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GENERAL DESCRIPTION
The MSA260 is a surface mount constructed PWM
amplier that provides a cost effective solution in many
industrial applications. The MSA260 offers outstand-
ing performance that rivals many much more expen-
sive hybrid components. The MSA260 is a complete
PWM amplier including an oscillator, comparator, er-
ror amplier, current limit comparators, 5V reference,
a smart controller and a full bridge IGBT output circuit.
The switching frequency is user programmable up to
50 kHz. The MSA260 is built on a thermally conductive
but electrically insulating substrate that can be mount-
ed to a heatsink.
FEATURES
• LOW COST
• HIGH VOLTAGE - 450 VOLTS
• HIGH OUTPUT CURRENT - 20 AMPS
• 9kW OUTPUT CAPABILITY
• VARIABLE SWITCHING FREQUENCY
• IGBT FULL BRIDGE OUTPUT
APPLICATIONS
• BRUSH MOTOR CONTROL
• MRI
• MAGNETIC BEARINGS
• CLASS D SWITCHMODE AMPLIFIER
Pulse Width Modulation Amplifier
MSA260
P r o d u c t I n n o v a t i o n F r o m
EQUIVALENT CIRCUIT DIAGRAM
Copyright © Cirrus Logic, Inc. 2008
(All Rights Reserved)
http://www.cirrus.com
NOV 2008
APEX − MSA260UREVC
P r o d u c t I n n o v a t i o n F r o m
MSA260
2 MSA260U
Parameter Symbol Min Max Units
SUPPLY VOLTAGE VS450 V
SUPPLY VOLTAGE VCC 16 V
OUTPUT CURRENT, peak, within SOA 30 A
POWER DISSIPATION, internal, DC (Note 3) 250 W
SIGNAL INPUT VOLTAGES 5.4 V
TEMPERATURE, pin solder, 10s 225 °C
TEMPERATURE, junction (Note 2) 150 °C
TEMPERATURE RANGE, storage −40 105 °C
OPERATING TEMPERATURE, case −40 85 °C
CHARACTERISTICS AND SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
Parameter Test Conditions (Note 1) Min Typ Max Units
ERROR AMPLIFIER
OFFSET VOLTAGE Full temperature range 9mV
BIAS CURRENT, initial (Note 3) Full temperature range 500 nA
OFFSET CURRENT, initial Full temperature range 150 nA
COMMON MODE VOLTAGE RANGE, pos. Full temperature range 04 V
SLEW RATE Full temperature range 1V/µs
OPEN LOOP GAIN RL = 2KΩ 96 dB
UNITY GAIN BANDWIDTH 1MHz
CLOCK
LOW LEVEL OUTPUT VOLTAGE Full temperature range 0.2 V
HIGH LEVEL OUTPUT VOLTAGE Full temperature range 4.8 V
RISE TIME 7 nS
FALL TIME 7 nS
BIAS CURRENT, pin 22 Full temperature range 0.6 µA
5V REFERENCE OUTPUT
VOLTAGE 4.85 5.15 V
LOAD CURRENT 2 mA
OUTPUT (Note 4)
VCE(ON), each active IGBT ICE = 15A 2.25 V
CURRENT, continuous VS = 400V, F = 22kHz 20 A
CURRENT, peak 1mS, VS = 400V, F = 22kHz 30 A
FLYBACK DIODE
CONTINUOUS CURRENT 44 20 A
FORWARD VOLTAGE IF = 15A 200 1.5 V
REVERSE RECOVERY IF = 15A 0.2 0.7 150 nS
SPECIFICATIONS
P r o d u c t I n n o v a t i o n F r o m MSA260
MSA260U 3
NOTES:
1. Unless otherwise noted: TC=25°C, VCC = 15V, VS = 400V, F = 22kHz.
2. Long term operation at the maximum junction temperature will result in reduced product life. Derate
internal power dissipation to achieve high MTBF.
3. Each of the two output transistors on at any one time can dissipate 125W.
4. Maximumspecicationguaranteedbutnottested.
Parameter Test Conditions (Note 1) Min Typ Max Units
POWER SUPPLY
VOLTAGE, VS5 400 450 V
VOLTAGE, VCC 14 15 16 V
CURRENT, VS, quiescent 22kHz switching 9 28 mA
CURRENT, VCC, quiescent 22kHzswitching 18 mA
CURRENT, VCC, shutdown 10 mA
THERMAL
RESISTANCE, DC, junction to case Full temperature range 1°C/W
RESISTANCE, junction to air Full temperature range 14 °C/W
TEMPERATURE RANGE, case -40 85 °C
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MSA260
4 MSA260U
EXTERNAL CONNECTIONS
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P r o d u c t I n n o v a t i o n F r o m MSA260
MSA260U 5
TYPICAL APPLICATION
TORQUE MOTOR CONTROL
With the addition of a few exter-
nal components the MSA260 be-
comes a motor torque controller.
In the MSA260 the source termi-
nal of each low side IGBT driver
is brought out for current sensing
via RSA and RSB. A1 is a differen-
tial amplier that amplies the dif-
ference in currents of the two half
bridges. This signal is fed into the
internal error amplier that mixes
the current signal and the control
signal. The result is an input sig-
nal to the MSA260 that controls
the torque on the motor.
GENERAL
Please read Application Note 30 “PWM Basics”. Refer also to Application Note 1 “General Operating Consider-
ations” for helpful information regarding power supplies, heat sinking, mounting, SOA interpretation, and specica-
tion interpretation. Visit www.cirrus.com for design tools that help automate tasks such as calculations for stability,
internal power dissipation, current limit, heat sink selection, Cirrus’s complete Application Notes library, Technical
Seminar Workbook and Evaluation Kits.
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P r o d u c t I n n o v a t i o n F r o m
MSA260
6 MSA260U
OSCILLATOR
The MSA260 includes a user frequency programmable oscillator. The oscillator determines the switching frequency
of the amplier. The switching frequency of the amplier is 1/2 the oscillator frequency. Two resistor values must
be chosen to properly program the switching frequency of the amplier. One resistor, ROSC, sets the oscillator fre-
quency. The other resistor, RRAMP
, sets the ramp amplitude. In all cases the ramp voltage will oscillate between 1.5V
and 3.5V. See Figure 1. If an external oscillator is applied use the equations to calculate RRAMP .
To program the oscillator, ROSC is given by:
ROSC = (1.32X108 / F) - 2680
where F is the desired switching frequency and:
RRAMP = 2 X ROSC
Use 1% resistors with 100ppm drift (RN55C type resistors,
for example). Maximum switching frequency is 50kHz.
Example:
If the desired switching frequency is 22kHz then ROSC =
3.32K and RRAMP = 6.64K. Choose the closest standard 1%
values: ROSC = 3.32K and RRAMP = 6.65K or simply use two
of selected ROSC in series for RRAMP.
SHUTDOWN
The MSA260 output stage can be turned off with a shutdown command volt-
age applied to Pin 10 as shown in Figure 2. The shutdown signal is OR’ed
with the current limit signal and simply overrides it. As long as the shutdown
signal remains high the output will be off.
CURRENT SENSING
The low side drive transistors of the MSA260 are brought out for sensing the
current in each half bridge. A resistor from each sense line to PWR GND (pin
58) develops the current sense voltage. Choose R and C such that the time
constant is equal to 10 periods of the selected switching frequency. The in-
ternal current limit comparators trip at 200mV. Therefore, current limit occurs
at I = 0.2/RSENSE for each half bridge. See Figure 2. Accurate milliohm power resistors are required and there are
several sources for these listed in the Accessories Vendors section of the Databook.
POWER SUPPLY BYPASSING
Bypass capacitors to power supply terminals +VS must be connected physically close to the pins to prevent local
parasitic oscillation and overshoot. All +VS must be connected together. Place and electrolytic capacitor of at least
10µF per output amp required midpoint between these sets of pins. In addition place a ceramic capacitor 1.0µF or
greater directly at each set of pins for high frequency bypassing. VCC is bypassed internally.
GROUNDING AND PCB LAYOUT
Switching ampliers combine millivolt level analog signals and large amplitude switching voltages and currents with
fast rise times. As such grounding is crucial. Use a single point ground at SIG GND (pin 26). Connect signal ground
pins 2 and 18 directly to the single point ground on pin 26. Connect the digital return pin 23 directly to pin 26 as well.
Connect PWR GND pin 58 also to pin 26. Connect AC BACKPLATE pin 28 also to the single point ground at pin 26.
Connect the ground terminal of the VCC supply directly to pin 26 as well. Make sure no current from the load return
to PWR GND ows in the analog signal ground. Make sure that the power portion of the PCB layout does not pass
over low-level analog signal traces on the opposite side of the PCB. Capacitive coupling through the PCB may inject
switching voltages into the analog signal path. Further, make sure that the power side of the PCB layout does not
come close to the analog signal side. Fast rising output signal can couple through the trace-to-trace capacitance on
the same side of the PCB.
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FIGURE 2. CURRENT LIMIT WITH
OPTIONAL SHUTDOWN
P r o d u c t I n n o v a t i o n F r o m MSA260
MSA260U 7
DETERMINING THE OUTPUT STATE
The input signal is applied to +IN (Pin 13) and varies from 1.5 to 3.5 volts, zero to full scale. The ramp also varies
over the same range. When:
Ramp > +IN AOUT > BOUT
The output duty cycle extremes vary somewhat with switching frequency and are internally limited to approximately
5% to 95% at 10kHz and 7% to 93% at 50kHz.
CALCULATING INTERNAL POWER DISSIPATION
Detailed calculation of internal power dissipation is complex but can be approximated with simple equations. Con-
duction loss is given by:
W = I • 2.5 + I2 • 0.095
where I = output current
Switching loss is given by:
W = 0.00046 • I • Vsupply • Fswitching (in kHz)
Combine these two losses to obtain total loss. Calculate heatsink ratings and case temperatures as would be done
for a linear amplier. For calculation of junction temperatures, assume half the loss is dissipated in each of two
switches:
Tj = Ta + Wtotal • RØhs + 1/2Wtotal • RØjc, where:
RØhs = heatsink rating
RØjc = junction-to-case thermal resistance of the MSA260.
The SOA typical performance graphs below show performance with the MSA260 mounted with thermal grease on
the Cirrus HS26. The Free Air graph assumes vertical orientation of the heatsink and no obstruction to air ow in an
ambient temperature of 30°C. The other two graphs show performance with two levels of forced air. Note that air
velocity is given in linear feet per minute. As fans are rated in cubic delivery capability, divide the cubic rating by the
square area this air ows through to nd velocity. As fan delivery varies with static pressure, these calculations are
approximations, and heatsink ratings vary with amount of power dissipated, there is no substitute for temperature
measurements on the heatsink in the center of the amplier footprint as a nal check.
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CONTACTING CIRRUS LOGIC SUPPORT
For all Apex Precision Power product questions and inquiries, call toll free 800-546-2739 in North America.
For inquiries via email, please contact tucson.support@cirrus.com.
International customers can also request support by contacting their local Cirrus Logic Sales Representative.
To nd the one nearest to you, go to www.cirrus.com
IMPORTANT NOTICE
Cirrus Logic, Inc. and its subsidiaries ("Cirrus") believe that the information contained in this document is accurate and reliable. However, the information is subject
to change without notice and is provided "AS IS" without warranty of any kind (express or implied). Customers are advised to obtain the latest version of relevant
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does not extend to other copying such as copying for general distribution, advertising or promotional purposes, or for creating any work for resale.
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All other brand and product names in this document may be trademarks or service marks of their respective owners.
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