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Número de pieza | MAQ4123 | |
Descripción | Automotive AEC-Q100 Qualified Dual 3A Peak Low-Side MOSFET Driver | |
Fabricantes | Micrel Semiconductor | |
Logotipo | ||
Hay una vista previa y un enlace de descarga de MAQ4123 (archivo pdf) en la parte inferior de esta página. Total 18 Páginas | ||
No Preview Available ! MAQ4123/MAQ4124/MAQ4125
Automotive AEC-Q100 Qualified Dual
3A Peak Low-Side MOSFET Driver
Bipolar/CMOS/DMOS Process
General Description
The MAQ4123/MAQ4124/MAQ4125 are a family of dual
3A buffer/MOSFET drivers intended for driving power
MOSFETs, IGBTs and other heavy loads (capacitive,
resistive or inductive) which require low-impedance, high
peak currents and fast switching times. They are available
in inverting, non-inverting and complementary
configurations.
The MAQ4123/MAQ4124/MAQ4125 operate from a 4.5V
to 20V supply, feature an output resistance of 2.3Ω, sink or
source 3A of peak current, and switch an 1800pF
capacitive load in 10ns with typical propagation delay
times of 50ns.
The MAQ4123/MAQ4124/MAQ4125 feature TTL or CMOS
compatible inputs with 400mV of hysteresis to provide
noise immunity. The inputs can withstand negative voltage
swings of 5V and are latch-up protected to withstand
200mA of reverse current.
The MAQ4123/MAQ4124/MAQ4125 are rated for the
−40°C to +125°C operating temperature range, have been
AEC-Q100 qualified for automotive applications, and are
available in the ePad SOIC-8 package for improved power
dissipation and thermal performance required by
automotive applications.
Data sheets and support documentation can be found on
Micrel’s web site at: www.micrel.com.
Features
• Automotive AEC-Q100 Qualified
• High ±3A peak output current
• Wide 4.5V to 20V supply voltage range
• Low 2.3Ω output resistance
• Matched rise and fall times
• Fast 10ns rise/fall times with 1800pF capacitive load
• Low propagation delay time of 50ns (typical)
• TTL/CMOS logic inputs independent of supply voltage
• Latch-up protected to 200mA reverse current
• Logic input withstands swing to −5V
• Low equivalent 6pF input capacitance
• Output voltage swings within 25mV of ground or VS
• Low supply current
− 2.0mA with logic-1 input (maximum over
temperature)
− 300μA with logic-0 input (maximum over
temperature)
• ‘426/7/8-, ‘1426/7/8-, ‘4426/7/8 industry standard pin
out
• Inverting, non-inverting, and differential configurations
• −40°C to +125°C temperature range
• Exposed backside pad (ePad) packaging for improved
power dissipation
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 2011
M9999-072511-A
1 page Micrel, Inc.
Test Circuit
MAQ4123/MAQ4124/MAQ4125
Figure 1a. Inverting Driver Switching Time
July 2011
Figure 1b. Non-Inverting Driver Switching Time
5
M9999-072511-A
5 Page Micrel, Inc.
Application Information
The MAQ4123/24/25 drivers have been specifically
constructed to operate reliably under any practical
circumstances, the following details of usage provide for
better operation of the device.
Supply Bypassing
Charging and discharging large capacitive loads quickly
requires large currents. For example, charging 2000pF
from 0 to 15 volts in 20ns requires a constant current of
1.5A. In practice, the charging current is not constant,
and will usually peak at around 3A. In order to charge
the capacitor, the driver must be capable of drawing this
much current, this quickly, from the system power
supply. In turn, this means that as far as the driver is
concerned, the system power supply, as seen by the
driver, must have very low impedance.
As a practical matter, this means the power supply bus
decoupling capacitance must be much larger than the
driver output load capacitance to achieve optimum
driving speed. Additionally, the bypassing capacitors
must have very low internal inductance and resistance at
all frequencies of interest. High quality X5R or X7R
ceramic capacitors meet these requirements. Two
capacitors may be used to meet the decoupling
requirements. A larger ceramic capacitor in the 1μF to
4.7μF range and a 0.1μF capacitor may be used, as
together the valleys in their two impedance curves allow
adequate performance over a broad enough band to get
the job done. Z5U type ceramic capacitor dielectrics are
not recommended due to the large change in
capacitance over temperature and voltage. The high
pulse current demands of capacitive drivers also mean
that the bypass capacitors must be mounted very close
to the driver in order to prevent the effects of lead
inductance or PCB land inductance from nullifying what
the designer is trying to accomplish. For optimum
results, the sum of the lengths of the leads and the lands
from the capacitor body to the driver body should total
2.5cm or less.
Bypass capacitance, and its close mounting to the driver
serves two purposes. Not only does it allow optimum
performance from the driver, it minimizes the amount of
lead length radiating at high frequency during switching,
(due to the large Δ I) thus minimizing the amount of EMI
later available for system disruption and subsequent
cleanup. It should also be noted that the actual
frequency of the EMI produced by a driver is not the
clock frequency at which it is driven, but is related to the
highest rate of change of current produced during
switching, a frequency generally one or two orders of
magnitude higher, and thus more difficult to filter if you
let it permeate your system. Good bypassing practice is
essential to proper operation of high speed driver ICs.
MAQ4123/MAQ4124/MAQ4125
Grounding
Both proper bypassing and proper grounding are
necessary for optimum driver operation. Bypassing
capacitance only allows a driver to turn the load on.
Eventually (except in rare circumstances) it is also
necessary to turn the load OFF. This requires attention
to the ground path. Two things other than the driver
affect the rate at which it is possible to turn a load off:
The adequacy of the grounding available for the driver,
and the inductance of the leads from the driver to the
load. The latter will be discussed in a separate section.
The ePad package has an exposed pad under the
package. It's important for good thermal performance
that this pad is connected to a ground plane.
Best practice for a ground path is a well laid out ground
plane. However, this is not always practical, though a
poorly-laid out ground plane can be worse than none.
Attention to the paths taken by return currents, even in a
ground plane, is essential. In general, the leads from the
driver to its load, the driver to the power supply, and the
driver to whatever is driving it should all be as low in
resistance and inductance as possible. Of the three
paths, the ground lead from the driver to the logic driving
it, is most sensitive to resistance or inductance, and
ground current from the load is what is most likely to
cause disruption. Thus, these ground paths should be
arranged so that they never share a land, or do so for as
short a distance as is practical.
To illustrate what can happen, consider the following: the
inductance of a 2cm long land, 1.59mm (0.062") wide on
a PCB with no ground plane is approximately 45nH.
Assuming a di/dt of 0.3A/ns (which will allow a current of
3A to flow after 10ns, and is thus slightly slow for these
purposes) a voltage of 13.5V will develop along this land
in response to our postulated Δi. For a 1cm land,
(approximately 15nH) 4.5V is developed. Either way,
users employing TTL-level input signals to the driver will
find that the response of a driver that has been seriously
degraded by a common ground path for input to and
output from the driver of the given dimensions. Note that
this is before accounting for any resistive drops in the
circuit. The resistive drop in a 1.59mm (0.062") land of
2oz. Copper carrying 3A will be about 4mV/cm (10mV/in)
at DC, and the resistance will increase with frequency as
skin effect comes into play.
The problem is most obvious in inverting drivers where
the input and output currents are in phase so that any
attempt to raise the driver’s input voltage (in order to turn
the driver’s load off) is countered by the voltage
developed on the common ground path as the driver
attempts to do what it was supposed to. It takes very
little common ground path, under these circumstances,
to alter circuit operation drastically.
July 2011
11 M9999-072511-A
11 Page |
Páginas | Total 18 Páginas | |
PDF Descargar | [ Datasheet MAQ4123.PDF ] |
Número de pieza | Descripción | Fabricantes |
MAQ4123 | Automotive AEC-Q100 Qualified Dual 3A Peak Low-Side MOSFET Driver | Micrel Semiconductor |
MAQ4124 | Automotive AEC-Q100 Qualified Dual 3A Peak Low-Side MOSFET Driver | Micrel Semiconductor |
MAQ4125 | Automotive AEC-Q100 Qualified Dual 3A Peak Low-Side MOSFET Driver | Micrel Semiconductor |
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