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FEATURES
• LOW COST
• HIGH VOLTAGE - 100 VOLTS
• HIGH OUTPUT CURRENT - 20 AMPS
• 2kW OUTPUT CAPABILITY
• VARIABLE SWITCHING FREQUENCY
APPLICATIONS
• BRUSH MOTOR CONTROL
• MRI
• MAGNETIC BEARINGS
• CLASS D SWITCHMODE AMPLIFIER
DESCRIPTION
The MSA240 is a surface mount constructed PWM amplifier
that provides a cost effective solution in many industrial applica-
tions. The MSA240 offers outstanding performance that rivals
many much more expensive hybrid components. The MSA240
is a complete PWM amplifier including an oscillator, comparator,
error amplifier, current limit comparators, 5V reference, a smart
controller and a full bridge output circuit. The switching frequency
is user programmable up to 50 kHz. The MSA240 is built on
a thermally conductive but electrically insulating substrate that
can be mounted to a heatsink.
EQUIVALENT CIRCUIT DIAGRAM
58-PIN DIP
PACKAGE STYLE KC
TYPICAL APPLICATION
TORQUE MOTOR CONTROL
With the addition of a few external components the MSA240
becomes a motor torque controller. In the MSA240 the source
terminal of each low side MOSFET 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 MSA240 that controls the torque on the motor.
EXTERNAL CONNECTIONS
VIEW FROM
COMPONENT SIDE
ROSC
RRAMP
+
SINGLE
POINT
GND
C3
C1 C2
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ABSOLUTE MAXIMUM RATINGS
SPECIFICATIONS
MSA240
SPECIFICATIONS
ABSOLUTE MAXIMUM RATINGS
PARAMETER TEST CONDITIONS1 MIN TYP MAX UNITS
ERROR AMPLIFIER
OFFSET VOLTAGE Full temperature range 9 mV
BIAS CURRENT Full temperature range 500 nA
OFFSET CURRENT Full temperature range 150 nA
COMMON MODE VOLTAGE RANGE Full temperature range 0 4 V
SLEW RATE Full temperature range 1 V/µS
OPEN LOOP GAIN RL = 2KΩ 96 dB
UNITY GAIN BANDWIDTH 1 MHz
CLOCK
LOW LEVEL OUTPUT VOLTAGE Full temperature range .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
TOTAL RON, both MOSFETs4 IO = 20A , TJ = 85°C 155 mΩ
CURRENT, continuous 20 A
CURRENT, peak 100mS 30 A
OUTPUT MOSFET BODY DIODE
CONTINUOUS CURRENT 20 A
FORWARD VOLTAGE I = 16A 1.3 V
REVERSE RECOVERY IF = 16A 250 nS
POWER SUPPLY
VOLTAGE, VS 3 60 100 V
VOLTAGE, VCC 14 15 16 V
CURRENT, VS, quiescent 22kHz switching 4 28 mA
CURRENT, VCC, quiescent 22kHz switching 18 mA
CURRENT, VCC, shutdown 10 mA
THERMAL
RESISTANCE, DC, junction to case Full temperature range 1.2 °C/W
RESISTANCE, junction to air Full temperature range 14 °C/W
TEMPERATURE RANGE, case -40 85 °C/W
SUPPLY VOLTAGE, VS 100V
SUPPLY VOLTAGE, VCC 16V
OUTPUT CURRENT, peak 30A, within SOA
POWER DISSIPATION, internal, DC 250W3
SIGNAL INPUT VOLTAGES 5.4V
TEMPERATURE, pin solder, 10s 225°C.
TEMPERATURE, junction2 175°C.
TEMPERATURE RANGE, storage -40° to 105°C.
OPERATING TEMPERATURE, case -40° to 85°C.
NOTES: 1. Unless otherwise noted: TC=25°C, VCC = 15V, VS = 60V
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.
APEX MICROTECHNOLOGY CORPORATION • TELEPHONE (520) 690-8600 • FAX (520) 888-3329 • ORDERS (520) 690-8601 • EMAIL prodlit@apexmicrotech.com
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TYPICAL PERFORMANCE
GRAPHS MSA240
APEX MICROTECHNOLOGY CORPORATION • 5980 NORTH SHANNON ROAD • TUCSON, ARIZONA 85741 • USA • APPLICATIONS HOTLINE: 1 (800) 546-2739
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OPERATING
CONSIDERATIONS
MSA240
This data sheet has been carefully checked and is believed to be reliable, however, no responsibility is assumed for possible inaccuracies or omissions. All specifications are subject to change without notice.
MSA240U REV C JULY 2004 © 2004 Apex Microtechnology Corp.
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 interpreta-
tion. Visit www.apexmicrotech.com for design tools that help
automate tasks such as calculations for stability, internal power
dissipation, current limit, heat sink selection, Apex’s complete
Application Notes library, Technical Seminar Workbook and
Evaluation Kits.
OSCILLATOR
The MSA240 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 internal 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.
FIGURE 1. EXTERNAL OSCILLATOR CONNECTIONS
SHUTDOWN
The MSA240 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.
CURRENT SENSING
The low side drive transistors of the MSA240 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
internal 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.
FIGURE 2. CURRENT LIMIT WITH OPTIONAL SHUTDOWN
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 pins must be con-
nected together. Place an electrolytic capacitor of at least
10µF per output amp required midpoint between these sets
of pins. In addition place a ceramic capacitor 1µF 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.
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. As +IN varies from 1.5 to
2.5 volts the A output "high" duty cycle (relative to ground) is
greater than the B output "high" duty cycle. The reverse occurs
as the input signal varies from 2.5 to 3.5 volts. When +IN =
2.5 volts the duty cycles of both A and B outputs are 50%.
Consequently, when the input voltage is 1.5V the A output
is close to 100% duty cycle and the B output is close to 0%
duty cycle. The reverse occurs with an input voltage of 3.5V.
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.
