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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
58-PIN DIP PACKAGE STYLE KC TYPICAL APPLICATION
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.

EQUIVALENT CIRCUIT DIAGRAM

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.

EXTERNAL CONNECTIONS

RRAMP VIEW FROM COMPONENT SIDE
C1
C2 +
ROSC
C3
SINGLE POINT GND

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MSA260
ABSOLUTE MAXIMUM RATINGS
SUPPLY VOLTAGE, VS SUPPLY VOLTAGE, VCC OUTPUT CURRENT, peak POWER DISSIPATION, internal, DC SIGNAL INPUT VOLTAGES TEMPERATURE, pin solder, 10s TEMPERATURE, junction2 TEMPERATURE RANGE, storage OPERATING TEMPERATURE, case
ABSOLUTE MAXIMUM RATINGS SPECIFICATIONS
450V 16V 30A, within SOA 250W3 5.4V 225C 150C -40 to 105C -40 to 85C
SPECIFICATIONS
PARAMETER ERROR AMPLIFIER OFFSET VOLTAGE BIAS CURRENT OFFSET CURRENT COMMON MODE VOLTAGE RANGE SLEW RATE OPEN LOOP GAIN UNITY GAIN BANDWIDTH CLOCK LOW LEVEL OUTPUT VOLTAGE HIGH LEVEL OUTPUT VOLTAGE RISE TIME FALL TIME BIAS CURRENT, pin 22 5V REFERENCE OUTPUT VOLTAGE LOAD CURRENT OUTPUT4 VCE(ON), each active IGBT CURRENT, continuous CURRENT, peak FLYBACK DIODE CONTINUOUS CURRENT FORWARD VOLTAGE REVERSE RECOVERY POWER SUPPLY VOLTAGE, VS VOLTAGE, VCC CURRENT, VS, quiescent CURRENT, VCC, quiescent CURRENT, VCC, shutdown THERMAL RESISTANCE, DC, junction to case RESISTANCE, junction to air TEMPERATURE RANGE, case ICE = 15A VS = 400V, F = 22kHz 1mS, VS = 400V, F = 22kHz TEST CONDITIONS1 Full temperature range Full temperature range Full temperature range Full temperature range Full temperature range RL = 2K MIN TYP MAX 9 500 150 4 1 96 1 0.2 4.8 7 7 Full temperature range 4.85 0.6 5.15 2 2.25 20 30 20 1.5 150 5 14 22kHz switching 22kHz switching 400 15 9 450 16 28 18 10 1 14 85 UNITS mV nA nA V V/S dB MHz V V nS nS A V mA V A A A V nS V V mA mA mA C/W C/W C/W
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Full temperature range Full temperature range
IF = 15A IF = 15A
Full temperature range Full temperature range -40
NOTES: 1. 2. 3. 4.
Unless otherwise noted: TC=25C, VCC = 15V, VS = 400V, F = 22kHz. Long term operation at the maximum junction temperature will result in reduced product life. Derate internal power dissipation to achieve high MTBF. Each of the two output transistors on at any one time can dissipate 125W. Maximum specification guaranteed but not tested.
APEX MICROTECHNOLOGY CORPORATION * 5980 NORTH SHANNON ROAD * TUCSON, ARIZONA 85741 * USA * APPLICATIONS HOTLINE: 1 (800) 546-2739
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TYPICAL PERFORMANCE GRAPHS
MSA260

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MSA260
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.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.
OPERATING CONSIDERATIONS
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

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 . 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.

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 must be connected together. Place and electrolytic capacitor of at least 10F per output amp required midpoint between these sets of pins. In addition place a ceramic capacitor 1.0F 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.

FIGURE 1. EXTERNAL OSCILLATOR CONNECTIONS
SHUTDOWN
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.
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.
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
APEX MICROTECHNOLOGY CORPORATION * 5980 NORTH SHANNON ROAD * TUCSON, ARIZONA 85741 * USA * APPLICATIONS HOTLINE: 1 (800) 546-2739
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OPERATING CONSIDERATIONS
MSA260
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 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 * ROhs + 1/2Wtotal * ROjc, where: ROhs = heatsink rating ROjc = 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 Apex HS26. The Free Air graph assumes vertical orientation of the heatsink and no obstruction to air flow in an ambient temperature of 30C. 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.

This MICROTECHNOLOGY CORPORATION * TELEPHONE (520) 690-8600 * FAX is assumed for possible ORDERS or omissions. All specifications are subject to change without notice. APEXdata sheet has been carefully checked and is believed to be reliable, however, no responsibility (520) 888-3329 *inaccuracies(520) 690-8601 * EMAIL prodlit@apexmicrotech.com MSA260U REV B JULY 2004 (c) 2004 Apex Microtechnology Corp.
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