MIC5020BMT&R [MICREL]
Buffer/Inverter Based MOSFET Driver, BIMOS, PDSO8, SOIC-8;
| 型号： | MIC5020BMT&R |
| 厂家： | 
MICREL SEMICONDUCTOR |
| 描述： | Buffer/Inverter Based MOSFET Driver, BIMOS, PDSO8, SOIC-8 驱动器 |
| 文件： | 总7页 (文件大小：102K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
MIC5020
Current-Sensing Low-Side MOSFET Driver
General Description
Features
The MIC5020 low-side MOSFET driver is designed to oper-
ate at frequencies greater than 100kHz (5kHz PWM for 2% to
100% duty cycle) and is an ideal choice for high-speed
applications such as motor control, SMPS (switch mode
powersupplies),andapplicationsusing IGBTs. TheMIC5020
canalsooperateasacircuitbreakerwithorwithoutautomatic
retry. The MIC5020’s maximum supply voltage lends itself to
control applications using up to 50V. The MIC5020 can
control MOSFETs that switch voltages greater than 50V.
• 11V to 50V operation
• 175ns rise/fall time driving 2000pF
• TTL compatible input with internal pull-down resistor
• Overcurrent limit
• Fault output indication
• Gate to source protection
• Compatible with current sensing MOSFETs
Applications
• Lamp control
• Heater control
• Motor control
• Solenoid switching
• Switch-mode power supplies
• Circuit breaker
A rising or falling edge on the input results in a current source
orsinkpulseonthegateoutput. Thisoutputcurrentpulsecan
turn on or off a 2000pF MOSFET in approximately 175ns.
The MIC5020 then supplies a limited current (< 2mA), if
necessary, to maintain the output state.
Anovercurrentcomparatorwithatripvoltageof50mVmakes
the MIC5020 ideal for use with a current sensing MOSFET.
An external low value resistor may be used instead of a
sensing MOSFET for more precise overcurrent control. An
optional external capacitor connected to the C pin may be
T
Ordering Information
used to control the current shutdown duty cycle from 20% to
< 1%. A duty cycle from 20% to about 75% is possible with
an optional pull-up resistor from C to V . An open collector
Part Number
MIC5020BM
MIC5020BN
Temperature Range
–40°C to +85°C
Package
8-pin SOIC
T
DD
output provides a fault indication when the sense inputs are
tripped.
–40°C to +85°C
8-pin Plastic DIP
The MIC5020 is available in 8-pin SOIC and plastic DIP
packages.
Other members of the MIC502x series include the MIC5021
high-side driver and the MIC5022 half-bridge driver with a
cross-conduction interlock.
Typical Application
V+
+11V to +50V
10µF
MIC5020
1
2
3
4
8
7
6
5
N-Channel
Power MOSFET
VDD
Gate
150kHz max.
Input
Fault
CT
Sense−
Sense+
Gnd
50mV
ITRIP
RSENSE
=
optional*
RSENSE
* increases time before retry
Low-Side Driver with Overcurrent Trip and Retry
5-162
October 1998
MIC5020
Micrel
Pin Configuration
1 VDD
Gate 8
1
2
VDD
Input Sense− 7
Fault Sense+
Gate 8
2 Input Sense− 7
Fault Sense+
3
6
3
4
6
4 CT
Gnd 5
CT
Gnd 5
DIP Package
(N)
SOIC Package
(M)
Block Diagram
6V Internal Regulator
I1
Fault
CT
CINT
2I1
Normal
Fault
Q1
Sense +
VDD
Sense –
50mV
ON
OFF
6V
↑
↓
ONE-
SHOT
10I2
I2
Gate
Input
5
Transistor Count: 82
Pin Description
Pin Number
Pin Name
VDD
Pin Function
Supply: +11V to +50V. Decouple with ≥ 10µF capacitor.
1
2
Input
TTL Compatible Input: Logic high turns the external MOSFET on. An internal
pull-down returns an open pin to logic low.
3
4
Fault
CT
Overcurrent Fault Indicator: When the sense voltage exceeds threshold,
open collector output is open circuit for 5µs (tG(ON)), then pulled low for
tG(OFF). tG(OFF) is adjustable from CT.
Retry Timing Capacitor: Controls the off time (tG(OFF)) of the overcurrent
retry cycle. (Duty cycle adjustment.)
• Open = 20% duty cycle.
• Capacitor to Ground = approx. 20% to <1% duty cycle.
• Pull-Up resistor = approx. 20% to approx. 75% duty cycle.
• Ground = maintained shutdown upon overcurrent condition.
5
6
Gnd
Circuit Ground
Sense +
Current Sense Comparator (+) Input: Connect to high side of sense resistor
or current sensing MOSFET sense lead. A built-in offset in conjunction with
RSENSE sets the load overcurrent trip point.
7
8
Sense –
Gate
Current Sense Comparator (–) Input: Connect to the low side of the sense
resistor (usually power ground).
Gate Drive: Drives the gate of an external power MOSFET. Also limits VGS
to 15V max. to prevent Gate to Source damage. Will sink and source
current.
October 1998
5-163
MIC5020
Micrel
Absolute Maximum Ratings
Operating Ratings
Supply Voltage (V ) ..................................................+55V
Supply Voltage (V ) .................................... +11V to +50V
DD
DD
Input Voltage ................................................ –0.5V to +15V
Sense Differential Voltage..........................................±6.5V
Sense + or Sense – to Gnd.......................... –0.5V to +50V
Fault Voltage ...............................................................+50V
Current into Fault ....................................................... 50mA
Temperature Range
SOIC ...................................................... –40°C to +85°C
Plastic DIP.............................................. –40°C to +85°C
Timer Voltage (C ) .....................................................+5.5V
T
Electrical Characteristics
TA = 25°C, Gnd = 0V, VDD = 12V, Sense +,– = 0V, Fault = Open, CT = Open, Gate CL = 1500pF unless otherwise specificed
Symbol
Parameter
Condition
Min
Typ
0.8
2
Max
2
Units
mA
mA
mA
mA
V
D.C. Supply Current
VDD = 12V, Input = 0V
VDD = 50V, Input = 0V
VDD = 12V, Input = 5V
VDD = 50V, Input = 5V
10
2
0.8
4
25
2.0
Input Threshold
0.8
10
1.4
0.1
20
Input Hysteresis
V
Input Pull-Down Current
Input = 5V
40
µA
V
Fault Output
Fault Current = 1.6mA
0.15
0.4
Saturation Voltage
Note 1
Fault Output Leakage
Current Limit Threshold
Gate On Voltage
Fault = 50V
–1
30
10
14
2
0.01
50
+1
70
µA
mV
V
Note 2
VDD = 12V
11
VDD = 50V
15
18
10
V
tG(ON)
tG(OFF)
tDLH
tR
Gate On Time, Fixed
Gate Off Time, Adjustable
Gate Turn-On Delay
Gate Rise Time
Sense Differential > 70mV
5
µs
µs
ns
ns
ns
ns
kHz
Sense Differential > 70mV, CT = 0pF
10
20
50
Note 3
Note 4
Note 5
Note 6
Note 7
400
700
900
500
150
800
1500
1500
1500
tDLH
tF
Gate Turn-Off Delay
Gate Fall Time
fmax
Maximum Operating Frequency
100
Note 1 Voltage remains low for time affected by C .
T
Note 2 When using sense MOSFETs, it is recommended that R
< 50Ω. Higher values may affect the sense MOSFET’s current transfer ratio.
SENSE
Note 3 Input switched from 0.8V (TTL low) to 2.0V (TTL high), time for Gate transition from 0V to 2V.
Note 4 Input switched from 0.8V (TTL low) to 2.0V (TTL high), time for Gate transition from 2V to 10V.
Note 5 Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 11V (Gate ON voltage) to 10V.
Note 6 Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 10V from 2V.
Note 7 Frequency where gate on voltage reduces to 10V with 50% input duty cycle.
5-164
October 1998
MIC5020
Micrel
Typical Characteristics
Turn-Off Time vs.
Supply Voltage
Supply Current vs.
Turn-On Time vs.
Supply Voltage
Supply Voltage
1200
1100
1000
900
3.5
900
800
700
600
500
400
VIN = 5V
VGATE = 4V
CL = 1500pF
VIN = 0 to 5V Sq. Wave
3.0
2.5
2.0
1.5
VGATE = 4V
CL = 1500pF
VIN = 0 to 5V
Sq. Wave
VIN = 0V
800
1.0
INCLUDES PROPAGATION DELAY
INCLUDES PROPAGATION DELAY
700
0.5
5
10
15
20
(V)
25
30
5
10 15 20 25 30 35 40 45 50
(V)
5
10 15 20 25 30 35 40 45 50
V
SUPPLY
V
V
(V)
SUPPLY
SUPPLY
Input Current vs.
Input Voltage
Turn-On Time vs.
Gate Capacitance
Overcurrent Shutdown
Retry Duty Cycle
1200
1000
800
100
80
60
40
20
0
25.0
20.0
15.0
10.0
5.0
VGATE = 4V
VSUPPLY = 12V
tON = 5µs
V
SUPPLY = 12V
600
400
INCLUDES PROPAGATION DELAY
200
1x10
5
0.0
2
3
4
5
1x10
C
1x10
(pF)
1x10
0
5
10
V
15
(V)
20
25
0.1
1
10 100 1000 10000
C (pF)
T
GATE
IN
Sense Threshold vs.
Temperature
80
TTL (H)
0V
Input
Gate
70
60
50
40
30
20
15V (max.)
0V
Sense +, –
Differential
50mV
0V
Off
On
Fault
Timing Diagram 1. Normal Operation
-60 -30
0
30 60 90 120 150
TEMPERATURE (°C)
5µs
20µs
5µs
TTL (H)
TTL (H)
Input
Gate
0V
Input
0V
15V (max.)
0V
15V (max.)
Gate
0V
Sense +, –
Differential
50mV
0V
Sense +, –
Differential
50mV
0V
Off
On
Off
On
Fault
Fault
Timing Diagram 2. Fault Condition, C = Open
Timing Diagram 3. Fault Condition, C = Grounded
T
T
October 1998
5-165
MIC5020
Micrel
Functional Description
Refer to the MIC5020 block diagram.
Input
MOSFET Q1.
A fault condition (> 50mV from SENSE + to SENSE –) causes
the overcurrent comparator to enable current sink 2I which
A signal greater than 1.4V (nominal) applied to the MIC5020
INPUT causes gate enhancement on an external MOSFET
turning the external MOSFET on.
1
overcomescurrentsourceI todischargeC inashorttime.
1
INT
When C
is discharged, the INPUT is disabled, which turns
INT
off the GATE output; the FAULT output is enabled; and C
INT
An internal pull-down resistor insures that an open INPUT
remains low, keeping the external MOSFET turned off.
and C are ready to be charged.
T
WhentheGATEoutputturnstheMOSFEToff,theovercurrent
signal is removed from the sense inputs which deactivates
Gate Output
Rapid rise and fall times on the GATE output are possible
because each input state change triggers a one-shot which
current sink 2I . This allows C
and the optional capacitor
1
INT
connected to C to recharge. A Schmitt trigger delays the
T
activatesahigh-valuecurrentsink(10I )forashorttime. This
2
retry while the capacitor(s) recharge. Retry delay is in-
draws a high current through a current mirror circuit causing
the output transistors to quickly charge or discharge the
external MOSFET’s gate.
creased by connecting a capacitor to C (optional).
T
The retry cycle will continue until the the fault is removed or
the input is changed to TTL low.
A second current sink continuously draws the lower value of
current used to maintain the gate voltage for the selected
state.
If C is connected to ground, the circuit will not retry upon a
T
fault condition.
Fault Output
An internal 15V Zener diode protects the external MOSFET
The FAULT output is an open collector transistor. FAULT is
active at approximately the same time the output is disabled
by a fault condition (5µs after an overcurrent condition is
sensed). The FAULT output is open circuit (off) during each
successive retry (5µs).
by limiting the gate output voltage when V is connected to
higher voltages.
DD
Overcurrent Limiting
Current source I charges C
upon power up. An optional
INT
1
external capacitor connected to C is discharged through
T
Applications Information
TheMIC5020MOSFETdriverisintendedforlow-sideswitch-
ing applications where higher supply voltage, overcurrent
sensing, and moderate speed are required.
source side sensing is provided by access to both SENSE +
and SENSE – comparator inputs.
The adjustable retry feature can be used to handle loads with
high initial currents, such as lamps, motors, or heating
Supply Voltage
elements and can be adjusted from the C connection.
A feature of the MIC5020 is that its supply voltage rating of up
to 50V is higher than many other low-side drivers.
T
C to ground causes maintained gate drive shutdown follow-
T
ing overcurrent detection.
The minimum supply voltage required to fully enhance an N-
channel MOSFET is 11V.
C open, or through a capacitor to ground, causes automatic
T
retry. Thedefaultdutycycle(C open)isapproximately20%.
Refer to the electrical characteristics when selecting a ca-
pacitor for a reduced duty cycle.
AlowersupplyvoltagemaybeusedwithlogiclevelMOSFETs.
Approximately 6V is needed to provide 5V of gate enhance-
ment.
T
C through a pull-up resistor to V increases the duty cycle.
Low-Side Switch Circuit Advantages
T
DD
Increasing the duty cycle increases the power dissipation in
the load and MOSFET. Circuits may become unstable at a
duty cycles of about 75% or higher, depending on the
conditions. Caution: The MIC5020 may be damaged if the
A moderate-speed low-side driver is generally much faster
than a comparable high-side driver. The MIC5020 can
provide the gate drive switching times and low propagation
delay times that are necessary for high-frequency high-
efficiency circuit operation in PWM (pulse width modulation)
designs used for motor control, SMPS (switch mode power
supply) and heating element control. Switched loads (on/off)
can benefit from the MIC5020’s fast switching times by
allowing use of MOSFETs with smaller safe operating areas.
(Larger MOSFETs are often required when using slower
drivers.)
voltage on C exceeds the absolute maximum rating.
T
An overcurrent condition is externally signaled by an open
collector (FAULT) output.
The MIC5020 may be used without current sensing by
connecting SENSE + and SENSE – to ground.
Current Sense Resistors
Lead length can be significant when using low value (< 1Ω)
resistors for current sensing. Errors caused by lead length
can be avoided by using four-terminal current sensing resis-
tors. Four-terminal resistors are available from several
manufacturers.
Overcurrent Limiting
A 50mV comparator is provided for current sensing. The low
2
leveltrippointminimizesI Rlosseswhenpowerresistorsare
used for current sensing. Flexibility in choosing drain or
5-166
October 1998
MIC5020
Micrel
Lamp Driver Application
Current Sensing MOSFET Application
Incandescent lamps have a high inrush current (low resis-
tance) when turned on. The MIC5020 can perform a “soft
start” by pulsing the MOSFET (overcurrent condition) until
the filament is warm enough for its current to decrease
(resistance increases). The sense resistor is selected so the
voltage across the sense resistor drops below the sense
threshold (50mV) as the filament becomes warm. The
MOSFET is no longer pulsed to limit current and the lamp
turns completely on.
A current sensing MOSFET allows current sensing without
adding additional resistance to the power switching circuit.
A current sensing MOSFET has two source connections: a
“power source” for power switching and a “current source” for
current sensing. The current from the current source is
approximately proportional to the current through the power
source, but much smaller. A current sensing ratio (I
/
SOURCE
I
) is provided by the MOSFET manufacturer.
SENSE
V+
(+13.2V, > 4.4A)
V+
(+11V to +12V)
(3Ω, > 60W)
Incandescent
Lamp (#1157)
+11V to +50V
(+13.2V)
N-Channel
Current Sensing
Power MOSFET
MIC5020
MIC5020
1
2
3
4
8
7
6
5
N-Channel
Power MOSFET
(IRF540)
1
2
3
4
8
7
6
5
10µF
TTL Input
10µF
VDD
Gate
VDD
Input
Fault
CT
Gate
(IRCZ24)
TTL Input
(0V/5V)
Input
Fault
CT
Sense−
Sense+
Gnd
Sense−
Sense+
Gnd
(0V/5V)
RSENSE
(10Ω)
RSENSE
(0.041Ω)
“( )” values apply to
demo circuit. See text.
“( )” values apply to
demo circuit. See text.
Figure 3. Using a Current Sensing MOSFET
Figure 1. Lamp Driver with
Current Sensing
The MOSFET current source is used to develop a voltage
across a sense resistor. This voltage is monitored by the
MIC5020 (SENSE + and SENSE – pins) to identify an overcur-
rent condition.
A lamp may not fully turn on if the filament does not heat up
adequately. Changing the duty cycle, sense resistor, or both
tomatchthefilamentcharacteristicscancorrecttheproblem.
5
The value of the sense resistor can be estimated with:
Soft start can be demonstrated using a #1157 dual-filament
automotivelamp. ThevalueofR showninfigure1allowsfor
softstartofthehigher-resistancefilament(measuresapprox.
2.1Ω cold or 21Ω hot).
R
= (r V
R
) / (I
R
– V
)
TRIP
S
SENSE
TRIP
DS(ON)
LOAD
DS(ON)
where:
R
V
= external “sense” resistor
SENSE
Solenoid Driver Application
= 50mV (0.050V) for the MIC5020
TRIP
The MIC5020 can be directly powered by the control voltage
supply in typical 11Vdc through 50Vdc control applications.
Current sensing has been omitted as an example.
r = manufacturer’s current sense ratio: (I
/I
)
SOURCE SENSE
R
I
= manufacturer’s power source on resistance
DS(ON)
= load current (power source current)
LOAD
V+
The drain to source voltage under different fault conditions
affects the behavior of the MOSFET current source; that is,
the current source will respond differently to a slight over-
Diode
Solenoid
current condition (V
very small) than to a short circuit
+11V to +50V
DS(ON)
(whereV
isapproximatelyequaltothesupplyvoltage).
DS(ON)
MIC5020
Adjustmentofthesenseresistorvaluebyexperimentstarting
from the above formula will provide the quickest selection of
1
2
3
4
8
7
6
5
10µF
TTL Input
N-Channel
Power MOSFET
VDD
Input
Fault
CT
Gate
R
.
Sense−
Sense+
Gnd
SENSE
Refer to manufacture’s data sheets and application notes for
detailed information on current sensing MOSFET character-
istics.
Figure 3 includes values which can be used to demonstrate
circuit operation. The IRCZ24 MOSFET has a typical sense
ratio of 780 and a R
of 0.10Ω. A large 3Ω wirewound
DS(ON)
Figure 2. Solenoid Driver,
Without Current Sensing
load resistor will cause inductive spikes which should be
suppressed using a diode (using the same configuration as
figure 2).
A diode across the load protects the MOSFET from the
voltage spike generated by the inductive load upon MOSFET
turn off. The peak forward current rating of the diode should
be greater than the load current.
October 1998
5-167
MIC5020
Micrel
Faster MOSFET Switching
Fortestpurposes,a680Ω loadresistorand3Ω senseresistor
will produce an overcurrent condition when the load’s supply
(V+) is approximately 12V or greater.
The MIC5020’s GATE current can be multiplied using a pair
of bipolar transistors to permit faster charging and discharg-
ing of the external MOSFET’s gate.
Low-Temperature Operation
As the temperature of the MIC5020AJB (extended tempera-
ture range version—no longer available) approaches –55°C,
the driver’s off-state, gate-output offset from ground in-
creases. If the operating environment of the MIC5020AJB
includes low temperatures (–40°C to –55°C), add an external
2.2MΩ resistor as shown in Figures 6a or 6b. This assures
that the driver’s gate-to-source voltage is far below the
external MOSFET’s gate threshold voltage, forcing the
MOSFET fully off.
+40V max.
2N3904
+11V to +50V
10µF
MIC5020
N-Channel
Power MOSFET
(IRF540)
1
2
3
4
8
7
6
5
VDD
Gate
150kHz max.
Input
Fault
CT
Sense−
Sense+
Gnd
2N3906
V+
MIC5020
+11V to +50V
10µF
1
2
3
4
8
7
6
5
VDD
Gate
Figure 4. Faster MOSFET Switching Circuit
Input
Fault
CT
Sens
Sens
Gnd
2.2M
NPN and PNP transistors are used to respectively charge
anddischargetheMOSFETgate. TheMIC5020gatecurrent
is multiplied by the transistor β.
RSENSE
The switched circuit voltage can be increased above 40V by
selecting transistors with higher ratings.
Remote Overcurrent Limiting Reset
Figure 6a. Gate-to-Source Pull Down
In circuit breaker applications where the MIC5020 maintains
an off condition after an overcurrent condition is sensed, the
The gate-to-source configuration (refer to Figure 6a) is ap-
propriate for resistive and inductive loads. This also causes
the smallest decrease in gate output voltage.
C pin can be used to reset the MIC5020.
T
V+
V+
MIC5020
+11V to +50V
10µF
MIC5020
+11V to +50V
10µF
1
2
3
4
8
7
6
5
1
2
3
4
8
7
6
5
N-Channel
VDD
Gate
VDD
Gate
Power MOSFET
Input
Fault
CT
Sens
Sens
Gnd
TTL input
Input
Fault
CT
Sense−
Sense+
Gnd
Retry (H)
Maintained (L)
10k to
100k
RSENSE
2.2M
RSENSE
Q1
2N3904
74HC04
(example)
Figure 6b. Gate-to-Ground Pull Down
The gate-to-ground configuration (refer to Figure 6b) is
appropriate for resistive, inductive, or capacitive loads. This
configuration will decrease the gate output voltage slightly
more than the circuit shown in Figure 6a.
Figure 5. Remote Control Circuit
SwitchingQ1onpullsC lowwhichkeepstheMIC5020GATE
T
output off when an overcurrent is sensed. Switching Q1 off
causes C to appear open. The MIC5020 retries in about
T
20µs and continues to retry until the overcurrent condition is
removed.
5-168
October 1998
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