Micrel MIC5010BN Full-featured high- or low-side mosfet driver Datasheet

MIC5010
Micrel
MIC5010
Full-Featured High- or Low-Side MOSFET Driver
Not Recommended for New Designs
General Description
Features
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 60µs 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 programmable 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.
• 7V to 32V operation
• Less than 1µA 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
• 25µs 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
•
•
•
•
•
•
Typical Application
RTH
20kΩ
5
Ordering Information
MIC5010
Control Input
Lamp drivers
Relay and solenoid drivers
Heater switching
Power bus switching
Motion control
Half or full H-bridge drivers
1 Inhibit
2 NC
Fault 14
V+ 13
3 Input
4 Thresh
NC
5 Sense
6 Source
7 Gnd
12
C1 11
Com 10
Temperature Range
MIC5010BN
–40°C to +85°C
14-pin Plastic DIP
Package
MIC5010BM
–40°C to +85°C
14-pin SOIC
V+ =24V
+
10µF
R =
S
C2 9
Gate 8
SR( V
TRIP
R IL – ( V
+100mV)
TRIP
IRCZ44
(S=2590,
R=11mΩ)
SENSE
RS
+100mV)
V+SRRS
R1=
100mV (SR+R S)
SOURCE
43Ω
Note: The MIC5010 is ESD sensitive.
Part Number
R TH =
2200
–1000
V
TRIP
LOAD
KELVIN
For this example:
I =30A (trip current)
R1
4.3kΩ
L
V
TRIP
=100mV
Figure 1. High-Side Driver with
Current-Sensing MOSFET
Protected under one or more of the following Micrel patents:
patent #4,951,101; patent #4,914,546
April 1998
5-87
MIC5010
Micrel
Absolute Maximum Ratings (Note 1, 2)
Operating Ratings (Notes 1, 2)
Inhibit Voltage, Pin 1
Input Voltage, Pin 3
Threshold Voltage, Pin 4
Sense Voltage, Pin 5
Source Voltage, Pin 6
Current into Pin 6
Gate Voltage, Pin 8
Supply Voltage (V+), Pin 13
Fault Output Current, Pin 14
Junction Temperature
Power Dissipation
θJA (Plastic DIP)
θJA (SOIC)
Ambient Temperature: B version
Storage Temperature
Lead Temperature
(Soldering, 10 seconds)
Supply Voltage (V+), Pin 13
–1V to V+
–10V to V+
– 0.5 to +5V
–10V to V+
–10V to V+
50 mA
–1V to 50V
–0.5V to 36V
–1mA to +1mA
150°C
1.56W
80 °C/W
115°C/W
–40°C to +85°C
–65°C to +150°C
260°C
7V to 32V high side
7V to 15V low side
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 <1µA to switch.
4
Threshold
Sets current sense trip voltage according to:
VTRIP =
2200
R TH +1000
where RTH to ground is 3.3k to 20kΩ. Adding capacitor CTH increases the
trip voltage at turn-on to 2V. Use CTH =10µF for a 10mS turn-on time
constant.
5
Sense
The sense pin causes the current sense to trip when VSENSE is VTRIP above
VSOURCE. Pin 5 is used in conjunction with a current shunt in the source of
a 3 lead FET or a resistor RS 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. 10µF 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.
Pin Configuration
MIC5010
1
2
3
4
5
6
7
Inhibit Fault
NC
V+
Input
NC
Thresh
C1
Sense Com
Source
Gnd
C2
Gate
5-88
14
13
12
11
10
9
8
April 1998
MIC5010
Micrel
Electrical Characteristics (Note 3) Test circuit. TA = –55°C to +125°C, V+ = 15V, V1 = 0 V, I4 = I5 = I14 = 0, all
switches open, unless otherwise specified.
Parameter
Conditions
Supply Current, I13
V+
Logic Input Voltage, VIN
V+
= 32V
Min
VIN = 0V, S4 closed
VIN = VS = 32V, I4 = 200µA
V+
Logic Input Current, I3
= 4.75V
= 15V
V+ = 32V
Typical
Max
Units
0.1
10
µA
8
20
mA
2
V
Adjust VIN for VGATE low
Adjust VIN for VGATE high
4.5
V
Adjust VIN for VGATE high
5.0
V
VIN = 0V
–1
µA
VIN = 32V
Input Capacitance
Gate Drive, VGATE
Zener Clamp,
1
Pin 3
5
pF
13
15
V
24
27
V
V+ = 15V, VS = 15V
11
12.5
15
V
V+
11
13
16
V
S1, S2 closed,
V+
= 7V, I8 = 0
VS = V+, VIN = 5V
V+
= 15V, I8 = 100 µA
S2 closed, VIN = 5V
VGATE – VSOURCE
µA
= 32V, VS = 32V
Gate Turn-on Time, tON
(Note 4)
VIN switched from 0 to 5V; measure time
for VGATE to reach 20V
25
50
µs
Gate Turn-off Time, tOFF
VIN switched from 5 to 0V; measure time
for VGATE to reach 1V
4
10
µs
Threshold Bias Voltage, V4
I4 = 200 µA
1.7
2
2.2
V
Current Sense Trip Voltage,
S2 closed, VIN = 5V,
V+
= 7V,
S4 closed
75
105
135
mV
VSENSE – VSOURCE
Increase I5
I4 = 100 µA
VS = 4.9V
70
100
130
mV
V+ = 15V
S4 closed
150
210
270
mV
I4 = 200 µA
VS = 11.8V
140
200
260
mV
V+
VS = 0V
360
520
680
mV
VS = 25.5V
350
500
650
mV
1.6
2.1
= 32V
I4 = 500 µA
Peak Current Trip Voltage,
VSENSE – VSOURCE
S3, S4 closed,
V+ = 15V, VIN = 5V
Fault Output Voltage, V14
VIN = 0V, I14 = –100 µA
0.4
VIN = 5V, I14 = 100 µA, current sense tripped
Current Sense Inhibit, V1
V1 above which current sense is disabled
Minimum possible V1
14
V
1
14.6
7.5
V
V
13
1
V
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 TA = 25°C and TA = 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.
April 1998
5-89
5
MIC5010
Micrel
Test Circuit
V+
+ 1µF
I5
MIC5010
V1
1
2
3
4
V3
50Ω
5
6
500Ω
1W
S3 I4
3.5k
7
Inhibit Fault
NC
V+
Input
NC
Thresh
C1
Sense Com
Source
Gnd
C2
Gate
14
13
I14
12
11
1nF
10
1nF
9
8
1nF
S4
S2
S1
I8
VS
Typical Characteristics
DC Gate Voltage
above Supply
12
14
10
12
VGATE – V+ (V)
SUPPLY CURRENT (mA)
Supply Current
8
6
4
2
0
10
8
6
4
2
0
0
5
10
15
20
25
30
35
0
3
6
9
12
15
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
5-90
April 1998
MIC5010
Micrel
Typical Characteristics (Continued)
High-side Turn-on Time*
350
140
300
120
TURN-ON TIME (µS)
TURN-ON TIME (µS)
High-side Turn-on Time*
CGATE =1 nF
250
200
150
100
50
C2=1 nF
80
60
40
20
0
3
6
9
12
0
15
0
9
12
15
High-side Turn-on Time*
High-side Turn-on Time*
3.5
1.4
3.0
1.2
CGATE =10 nF
2.5
2.0
1.5
1.0
0.5
3
6
9
12
0.6
0.4
0.2
0
CHARGE-PUMP CURRENT (mA)
250
VGATE =V+
200
150
VGATE =V++5V
100
50
VS=V +–5V
0
5
10
15
20
25
* Time for gate to reach
+ 5V in test circuit with VS =
6
9
12
15
Charge Pump
Output Current
1.0
VGATE =V+
0.8
0.6
0.4
VGATE =V ++5V
0.2
C2=1 nF
VS=V +–5V
0
0
30
SUPPLY VOLTAGE (V)
V+
3
SUPPLY VOLTAGE (V)
Charge Pump
Output Current
0
5
C2=1 nF
0.8
0
15
CGATE =10 nF
1.0
SUPPLY VOLTAGE (V)
CHARGE-PUMP CURRENT (µA)
6
SUPPLY VOLTAGE (V)
0
0
April 1998
3
SUPPLY VOLTAGE (V)
TURN-ON TIME (mS)
TURN-ON TIME (mS)
0
CGATE =1 nF
100
5
10
15
20
25
SUPPLY VOLTAGE (V)
V+
– 5V (prevents gate clamp from interfering with measurement).
5-91
30
MIC5010
Micrel
Typical Characteristics (Continued)
Turn-on Time
NORMALIZED TURN-ON TIME
Turn-off Time
TURN-OFF TIME (µS)
50
CGATE =10 nF
40
30
20
CGATE =1 nF
10
0
0
3
6
9
12
2.0
1.75
1.5
1.25
1.0
0.75
0.5
15
–25
SUPPLY VOLTAGE (V)
50
TURN-ON TIME (µS)
1000
300
CGATE =10 nF
100
30
10
75
100 125
Low-side Turn-on Time
for Gate = 5V
1000
TURN-ON TIME (µS)
25
DIE TEMPERATURE (°C)
Low-side Turn-on Time
for Gate = 5V
CGATE =1 nF
3
1
C2=1 nF
300
CGATE =10 nF
100
30
10
CGATE =1 nF
3
1
0
3
6
9
12
15
0
SUPPLY VOLTAGE (V)
3000
TURN-ON TIME (µS)
CGATE =10 nF
1000
300
100
CGATE =1 nF
10
3
0
6
3
6
9
12
9
12
15
Low-side Turn-on Time
for Gate = 10V
3000
30
3
SUPPLY VOLTAGE (V)
Low-side Turn-on Time
for Gate = 10V
TURN-ON TIME (µS)
0
1000
CGATE =10 nF
300
100
30
CGATE =1 nF
10
3
0
15
C2=1 nF
3
6
9
12
15
SUPPLY VOLTAGE (V)
SUPPLY VOLTAGE (V)
5-92
April 1998
MIC5010
Micrel
A resistor RTH from pin 4 to ground sets I4, and hence VTRIP.
An additional capacitor CTH 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.
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 500Ω to an
N-channel switch. When the input is taken above the turnon 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 onchip pump capacitors capable of charging 1 nF to 5V above
supply in 60µS typical. With the addition of 1nF capacitors
at C1 and C2, the turn-on time is reduced to 25µS 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 VGS rating of the
MOSFET at high supplies.
The current sense operates by comparing the sense voltage 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 1kΩ resistor to set the offset or
trip voltage. When (VSENSE – VSOURCE) exceeds VTRIP , 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.
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
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 voltage that appears at the drain of a high-side driver (or the
supply side of the load in 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
over-stress various components—especially electrolytic
capacitors—with possibly catastrophic results. A 10µF supply bypass capacitor at the chip is recommended.
Block Diagram
V+
13
C1 Com C2
11 10 9
CHARGE
PUMP
8 Gate
500Ω
Input 3
LOGIC
V+
CURRENT
SENSE
LATCH
Q
Fault 14
MIC5010
R
5 Sense
+
S
I4
-
TEMP
SENSE
+
VTRIP
V. REG
1k
7
Ground
April 1998
12.5V
1
Inhibit
5-93
4
Threshold
1k
6 Source
5
MIC5010
Micrel
Applications Information (Continued)
Residual Resistances: Resistances in circuit connections
may also cause confusing results. For example, a circuit
may employ a 50mΩ power MOSFET for low drop, but
careless construction techniques could easily add 50 to 100
mΩ 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 under load.
Circuit Topologies
The MIC5010 is suited for use in high- or low-side driver
applications with over-current protection for both currentsensing and standard MOSFETs. In addition, the MIC5010
works well in applications where, for faster switching times,
the supply is bootstrapped from the MOSFET source output. 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 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 overcurrent comparator monitors RS and trips if IL × RS exceeds
VTRIP. RTH 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 (V4). 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
RS, 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 BVDSS rating. Clamping 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 10µs 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 (RS) on top of the load. R1 and R2
add a small, additional potential to VTRIP to prevent falsetriggering 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
V+=7 to 15V
VLOAD
MIC5010
1 Inhibit
2 NC
Control Input
RTH
10kΩ
Fault 14
V+ 13
3 Input
NC 12
4 Thresh
C1 11
5 Sense
Com 10
6 Source
C2 9
7 Gnd
RS=
+
10µF
RTH =
LOAD
V
TRIP
I
L
2200
–1000
V
TRIP
For this example:
Gate 8
IRF540
I =20A (trip current)
L
VTRIP = 200mV
RS
10mΩ
IRC 4LPW-5
(International Resistive Company)
Figure 2. Low-Side Driver with
Current Shunt
5-94
April 1998
MIC5010
Micrel
Applications Information (Continued)
+
V =24V
MIC5010
Control Input
R
TH
20kΩ
1 Inhibit
2 NC
Fault 14
V+ 13
3 Input
4 Thresh
NC
5 Sense
6 Source
7 Gnd
R1=
V+
1mA
+
12
R2=100Ω
10µF
C1 11
Com 10
RS =
C2 9
Gate 8
IRF541
RTH =
TRIP
IL
2200
–1000
V
TRIP
100Ω
RS
18mΩ
IRC 4LPW-5*
R2
100mV+V
For this example:
I L =10A (trip current)
VTRIP =100mV
R1
24kΩ
LOAD
*International Resistive Company
Figure 3. High-Side Driver
with Current Shunt
self-protected against inductive switching transients. During 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. External clamp diodes are unnecessary, but may be added to
reduce power dissipation in the MOSFET.
Current Shunts (RS). Low-valued resistors are necessary
for use at RS.Values for RS range from 5 to 50mΩ, at 2 to
10W. Worthy of special mention are Kelvin-sensed, “fourterminal” units supplied by a number of manufacturers†.
Kelvin-sensed resistors eliminate errors that are caused by
lead and terminal resistances, and simplify product assembly. 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 overcurrent 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 specified 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. VTRIP must be less than R × IL, or else RS will
become negative. Substituting a MOSFET with higher onresistance, or reducing VTRIP fixes this problem. VTRIP =
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. RDS(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
(RDS(ON) ≤ 100mΩ) by simply halving the stated RDS(ON), or
by subtracting 20 to 50mΩ from the stated RDS(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 lowside version). Let VTRIP = 100 mV, and calculate RS for a
desired trip current. Next calculate RTH and R1. The trip
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
April 1998
5-95
5
MIC5010
Micrel
Applications Information (Continued)
MIC5010
1 Inhibit
Control Input
R TH
20kΩ
2 NC
3 Input
+
V =15V
V
LOAD
Fault 14
V+ 13
NC 12
4 Thresh
C1 11
5 Sense
Com 10
RS =
+
10µF
SR V
TRIP
R I –V
L
R TH=
LOAD
TRIP
2200
–1000
V
TRIP
6 Source
C2 9
7 Gnd
Gate 8
IRCZ44
(S=2590,
R=11mΩ)
For this example:
I =20A (trip current)
L
SENSE
V
TRIP
RS
22Ω
=100mV
SOURCE
KELVIN
Figure 4. Low-Side Driver with
Current-Sensing MOSFET
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 10µs. 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 10µs SOA, a small inductance in series with the source
can help limit di/dt to control the peak current during the 5
to 10µs 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 100µs can be observed at the threshold of shutdown. A 20% overdrive reduces the delay to near minimum.
Incandescent Lamps. The cold filament of an incandescent 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-current 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). RTH1 functions in the conventional manner,
providing a current limit of approximately twice that required
by the lamp. RTH2 acts to increase the current limit at turnon to approximately 10 times the steady-state lamp current.
The high initial trip point decays away according to a 20ms
time constant contributed by CTH. RTH2 could be eliminated
with CTH working against the internal 1kΩ 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 RTH2/CTH network to allow for lamp
start-up. Let RTH2 = (RTH1 ÷ 10) – 1kΩ, and choose a
capacitor that provides the desired time constant working
against RTH2 and the internal 1kΩ resistor.
When the MIC5010 is turned off, the threshold pin (4)
appears as an open circuit, and CTH is discharged through
RTH1 and RTH2. This is much slower than the turn-on time
5-96
MIC5010
RTH2
1kΩ
Control Input
RTH1
22kΩ
1 Inhibit
2 NC
Fault 14
V+ 13
3 Input
4 Thresh
NC 12
C1 11
12V
+
10µF
5 Sense Com 10
6 Source
C2 9
7 Gnd
Gate 8
IRCZ44
CTH
22µF
43Ω
3.9kΩ
#6014
Figure 5. Time-Variable
Trip Threshold
April 1998
MIC5010
Micrel
Applications Information (Continued)
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 CTH.
Modifying Switching Times. Do not add external capacitors to the gate to slow down the switching time. Add a
resistor (1kΩ to 51kΩ) in series with the gate of the MOSFET 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 10µs by
bootstrapping the supply off of the MOSFET source. This
topology can be used where the load is pulse-width modulated (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+ = VDD
– 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; 1000µF 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.
V DD =7 to 15V
MIC5010
1 Inhibit
2 NC
Control Input
1N4001 (2)
100nF
NC 12
C1 11
3 Input
4 Thresh
100Ω
18mΩ
+
R1= V
1mA
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
MIC5010
1 Inhibit
2 NC
3 Input
4 Thresh
MPSA05
20kΩ
Fault 14
V+ 13
NC 12
C1 11
+
10µF
5 Sense Com 10
6 Source
C2 9
7 Gnd
Gate 8
IRFZ40
100Ω
22mΩ
CPSL-3 (Dale)
1N4148
10kΩ
Figure 7. 10-Ampere
Electronic Circuit Breaker
April 1998
LOAD
Figure 6. Bootstrapped
High-Side Driver
100kΩ
10kΩ
10µF
IRF540
12V
100nF
+
20kΩ 5
Sense Com 10
6 Source
C2 9
7 Gnd
Gate 8
12V
100kΩ 100kΩ
1N5817
Fault 14
V+ 13
5-97
LOAD
5
MIC5010
Micrel
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 precedence. 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 distributes 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 100µF 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 dissipation and, in the case of the MIC5010, could trip the overcurrent 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 3µs dead time effectively eliminating
Applications Information (Continued)
15V
33kΩ
33pF
To MIC5010 Input
100kΩ
MPSA05
10mA
Control Input
4N35
100kΩ
1kΩ
Figure 8. Improved
Opto-Isolator Performance
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 oscillations 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
24V
24V
MIC5010
100kΩ
ON
1 Inhibit
2 NC
OFF
3 Input
4 Thresh
CR2943-NA102A
(GE)
20kΩ
5 Sense
6 Source
7 Gnd
Fault 14
V+ 13
NC 12
C1 11
Com 10
+
10µF
C2 9
Gate 8
IRFP044 (2)
100Ω
5mΩ
330kΩ
LVF-15 (RCD)
15kΩ
LOAD
Figure 9. 50-Ampere
Industrial Switch
5-98
April 1998
MIC5010
Micrel
Applications Information (Continued)
15V
1N4003 (2)
MIC5010
1
Fault 14
V+ 13
2 NC
3
NC 12
Input
MPSA05
4
C1 11
Thresh
6.2kΩ 5
Sense Com 10
33kΩ
33pF
100kΩ
10mA
Control Input
Inhibit
4N35
6
C2 9
Source
7 Gnd
Gate 8
100kΩ
1N4746
+
100µF
90V
1nF
IRFP250
1kΩ
100nF
200V
10mΩ
KC1000-4T
(Kelvin)
1/4 HP, 90V
5BPB56HAA100
(GE)
1N4003
M
15Vp-p, 20kHz
Squarewave
Figure 10. High-Voltage
Bootstrapped Driver
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 (1µF) 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 Hbridge 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 22mΩ
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 100kΩ/1N4148
April 1998
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). 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 MIC5010 input ON. If the motor slows down, the tach
output is reduced, and the MIC5010 switches OFF. Resistor “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.
5-99
5
MIC5010
Micrel
Applications Information (Continued)
15V
MIC5010
1N4148
1 Inhibit
2 NC
22kΩ
3 Input
4 Thresh
220pF
20kΩ
5 Sense
6 Source
7 Gnd
Fault 14
V+ 13
1N5817
1N4001 (2)
100nF
NC 12
+
C1 11
Com 10
1µF
C2 9
Gate 8
IRF541
100Ω
22mΩ
CPSL-3
(Dale)
15kΩ
PWM
INPUT
15V
12V,
M 10A Stalled
MIC5010
1 Inhibit
2 NC
10kΩ
22kΩ
3 Input
4 Thresh
1nF
10kΩ
2N3904
5 Sense
6 Source
7 Gnd
Fault 14
V+ 13
NC 12
+
10µF
C1 11
Com 10
C2 9
Gate 8
IRF541
22mΩ
CPSL-3
(Dale)
Figure 11. Half-Bridge
Motor Driver
5-100
April 1998
MIC5010
Micrel
Applications Information (Continued)
MIC5010
1 Inhibit
2 NC
100kΩ
1N4148
20kΩ
12V
Fault 14
V+ 13
3 Input
4 Thresh
NC 12
5 Sense
Com 10
+
10µF
C1 11
6 Source
C2 9
7 Gnd
Gate 8
100µF
IRCZ44
+
OUTPUT
(Delay=5S)
10kΩ
43Ω
100Ω
4.3kΩ
Figure 12. Time-Delay Relay
with 30A Over-Current Protection
1N4148
5
330kΩ
MIC5010
RESET
1 Inhibit
2 NC
3 Input
4 Thresh
330kΩ
R
330kΩ
20kΩ
Fault 14
V+ 13
NC 12
C1 11
12V
+
10µF
5 Sense Com 10
6 Source
C2 9
7 Gnd
Gate 8
IRCZ44
43Ω
1N4148
4.3kΩ
100nF
T
12V
START
RUN
STOP
Figure 13. Motor Stall
Shutdown
April 1998
5-101
M
MIC5010
Micrel
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 MOSFET 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 lowside drivers since the chip supply is boosted well above the
drain at turn-on.
+
V
Q3
Q5
Q1
125pF
C1
125pF
C1
100 kHz
OSCILLATOR
C2
COM
C2
Q2
G
Q4
500Ω
OFF
GATE CLAMP
ZENER
12.5V
Q6
S
ON
Figure 14. Gate Control
Circuit Detail
5-102
April 1998