MIC5021BM Micrel Inc, MIC5021BM Datasheet - Page 7

• Manufacturer Part Number: MIC5021BM
• Description: IC DRIVER MOSFET HISIDE HS 8SOIC
• Manufacturer: Micrel Inc

Specifications of MIC5021BM

• Configuration: High-Side
• Input Type: Non-Inverting
• Delay Time: 500ns
• Number Of Configurations: 1
• Number Of Outputs: 1
• Voltage - Supply: 12 V ~ 36 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Number Of Drivers: 1
• Driver Configuration: Non-Inverting
• Driver Type: High Side
• Input Logic Level: TTL
• Rise Time: 500ns
• Fall Time: 500ns
• Frequency (max): 150MHz
• Operating Supply Voltage (max): 36V
• Operating Supply Voltage (min): 12V
• Operating Supply Voltage (typ): 15V
• Turn Off Delay Time: 1.5ps
• Turn On Delay Time (max): 1ns
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 8
• Package Type: SOIC
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Current - Peak: -
• High Side Voltage - Max (bootstrap): -
• Lead Free Status / RoHS Status: Not Compliant, Contains lead / RoHS non-compliant

Circuits Without Current Sensing
Current sensing may be omitted by connecting the
and
ply. Connecting the
inductive loads. Do not connect the
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.
July 2005
MIC5021
TTL Input
TTL Input
SENSE
Figure 4b. Connecting Sense to Supply
Figure 4a. Connecting Sense to Source
10µF
10µF
– pins to the source of the MOSFET or to the sup-
1
2
3
4
1
2
3
4
SENSE
V
Input
C
Gnd
V
Input
C
Gnd
DD
T
DD
T
MIC5021
MIC5021
V
Sense-
Sense+
V
Sense-
Sense+
pins to the supply is preferred for
B O O S T
B O O S T
Gate
Gate
8
7
6
5
8
7
6
5
SENSE
0.01
µF
0.01
µF
V+
V+
N-Channel
Power MOSFET
Load
N-Channel
Power MOSFET
Load
pins to ground.
SENSE
+
7
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.
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.
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.
TTL Input
10µF
Forward drop across diodes
allows leads to go negative.
Current flows from ground (0V)
through the diodes to the load
during negative transcients.
Figure 6. Inductive Load Turnoff
1
2
3
4
Figure 5. Solenoid Driver
V
Input
C
DD
T
with Current Sensing
MIC5021
1
2
3
4
V
Input
C
Gnd
DD
T
MIC5021
Gate
V
Sense-
Sense+
B O O S T
Gate
8
7
6
5
(24V, 47Ω)
8
7
6
5
Solenoid
+20V to +36V
M OS FE T
Turnoff
0.01
µF
Inductive
Load
(+24V)
N-Channel
Power MOSFET
(IRF540)
R
(< 0.08Ω)
S E N S E
~V
0V
Negative
Spike
DD
Schottky
Diode
(1N5822)
Micrel, Inc.
MIC5021