MIC5021
Micrel
MIC5021
High-Speed High-Side MOSFET Driver
Final Information
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 C
T
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 C
T
to V
DD
.
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.
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
•
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Applications
•
•
•
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Lamp control
Heater control
Motor control
Solenoid switching
Switch-mode power supplies
Circuit breaker
Ordering Information
Part Number
MIC5021BM
MIC5021BN
Temperature Range
–40°C to +85°C
–40°C to +85°C
Package
8-pin SOIC
8-pin Plastic DIP
Typical Application
+12V to +36V
MIC5021
10µF
TTL Input
optional*
1
2
3
4
V
DD
Input
C
T
Gnd
V
BOOST
Gate
Sense
Sense
8
7
6
5
2.7
nF
R
SENSE
R
SENSE =
50mV
I
TRIP
* increases time before retry
N-Channel
Power MOSFET
High-Side Driver with Overcurrent Trip and Retry
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
October 1998
1
Load
MIC5021
MIC5021
Micrel
Pin Configuration
1 V
DD
2 Input
3 C
T
4 Gnd
V
BOOST
8
Gate 7
Sense− 6
Sense+ 5
1
2
3
4
V
DD
Input
C
T
V
BOOST
8
Gate 7
Sense− 6
Gnd Sense+ 5
DIP Package
(N)
SOIC Package
(M)
Block Diagram
6V Internal Regulator
I
1
C
INT
2I
1
Fault
C
T
Normal
V
DD
CHARGE
PUMP
V
BOOST
Q1
Sense +
Sense –
ON
15V
50mV
OFF
Input
↑
ONE-
↓
SHOT
6V
Gate
10I
2
I
2
Transistor: 106
Pin Description
Pin Number
1
2
3
Pin Name
V
DD
Input
C
T
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 (t
G(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.
Circuit Ground
Current Sense Comparator (+) Input: Connect to high side of sense resistor
or current sensing MOSFET sense lead. A built-in offset in conjunction with
R
SENSE
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).
Gate Drive: Drives the gate of an external power MOSFET. Also limits V
GS
to 15V max. to prevent Gate-to-Source damage. Will sink and source
current.
Charge Pump Boost Capacitor: A bootstrap capacitor from V
BOOST
to the
FET source pin supplies charge to quickly enhance the Gate output during
turn-on.
4
5
Gnd
Sense +
6
7
Sense –
Gate
8
V
BOOST
MIC5021
2
October 1998
MIC5021
Micrel
Absolute Maximum Ratings
Supply Voltage (V
DD
) .................................................. +40V
Input Voltage ................................................ –0.5V to +15V
Sense Differential Voltage ..........................................
±6.5V
Sense + or Sense – to Gnd .......................... –0.5V to +36V
Timer Voltage (C
T
) ..................................................... +5.5V
V
BOOST
Capacitor .................................................... 0.01µF
Operating Ratings
Supply Voltage (V
DD
) .................................... +12V to +36V
Temperature Range
PDIP ....................................................... –40°C to +85°C
SOIC ...................................................... –40°C to +85°C
Electrical Characteristics
T
A
= 25°C, Gnd = 0V, V
DD
= 12V, C
T
= Open, Gate C
L
= 1500pF (IRF540 MOSFET) unless otherwise specified
Symbol
Parameter
D.C. Supply Current
Condition
V
DD
= 12V, Input = 0V
V
DD
= 36V, Input = 0V
V
DD
= 12V, Input = 5V
V
DD
= 36V, Input = 5V
Input Threshold
Input Hysteresis
Input Pull-Down Current
Current Limit Threshold
Gate On Voltage
Input = 5V
Note 1
V
DD
= 12V
Note 2
V
DD
= 36V
Note 2
t
G(ON)
t
G(OFF)
t
DLH
t
R
t
DLH
t
F
f
max
Note 1
Note 2
Note 3
Note 4
Note 5
Note 6
Note 7
Min
Typ
1.8
2.5
1.7
2.5
Max
4
6
4
6
2.0
Units
mA
mA
mA
mA
V
V
µA
mV
V
V
µs
µs
ns
ns
ns
ns
kHz
0.8
1.4
0.1
10
30
16
46
2
10
20
50
18
50
6
20
500
400
800
400
40
70
21
52
10
50
1000
500
1500
500
Gate On Time, Fixed
Gate Off Time, Adjustable
Gate Turn-On Delay
Gate Rise Time
Gate Turn-Off Delay
Gate Fall Time
Maximum Operating Frequency
Sense Differential > 70mV
Sense Differential > 70mV, C
T
= 0pF
Note 3
Note 4
Note 5
Note 6
Note 7
100
150
When using sense MOSFETs, it is recommended that R
SENSE
< 50Ω. Higher values may affect the sense MOSFET’s current transfer ratio.
DC measurement.
Input switched from 0.8V (TTL low) to 2.0V (TTL high), time for Gate transition from 0V to 2V.
Input switched from 0.8V (TTL low) to 2.0V (TTL high), time for Gate transition from 2V to 17V.
Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 20V (Gate on voltage) to 17V.
Input switched from 2.0V (TTL high) to 0.8V (TTL low), time for Gate transition from 17V to 2V.
Frequency where gate on voltage reduces to 17V with 50% input duty cycle.
October 1998
3
MIC5021
MIC5021
Micrel
Typical Characteristics
Supply Current vs.
Supply Voltage
V
IN
= 0V
V
GATE
(V)
Gate Voltage Change
vs. Supply Voltage
25
V
GATE
= V
GATE
– V
SUPPLY
20
15
10
5
0
Gate Turn-On Delay vs.
Supply Voltage
900
850
t
ON 4V
(ns)
800
750
INCLUDES PROPAGATION DELAY
2.5
2.0
I
SUPPLY
(mA)
1.5
1.0
0.5
0.0
V
GATE
= V
SUPPLY
+ 4V
C
L
= 1500pF (IRCZ34)
C
BOOST
= 0.01µF
V
IN
= 5V
700
650
5
10
15
25 30
V
SUPPLY
(V)
20
35
40
5
10
15
25 30
V
SUPPLY
(V)
20
35
40
5
10
15
20 25 30
V
SUPPLY
(V)
35
40
Gate Turn-On Delay vs.
Supply Voltage
1000
950
t
ON 10V
(ns)
900
850
800
INCLUDES PROPAGATION DELAY
Gate Turn-On Delay vs.
Gate Capacitance
2.5
Gate Turn-Off Delay vs.
Supply Voltage
2000
V
GATE
= V
SUPPLY
+ 4V
R
L
= 400
V
GATE
= V
SUPPLY
+ 10V
C
L
= 1500pF (IRCZ34)
C
BOOST
= 0.01µF
t
ON
(µs)
2.0
1.5
1.0
0.5
V
GATE
= V
SUPPLY
+ 4V
V
SUPPLY
= 12V
1750
t
OFF 4V
(ns)
1500
1250
1000
C
GATE
= 1500pF
(IRCZ34)
INCLUDES PROPAGATION DELAY
INCLUDES PROPAGATION DELAY
750
5
10
15
25 30
V
SUPPLY
(V)
20
35
40
0.0
1x10
0
1x10
1
1x10
2
1x10
3
1x10
4
1x10
5
C
GATE
(pF)
750
5
10
15
20 25 30
V
SUPPLY
(V)
35
40
Overcurrent Retry Duty
Cycle vs. Timing Capacitance
25
RETRY DUTY CYCLE (%)
20
15
10
5
0
0.1
NOTE:
t
ON
, t
OFF
TIME
INDEPENDENT
OF V
SUPPLY
1
10
100
C
T
(pF)
1000 10000
t
ON
= 5µs
V
SUPPLY
= 12V
I
IN
(µA)
100
80
Input Current vs.
Input Voltage
V
SUPPLY
= 12V
VOLTAGE (mV)
Sense Threshold vs.
Temperature
80
70
60
50
40
30
60
40
20
0
0
5
10
15
V
IN
(V)
20
25
20
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
Input
Gate
Sense +, –
Differential
TTL (H)
0V
15V (max.)
Source
50mV
0V
Timing Diagram 1. Normal Operation
6µs
20µs
6µs
Input
Gate
Sense +, –
Differential
TTL (H)
0V
15V (max.)
Source
50mV
0V
Input
Gate
Sense +, –
Differential
TTL (H)
0V
15V (max.)
Source
50mV
0V
Timing Diagram 2. Fault Condition, C
T
= Open
MIC5021
4
Timing Diagram 3. Fault Condition, C
T
= Grounded
October 1998
MIC5021
Micrel
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 I
1
charges C
INT
upon power up. An optional
external capacitor connected to C
T
is kept discharged through
a MOSFET Q1.
A fault condition (> 50mV from
SENSE
+ to
SENSE
–) causes
the overcurrent comparator to enable current sink 2I
1
which
overcomes current source I
1
to discharge C
INT
in a short time.
When C
INT
is discharged, the
INPUT
is disabled, which turns
off the gate output, and C
INT
and C
T
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 2I
1
. This allows C
INT
and the optional capacitor
connected to C
T
to recharge. A Schmitt trigger delays the
retry while the capacitor(s) recharge. Retry delay is in-
creased by connecting a capacitor to C
T
(optional).
The retry cycle will continue until the fault is removed or the
input is changed to TTL low.
If C
T
is connected to ground, the circuit will not retry upon a
fault condition.
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 (10I
2
) 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 V
BOOST
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 V
BOOST
pin
voltage. The boost capacitor charge is directed through the
GATE
pin to quickly charge the MOSFET’s gate to 16V
maximum above V
DD
. The internal charge pump maintains
the gate voltage.
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 compo-
nents 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.)
Supply Voltage
The MIC5021’s supply input (V
DD
) 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 enhance-
ment).
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.
October 1998
5
MIC5021
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