MIC5020 DATA SHEET (11/05/2015) DOWNLOAD

MIC5020
Micrel, Inc.
MIC5020
Current-Sensing Low-Side MOSFET Driver
General Description
Features
The MIC5020 low-side MOSFET driver is designed to operate
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 power
supplies), and applications using IGBTs. The MIC5020 can
also operate as a circuit breaker with or without automatic
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.
A rising or falling edge on the input results in a current source
or sink pulse on the gate output. This output current pulse
can 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.
An overcurrent comparator with a trip voltage of 50mV makes
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 CT pin may be
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 CT to VDD. An open
collector output provides a fault indication when the sense
inputs are tripped.
The MIC5020 is available in 8-pin SOIC package.
Other members of the MIC502x series include the MIC5021
high-side driver and the MIC5022 half-bridge driver with a
cross-conduction interlock.
•
•
•
•
•
•
•
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
Ordering Information
Part Number
Standard
Pb-Free
MIC5020BM
MIC5020YM
Temperature
Range
Package
–40ºC to +85ºC
8-pin SOIC
Typical Application
V+
+11V to +50V
10µF
150kHz max.
1
2
3
optional*
4
MIC5020
V DD
Gate
Input
Sense-
Fault
Sense+
CT
Gnd
8
7
N-Channel
Power MOSFET
6
5
R SENSE
R S E N S E = 50mV
I TR IP
* increases time before retry
Low-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
MIC5020
MIC5020
Micrel, Inc.
Pin Configuration
1
V DD
Gate 8
2
Input Sense- 7
3
Fault Sense+ 6
4
CT
Gnd 5
SOIC Package
(M)
Block Diagram
6V Internal Regulator
I1
Fault
CINT
2I1
CT
Normal
Fault
Q1
Sense+
VDD
Sense50mV
ON
OFF
↑ ONE↓ SHOT
Input
10I2
I2
6V
Gate
Transistor Count: 82
Pin Description
Pin Number
Pin Name
1
Supply: +11V to +50V. Decouple with ≥ 10µF capacitor.
2
VDD
Input
TTL Compatible Input: Logic high turns the external MOSFET on. An internal
pull-down returns an open pin to logic low.
3
Fault
4
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.
5
Gnd
6
Sense +
7
Sense –
8
Gate
MIC5020
Pin Function
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.
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
RSENSE sets the load overcurrent trip point.
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.
2
July 2005
MIC5020
Micrel, Inc.
Absolute Maximum Ratings
Operating Ratings
Supply Voltage (VDD)................................................... +55V
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
Timer Voltage (CT) ...................................................... +5.5V
Supply Voltage (VDD)......................................+11V to +50V
Temperature Range
SOIC ....................................................... –40°C to +85°C
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
D.C. Supply Current
VDD = 12V, Input = 0V
0.8
2
mA
2
10
mA
VDD = 12V, Input = 5V
0.8
2
mA
4
25
mA
1.4
2.0
VDD = 50V, Input = 0V
Input Threshold
VDD = 50V, Input = 5V
0.8
Input Hysteresis
tG(ON)
Input = 5V
Fault Output
Saturation Voltage
Fault Current = 1.6mA
Note 1
Fault Output Leakage
Fault = 50V
Current Limit Threshold
Gate On Voltage
tG(OFF)
Gate Off Time, Adjustable
tR
tF
tDLH
fmax
Note 1
Note 2
Note 3
Units
V
10
V
20
40
µA
0.15
0.4
V
–1
0.01
+1
µA
Note 2
30
50
70
mV
VDD = 12V
10
11
VDD = 50V
14
15
18
V
Sense Differential > 70mV
2
5
10
µs
Sense Differential > 70mV, CT = 0pF
10
V
20
50
µs
Note 3
400
800
ns
Gate Rise Time
Note 4
700
1500
ns
Gate Turn-Off Delay
Note 5
900
1500
ns
Gate Fall Time
Note 6
500
1500
Maximum Operating Frequency
Note 7
Gate Turn-On Delay
tDLH
Max
0.1
Input Pull-Down Current
Gate On Time, Fixed
Typ
100
150
ns
kHz
Voltage remains low for time affected by CT.
When using sense MOSFETs, it is recommended that RSENSE < 50Ω. Higher values may affect the sense MOSFET’s current transfer ratio.
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.
July 2005
3
MIC5020
MIC5020
Micrel, Inc.
Typical Characteristics
3.5
2.5
2.0
1.5
VIN = 0V
1.0
400
5 10 15 20 25 30 35 40 45 50
VSUPPLY (V)
Input Current vs.
Input Voltage
1000
60
800
40
INCLUDES PROPAGATION DALAY
700
Turn-On Time vs.
Gate Capacitance
80
10
15
VIN (V)
5
20
15
20
VSUPPLY (V)
25
30
Overcurrent Shutdown
Retry Duty Cycle
tON = 5µs
VSUPPLY = 12V
15.0
600
10.0
200
1x102
25
10
20.0
INCLUDES PROPAGATION DELAY
0
5
25.0
VG AT E = 4V
400
20
900
5 10 15 20 25 30 35 40 45 50
VSUPPLY (V)
1200
VSUPPLY = 12V
VG AT E = 4V
CL = 1500pF
VIN = 0 to 5V
Sq. Wave
800
500
tON (ns)
IIN (µA)
600
80
1x103
1x104
CGATE (pF)
5.0
0.0
0.1
1x105
1
10
100
CT (pF)
1000 10000
Sense Threshold vs.
Temperature
TTL (H)
Input
VOLTAGE (mV)
70
Gate
60
0V
15V (max.)
Sense +,–
Differential
50
40
Gate
20µs
5µs
TTL (H)
Input
0V
15V (max.)
Sense +,–
Differential
Fault
On
TTL (H)
Input
0V
Timing Diagram 1. Normal Operation
20
-60 -30 0 30 60 90 120 150
TEMPERATURE (°C)
5µs
0V
50mV
Off
Fault
30
Gate
0V
0V
15V (max.)
Sense +,–
Differential
50mV
0V
Off
Fault
On
Timing Diagram 2. Fault Condition, CT = Open
MIC5020
1000
700
INCLUDES PROPAGATION DELAY
100
0
1100
Shutdown Duty Cycle (%)
0.5
Turn-Off Time vs.
Supply Voltage
1200
VG AT E = 4V
CL = 1500pF
VIN = 0 to 5V Sq. Wave
800
tON (nS)
ISUPPLY (mA)
900
VIN = 5V
3.0
Turn-On Time vs.
Supply Voltage
tOFF (ns)
Supply Current vs.
Supply Voltage
0V
50mV
0V
Off
On
Timing Diagram 3. Fault Condition, CT = Grounded
4
July 2005
MIC5020
Micrel, Inc.
Functional Description
Refer to the MIC5020 block diagram.
Input
A signal greater than 1.4V (nominal) applied to the MIC5020
INPUT causes gate enhancement on an external MOSFET
turning the external 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 through 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 15V Zener diode protects the external MOSFET
by limiting the gate output voltage when VDD is connected
to higher voltages.
Overcurrent Limiting
Current source I1 charges CINT upon power up. An optional
external capacitor connected to CT is discharged through
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; the FAULT output is enabled; 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 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
fault condition.
Fault Output
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).
Applications Information
The MIC5020 MOSFET driver is intended for low-side switching applications where higher supply voltage, overcurrent
sensing, and moderate speed are required.
Supply Voltage
A feature of the MIC5020 is that its supply voltage rating of
up to 50V is higher than many other low-side drivers.
The minimum supply voltage required to fully enhance an
N-channel MOSFET is 11V.
A lower supply voltage may be used with logic level MOSFETs. Approximately 6V is needed to provide 5V of gate
enhancement.
Low-Side Switch Circuit Advantages
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.)
Overcurrent Limiting
A 50mV comparator is provided for current sensing. The low
level trip point minimizes I2R losses when power resistors
are used for current sensing. Flexibility in choosing drain or
source side sensing is provided by access to both SENSE +
July 2005
and SENSE – comparator inputs.
The adjustable retry feature can be used to handle loads
with high initial currents, such as lamps, motors, or heating
elements and can be adjusted from the CT connection.
CT to ground causes maintained gate drive shutdown following overcurrent detection.
CT open, or through 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 a 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. 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 voltage
on CT exceeds the absolute maximum rating.
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 resistors. Four-terminal resistors are available from several
manufacturers.
5
MIC5020
MIC5020
Micrel, Inc.
Current Sensing MOSFET Application
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 (ISOURCE/
ISENSE) is provided by the MOSFET manufacturer.
Lamp Driver Application
Incandescent lamps have a high inrush current (low resistance) 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.
V+
10µF
TTL Input
(0V/5V)
1
2
3
4
Gate
Input
Sense-
Fault
Sense+
Gnd
CT
(+11V to +12V)
(3Ω, > 60W)
Incandescent
Lamp (#1157)
MIC5020
V DD
V+
(+13.2V, > 4.4A)
+11V to +50V
(+13.2V)
10µF
N-Channel
Power MOSFET
(IRF540)
8
7
TTL Input
(0V/5V)
6
5
RS E N S E
(0.041Ω)
TTL Input
2
3
4
MIC5020
V DD
Gate
Input
Sense-
Fault
Sense+
CT
Gnd
8
7
Diode
N-Channel
Power MOSFET
6
5
Figure 2. Solenoid Driver,
Without Current Sensing
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.
MIC5020
Gate
Input
Sense-
Fault
Sense+
CT
Gnd
7
6
5
N-Channel
Current Sensing
Power MOSFET
(IRCZ24)
R SENSE
(10Ω)
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 overcurrent condition.
The value of the sense resistor can be estimated with:
RSENSE = (r VTRIP RDS(ON)) / (ILOAD RDS(ON) – VTRIP)
where:
RSENSE = external “sense” resistor
VTRIP = 50mV (0.050V) for the MIC5020
r = manufacturer’s current sense ratio: (ISOURCE/ISENSE)
RDS(ON) = manufacturer’s power source on resistance
ILOAD = load current (power source current)
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-current
condition (VDS(ON) very small) than to a short circuit (where
VDS(ON) is approximately equal to the supply voltage).
Adjustment of the sense resistor value by experiment starting
from the above formula will provide the quickest selection
of RSENSE.
Refer to manufacture’s data sheets and application notes
for detailed information on current sensing MOSFET characteristics.
Figure 3 includes values which can be used to demonstrate
circuit operation. The IRCZ24 MOSFET has a typical sense
ratio of 780 and a RDS(ON) of 0.10Ω. A large 3Ω wirewound
load resistor will cause inductive spikes which should be
suppressed using a diode (using the same configuration as
figure 2).
V+
1
V DD
8
Figure 3. Using a Current Sensing MOSFET
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 1 allows
for soft start of the higher-resistance filament (measures
approx. 2.1Ω cold or 21Ω hot).
Solenoid Driver Application
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.
10µF
3
MIC5020
“( )” values apply to
demo circuit. See text.
Figure 1. Lamp Driver with
Current Sensing
Solenoid
2
4
“( )” values apply to
demo circuit. See text.
+11V to +50V
1
6
July 2005
MIC5020
Micrel, Inc.
Faster MOSFET Switching
The MIC5020’s GATE current can be multiplied using a pair of
bipolar transistors to permit faster charging and discharging
of the external MOSFET’s gate.
For test 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 MIC5020AJB (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 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.
+11V to +50V
10µF
1
2
150kHz max.
3
4
2N3904
MIC5020
Gate
V DD
Input
Sense-
Fault
Sense+
Gnd
CT
N-Channel
Power MOSFET
(IRF540)
8
7
6
V+
2N3906
5
Figure 4. Faster MOSFET Switching Circuit
+11V to +50V
1
10µF
2
3
NPN and PNP transistors are used to respectively charge
and discharge the MOSFET gate. The MIC5020 gate current
is multiplied by the transistor β.
The switched circuit voltage can be increased above 40V by
selecting transistors with higher ratings.
Remote Overcurrent Limiting Reset
In circuit breaker applications where the MIC5020 maintains
an off condition after an overcurrent condition is sensed, the
CT pin can be used to reset the MIC5020.
4
MIC5020
V DD
Gate
Input
Sense-
Fault
Sense+
CT
Gnd
TTL input
Retry (H)
Maintained (L)
1
2
3
10k to
100k
74HC04
(example)
4
MIC5020
V DD
Gate
Input
Sense-
Fault
Sense+
CT
Q1
2N3904
Gnd
8
7
5
2.2M
RS E NS E
V+
N-Channel
Power MOSFET
+11V to +50V
1
10µF
2
3
4
RS E N S E
MIC5020
V DD
Gate
Input
Sense-
Fault
Sense+
CT
Gnd
8
7
6
5
2.2M RS E N S E
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
Switching Q1 on pulls CT low which keeps the MIC5020 GATE
output off when an overcurrent is sensed. Switching Q1 off
causes CT to appear open. The MIC5020 retries in about
20µs and continues to retry until the overcurrent condition
is removed.
July 2005
6
The gate-to-source configuration (refer to Figure 6a) is appropriate for resistive and inductive loads. This also causes
the smallest decrease in gate output voltage.
6
5
7
Figure 6a. Gate-to-Source Pull Down
V+
+11V to +50V
10µF
8
7
MIC5020
MIC5020
Micrel, Inc.
Package Information
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.
© 1998 Micrel, Inc.
MIC5020
8
July 2005