July 2005 1 MIC5021
MIC5021 Micrel, Inc.
MIC5021
High-Speed High-Side MOSFET Driver
Ordering Information
Part Number Temperature
Range
Package
Standard Pb-Free
MIC5021BM MIC5021YM –40ºC to +85ºC 8-pin SOIC
MIC5021BN MIC5021YN –40ºC to +85ºC 8-pin Plastic DIP
Features
• 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
General Description
The MIC5021 high-side MOSFET driver is designed to oper-
ate 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.
Typical Application
VDD
Input
CT
Gnd
VB O OS T
Gate
Se n se-
Se n se+
TTL Input
R
SENSE
N-Channel
Power MOSFET
+12V to +36V
MIC5021
1
2
3
4
8
7
6
5
10µF
2.7
nF
Load
RSENSE = 50mV
ITR I P
* increases time before retry
optional*
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
MIC5021 Micrel, Inc.
MIC5021 2 July 2005
Pin Description
Pin Number Pin Name Pin Function
1 VDD Supply: +12V to +36V. Decouple with ≥ 10µF capacitor.
2 Input TTL Compatible Input: Logic high turns the external MOSFET on. An inter-
nal pull-down returns an open pin to logic low.
3 CT 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 Circuit Ground
5 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.
6 Sense – Current Sense Comparator (–) Input: Connect to the low side of the sense
resistor (usually the high side of the load).
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 cur-
rent.
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.
Pin Configuration
1
2
3
4
8
7
6
5
VDD
Input
CT
Gnd
VB O OS T
Gate
Sense-
Sense+
1
2
3
4
8
7
6
5
VB O OS T
Gate
Sense-
Sense+
VDD
Input
CT
Gnd
Block Diagram
Sense-
Sense+
6V Internal Regulator
CINT
I1
2I1
50mV
Input
ONE-
SHOT
Gate
CT
6V
OFF
ON
Fault
Normal
I2
10I2
15V
Q1
C H A R G E
PU M P
VDD
VB OO S T
↓
↑
Transistor: 106
DIP Package SOIC Package
(N) (M)
July 2005 3 MIC5021
MIC5021 Micrel, Inc.
Electrical Characteristics
TA = 25°C, Gnd = 0V, VDD = 12V, CT = Open, Gate CL = 1500pF (IRF540 MOSFET) unless otherwise specified
Symbol Parameter Condition Min Typ Max Units
D.C. Supply Current VDD = 12V, Input = 0V 1.8 4 mA
VDD = 36V, Input = 0V 2.5 6 mA
VDD = 12V, Input = 5V 1.7 4 mA
VDD = 36V, Input = 5V 2.5 6 mA
Input Threshold 0.8 1.4 2.0 V
Input Hysteresis 0.1 V
Input Pull-Down Current Input = 5V 10 20 40 µA
Current Limit Threshold Note 1 30 50 70 mV
Gate On Voltage VDD = 12V Note 2 16 18 21 V
VDD = 36V Note 2 46 50 52 V
tG(ON) Gate On Time, Fixed Sense Differential > 70mV 2 6 10 µs
tG(OFF) Gate Off Time, Adjustable Sense Differential > 70mV, CT = 0pF 10 20 50 µs
tDLH Gate Turn-On Delay Note 3 500 1000 ns
tR Gate Rise Time Note 4 400 500 ns
tDLH Gate Turn-Off Delay Note 5 800 1500 ns
tF Gate Fall Time Note 6 400 500 ns
fmax Maximum Operating Frequency Note 7 100 150 kHz
Note 1 When using sense MOSFETs, it is recommended that RSENSE < 50Ω. Higher values may affect the sense MOSFET’s current transfer ratio.
Note 2 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.
Absolute Maximum 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
Operating Ratings
Supply Voltage (VDD) ..................................... +12V to +36V
Temperature Range
PDIP ..................................................................... –40°C to +85°C
SOIC ...................................................... –40°C to +85°C
MIC5021 Micrel, Inc.
MIC5021 4 July 2005
0.0
0.5
1.0
1.5
2.0
2.5
5 10 15 20 25 30 35 40
ISUPPLY (mA)
VSUPPLY (V)
Supply Current vs.
Supply Voltage
VIN = 0V
VIN = 5V
650
700
750
800
850
900
5 10 15 20 25 30 35 40
tON 4V (ns)
VSUPPLY (V)
Gate Turn-On Dalay vs.
Supply Voltage
VGATE = VSUPPLY + 4V
CL= 1500pF (IRCZ34)
CBOOST = 0.01µF
INCLUDES PROPAGATION DELAY
750
800
850
900
950
1000
5 10 15 20 25 30 35 40
tON 10V (ns)
VSUPPLY (V)
Gate Turn-On Delay vs.
Supply Voltage
VGATE = VSUPPLY + 10V
CL= 1500pF (IRCZ34)
CBOOST = 0.01µF
INCLUDES PROPAGATION DELAY
0.0
0.5
1.0
1.5
2.0
2.5
1x1001x1011x1021x1031x1041x105
tON (µs)
CGATE (pF)
Gate Turn-On Delay vs.
Gate Capacitance
VGATE = VSUPPLY + 4V
VSUPPLY = 12V
INCLUDES PROPAGATION DELAY
750
1000
1250
1500
1750
2000
5 10 15 20 25 30 35 40
tOFF 4V (ns)
VSUPPLY (V)
Gate Turn-Off Delay vs.
Supply Voltage
VG AT E = VSUPPLY + 4V
RL= 400
INCLUDES PROPAGATION DELAY
CG AT E = 1500pF
(IRCZ34)
0
5
10
15
20
25
0.1 1 10 100 1000 10000
RETRY DUTY CYCLE (%)
CT (pF)
NOT E:
tON, tOFF T I ME
INDEPENDENT
OF VSUPPLY
Overcurrent Retry Duty
Cycle vs. Timing Capacitance
tON = 5µs
VSUPPLY = 12V
0
5
10
15
20
25
5 10 15 20 25 30 35 40
VGATE (V)
VSUPPLY (V)
Gate Voltage Change
vs. Supply Voltage
VG AT E = VG AT E – VSUPPLY
0
20
40
60
80
100
0 5 10 15 20 25
IIN (µA)
VIN (V)
Input Current vs.
Input Voltage
VSUPPLY = 12V
Typical Characteristics
Timing Diagram 2. Fault Condition, CT = Open Timing Diagram 3. Fault Condition, CT = Grounded
Input 0V
TTL (H)
Source
50mV
Sense +,–
Differential
Gate
0V
15V (max.)
6µs
20µs
Input 0V
TTL ( H)
Source
50mV
Sense +,–
Differential
Gate
0V
15V (max.)
6µs
Input 0V
TTL ( H)
Source
50mV
Sense +,–
Differential
Gate
0V
15V (max.)
Timing Diagram 1. Normal Operation
July 2005 5 MIC5021
MIC5021 Micrel, Inc.
Functional Description
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.
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
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 continu-
ous 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 volt-
age supply than the internal charge pump.
Applications Information
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 com-
ponents 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 modu-
lation) 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.)
MIC5021 Micrel, Inc.
MIC5021 6 July 2005
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.
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.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense -
Sense +
TTL Input
+12V to +20V
MIC5021
1
2
3
4
8
7
6
5
10µF
0.01
µF
Load
Figure 1. 12V to 20V Configuration
A 0.01µF boost capacitor is recommended for best perfor-
mance in the 12V to 20V range. Refer to figure 1. Larger
capacitors may damage the MIC5021.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense -
Sense +
TTL Input
+12V to +36V
MIC5021
1
2
3
4
8
7
6
5
10µF
2.7
nF
Load
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.
VDD
Input
CT
Gnd
VBOOST
Gate
Sense-
Sense+
TTL Input
+12V to +36V
MIC5021
1
2
3
4
8
7
6
5
10µF
Load
0.01
µF
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 re-
sistors. Four-terminal resistors are available from several
manufacturers.
July 2005 7 MIC5021
MIC5021 Micrel, Inc.
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.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense -
Sense +
TTL Input
RSENSE
N-Channel
Power MOSFET
(IRF540)
+20V to +36V
MIC5021
1
2
3
4
8
7
6
5
10µF
Solenoid
(24V, 47Ω)
0.01
µF
Schottky
Diode
(1N5822)
(+24V)
(< 0.08Ω)
Figure 5. Solenoid Driver
with Current Sensing
Sense Pin Considerations
The sense pins of the MIC5021 are sensitive to negative volt-
ages. Forcing the sense pins much below –0.5V effectively
reverses the supply voltage on portions of the driver resulting
in unpredictable operation or damage.
M O S FE T
Turnoff
0V
Negative
Spike
~VDD
VDD
Input
CT
Gate
MIC5021
1
2
3
4
8
7
6
5
Inductive
Load
Current flows from ground (0V)
through the diodes to the load
during negative transcients.
Forward drop across diodes
allows leads to go negative.
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 resis-
tive loads. Because of their small size, the diodes’ forward
voltage drop quickly exceeds 0.5V as current increases.
Circuits Without Current Sensing
V
DD
Input
C
T
Gnd
V
B O O S T
Gate
Sense-
Sense+
TTL Input
Load
N-Channel
Power MOSFET
V+
MIC5021
1
2
3
4
8
7
6
5
10µF
0.01
µF
Figure 4a. Connecting Sense to Source
V
DD
Input
C
T
Gnd
V
B O O S T
Gate
Sense-
Sense+
TTL Input
Load
N-Channel
Power MOSFET
V+
MIC5021
1
2
3
4
8
7
6
5
10µF
0.01
µF
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 sup-
ply. 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 at-
tempts 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 connect-
ing 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.
MIC5021 Micrel, Inc.
MIC5021 8 July 2005
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.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense-
Sense+
N-Channel
Power MOSFET
MIC5021
1
2
3
4
8
7
6
5
RS
Load
5µA
15µA
VR2
R1
R2
VR1
= VR2
to avoid skewing
the 50mV trip point.
(5mV suggested)
R1
≅
3
×
R2
VR1
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 volt-
ages 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.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense -
Sense +
TTL Input
Inductive
Load
N-Channel
Power MOSFET
+12V to +36V
MIC5021
1
2
3
4
8
7
6
5
10µF
2.7
nF
RSENSE
1.0k
330Ω
R2
D2
11DQ03
D3
11DQ03
D1
R1
Figure 8. Protection from Inductive Kick
High-Side Sensing
Sensing the current on the high side of the MOSFET isolates
the SENSE pins from the inductive spike.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense -
Sense +
TTL Input
Wirewound
Resistor
(3Ω)
N-Channel
Power MOSFET
(IRFZ44)
+12V to +20V
RSENSE
(< 0.01Ω)
(+12V)
MIC5021
1
2
3
4
8
7
6
5
10µF
0.01
µF
Figure 9. High Side Sensing
Lamp Driver Application
Incandescent lamps have a high inrush current (low resis-
tance) 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.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense-
Sense+
TTL Input
RSENSE
(0.041Ω)
N-Channel
Power MOSFET
(IRF540)
V+
MIC5021
1
2
3
4
8
7
6
5
10µF
0.01
µF
Incandescent
Lamp (#1157)
(+12V)
"( )" values apply to demo circuit.
See text.
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 ap-
prox. 2.1Ω cold or 21Ω hot).
July 2005 9 MIC5021
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.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense -
Sense +
TTL Input
RSENSE
N-Channel
Power
MOSFET
+12V to +20V
MIC5021
1
2
3
4
8
7
6
5
10µF
0.01
µF
Load
74HC04
(example)
2N3904
Q1
10k to
100k
Retry (H)
Maintained (L)
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.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense -
Sense +
TTL Input
RSENSE
+12V to +36V
MIC5021AJB
1
2
3
4
8
7
6
5
10µF
2.7
nF
Load
2.2M
add resistor for
–40
°
C to –55
°
C
operation
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.
VDD
Input
CT
Gnd
VB O O S T
Gate
Sense -
Sense +
TTL Input
RSENSE
+12V to +36V
MIC5021AJB
1
2
3
4
8
7
6
5
10µF
2.7
nF
Load
2.2M
add resistor for
–40
°
C to –55
°
C
operation
Figure 12b. Gate-to-Ground Pull Down
The gate-to-ground configuration (refer to Figure 12b) is ap-
propriate for resistive, inductive, or capacitive loads. This
configuration will decrease the gate output voltage slightly
more than the circuit shown in Figure 12a.
MIC5021 Micrel, Inc.
MIC5021 10 July 2005
Package Information
0.380 (9.65)
0.370 (9.40) 0.135 (3.43)
0.125 (3.18)
PIN 1
DIMENSIONS:
INCH (MM)
0.018 (0.57)
0.100 (2.54)
0.013 (0.330)
0.010 (0.254)
0.300 (7.62)
0.255 (6.48)
0.245 (6.22)
0.380 (9.65)
0.320 (8.13)
0.0375 (0.952)
0.130 (3.30)
8-Pin Plastic DIP (N)
45°
0°–8°
0.244 (6.20)
0.228 (5.79)
0.197 (5.0)
0.189 (4.8) SEATING
PLANE
0.026 (0.65)
MAX)
0.010 (0.25)
0.007 (0.18)
0.064 (1.63)
0.045 (1.14)
0.0098 (0.249)
0.0040 (0.102)
0.020 (0.51)
0.013 (0.33)
0.157 (3.99)
0.150 (3.81)
0.050 (1.27)
TYP
PIN 1
DIMENSIONS:
INCHES (MM)
0.050 (1.27)
0.016 (0.40)
8-Pin SOIC (M)
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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
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Micrel for any damages resulting from such use or sale.
© 2003 Micrel, Inc.