MIC5021 DATA SHEET (11/05/2015) DOWNLOAD

MIC5021
Micrel, Inc.
MIC5021
High-Speed High-Side MOSFET Driver
General Description
Features
The MIC5021 high-side MOSFET driver is designed to operate at frequencies up to 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 power supplies),
and applications using IGBTs. The MIC5021 can also operate
as a circuit breaker with or without automatic retry.
A rising or falling edge on the input results in a current source
pulse or sink pulse on the gate output. This output current
pulse can turn on a 2000pF MOSFET in approximately 550ns.
The MIC5021 then supplies a limited current (< 2mA), if
necessary, to maintain the output state.
An overcurrent comparator with a trip voltage of 50mV makes
the MIC5021 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 placed from the CT pin to ground may be
used to control the current shutdown duty cycle (dead time)
from 20% to < 1%. A duty cycle from 20% to about 75% is
possible with an optional pull-up resistor from CT to VDD.
The MIC5021 is available in 8-pin SOIC and plastic DIP
packages.
Other members of the MIC502x family include the MIC5020
low-side driver and the MIC5022 half-bridge driver with a
cross-conduction interlock.
•
•
•
•
•
•
•
12V to 36V operation
550ns rise/fall time driving 2000pF
TTL compatible input with internal pull-down resistor
Overcurrent limit
Gate to source protection
Internal charge pump
100kHz operation guaranteed over full temperature and
operating voltage range
• Compatible with current sensing MOSFETs
• Current source drive reduces EMI
Applications
•
•
•
•
•
•
Lamp control
Heater control
Motor control
Solenoid switching
Switch-mode power supplies
Circuit breaker
Ordering Information
Part Number
Standard
Pb-Free
Temperature
Range
Package
MIC5021BM MIC5021YM –40ºC to +85ºC 8-pin SOIC
MIC5021BN
MIC5021YN
–40ºC to +85ºC 8-pin Plastic DIP
Typical Application
+12V to +36V
10µF
TTL Input
1
2
3
optional*
4
MIC5021
V DD
Input
V B OOS T
Gate
CT
Sense-
Gnd
Sense+
8
7
N-Channel
Power MOSFET
6
2.7
nF
5
RS E N S E
RS E N S E
Load
=
50mV
ITR IP
* increases time before retry
High-Side Driver with Overcurrent Trip and Retry
Micrel, Inc. • 2180 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 474-1000 • http://www.micrel.com
July 2005
1
MIC5021
MIC5021
Micrel, Inc.
Pin Configuration
1
V DD
8
1
V DD V B OOS T
2
Input
Gate
7
2
Input
3
CT
Sense-
6
3
4
Gnd
Sense+
5
4
V B OOS T
DIP Package
(N)
Block Diagram
8
Gate
7
CT
Sense-
6
Gnd
Sense+
5
SOIC Package
(M)
6V Internal Regulator
I1
Fault
CINT
2I1
CT
VDD
Normal
CHARGE
PUM P
Q1
Sense+
VB OOS T
15V
Sense-
ON
50mV
OFF
↑ ONE↓ SHOT
Input
10I2
I2
6V
Gate
Transistor: 106
Pin Description
Pin Number
1
MIC5021
Pin Name
VDD
2
Input
3
CT
Pin Function
Supply: +12V to +36V. Decouple with ≥ 10µF capacitor.
TTL Compatible Input: Logic high turns the external MOSFET on. An internal pull-down returns an open pin to logic low.
Retry Timing Capacitor: Controls the off time (tG(OFF)) of the overcurrent
retry cycle. (Duty cycle adjustment.)
• Open = approx. 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.
4
Gnd
5
Sense +
Circuit Ground
6
Sense –
7
Gate
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.
8
VBOOST
Charge Pump Boost Capacitor: A bootstrap capacitor from VBOOST to the
FET source pin supplies charge to quickly enhance the Gate output during
turn-on.
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.
Current Sense Comparator (–) Input: Connect to the low side of the sense
resistor (usually the high side of the load).
2
July 2005
MIC5021
Micrel, Inc.
Absolute Maximum Ratings
Operating Ratings
Supply Voltage (VDD)................................................... +40V
Input Voltage .................................................–0.5V to +15V
Sense Differential Voltage .......................................... ±6.5V
Sense + or Sense – to Gnd ...........................–0.5V to +36V
Timer Voltage (CT) ...................................................... +5.5V
VBOOST Capacitor ..................................................... 0.01µF
Supply Voltage (VDD)..................................... +12V to +36V
Temperature Range
PDIP ..................................................................... –40°C to +85°C
SOIC ...................................................... –40°C to +85°C
Electrical Characteristics
TA = 25°C, Gnd = 0V, VDD = 12V, CT = Open, Gate CL = 1500pF (IRF540 MOSFET) unless otherwise specified
Symbol
Parameter
Condition
D.C. Supply Current
Input Threshold
Min
Typ
Max
Units
VDD = 12V, Input = 0V
VDD = 12V, Input = 5V
1.8
4
mA
VDD = 36V, Input = 0V
2.5
6
mA
1.7
4
mA
VDD = 36V, Input = 5V
2.5
6
mA
1.4
2.0
0.8
Input Hysteresis
V
Input Pull-Down Current
Input = 5V
10
20
40
µA
Current Limit Threshold
Note 1
30
50
70
mV
VDD = 12V Note 2
Gate On Voltage
tG(ON)
V
0.1
Gate On Time, Fixed
16
18
21
V
VDD = 36V Note 2
46
50
52
V
Sense Differential > 70mV
2
6
10
µs
Sense Differential > 70mV, CT = 0pF
10
20
50
µs
tG(OFF)
Gate Off Time, Adjustable
Note 3
500
1000
ns
tR
Gate Rise Time
Note 4
400
500
ns
Gate Turn-Off Delay
Note 5
800
1500
ns
tF
Gate Fall Time
Note 6
400
500
ns
Maximum Operating Frequency
Note 7
tDLH
Gate Turn-On Delay
tDLH
fmax
Note 1
Note 2
100
150
kHz
When using sense MOSFETs, it is recommended that RSENSE < 50Ω. Higher values may affect the sense MOSFET’s current transfer ratio.
DC measurement.
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 17V.
Note 5
Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 20V (Gate on voltage) to 17V.
Note 6
Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 17V to 2V.
Note 7
Frequency where gate on voltage reduces to 17V with 50% input duty cycle.
July 2005
3
MIC5021
MIC5021
Micrel, Inc.
Typical Characteristics
Supply Current vs.
Supply Voltage
VIN = 0V
1.5
VIN = 5V
1.0
5
10
15
20 25 30
VSUPPLY (V)
35
10
0
40
Gate Turn-On Delay vs.
Supply Voltage
1000
5
tON (µs)
850
20 25 30
VSUPPLY (V)
35
10
15
20 25 30
VSUPPLY (V)
35
2000
1750
1.5
40
1.0
5
0
0.1
NOT E:
tON, tOFF T I M E
INDEPENDENT
OF VSUPPLY
1
10
100
CT (pF)
Input Current vs.
Input Voltage
80
VSUPPLY = 12V
40
Gate Turn-Off Delay vs.
Supply Voltage
VG AT E = VSUPPLY + 4V
RL = 400
CG AT E = 1500pF
(IRCZ34)
10
15
20 25 30
VSUPPLY (V)
35
40
Sense Threshold vs.
Temperature
70
60
60
50
40
0
40
30
0
5
10
15
VIN (V)
20
20
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
25
TTL (H)
Input
Gate
35
INCLUDES PROPAGATION DELAY
750
5
20
1000 10000
20 25 30
VSUPPLY (V)
1000
80
IIN (µA)
10
15
1250
100
15
10
1500
0.0
1x100 1x101 1x102 1x103 1x104 1x105
CGATE (pF)
tON = 5µs
VSUPPLY = 12V
20
5
INCLUDES PROPAGATION DELAY
Overcurrent Retry Duty
Cycle vs. Timing Capacitance
25
INCLUDES PROPAGATION DELAY
VOLTAGE (mV)
5
750
650
40
VGATE = VSUPPLY + 4V
VSUPPLY = 12V
INCLUDES PROPAGATION DELAY
RETRY DUTY CYCLE (%)
15
0.5
800
750
10
Gate Turn-On Delay vs.
Gate Capacitance
2.0
900
800
700
2.5
VGATE = VSUPPLY + 10V
CL = 1500pF (IRCZ34)
CBOOST = 0.01µF
950
tON 10V (ns)
15
tOFF 4V (ns)
0.0
VGATE = VSUPPLY + 4V
CL = 1500pF (IRCZ34)
CBOOST = 0.01µF
850
5
0.5
Gate Turn-On Dalay vs.
Supply Voltage
900
VG AT E = VG AT E – VS U P P L Y
20
VGATE (V)
2.0
ISUPPLY (mA)
25
tON 4V (ns)
2.5
Gate Voltage Change
vs. Supply Voltage
0V
15V (max.)
Sense +,–
Differential
Source
50mV
0V
Timing Diagram 1. Normal Operation
6µs
Input
Gate
6µs
20µs
TTL (H)
Input
0V
15V (max.)
Sense +,–
Differential
Gate
Source
0V
15V (max.)
Sense +,–
Differential
50mV
0V
Timing Diagram 2. Fault Condition, CT = Open
MIC5021
TTL (H)
Source
50mV
0V
Timing Diagram 3. Fault Condition, CT = Grounded
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July 2005
MIC5021
Micrel, Inc.
Functional Description
An internal zener diode protects the external MOSFET by
limiting the gate to source voltage.
Sense Inputs
The MIC5021’s 50mV (nominal) trip voltage is created by
internal current sources that force approximately 5µA out of
SENSE + and approximately 15µA (at trip) out of SENSE –.
When SENSE – is 50mV or more below SENSE +, SENSE –
steals base current from an internal drive transistor shutting
off the external MOSFET.
Overcurrent Limiting
Current source I1 charges CINT upon power up. An optional
external capacitor connected to CT is kept discharged through
a MOSFET Q1.
A fault condition (> 50mV from SENSE + to SENSE –) causes
the overcurrent comparator to enable current sink 2I1 which
overcomes current source I1 to discharge CINT in a short
time. When CINT is discharged, the INPUT is disabled, which
turns off the gate output, and CINT and CT are ready to be
charged.
When the gate output turns the MOSFET off, the overcurrent
signal is removed from the sense inputs which deactivates
current sink 2I1. This allows CINT and the optional capacitor
connected to CT to recharge. A Schmitt trigger delays the
retry while the capacitor(s) recharge. Retry delay is increased
by connecting a capacitor to CT (optional).
The retry cycle will continue until the fault is removed or the
input is changed to TTL low.
If CT is connected to ground, the circuit will not retry upon a
Refer to the MIC5021 block diagram.
Input
A signal greater than 1.4V (nominal) applied to the MIC5021
INPUT causes gate enhancement on an external MOSFET
turning the MOSFET on.
An internal pull-down resistor insures that an open INPUT
remains low, keeping the external MOSFET turned off.
Gate Output
Rapid rise and fall times on the GATE output are possible
because each input state change triggers a one-shot which
activates a high-value current sink (10I2) for a short time.
This draws a high current though a current mirror circuit
causing the output transistors to quickly charge or discharge
the external MOSFET’s gate.
A second current sink continuously draws the lower value
of current used to maintain the gate voltage for the selected
state.
An internal charge pump utilizes an external “boost” capacitor
connected between VBOOST and the source of the external
MOSFET. (Refer to typical application.) The boost capacitor
stores charge when the MOSFET is off. As the MOSFET
turns on, its source to ground voltage increases and is added
to the voltage across the capacitor, raising the VBOOST pin
voltage. The boost capacitor charge is directed through
the GATE pin to quickly charge the MOSFET’s gate to 16V
maximum above VDD. The internal charge pump maintains
the gate voltage.
Applications Information
Supply Voltage
The MIC5021’s supply input (VDD) is rated up to 36V. The
supply voltage must be equal to or greater than the voltage
applied to the drain of the external N-channel MOSFET.
A 16V minimum supply is recommended to produce continuous on-state, gate drive voltage for standard MOSFETs (10V
nominal gate enhancement).
When the driver is powered from a 12V to 16V supply, a
logic-level MOSFET is recommended (5V nominal gate
enhancement).
PWM operation may produce satisfactory gate enhancement
at lower supply voltages. This occurs when fast switching
repetition makes the boost capacitor a more significant voltage supply than the internal charge pump.
The MIC5021 MOSFET driver is intended for high-side
switching applications where overcurrent limiting and high
speed are required. The MIC5021 can control MOSFETs
that switch voltages up to 36V.
High-Side Switch Circuit Advantages
High-side switching allows more of the load related components and wiring to remain near ground potential when
compared to low-side switching. This reduces the chances
of short-to-ground accidents or failures.
Speed Advantage
The MIC5021 is about two orders of magnitude faster than
the low cost MIC5014 making it suitable 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) benefit from the MIC5021’s fast
switching times by allowing use of MOSFETs with smaller
safe operating areas. (Larger MOSFETs are often required
when using slower drivers.)
July 2005
5
MIC5021
MIC5021
Micrel, Inc.
Logic-Level MOSFET Precautions
Logic-level MOSFETs have lower maximum gate-to-source
voltage ratings (typically ±10V) than standard MOSFETs
(typically ±20V). When an external MOSFET is turned on,
the doubling effect of the boost capacitor can cause the
gate-to-source voltage to momentarily exceed 10V. Internal
zener diodes clamp this voltage to 16V maximum which
is too high for logic-level MOSFETs. To protect logic-level
MOSFETs, connect a zener diode (5V≤VZener<10V) from
gate to source.
Overcurrent Limiting
A 50mV comparator is provided for current sensing. The low
level trip point minimizes I2R losses when a power resistor
is used for current sensing.
The adjustable retry feature can be used to handle loads with
high initial currents, such as lamps or heating elements, and
can be adjusted from the CT connection.
CT to ground maintains gate drive shutdown following an
overcurrent condition.
A 0.01µF boost capacitor is recommended for best performance in the 12V to 20V range. Refer to figure 1. Larger
capacitors may damage the MIC5021.
+12V to +36V
10µF
TTL Input
4
TTL Input
2
3
4
MIC5021
V DD
Input
V BOOST
Gate
CT
Sense-
Gnd
Sense+
Input
Gate
CT
Sense-
Gnd
Sense+
8
7
6
5
2.7
nF
+12V to +36V
10µF
TTL Input
1
2
3
4
MIC5021
V DD
Input
V BOOST
Gate
CT
Sense-
Gnd
Sense+
8
0.01
µF
7
6
5
Load
Figure 3. Preferred 20V to 36V Configuration
Do not use both boost capacitor between VBOOST and the
MOSFET source and VBOOST and VDD at the same time.
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-teminal current sensing resistors. Four-terminal resistors are available from several
manufacturers.
7
5
V BOOST
Figure 2. 12V to 36V Configuration
If the full 12V to 36V voltage range is required, the boost
capacitor value must be reduced to 2.7nF. Refer to Figure
2. The recommended configuration for the 20V to 36V range
is to place the capacitor is placed between VDD and VBOOST
as shown in Figure 3.
8
6
MIC5021
V DD
Load
+12V to +20V
1
2
3
CT open, or a capacitor to ground, causes automatic retry.
The default duty cycle (CT open) is approximately 20%. Refer
to the electrical characteristics when selecting a capacitor for
reduced duty cycle.
CT through a pull-up resistor to VDD increases the duty cycle.
Increasing the duty cycle increases the power dissipation
in the load and MOSFET under a “fault” condition. Circuits
may become unstable at a duty cycle of about 75% or higher,
depending on conditions. Caution: The MIC5021 may be
damaged if the voltage applied to CT exceeds the absolute
maximum voltage rating.
Boost Capacitor Selection
The boost capacitor value will vary depending on the supply
voltage range.
10µF
1
0.01
µF
Load
Figure 1. 12V to 20V Configuration
MIC5021
6
July 2005
MIC5021
Micrel, Inc.
Circuits Without Current Sensing
10µF
TTL Input
1
2
3
4
MIC5021
V DD
Input
V BOOST
Gate
CT
Sense-
Gnd
Sense+
The diode should have a peak forward current rating greater
than the load current. This is because the current through
the diode is the same as the load current at the instant the
MOSFET is turned off.
V+
8
+20V to +36V
7
6
5
(+24V)
N-Channel
Power MOSFET
1
10µF
0.01
µF
2
TTL Input
Load
3
4
Figure 4a. Connecting Sense to Source
MIC5021
V BOOST
V DD
Gate
Input
CT
Sense-
Gnd
Sense+
8
0.01
µF
7
N-Channel
Power MOSFET
(IRF540)
6
5
RS E N S E
(< 0.08Ω)
V+
10µF
TTL Input
1
2
3
4
MIC5021
V DD
Input
V BOOST
Gate
CT
Sense-
Gnd
Sense+
7
6
5
N-Channel
Power MOSFET
Figure 5. Solenoid Driver
with Current Sensing
0.01
µF
Sense Pin Considerations
The sense pins of the MIC5021 are sensitive to negative voltages. Forcing the sense pins much below –0.5V effectively
reverses the supply voltage on portions of the driver resulting
in unpredictable operation or damage.
Load
Figure 4b. Connecting Sense to Supply
Current sensing may be omitted by connecting the SENSE +
and SENSE – pins to the source of the MOSFET or to the supply. Connecting the SENSE pins to the supply is preferred for
inductive loads. Do not connect the SENSE pins to ground.
Inductive Load Precautions
Circuits controlling inductive loads, such as solenoids (Figure
5) and motors, require precautions when controlled by the
MIC5021. Wire wound resistors, which are sometimes used
to simulate other loads, can also show significant inductive
properties.
An inductive load releases stored energy when its current
flow is interrupted (when the MOSFET is switched off). The
voltage across the inductor reverses and the inductor attempts to force current flow. Since the circuit appears open
(the MOSFET appears as a very high resistance) a very large
negative voltage occurs across the inductor.
Limiting Inductive Spikes
The voltage across the inductor can be limited by connecting a Schottky diode across the load. The diode is forward
biased only when the load is switched off. The Schottky diode
clamps negative transients to a few volts. This protects the
MOSFET from drain-to-source breakdown and prevents the
transient from damaging the charge pump by way of the boost
capacitor. Also see Sense Pin Considerations below.
July 2005
Schottky
Diode
(1N5822)
Solenoid
(24V, 47Ω)
8
1
2
3
4
MIC5021
VDD
Input
CT
Gate
8
7
6
5
M OS FE T
Turnoff
~VDD
0V
Negative
Spike
Forward drop across diodes
allows leads to go negative.
Current flows from ground (0V)
through the diodes to the load
during negative transcients.
Inductive
Load
Figure 6. Inductive Load Turnoff
Figure 6 shows current flowing out of the sense leads of an
MIC5021 during a negative transient (inductive kick). Internal
Schottky diodes attempt to limit the negative transient by
maintaining a low forward drop.
Although the internal Schottky diodes can protect the driver
in low-current resistive applications, they are inadequate for
inductive loads or the lead inductance in high-current resistive loads. Because of their small size, the diodes’ forward
voltage drop quickly exceeds 0.5V as current increases.
7
MIC5021
MIC5021
Micrel, Inc.
External Protection
Resistors placed in series with each SENSE connection limit
the current drawn from the internal Schottky diodes during a
negative transient. This minimizes the forward drop across
the diodes.
1
2
3
4
MIC5021
V DD
V BOOST
Input
Gate
Sense-
Gnd
Sense+
+12V to +20V
(+12V)
8
7
N-Channel
Power MOSFET
5
VR 1 = VR 2
to avoid skewing
the 50mV trip point.
(5mV suggested)
4
5µA
VR 1
R2
TTL Input
2
3
4
V DD
Input
V BOOST
Gate
CT
Sense-
15µA
VR 2
Gnd
Sense+
10µF
1
2
4
2.7
nF
R1
1.0k
N-Channel
Power MOSFET
MIC5021
VDD
V BOOST
Input
Gate
CT
Sense-
Gnd
Sense+
8
7
6
5
0.01
µF
N-Channel
Power MOSFET
(IRF540)
RS E N S E
(0.041Ω)
"( )" values apply to demo circuit.
See text.
RS E N S E
R2
Incandescent
Lamp (#1157)
330Ω
D1
Figure 10. Lamp Driver with
Current Sensing
A lamp may not fully turn on if the filament does not heat up
adequately. Changing the duty cycle, sense resistor, or both to
match the filament characteristics can correct the problem.
Soft start can be demonstrated using a #1157 dual filament
automotive lamp. The value of RS shown in Figure 10 allows
for soft start of the higher-resistance filament (measures approx. 2.1Ω cold or 21Ω hot).
Inductive
Load
Figure 8. Protection from Inductive Kick
MIC5021
Wirewound
Resistor
(3Ω)
(+12V)
7
D3
11DQ03
5
V+
3
D2
11DQ03
Sense+
Figure 9. High Side Sensing
Lamp Driver Application
Incandescent lamps have a high inrush current (low resistance) when turned on. The MIC5021 can perform a “soft
start” by pulsing the MOSFET (overcurrent condition) until
the filament is warm and its current decreases (resistance
increases). The sense resistor value is selected so the voltage
drop across the sense resistor decreases below the sense
threshold (50mV) as the filament becomes warm. The FET
is no longer pulsed and the lamp turns completely on.
8
5
Gnd
N-Channel
Power MOSFET
(IRFZ44)
6
Load
TTL Input
6
Sense-
7
0.01
µF
+12V to +36V
1
CT
RS E N S E
(< 0.01Ω)
8
RS 50mV nominal
(at trip)
Figure 7. Resistor Voltage Drop
During normal operation, sensing current from the sense pins
is unequal (5µA and 15µA). The internal Schottky diodes are
reverse biased and have no effect. To avoid skewing the trip
voltage, the current limiting resistors must drop equal voltages at the trip point currents. See Figure 7. To minimize
resistor tolerance error, use a voltage drop lower than the
trip voltage of 50mV. 5mV is suggested.
External Schottky diodes are also recommended. See D2
and D3 in Figure 8. The external diodes clamp negative
transients better than the internal diodes because their larger
size minimizes the forward voltage drop at higher currents.
10µF
Gate
Input
3
R1
V BOOST
VDD
2
TTL Input
R1≅ 3 × R2
MIC5021
MIC5021
1
10µF
6
CT
High-Side Sensing
Sensing the current on the high side of the MOSFET isolates
the SENSE pins from the inductive spike.
8
July 2005
MIC5021
Micrel, Inc.
Remote Overcurrent Limiting Reset
In circuit breaker applications where the MIC5021 maintains
an off condition after an overcurrent condition is sensed, the
CT pin can be used to reset the MIC5021.
+12V to +36V
10µF
+12V to +20V
1
MIC5021AJB
V DD
2
TTL Input
Input
3
10µF
TTL Input
10k to
100k
74HC04
(example)
1
2
3
2N3904
4
Q1
MIC5021
V DD
Input
V BOOST
Gate
CT
Sense-
Gnd
Sense+
4
8
7
6
5
0.01
µF
Gate
CT
Sense-
Gnd
Sense+
8
7
6
2.7
nF
5
2.2M
RS E NS E
N-Channel
Power
MO S F E T
add resistor for
–40°C to –55°C
operation
Load
RS E N S E
Retry (H)
Maintained (L)
Figure 12a. Gate-to-Source Pull Down
The gate-to-source configuration (refer to Figure 12a) is
appropriate for resistive and inductive loads. This also causes
the smallest decrease in gate output voltage.
Load
Figure 11. Remote Control Circuit
Switching Q1 on pulls CT low which keeps the MIC5021 GATE
output off when an overcurrent is sensed. Switching Q1 off
causes CT to appear open. The MIC5021 retries in about
20µs and continues to retry until the overcurrent condition
is removed.
For demonstration purposes, a 680Ω load resistor and 3Ω
sense resistor will produce an overcurrent condition when the
load’s supply (V+) is approximately 12V or greater.
Low-Temperature Operation
As the temperature of the MIC5021AJB (extended temperature
range version—no longer available) approaches –55°C, the
driver’s off-state, gate-output offset from ground increases.
If the operating environment of the MIC5021AJB includes
low temperatures (–40°C to –55°C), add an external 2.2MΩ
resistor as shown in Figures 12a or 12b. 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.
July 2005
V BOOST
+12V to +36V
10µF
TTL Input
1
2
3
4
MIC5021AJB
V DD
Input
V BOOST
Gate
CT
Sense-
Gnd
Sense+
8
7
6
5
2.7
nF
RS E N S E
add resistor for
–40°C to –55°C
operation
2.2M
Load
Figure 12b. Gate-to-Ground Pull Down
The gate-to-ground configuration (refer to Figure 12b) is appropriate for resistive, inductive, or capacitive loads. This
configuration will decrease the gate output voltage slightly
more than the circuit shown in Figure 12a.
9
MIC5021
MIC5021
Micrel, Inc.
Package Information
PIN 1
DIMENSIONS:
INCH (MM)
0.380 (9.65)
0.370 (9.40)
0.255 (6.48)
0.245 (6.22)
0.135 (3.43)
0.125 (3.18)
0.300 (7.62)
0.013 (0.330)
0.010 (0.254)
0.018 (0.57)
0.130 (3.30)
0.100 (2.54)
0.0375 (0.952)
0.380 (9.65)
0.320 (8.13)
8-Pin Plastic DIP (N)
0.026 (0.65)
MAX)
PIN 1
0.157 (3.99)
0.150 (3.81)
DIMENSIONS:
INCHES (MM)
0.050 (1.27)
TYP
0.064 (1.63)
0.045 (1.14)
0.197 (5.0)
0.189 (4.8)
0.020 (0.51)
0.013 (0.33)
45°
0.0098 (0.249)
0.0040 (0.102)
0°–8°
0.010 (0.25)
0.007 (0.18)
0.050 (1.27)
0.016 (0.40)
SEATING
PLANE
0.244 (6.20)
0.228 (5.79)
8-Pin SOIC (M)
MICREL INC.
2180 FORTUNE DRIVE
SAN JOSE, CA 95131
USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 474-1000 WEB http://www.micrel.com
This information furnished by Micrel in this data sheet is believed to be accurate and reliable. However no responsibility is assumed by Micrel for its use.
Micrel reserves the right to change circuitry and specifications at any time without notification to the customer.
Micrel Products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can
reasonably be expected to result in personal injury. Life support devices or systems are devices or systems that (a) are intended for surgical implant into
the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. A Purchaser's
use or sale of Micrel Products for use in life support appliances, devices or systems is a Purchaser's own risk and Purchaser agrees to fully indemnify
Micrel for any damages resulting from such use or sale.
© 2003 Micrel, Inc.
MIC5021
10
July 2005