CIRRUS MSA260

MSA260
MSA260
P r o d u c t IInnnnoovvaa t i o n FFr roomm
Pulse Width Modulation Amplifier
FEATURES
General Description
The MSA260 is a surface mount constructed PWM
amplifier that provides a cost effective solution in many
industrial applications. The MSA260 offers outstanding performance that rivals many much more expensive hybrid components. The MSA260 is a complete
PWM amplifier including an oscillator, comparator, error amplifier, 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 mounted to a heatsink.
• 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
Equivalent Circuit Diagram
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Copyright
© Cirrus
Logic, Inc. 2008
(All Rights Reserved)
NOV 2008
APEX − MSA260UREVC
MSA260
P r o d u c t I n n o v a t i o nF r o m
Characteristics and Specifications
Absolute Maximum Ratings
Parameter
Symbol
Min
Max
Units
SUPPLY VOLTAGE
VS
450
V
SUPPLY VOLTAGE
VCC
16
V
OUTPUT CURRENT, peak, within SOA
POWER DISSIPATION, internal, DC
(Note 3)
SIGNAL INPUT VOLTAGES
TEMPERATURE, pin solder, 10s
TEMPERATURE, junction
(Note 2)
30
A
250
W
5.4
V
225
°C
150
°C
TEMPERATURE RANGE, storage
−40
105
°C
OPERATING TEMPERATURE, case
−40
85
°C
Specifications
Parameter
Test Conditions (Note 1)
Min
Typ
Max
Units
Full temperature range
9
mV
ERROR AMPLIFIER OFFSET VOLTAGE
BIAS CURRENT, initial
Full temperature range
500
nA
OFFSET CURRENT, initial
(Note 3)
Full temperature range
150
nA
COMMON MODE VOLTAGE RANGE, pos.
Full temperature range
4
V
SLEW RATE
Full temperature range
1
V/µs
OPEN LOOP GAIN
RL = 2KΩ
96
dB
1
MHz
0
UNITY GAIN BANDWIDTH
CLOCK
LOW LEVEL OUTPUT VOLTAGE
Full temperature range
HIGH LEVEL OUTPUT VOLTAGE
Full temperature range
0.2
4.8
V
V
RISE TIME
7
nS
FALL TIME
7
nS
BIAS CURRENT, pin 22
Full temperature range
0.6
µA
5.15
V
2
mA
2.25
V
5V REFERENCE OUTPUT
VOLTAGE
4.85
LOAD CURRENT
OUTPUT
(Note 4)
VCE(ON), each active IGBT
ICE = 15A
CURRENT, continuous
VS = 400V, F = 22kHz
20
A
CURRENT, peak
1mS, VS = 400V, F = 22kHz
30
A
FLYBACK DIODE
CONTINUOUS CURRENT
FORWARD VOLTAGE
IF = 15A
REVERSE RECOVERY
IF = 15A
0.2
44
20
A
200
1.5
V
0.7
150
nS
MSA260U
MSA260
P r o d u c t I n n o v a t i o nF r o m
Parameter
Test Conditions (Note 1)
Min
Typ
Max
Units
5
400
450
V
14
15
16
V
9
28
mA
18
mA
10
mA
1
°C/W
14
°C/W
85
°C
POWER SUPPLY
VOLTAGE, VS
VOLTAGE, VCC
CURRENT, VS, quiescent
22kHz switching
CURRENT, VCC, quiescent
22kHz switching
CURRENT, VCC, shutdown
THERMAL
RESISTANCE, DC, junction to case
Full temperature range
RESISTANCE, junction to air
Full temperature range
TEMPERATURE RANGE, case
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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. Maximum specification guaranteed but not tested.
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External Connections
RRAMP
VIEW FROM
COMPONENT SIDE
ROSC
C1
C2
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C3
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MSA260U
MSA260
P r o d u c t I n n o v a t i o nF r o m
58-pin DIP
PACKAGE STYLE KC
Typical Application
TORQUE MOTOR CONTROL
With the addition of a few external components the MSA260 becomes a motor torque controller.
In the MSA260 the source terminal of each low side IGBT driver
is brought out for current sensing
via RSA and RSB. A1 is a differential amplifier that amplifies the difference in currents of the two half
bridges. This signal is fed into the
internal error amplifier that mixes
the current signal and the control
signal. The result is an input signal to the MSA260 that controls
the torque on the motor.
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General
Please read Application Note 30 “PWM Basics”. Refer also to Application Note 1 “General Operating Considerations” for helpful information regarding power supplies, heat sinking, mounting, SOA interpretation, and specification 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.
MSA260U
MSA260
P r o d u c t I n n o v a t i o nF r o m
OSCILLATOR
The MSA260 includes a user frequency programmable oscillator. The oscillator determines the switching frequency
of the amplifier. The switching frequency of the amplifier is 1/2 the oscillator frequency. Two resistor values must
be chosen to properly program the switching frequency of the amplifier. One resistor, ROSC, sets the oscillator frequency. 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 .
RRAMP = 2 X ROSC
Use 1% resistors with 100ppm drift (RN55C type resistors,
for example). Maximum switching frequency is 50kHz.
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To program the oscillator, ROSC is given by:
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Example:
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If the desired switching frequency is 22kHz then ROSC =
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3.32K and RRAMP = 6.64K. Choose the closest standard 1%
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of selected ROSC in series for RRAMP.
FIGURE 1. EXTERNAL OSCILLATOR CONNECTIONS
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The MSA260 output stage can be turned off with a shutdown command voltage 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.
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The low side drive transistors of the MSA260 are brought out for sensing the
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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 FIGURE 2. CURRENT LIMIT WITH
constant is equal to 10 periods of the selected switching frequency. The in- OPTIONAL SHUTDOWN
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 amplifiers 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 flows 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.
MSA260U
MSA260
P r o d u c t I n n o v a t i o nF r o m
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. Conduction 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 amplifier. 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 flow 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 flows through to find 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 amplifier footprint as a final 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 [email protected]
International customers can also request support by contacting their local Cirrus Logic Sales Representative.
To find the one nearest to you, go to www.cirrus.com
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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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CERTAIN APPLICATIONS USING SEMICONDUCTOR PRODUCTS MAY INVOLVE POTENTIAL RISKS OF DEATH, PERSONAL INJURY, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE (“CRITICAL APPLICATIONS”). CIRRUS PRODUCTS ARE NOT DESIGNED, AUTHORIZED OR WARRANTED TO BE
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MSA260U