Page 1
MIC5014/5015 Micrel
MIC5014/5015
Low-Cost High- or Low-Side MOSFET Driver
General Description
MIC5014 and MIC5015 MOSFET drivers are designed for
gate control of N-channel, enhancement-mode, power
MOSFETs used as high-side or low-side switches. The
MIC5014/5 can sustain an on-state output indefinitely.
The MIC5014/5 operates from a 2.75V to 30V supply. In highside configurations, the driver can control MOSFETs that
switch loads of up to 30V. In low-side configurations, with
separate supplies, the maximum switched voltage is limited
only by the MOSFET.
The MIC5014/5 has a TTL compatible control input. The
MIC5014 is noninverting while the MIC5015 is inverting.
The MIC5014/5 features an internal charge pump that can
sustain a gate voltage greater than the available supply
voltage. The driver is capable of turning on a logic-level
MOSFET from a 2.75V supply or a standard MOSFET from a
5V supply. The gate-to-source output voltage is internally
limited to approximately 15V.
The MIC5014/5 is protected against automotive load dump,
reversed battery, and inductive load spikes of –20V. The
driver’s overvoltage shutdown feature turns off the external
MOSFET at approximately 35V to protect the load against
power supply excursions.
The MIC5014 is an improved pin-for-pin compatible replacement in many MIC5011 applications.
The MIC5014/5 is available in plastic 8-pin DIP and 8-pin
SOIC pacakges.
Typical Application
+3V to +4V
Features
• 2.75V to 30V operation
• 100µA maximum supply current (5V supply)
•15µA typical off-state current
• Internal charge pump
• TTL compatible input
• Withstands 60V transient (load dump)
• Reverse battery protected to –20V
• Inductive spike protected to –20V
• Overvoltage shutdown at 35V
• Internal 15V gate protection
• Minimum external parts
• Operates in high-side or low-side configurations
•1µA control input pull-off
• Inverting and noninverting versions
Applications
• Automotive electrical load control
• Battery-powered computer power management
• Lamp control
• Heater control
• Motor control
• Power bus switching
Ordering Information
Part Number Temperature Range Package
Noninverting
MIC5014BM –40°C to +85°C 8-pin SOIC
MIC5014BN –40°C to +85°C 8-pin Plastic DIP
Inverting
MIC5015BM –40°C to +85°C 8-pin SOIC
MIC5015BN –40°C to +85°C 8-pin Plastic DIP
5
10µF
Control Input
ON
OFF
1
2
3
4
MIC5014
V+
Input
Source
8
NC
7
NC
6
NC
5
GateGnd
IRLZ24
Load
Figure 1. 3V “Sleep-Mode” Switch
with a Logic-Level MOSFET
1997 5-137
Page 2
MIC5014/5015 Micrel
Block Diagram
V+ (1)
Charge Pump
*Input (2)
* Only on the inverting version
Pin Description
Pin Number Pin Name Pin Function
1 V+ Supply. Must be decoupled to isolate from large transients caused by the
2 Input Turns on power MOSFET when taken above (or below) threshold (1.0V
3 Source Connects to source lead of power MOSFET and is the return for the gate
4 Ground
5 Gate Drives and clamps the gate of the power MOSFET.
6, 7, 8 NC Not internally connected.
Gate (5)
15V
Source (3)
Ground (4)
power MOSFET drain. 10µF is recommended close to pins 1 and 4.
typical). Pin 2 requires ~ 1µA to switch.
clamp zener. Pin 3 can safely swing to –20V when turning off inductive
loads.
5-138 1997
Page 3
MIC5014/5015 Micrel
Absolute Maximum Ratings (Notes 1,2) Operating Ratings (Notes 1,2)
Supply Voltage...............................................–20V to 60V
Input Voltage .....................................................–20V to V
Source Voltage..................................................–20V to V
Source Current..........................................................50mA
Gate Voltage ..................................................–20V to 50V
Junction Temperature .............................................. 150°C
θJA (Plastic DIP)..................................................... 160°C/W
+
θ
(SOIC) .............................................................170°C/W
JA
+
Ambient Temperature: B version ................–40°C to +85°C
Ambient Temperature: A version ..............+55°C to +125°C
Storage Temperature ................................–65°C to +150°C
Lead Temperature......................................................260°C
(max soldering time: 10 seconds)
Supply Voltage (V+) ......................................... 2.75V to 30V
Electrical Characteristics (Note 3) T
= –55°C to +125°C unless otherwise specified
A
Parameter Conditions Min Typ Max Units
Supply Current V+ = 30V V
V+ = 5V V
V+ = 3V V
De-Asserted (Note 5) 10 25 µA
IN
V
Asserted (Note 5) 5.0 10 mA
IN
De-Asserted 10 25
IN
V
Asserted 60 100
IN
De-Asserted 10 25
IN
V
Asserted 25 35
IN
µA
µA
Logic Input Voltage Threshold 3.0V ≤ V+ ≤ 30V Digital Low Level 0.8
V
IN
T
= 25°C Digital High Level 2.0
A
Logic Input Current 3.0V ≤ V+ ≤ 30V V
MIC5014 (non-inverting) V
Logic Input Current 3.0V ≤ V+ ≤ 30V V
MIC5015 (inverting) V
Low –2.0 0
IN
High 1.0 2.0
IN
Low –2.0 –1.0
IN
High –1.0 2.0
IN
V
µA
µA
Input Capacitance 5.0 pF
Gate Enhancement 3.0V ≤ V+ ≤ 30V V
V
– V
GATE
SUPPLY
Zener Clamp 8.0V ≤ V+ ≤ 30V V
V
– V
GATE
Gate Turn-on Time, t
SOURCE
ON
V+ = 4.5V V
(Note 4) CL = 1000pF time for V
Asserted 4.0 17 V
IN
Asserted 13 15 17 V
IN
switched on, measure 2.5 8.0 ms
IN
to reach V+ + 4V
GATE
V+ = 12V As above, measure time for 90 140 µs
CL = 1000pF V
Gate Turn-off Time, t
OFF
V+ = 4.5V V
(Note 4) CL = 1000pF time for V
to reach V+ + 4V
GATE
switched off, measure 6.0 30 µs
IN
to reach 1V
GATE
V+ = 12V As above, measure time for 6.0 30 µs
CL = 1000pF V
to reach 1V
GATE
Overvoltage Shutdown 35 37 41 V
Threshold
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 MIC5014/5015 is ESD sensitive.
Note 3: Minimum and maximum Electrical Characteristics are 100% tested at TA = 25°C and TA = 85°C, and 100% guaranteed over the
entire operating temperature 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. Maximum value of switching time seen at 125°C, unit operated at room temperature will reflect the typical value
shown.
Note 5: “Asserted” refers to a logic high on the MIC5014 and a logic low on the MIC5015.
5
1997 5-139
Page 4
MIC5014/5015 Micrel
Typical Characteristics All data measured using FET probe to minimize resistive loading
Supply Current
(Output Asserted)
6
5
4
3
2
1
SUPPLY CURRENT (mA)
0
0 5 10 15 20 25 30
SUPPLY VOLTAGE (V)
High-Side Turn-On Time
Until Gate = Supply + 4V
100
C
= 1300pF
10
1
0.1
TURN-ON TIME (ms)
0.01
0 4 8 12 16 20 24 28
GATE
SUPPLY VOLTAGE (V)
Gate Enhancement
vs. Supply Voltage
20
15
10
5
GATE ENHANCEMENT (V)
Gate Enhancement =
V
– V
GATE
0
0 5 10 15 20 25 30
SUPPLY VOLTAGE (V)
SUPPLY
High-Side Turn-On Time
Until Gate = Supply + 4V
100
C
= 3000pF
10
1
0.1
TURN-ON TIME (ms)
0.01
0 4 8 12 16 20 24 28
GATE
SUPPLY VOLTAGE (V)
High-Side Turn-On Time
vs. Gate Capacitance
300
250
200
150
100
TURN-ON TIME (µs)
50
0
0246810
Supply = 12V
GATE CAPACITANCE (nF)
High-Side Turn-On Time
180
160
140
120
100
HIGH-SIDE TURN-ON TIME (µs)
vs. Temperature
80
60
40
20
0
-60 -30 0 30 60 90 120 150
Supply = 12V
C
= 1000pF
GATE
AMBIENT TEMPERATURE (°C)
High-Side Turn-On Time
Until Gate = Supply + 10V
100
C
= 1300pF
10
1
0.1
TURN-ON TIME (ms)
0.01
0 5 10 15 20 25 30
GATE
SUPPLY VOLTAGE (V)
Charge-Pump
1000
100
10
OUTPUT CURRENT (µA)
Output Current
5V
1
0 5 10 15
GATE-TO-SOURCE VOLTAGE (V)
Source connected
3V
to supply: supply
voltage as noted
12V
28V
High-Side Turn-On Time
Until Gate = Supply + 10V
100
C
10
1
0.1
TURN-ON TIME (ms)
0.01
0 5 10 15 20 25 30
GATE
SUPPLY VOLTAGE (V)
Charge-Pump
10000
1000
100
10
OUTPUT CURRENT (µA)
Output Current
Source connected
to ground: supply
voltage as noted
5V
3V
1
0 5 10 15
GATE-TO-SOURCE VOLTAGE (V)
= 3000pF
12V
28V
High-Side Turn-Off Time
10
TURN-OFF TIME (µs)
Until Gate = 1V
8
6
C
= 3000pF
4
2
0
0 5 10 15 20 25 30
GATE
C
=
GATE
1300pF
SUPPLY VOLTAGE (V)
Low-Side Turn-On Time
10000
1000
TURN-ON TIME (µs)
100
10
Until Gate = 4V
C
GATE
C
= 1300pF
GATE
1
0 5 10 15 20 25 30
SUPPLY VOLTAGE (V)
= 3000pF
5-140 1997
Page 5
MIC5014/5015 Micrel
Applications Information
Functional Description
The MIC5014 is functionally and pin for pin compatible with
the MIC5011, except for the omission of the optional speedup capacitor pins, which are available on the MIC5011. The
MIC5015 is an inverting configuration of the MIC5014.
The internal functions of these devices are controlled via a
logic block (refer to block diagram) connected to the control
input (pin 2). When the input is off (low for the MIC5014, and
high for the MIC5015), all functions are turned off, and the
gate of the external power MOSFET is held low via two Nchannel switches. This results in a very low standby current;
15µA typical, which is necessary to power an internal bandgap.
When the input is driven to the “ON” state, the N-channel
switches are turned off, the charge pump is turned on, and the
P-channel switch between the charge pump and the gate
turns on, allowing the gate of the power FET to be charged.
The op amp and internal zener form an active regulator which
shuts off the charge pump when the gate voltage is high
enough. This is a feature not found on the MIC5011.
The charge pump incorporates a 100kHz oscillator and onchip pump capacitors capable of charging a 1,000pF load in
90µs typical. In addition to providing active regulation, the
internal 15V zener is included to prevent exceeding the V
rating of the power MOSFET at high supply voltages.
The MIC5014/15 devices have been improved for greater
ruggedness and durability. All pins can withstand being
pulled 20V below ground without sustaining damage, and the
supply pin can withstand an overvoltage transient of 60V for
1s. An overvoltage shutdown has also been included, which
turns off the device when the supply exceeds 35V.
GS
not use a socket for the MOSFET. If the MOSFET is a TO-220
type package, make high current connections to the drain tab.
Wiring losses have a profound effect on high-current circuits.
A floating milliohmeter can identify connections that are contributing excess drop under load.
Low Voltage Testing
As the MIC5014/MIC5015 have relatively high output impedances, a normal oscilloscope probe will load the device. This
is especially pronounced at low voltage operation. It is recommended that a FET probe or unity gain buffer be used for all
testing.
Circuit Topologies
The MIC5014 and MIC5015 are well suited for use with
standard power MOSFETs in both low and high side driver
configurations. In addition, the lowered supply voltage requirements of these devices make them ideal for use with logic
level FETs in high side applications with a supply voltage of 3
to 4V. (If higher supply voltages [>4V] are used with logic level
FETs, an external zener clamp must be supplied to ensure
that the maximum V
exceeded.) In addition, a standard IGBT can be driven using
these devices.
Choice of one topology over another is usually based on
speed vs. safety. The fastest topology is the low side driver,
however, it is not usually considered as safe as high side
driving as it is easier to accidentally short a load to ground than
to V
The slowest, but safest topology is the high side
CC.
driver; with speed being inversely proportional to supply
voltage. It is the preferred topology for most military and
automotive applications. Speed can be improved considerably by bootstrapping from the supply.
rating of the logic FET [10V] is not
GS
5
Construction Hints
High current pulse circuits demand equipment and assembly
techniques that are more stringent than normal, low current
lab practices. The following are the sources of pitfalls most
often encountered during prototyping:
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. Always monitor the power supply voltage that
appears at the drain of a high side driver (or the supply side
of the load for a low side driver) with an oscilloscope. 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 overstress various
components, especially electrolytic capacitors, with possibly
catastrophic results. A 10µF supply bypass capacitor
chip is
recommended.
Residual resistances
in circuit connections may also cause confusing results. For
example, a circuit may employ a 50mΩ power MOSFET for
low voltage drop, but unless careful construction techniques
are used, one could easily add 50 to 100mΩ resistance. Do
Supplies
: Many bench
at the
: Resistances
All topologies implemented using these devices are well
suited to driving inductive loads, as either the gate or the
source pin can be pulled 20V below ground with no effect.
External clamp diodes are unnecessary, except for the case
in which a transient may exceed the overvoltage trip point.
High Side Driver (Figure 1) The high side topology shown
here is an implementation of a “sleep-mode” switch for a
laptop or notebook computer which uses a logic level FET. A
standard power FET can easily be substituted when supply
voltages above 4V are required.
+3V to +30V
10µF
Control Input
ON
OFF
Figure 2. Low Side Driver
MIC5014
1
2
InputV+NC
3
Source
4
8
NC
NC
GateGnd
Load
7
6
5
1997 5-141
Page 6
MIC5014/5015 Micrel
Low Side Driver (Figure 2) A key advantage of this topology,
as previously mentioned, is speed. The MOSFET gate is
driven to near supply immediately when the MIC5014/15 is
turned on. Typical circuits reach full enhancement in 50µs or
less with a 15V supply.
Bootstrapped High Side Driver (Figure 3) The turn-on time of
a high side driver can be improved to faster than 40µs by
bootstrapping the supply with the MOSFET source. The
Schottky barrier diode prevents the supply pin from dropping
more than 200mV below the drain supply and improves turnon time. 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 MIC5014/15 is turned
off. Faster speeds can be obtained at the expense of supply
voltage (the overvoltage shutdown will turn the part off when
the bootstrapping action pulls the supply pin above 35V) by
using a larger capacitor at the junction of the two 1N4001
diodes. In a PWM application (this circuit can be used for either
PWM’ed or continuously energized loads), the chip supply is
sustained at a higher potential than the system supply, which
improves switching time.
1
Control Input
ON
OFF
2
InputV+NC
3
Source
4
100nF
MIC5015
GateGnd
1N5817
NC
NC
+2.75V to +30V
1N4001 (2)
8
7
6
5
1µF
1RF540
the short is removed, feedback to the input pin insures that the
MIC5014 will turn back on. This output can also be level
shifted and sent to an I/O port of a microcontroller for intelligent control.
Current Shunts (RS). Low valued resistors are necessary for
use at RS. Resistors are available with values ranging from 1
to 50mΩ, at 2 to 10W. If a precise overcurrent trip point is
not necessary, then a nonprecision resistor or even a measured PCB trace can serve as RS. The major cause of drift in
resistor values with such resistors is temperature coefficient;
the designer should be aware that a linear, 500 ppm/°C
change will contribute as much as 10% shift in the overcurrent
trip point. If this is not acceptable, a power resistor designed
for current shunt service (drifts less than 100 ppm/°C), or a
R
S
0.06Ω
R4
1kΩ
Load
†
12V
On
R1
1kΩ
R2
120kΩ
I
= V
TRIP
TRIP/RS
= 1.7A
V
= R1/(R1+R2)
TRIP
LM301A
2.2kΩ
Kelvin-sensed resistor may be used.
10µF
1
2
3
4
MIC5014
V+
Input
Source
8
NC
7
NC
6
NC
5
GateGnd
Figure 4. High Side Driver with Overcurrent Shutdown
Load
Figure 3. Bootstrapped Hgh-Side Driver
High Side Driver With Current Sense (Figure 4) Although no
current sense function is included on the MIC5014/15 devices,
a simple current sense function can be realized via the addition
of one more active component; an LM301A op amp used as
a comparator. The positive rail of the op amp is tied to V+, and
the negative rail is tied to ground. This op amp was chosen as
it can withstand having input transients that swing below the
negative rail, and has common mode range almost to the
positive rail.
The inverting side of this comparator is tied to a voltage divider
which sets the voltage to V+ – V
. The non inverting side
TRIP
is tied to the node between the drain of the FET and the sense
resistor. If the overcurrent trip point is not exceeded , this node
will always be pulled above V+ – V
, and the output of the
TRIP
comparator will be high which feeds the control input of the
MIC5014 (polarities should be reversed if the MIC5015 is
used). One the overcurrent trip point has been reached, the
comparator will go low, which shuts off the MIC5014. When the
† Suppliers of Precision Power Resistors:
Dale Electronics, Inc., 2064 12th Ave., Columbus, NE 68601. (402) 5653131
International Resistive Co., P.O. Box 1860, Boone,NC 28607-1860.
(704) 264-8861
Isotek Corp., 566 Wilbur Ave. Swansea, MA 02777. (508) 673-2900
Kelvin, 14724 Ventura Blvd., Ste. 1003, Sherman Oaks, CA 91403-3501.
(818) 990-1192
RCD Components, Inc., 520 E. Industrial Pk. Dr., Manchester, NH 03103.
(603) 669-0054
Ultronix, Inc., P.O. Box 1090, Grand Junction, CO 81502 (303) 242-0810
High Side Driver With Delayed Current Sense (Figure 5)
Delay of the overcurrent detection to accomodate high inrush
loads such as incandescent or halogen lamps can be accomplished by adding an LM3905 timer as a one shot to provide
an open collector pulldown for the comparator output such
that the control input of the MIC5015 stays low for a preset
amount of time without interference from the current sense
circuitry. Note that an MIC5015 must be used in this application (figure 5), as an inverting control input is necessary. The
delay time is set by the RC time constant of the external
components on pins 3 and 4 of the timer; in this case, 6ms was
chosen.
An LM3905 timer was used instead of a 555 as it provides a
clean transition, and is almost impossible to make oscillate.
Good bypassing and noise immunity is essential in this circuit
to prevent spurious op amp oscillations.
5-142 1997
Page 7
MIC5014/5015 Micrel
12V
12V
10µF
1kΩ
1
2
3
4
MIC5014
V+
Input
Source
8
NC
7
NC
6
NC
5
GateGnd
R
S
0.06Ω
Load
R4
1kΩ
Figure 5. High Side Driver with Delayed Overcurrent Shutdown
Typical Applications
Variable Supply Low Side Driver for Motor Speed Control
(Figure 6) The internal regulation in the MIC5014/15 allows
a steady gate enhancement to be supplied while the
MIC5014/15 supply varies from 5V to 30V, without damaging
the internal gate to source zener clamp. This allows the speed
of the DC motor shown to be varied by varying the supply
voltage.
= +5V to +30V
V
CC
MIC5014
1
V+
2
3
4
Input
Source
OFF
ON
Figure 6: DC Motor Speed Control/Driver
8
NC
NC
NC
GateGnd
M
7
6
5
IRF540
LM3905N
On
R1
1kΩ
1000pF
R2
120kΩ
LM301A
0.01µF
1
Trigger
2
V
3
R/C
4
2.2kΩ
REF
Logic
Emit
Coll
8
7
6
5
V+Gnd
applications, it is acceptable to allow this voltage to momentarily turn the MOSFET back on as a way of dissipating the
inductor’s current. However, if this occurs when driving a
solenoid valve with a fast switching speed, chemicals or
gases may be inadvertantly be dispensed at the wrong time
with possibly disasterous consequences. Also, too large of
a kickback voltage (as is found in larger solenoids) can
damage the MIC5014 or the power FET by forcing the Source
node below ground (the MIC5014 can be driven up to 20V
below ground before this happens). A catch diode has been
included in this design to provide an alternate route for the
inductive kickback current to flow. The 5kΩ resistor in series
with this diode has been included to set the recovery time of
the solenoid valve.
24V
OFF
MIC5015
1
V+
2
ON
3
4
Input
Source
8
NC
7
NC
6
NC
5
GateGnd
IRFZ40
5
Solenoid Valve Driver (Figure 7) High power solenoid valves
are used in many industrial applications requiring the timed
dispensing of chemicals or gases. When the solenoid is
activated, the valve opens (or closes), releasing (or stopping)
fluid flow. A solenoid valve, like all inductive loads, has a
considerable “kickback” voltage when turned off, as current
cannot change instantaneously through an inductor. In most
1997 5-143
ASCO
8320A
Solenoid
Figure 7: Solenoid Valve Driver
1N4005
5kΩ
Page 8
MIC5014/5015 Micrel
Incandescent/Halogen Lamp Driver (Figure 8) The combi-
nation of an MIC5014/5015 and a power FET makes an
effective driver for a standard incandescent or halogen lamp
load. Such loads often have high inrush currents, as the
resistance of a cold filament is less than one-tenth as much as
when it is hot. Power MOSFETs are well suited to this
application as they have wider safe operating areas than do
power bipolar transistors. It is important to check the SOA
curve on the data sheet of the power FET to be used against
the estimated or measured inrush current of the lamp in
question prior to prototyping to prevent “explosive” results.
If overcurrent sense is to be used, first measure the duration
of the inrush, then use the topology of Figure 5 with the RC of
the timer chosen to accomodate the duration with suitable
guardbanding.
10µF
Control Input
ON
OFF
1
2
3
4
MIC5014
V+
Input
Source
NC
NC
NC
GateGnd
12V
8
7
6
5
IRF540
Motor Driver With Stall Shutdown (Figure 10) Tachometer
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 MIC5014 input ON.
If the motor slows down, the tach output is reduced, and the
MIC5014 switches OFF. Resistor “R” sets the shutdown
threshold.
12V
10µF
8
NC
7
NC
6
NC
5
GateGnd
IRFZ44
MT
R
330kΩ
1N4148
330kΩ
1
V+
2
Input
3
Source
4
MIC5014
OSRAM
HLX64623
Figure 8. Halogen Lamp Driver
Relay Driver (Figure 9) Some power relay applications re-
quire the use of a separate switch or drive control, such as in
the case of microprocessor control of banks of relays where
a logic level control signal is used, or for drive of relays with
high power requirements. The combination of an MIC5014/
5015 and a power FET also provides an elegant solution to
power relay drive.
12V
10µF
Control Input
ON
OFF
1
2
3
4
MIC5014
V+
Input
Source
8
NC
7
NC
6
NC
5
GateGnd
IRF540
Guardian Electric
1725-1C-12D
Figure 10. Motor Stall Shutdowm
Simple DC-DC Converter (Figure 11) The simplest applica-
tion for the MIC5014 is as a basic one-chip DC-DC converter.
As the output (Gate) pin has a relatively high impedance, the
output voltage shown will vary significantly with applied load.
5V
10µF
1
2
3
4
MIC5014
V+
Input
Source
8
NC
7
NC
6
NC
5
GateGnd
V
= 12V
OUT
Figure 11. DC - DC Converter
Figure 9: Relay Driver
5-144 1997
Page 9
MIC5014/5015 Micrel
MIC5014
Control Input
1
2
3
4
8
7
6
5
IRFZ40
12V
NC
GateGnd
Source
Input
V+
NC
NC
10µF
MIC5015
1
2
3
4
8
7
6
5
NC
GateGnd
Source
Input
V+
NC
NC
12V
IRFZ40
V
OUT
High Side Driver With Load Protection (Figure 12) Although the MIC5014/15 devices are reverse battery protected, the load and power FET are not, in a typical high side
configuration. In the event of a reverse battery condition, the
internal body diode of the power FET will be forward biased.
This allows the reversed supply access to the load.
10µF
Control Input
ON
OFF
1
2
3
4
MIC5014
V+
Input
Source
The addition of a Schottky diode between the supply and the
FET eliminates this problem. The MBR2035CT was chosen
as it can withstand 20A continuous and 150A peak,
and should survive the rigors of an automotive environment.
The two diodes are paralleled to reduce switch loss (forward
voltage drop).
12V
8
NC
7
NC
6
NC
5
GateGnd
IRF540
Load
MBR2035CT
Figure 12: High Side Driver WIth Load Protection
Push-Pull Driver With No Cross-Conduction (Figure 13)
As the turn-off time of the MIC5014/15 devices is much faster
than the turn-on time, a simple push-pull driver with no cross
conduction can be made using one MIC5014 and one
MIC5015. The same control signal is applied to both inputs;
the MIC5014 turns on with the positive signal, and the
MIC5015 turns on when it swings low.
This scheme works with no additional components as the
relative time difference between the rise and fall times of the
MIC5014 is large. However, this does mean that there is
5
considerable deadtime (time when neither driver is turned on).
If this circuit is used to drive an inductive load, catch diodes
must be used on each half to provide an alternate path for the
kickback current that will flow during this deadtime.
This circuit is also a simple half H-bridge which can be driven
with a PWM signal on the input for SMPS or motor drive
applications in which high switching frequencies are not
desired.
Figure 13: Push-Pull Driver
1997 5-145
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