MIC5021 查看數據表（PDF） - Microchip Technology
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MIC5021
Microchip Technology
MIC5021 Datasheet PDF : 24 Pages
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6.0 APPLICATION 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.
6.1 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.
6.2 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 con-
trol, 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.
6.3 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 capac-
itor a more significant voltage supply than the internal
charge pump.
6.4 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 MOS-
FETs, connect a zener diode (5V ≤ VZENER < 10V) from
gate to source.
MIC5021
6.5 Overcurrent Limiting
A 50 mV 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 heat-
ing elements, and can be adjusted from the CT connec-
tion.
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 con-
dition. Circuits may become unstable at a duty cycle of
about 75% or higher, depending on conditions. Cau-
tion: The MIC5021 may be damaged if the voltage
applied to CT exceeds the absolute maximum voltage
rating.
6.6 Boost Capacitor Selection
The boost capacitor value will vary depending on the
supply voltage range.
A 0.01 μF boost capacitor is recommended for best
performance in the 12V to 20V range. (See Figure 6-1.)
Larger capacitors may damage the MIC5021.
+12V to +20V
10μF
TTL Input
MIC5021
1
V DD
8
V BOOST
2
Input
7
Gate
3
CT
4
Gnd
6
Sense-
5
Sense+
0.01
μF
Load
FIGURE 6-1:
12V to 20V Configuration.
If the full 12V to 36V voltage range is required, the
boost capacitor value must be reduced to 2.7 nF
(Figure 6-2). The recommended configuration for the
20V to 36V range is to place the capacitor is placed
between VDD and VBOOST as shown in Figure 6-3.
2016 Microchip Technology Inc.
DS20005677A-page 11
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