "S" which describes the relationship
between the on-resistance of the sense connection and the
body resistance "R" of the main source pin. Current sensing
MOSFETs eliminate the current shunt required by standard
MOSFETs.
The design equations for a low-side driver using a current
sensing MOSFET are shown in Figure 4. "S" is specified on
the MOSFET's datasheet, and "R" must be measured or
estimated. V
TRIP
must be less than R
I
L
, or else R
S
will
become negative. Substituting a MOSFET with higher on-
resistance, or reducing V
TRIP
fixes this problem. V
TRIP
=
100 to 200mV is suggested. Although the load supply is
limited only by MOSFET ratings, the MIC5010 supply
should be limited to 15V to prevent damage to the gate
clamp zener. Output clamping is necessary for inductive
loads.
"R" is the body resistance of the MOSFET, excluding bond
resistances. R
DS(ON)
as specified on MOSFET data sheets
includes bond resistances. A Kelvin-connected ohmmeter
(using TAB and SOURCE for forcing, and SENSE and
KELVIN for sensing) is the best method of evaluating "R."
Alternatively, "R" can be estimated for large MOSFETs
(R
DS(ON)
100m
) by simply halving the stated R
DS(ON)
, or
by subtracting 20 to 50m
from the stated R
DS(ON)
for
smaller MOSFETs.
High-Side Driver with Current Sensing MOSFET (Figure
1). The design starts by determining the value of "S" and "R"
for the MOSFET (use the guidelines described for the low-
side version). Let V
TRIP
= 100 mV, and calculate R
S
for a
desired trip current. Next calculate R
TH
and R1. The trip
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
=24V
IRF541
10F
100
20k
24k
18m
IRC 4LPW-5*
R1
Figure 3. High-Side Driver
with Current Shunt
LOAD
Control Input
V
+
+
NC
NC
*International Resistive Company
R2
R1=
R2=100
R =
R =
1mA
V
100mV+
2200
1000
+
I
L
For this example:
I =10A (trip current)
L
V =100mV
TRIP
V
TRIP
V
TRIP
S
R
S
TH
R
TH
Suppliers of Kelvin-sensed power resistors:
Dale Electronics, Inc., 2064 12th Ave., Columbus, NE 68601. Tel: (402) 564-3131
International Resistive Co., P.O. Box 1860, Boone, NC 28607-1860. Tel: (704) 264-8861
Kelvin, 14724 Ventura Blvd., Ste. 1003, Sherman Oaks, CA 91403-3501. Tel: (818) 990-1192
RCD Components, Inc., 520 E. Industrial Pk. Dr., Manchester, NH 03103. Tel: (603) 669-0054
Ultronix, Inc., P.O. Box 1090, Grand Junction, CO 81502. Tel: (303) 242-0810
MIC5010
Micrel
5-96
April 1998
point is somewhat reduced when the output is at ground as
the voltage drop across R1 is zero. No clamping is required
for inductive loads.
Typical Applications
Start-up into a Dead Short. If the MIC5010 attempts to turn
on a MOSFET when the load is shorted, a very high current
flows. The over-current shutdown will protect the MOSFET,
but only after a time delay of 5 to 10
s. The MOSFET must
be capable of handling the overload; consult the device's
SOA curve. If a short circuit causes the MOSFET to exceed
its 10
s SOA, a small inductance in series with the source
can help limit di/dt to control the peak current during the 5
to 10
s delay.
When testing short-circuit behavior, use a current probe
rated for both the peak current and the high di/dt.
The over-current shutdown delay varies with comparator
overdrive, owing to noise filtering in the comparator. A delay
of up to 100
s can be observed at the threshold of shut-
down. A 20% overdrive reduces the delay to near minimum.
Incandescent Lamps. The cold filament of an incandes-
cent lamp exhibits less than one-tenth as much resistance
as when the filament is hot. The initial turn-on current of a
#6014 lamp is about 70A, tapering to 4.4A after a few
hundred milliseconds. It is unwise to set the over-current trip
point to 70A to accommodate such a load. A "resistive" short
that draws less than 70A could destroy the MOSFET by
allowing sustained, excessive dissipation. If the over-cur-
rent trip point is set to less than 70A, the MIC5010 will not
start a cold filament. The solution is to start the lamp with a
high trip point, but reduce this to a reasonable value after the
lamp is hot.
The MIC5010 over-current shutdown circuit is designed to
handle this situation by varying the trip point with time (see
Figure 5). R
TH1
functions in the conventional manner,
providing a current limit of approximately twice that required
by the lamp. R
TH2
acts to increase the current limit at turn-
on to approximately 10 times the steady-state lamp current.
The high initial trip point decays away according to a 20ms
time constant contributed by C
TH
. R
TH2
could be eliminated
with C
TH
working against the internal 1k
resistor, but this
results in a very high over-current threshold. As a rule of
thumb design the over-current circuitry in the conventional
manner, then add the R
TH2
/C
TH
network to allow for lamp
start-up. Let R
TH2
= (R
TH1
10) 1k
, and choose a
capacitor that provides the desired time constant working
against R
TH2
and the internal 1k
resistor.
When the MIC5010 is turned off, the threshold pin (4)
appears as an open circuit, and C
TH
is discharged through
R
TH1
and R
TH2
. This is much slower than the turn-on time
Applications Information
(Continued)
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
IRCZ44
(S=2590,
R=11m
)
10F
22
20k
Figure 4. Low-Side Driver with
Current-Sensing MOSFET
LOAD
Control Input
=15V
V
+
+
NC
NC
R
TH
V
LOAD
SOURCE
KELVIN
SENSE
S
R
SR
R I
R =
L
V
TRIP
V
TRIP
S
R =
1000
2200
V
TRIP
TH
For this example:
=20A (trip current)
I
L
=100mV
V
TRIP
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
12V
IRCZ44
10F
43
3.9k
Figure 5. Time-Variable
Trip Threshold
Control Input
+
NC
NC
22k
R
TH1
C
TH
22F
1k
#6014
R
TH2
April 1998
5-97
MIC5010
Micrel
5
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
IRFZ40
10F
20k
Figure 7. 10-Ampere
Electronic Circuit Breaker
+
NC
NC
100
22m
LOAD
12V
10k
10k
100nF
1N4148
100k
100k
100k
MPSA05
12V
CPSL-3 (Dale)
constant, and it simulates the thermal response of the
filament. If the lamp is pulse-width modulated, the current
limit will be reduced by the residual charge left in C
TH
.
Modifying Switching Times. Do not add external capaci-
tors to the gate to slow down the switching time. Add a
resistor (1k
to 51k
) in series with the gate of the MOS-
FET to achieve this result.
External capacitors can be added at C1 and C2 for faster
switching times (see Block Diagram). Values of 100pF to
1nF produce useful speed increases. If component count is
critical, C2 (pins 9 to 10) can be used alone with only a small
loss of speed compared to using both capacitors.
Bootstrapped High-Side Driver (Figure 6). The speed of
a high-side driver can be increased to better than 10
s by
bootstrapping the supply off of the MOSFET source. This
topology can be used where the load is pulse-width modu-
lated (100Hz to 20kHz), or where it is energized for only a
short period of time (
25ms). If the load is left energized for
a long period of time (>25ms), the bootstrap capacitor will
discharge and the MIC5010 supply pin will fall to V
+
= V
DD
1.4. Under this condition pins 5 and 6 will be held above
V
+
and may false trigger the over-current circuit. A larger
capacitor will lengthen the maximum "on" time; 1000
F will
hold the circuit up for 2.5 seconds, but requires more charge
time when the circuit is turned off. The optional Schottky
barrier diode improves turn-on time on supplies of less than
10V.
Since the supply current in the "off" state is only a small
leakage, the 100nF bypass capacitor tends to remain
charged for several seconds after the MIC5010 is turned off.
In a PWM application the chip supply is actually much
higher than the system supply, which improves switching
time.
Electronic Circuit Breaker (Figure 7). The MIC5010 forms
the basis of a high-performance, fast-acting circuit breaker.
By adding feedback from FAULT to INPUT the breaker can
be made to automatically reset. If an over-current condition
Applications Information
(Continued)
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
IRF540
10F
20k
Figure 6. Bootstrapped
High-Side Driver
Control Input
+
NC
NC
100
18m
LOAD
100nF
1N4001 (2)
1N5817
=7 to 15V
+
V
1mA
R1=
V
DD
MIC5010
Micrel
5-98
April 1998
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
IRFP044 (2)
10F
20k
Figure 9. 50-Ampere
Industrial Switch
+
NC
NC
100
5m
LOAD
24V
15k
OFF
330k
100k
ON
24V
LVF-15 (RCD)
CR2943-NA102A
(GE)
extends out from the control box, is more easily pressed.
This circuit is compatible with control boxes such as the
CR2943 series (GE). The circuit is configured so that if both
switches close simultaneously, the "off" button has prece-
dence. If there is a fault condition the circuit will latch off, and
it can be reset by pushing the "on" button.
This application also illustrates how two (or more) MOSFETs
can be paralleled. This reduces the switch drop, and distrib-
utes the switch dissipation into multiple packages.
High-Voltage Bootstrap (Figure 10). Although the MIC5010
is limited to operation on 7 to 32V supplies, a floating
bootstrap arrangement can be used to build a high-side
switch that operates on much higher voltages. The MIC5010
and MOSFET are configured as a low-side driver, but the
load is connected in series with ground. The high speed
normally associated with low-side drivers is retained in this
circuit.
Power for the MIC5010 is supplied by a charge pump. A
20kHz square wave (15Vp-p) drives the pump capacitor
and delivers current to a 100
F storage capacitor. A zener
diode limits the supply to 18V. When the MIC5010 is off,
power is supplied by a diode connected to a 15V supply.
The circuit of Figure 8 is put to good use as a barrier
between low voltage control circuitry and the 90V motor
supply.
Half-Bridge Motor Driver (Figure 11). Closed loop control
of motor speed requires a half-bridge driver. This topology
presents an extra challenge since the two output devices
should not cross conduct (shoot-through) when switching.
Cross conduction increases output device power dissipa-
tion and, in the case of the MIC5010, could trip the over-
current comparator. Speed is also important, since PWM
control requires the outputs to switch in the 2 to 20kHz
range.
The circuit of Figure 11 utilizes fast configurations for both
the top- and bottom-side drivers. Delay networks at each
input provide a 2 to 3
s dead time effectively eliminating
occurs, the circuit breaker shuts off. The breaker tests the
load every 18ms until the short is removed, at which time the
circuit latches ON. No reset button is necessary.
Opto-Isolated Interface (Figure 8). Although the MIC5010
has no special input slew rate requirement, the lethargic
transitions provided by an opto-isolator may cause oscilla-
tions on the rise and fall of the output. The circuit shown
accelerates the input transitions from a 4N35 opto-isolator
by adding hysteresis. Opto-isolators are used where the
control circuitry cannot share a common ground with the
MIC5010 and high-current power supply, or where the
control circuitry is located remotely. This implementation is
intrinsically safe; if the control line is severed the MIC5010
will turn OFF.
Fault-Protected Industrial Switch (Figure 9). The most
common manual control for industrial loads is a push button
on/off switch. The "on" button is physically arranged in a
recess so that in a panic situation the "off" button, which
Applications Information
(Continued)
100k
Figure 8. Improved
Opto-Isolator Performance
1k
To MIC5010 Input
100k
4N35
33k
33pF
MPSA05
15V
10mA
Control Input
April 1998
5-99
MIC5010
Micrel
5
cross conduction. Both the top- and bottom-side drivers are
protected, so the output can be shorted to either rail without
damage.
The top-side driver is based on the bootstrapped circuit of
Figure 6, and cannot be switched on indefinitely. The
bootstrap capacitor (1
F) relies on being pulled to ground
by the bottom-side output to recharge. This limits the
maximum duty cycle to slightly less than 100%.
Two of these circuits can be connected together to form an
H-bridge. If the H-bridge is used for locked antiphase
control, no special considerations are necessary. In the
case of sign/magnitude control, the "sign" leg of the H-
bridge should be held low (PWM input held low) while the
other leg is driven by the magnitude signal.
If current feedback is required for torque control, it is
available in chopped form at the bottom-side driver's 22m
current-sensing resistor.
Time-Delay Relay (Figure 12). The MIC5010 forms the
basis of a simple time-delay relay. As shown, the delay
commences when power is applied, but the 100k
/1N4148
could be independently driven from an external source such
as a switch or another high-side driver to give a delay
relative to some other event in the system.
Hysteresis has been added to guarantee clean switching at
turn-on. Note that an over-current condition latches the
relay in a safe, OFF condition. Operation is restored by
either cycling power or by momentarily shorting pin 3 to
ground.
Motor Driver with Stall Shutdown (Figure 13). Tachom-
eter feedback can be used to shut down a motor driver
circuit when a stall condition occurs. The control switch is a
3-way type; the "START" position is momentary and forces
the driver ON. When released, the switch returns to the
"RUN" position, and the tachometer's output is used to hold
the MIC5010 input ON. If the motor slows down, the tach
output is reduced, and the MIC5010 switches OFF. Resis-
tor "R" sets the shutdown threshold. If the output current
exceeds 30A, the MIC5010 shuts down and remains in that
condition until the momentary "RESET" button is pushed.
Control is then returned to the START/RUN/STOP switch.
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
IRFP250
100F
6.2k
Figure 10. High-Voltage
Bootstrapped Driver
+
NC
NC
10m
1N4003
90V
100k
1k
100k
4N35
33k
33pF
MPSA05
10mA
Control Input
M
1nF
15V
1N4003 (2)
15Vp-p, 20kHz
Squarewave
1N4746
100nF
200V
KC1000-4T
(Kelvin)
1/4 HP, 90V
5BPB56HAA100
(GE)
Applications Information
(Continued)
MIC5010
Micrel
5-100
April 1998
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
IRF541
1F
20k
Figure 11. Half-Bridge
Motor Driver
+
NC
NC
100
100nF
1N4001 (2)
1N5817
15V
15k
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
IRF541
10F
10k
22m
CPSL-3
(Dale)
+
NC
NC
22m
CPSL-3
(Dale)
1nF
10k
2N3904
22k
220pF
1N4148
22k
15V
M
12V,
10A Stalled
PWM
INPUT
Applications Information
(Continued)
April 1998
5-101
MIC5010
Micrel
5
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
12V
IRCZ44
10F
43
20k
4.3k
Figure 13. Motor Stall
Shutdown
+
NC
NC
M
T
STOP
RUN
START
12V
100nF
1N4148
330k
330k
330k
1N4148
R
RESET
Inhibit
Input
Thresh
Sense
Source
Gnd
Fault
V+
C1
Com
C2
Gate
1
2
3
4
5
6
7
8
9
10
11
12
13
14
MIC5010
12V
IRCZ44
10F
43
4.3k
Figure 12. Time-Delay Relay
with 30A Over-Current Protection
+
NC
NC
OUTPUT
(Delay=5S)
10k
100
100F
+
20k
100k
1N4148
Applications Information
(Continued)
MIC5010
Micrel
5-102
April 1998
V
+
C1
C2
COM
500
12.5V
G
S
125pF
125pF
100 kHz
OSCILLATOR
OFF
ON
GATE CLAMP
ZENER
Figure 14. Gate Control
Circuit Detail
Q1
Q2
Q3
Q4
Q5
Q6
C1
C2
Applications Information
(Continued)
Gate Control Circuit
When applying the MIC5010, it is helpful to understand the
operation of the gate control circuitry (see Figure 14). The
gate circuitry can be divided into two sections: 1) charge
pump (oscillator, Q1-Q5, and the capacitors) and 2) gate
turn-off switch (Q6).
When the MIC5010 is in the OFF state, the oscillator is
turned off, thereby disabling the charge pump. Q5 is also
turned off, and Q6 is turned on. Q6 holds the gate pin (G) at
ground potential which effectively turns the external MOS-
FET off.
Q6 is turned off when the MIC5010 is commanded on. Q5
pulls the gate up to supply (through 2 diodes). Next, the
charge pump begins supplying current to the gate. The gate
accepts charge until the gate-source voltage reaches 12.5V
and is clamped by the zener diode.
A 2-output, three-phase clock switches Q1-Q4, providing a
quasi-tripling action. During the initial phase Q4 and Q2 are
ON. C1 is discharged, and C2 is charged to supply through
Q5. For the second phase Q4 turns off and Q3 turns on,
pushing pin C2 above supply (charge is dumped into the
gate). Q3 also charges C1. On the third phase Q2 turns off
and Q1 turns on, pushing the common point of the two
capacitors above supply. Some of the charge in C1 makes
its way to the gate. The sequence is repeated by turning Q2
and Q4 back on, and Q1 and Q3 off.
In a low-side application operating on a 12 to 15V supply,
the MOSFET is fully enhanced by the action of Q5 alone. On
supplies of more than approximately 14V, current flows
directly from Q5 through the zener diode to ground. To
prevent excessive current flow, the MIC5010 supply should
be limited to 15V in low-side applications.
The action of Q5 makes the MIC5010 operate quickly in
low-side applications. In high-side applications Q5
precharges the MOSFET gate to supply, leaving the charge
pump to carry the gate up to full enhancement 10V above
supply. Bootstrapped high-side drivers are as fast as low-
side drivers since the chip supply is boosted well above the
drain at turn-on.
PDF 
ZIP