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| MIL-PRF-38534 CERTIFIED M.S.KENNEDY CORP. 4707 Dey Road Liverpool, N.Y. 13088 HIGH EFFICIENCY, 8 AMP ADJUSTABLE SURFACE MOUNT SWITCHING REGULATOR 5043 (315) 701-6751 FEATURES: Up To 93% Efficiency For 5V Operation 8 Amp Output Current 4.5V to 30V Input Range User Adjustable Output Voltage from 1.2V to 5.5V 300KHz Switching Frequency @ 2.5 Amps User Programmable Soft-Start Quiescent Current < 2.5mA User Programmable Current Limit Contact MSK for MIL-PRF-38534 Qualification Status Available with Gull Wing Leads DESCRIPTION: The MSK 5043 is a high efficiency, 8 amp, surface mount switching regulator. Output voltage is user adjustable through the use of two external resistors or one external potentiometer. Output voltages from 1.2 volts to 5.5 volts are possible. The operating frequency of the MSK 5043 is 300KHz and is internally set. An external "soft start" capacitor allows the user to control how quickly the output comes up to regulation voltage after the application of an input. An extremely low quiescent current of typically less than 2.5mA and 93% operating efficiency at 5 volts out, keep the total internal power dissipation of the MSK 5043 down to an absolute minimum. EQUIVALENT SCHEMATIC TYPICAL APPLICATIONS Step-down Switching Regulator Microprocessor Power Source High Efficiency Low Voltage Subsystem Power Supply 1 2 3 4 5 6 7 1 PIN-OUT INFORMATION Case Sense High Sense Low N/C RF High Amp In N/C 34-44 23-33 11-22 10 9 8 Vout Ground Vin Enable Ref Out Cton Rev. A 2/06 ABSOLUTE MAXIMUM RATINGS 8 TC ELECTRICAL SPECIFICATIONS Group A Parameter Input Supply Range 2 Output Voltage Range Output Current Load Regulation Line Regulation Oscillator Frequency 2 Enable Input Voltage 2 7 2 IOUT=2.5A VIN=6.5V Within SOA VOUT=3.3V 0.75AIOUT4A 2,3 VOUT=3.3V IOUT=4A 5.0VVIN20V Internal IOUT2.5A High Low VEN=VIN Enable Input Current 2 Disabled Quiescent Current 2 Current Limit Threshold 2 Negative Source Cton Current 2 Fault Sink VIN=5.0V IOUT=2.5A VOUT=1.5V VIN=5.0V IOUT=2.5A VOUT=2.5V Efficiency VIN=5.0V IOUT=2.5A VOUT=3.3V VIN=6.5V IOUT=2.5A VOUT=5V VEN=0V VEN=0V VIN=30V Positive 1,2,3 1,2,3 1,2,3 1 1 1 1 1 1 1 Test Conditions 1 Subgroup 1,2,3 1 1 1 MSK 5043 H/E Min. 4.75 1.2 8.0 Typ. 8.5 1.5 0.9 300 0.5 0.2 2.0 100 -100 4.0 83 88 90 92 Max. 30 5.5 2.0 3.0 1.5 330 0.5 2.0 2.0 2.5 120 -160 6.5 Min. 4.75 1.2 8.0 270 2.0 75 -45 2.5 2.0 - MSK 5043 Typ. 8.5 1.5 0.9 300 0.5 0.2 2.0 100 -100 4.0 83 88 90 92 Max. 30 5.5 2.5 2.0 330 0.5 2.0 2.0 2.5 125 -165 6.5 - 270 2.0 80 -50 2.5 2.0 - NOTES: VIN=Enable=5V, 5mV(sense high-sense low)75mV, IL=0A, COUT=3x330F + 1F ceramic, CIN=6x10F, CTON=0.01F unless otherwise specified. This parameter is guaranteed by design but need not be tested. Typical parameters are representative of actual device performance but are for reference only. All output parameters are tested using a low duty cycle pulse to maintain TJ = TC. Industrial grade and 'E' suffix devices shall be tested to subgroup 1 unless otherwise specified. Military grade devices ('H' suffix) shall be 100% tested to subgroups 1,2 and 3. Subgroup 1 TA=TC=+25C Subgroup 2 TA=TC=+125C Subgroup 3 TA=TC=-55C 7 Actual switching frequency can be load dependent if output current is low. Refer to typical performance curves. 8 Continuous operation at or above absolute maximum ratings may adversely effect the device performance and/or life cycle. 1 2 3 4 5 6 2 Rev. A 2/06 TJ 6.5C/W -40C to +85C -55C to +125C +150C Input Voltage Enable Voltage Output Current Sense Pin Voltage Thermal Resistance (Each MOSFET) -0.3V, +36V -0.3V, +36V 8.5 Amps -0.3V, +7V TST TLD Storage Temperature Range Lead Temperature Range (10 Seconds) Case Operating Temperature MSK5043 MSK5043H/E Junction Temperature -65C to +150C 300C Units V V A % % % KHz V V A A mA mV mV A mA % % % % APPLICATION NOTES CURRENT LIMITING: The MSK 5043 is equipped with a pair of sense pins that are used to sense the load current using an external resistor (Rs). The current-limit circuit resets the main PWM latch and turns off the internal high-side MOSFET switch whenever the voltage difference between Sense High and Sense Low exceeds 100mV. This limiting occurs in both current flow directions, putting the threshold limit at 100mV. The tolerance on the positive current limit is 20%. The external low-value sense resistor must be sized for 80mV/Rs to guarantee enough load capacity. Load components must be designed to withstand continuous current stresses of 120mV/Rs. For very high-current applications, it may be useful to wire the sense inputs with a twisted pair instead of PCB traces. This twisted pair needn't be anything unique, perhaps two pieces of wire-wrap wire twisted together. Low inductance current sense resistors, such as metal film surface mount styles are best. INPUT CAPACITOR SELECTION: The MSK 5043 has an internal high frequency ceramic capacitor (0.1uF) between VIN and GND. Connect a low-ESR bulk capacitor directly to the input pin of the MSK 5043. Select the bulk input filter capacitor according to input ripplecurrent requirements and voltage rating, rather than capacitor value. Electrolytic capacitors that have low enough ESR to meet the ripple-current requirement invariably have more than adequate capacitance values. Aluminum-electrolytic capacitors are preferred over tantalum types, which could cause powerup surge-current failure when connecting to robust AC adapters or low-impedance batteries. RMS input ripple current is determined by the input voltage and load current, with the worst possible case occuring at VIN = 2 x VOUT: IRMS = ILOAD X VOUT(VIN-VOUT) VIN SOFT START/Cton: The internal soft-start circuitry allows a gradual increase of the internal current-limit level at start-up for the purpose of reducing input surge currents, and possibly for power-supply sequencing. In Disable mode, the soft-start circuit holds the Cton capacitor discharged to ground. When Enable goes high, a 4A current source charges the Cton capacitor up to 3.2V. The resulting linear ramp causes the internal current-limit threshold to increase proportionally from 20mV to 100mV. The output capacitors charge up relatively slowly, depending on the Cton capacitor value. The exact time of the output rise depends on output capacitance and load current and is typically 1mS per nanofarad of soft-start capacitance. With no capacitor connected, maximum current limit is reached typically within 10S. OUTPUT CAPACITOR SELECTION: The output capacitor values are generally determined by the ESR and voltage rating requirements rather than capacitance requirements for stability. Low ESR capacitors that meet the ESR requirement usually have more output capacitance than required for stability. Only specialized low-ESR capacitors intended for switching-regulator applications, such as AVX TPS, Sprague 595D, Sanyo OS-CON, Nichicon PL series or Kemet T510 series should be used. The capacitor must meet minimum capacitance and maximum ESR values as given in the following equations: CF > 2.5V(1 + VOUT/VIN(MIN)) VOUT x RSENSE x f RESR < RSENSE x VOUT 2.5V These equations provide 45 degrees of phase margin to ensure jitter-free fixed-frequency operation and provide a damped output response for zero to full-load step changes. Lower quality capacitors can be used if the load lacks large step changes. Bench testing over temperature is recommended to verify acceptable noise and transient response. As phase margin is reduced, the first symptom is timing jitter, which shows up in the switching waveforms. Technically speaking, this typically harmless jitter is unstable operation, since the switching frequency is non-constant. As the capacitor ESR is increased, the jitter becomes worse. Eventually, the load-transient waveform has enough ringing on it that the peak noise levels exceed the output voltage tolerance. With zero phase margin and instability present, the output voltage noise never gets much worse than IPEAK x RESR (under constant loads). Designers of industrial temperature range digital systems can usually multiply the calculated ESR value by a factor of 1.5 without hurting stability or transient response. The output ripple is usually dominated by the ESR of the filter capacitors and can be approximated as IRIPPLE x RESR. Including the capacitive term, the full equation for ripple in the continuous mode is VNOISE(p-p)=IRIPPLE x (RESR + 1/(2fC)). In idle mode, the inductor current becomes discontinuous with high peaks and widely spaced pulses, so the noise can actually be higher at light load compared to full load. In idle mode, the output ripple can be calculated as follows: VNOISE(p-p)= 0.02 x RESR + 0.0003 x 3.3H x [1/VOUT + 1/(VIN-VOUT)] RSENSE (RSENSE) x C ENABLE FUNCTION: The MSK 5043 is enabled by applying a logic level high to the Enable pin. A logic level low will disable the device and quiescent input current will reduce to approximately 2mA. The Enable threshold voltage is 1V. If automatic start up is required, simply connect the pin to VIN. Maximum Enable voltage is +36V. POWER DISSIPATION: In high current applications, it is very important to ensure that both MOSFETS are within their maximum junction temperature at high ambient temperatures. Temperature rise can be calculated based on package thermal resistance and worst case dissipation for each MOSFET. These worst case dissipations occur at minimum voltage for the high side MOSFET and at maximum voltage for the low side MOSFET. Calculate power dissipation using the following formulas: Pd (upper FET)=ILOAD x RDS x DUTY + VIN x ILOAD x f x VIN x CRSS+20ns IGATE Pd (lower FET)=ILOAD x RDS x (1-DUTY) DUTY= (VOUT+VQ2) (VIN-VQ1) Where: VQ1 or VQ2 (on state voltage drop)=ILOAD x RDS RDS=0.035 MAX at 25C CRSS=94pF RDS=0.080 MAX at 150C IGATE=1A During output short circuit, Q2, the synchronous-rectifier MOSFET, will have an increased duty factor and will see additional stress. This can be calculated by: Q2 DUTY=1VQ2 VIN(MAX)-VQ1 Where: VQ1 or VQ2=(120MV/RSENSE) x RDS 3 Rev. A 2/06 APPLICATION NOTES CONT'D RF HIGH: It is very important that the DC voltage returned to the RF high pin from the output be as noise and oscillation free as possible. This voltage helps to determine the final output and therefore must be a clean voltage. Excessive noise or oscillation can cause the device to have an incorrect output voltage. Proper PC board layout techniques can help to achieve a noise free voltage at the RF high pin. OUTPUT VOLTAGE ADJUSTMENT: The MSK 5043 has a user adjustable output voltage through the use of the AMP OUT and REF IN pins. The output voltage can be adjusted from 1.2 volts to 5.5 volts with 2 external resistors or an external potentiometer. Refer to the following formula for resistor divider selection: VOUT = 5.762 - 6.5 ( R1 R1+R2 ) It is possible to use a 20K potentiometer between pin 9 and ground with the center tap tied to pin 6. This will allow adjustment of the output voltage across the entire 1.2V to 5.5V range. MODES OF OPERATION: Under heavy loads, the MSK 5043 operates in full PWM mode. Each pulse from the oscillator sets the internal PWM latch that turns on the high-side MOSFET. As the high-switch turns off, the synchronous rectifier latch is set. 60ns later the low-side MOSFET turns on until the start of the next clock cycle or until the inductor current crosses zero. Under fault conditions the current exceeds the 100mV current-limit threshold and the high-side switch turns off. At light loads the inductor current does not exceed the 30mV threshold set by the minimum-current comparator. When this occurs, the MSK 5043 goes into idle mode, skipping most of the oscillator pulses in order to reduce the switching frequency and cut back gate-charge losses. The oscillator is gated off at light loads because the minimum-current comparator immediately resets the high-side latch at the start of each cycle. Refer to Table 1 for the operational characteristics. TABLE 1 OPERATIONAL CHARACTERISTICS ENABLE 0 1 1 1 LOAD X LOW <10% MED <30% HIGH >30% DESCRIPTION DEVICE DISABLED PULSE SKIPPING MODE DISCONTINUOUS INDUCTOR CURRENT PULSE SKIPPING MODE CONTINUOUS INDUCTOR CURRENT CONSTANT FREQ. PWM MODE CONTINUOUS INDUCTOR CURRENT TYPICAL 2.5V APPLICATION CIRCUIT 4 Rev. A 2/06 TYPICAL PERFORMANCE CURVES 5 Rev. A 2/06 MECHANICAL SPECIFICATIONS ESD Triangle indicates Pin 1. Weight=15 Grams Typical NOTE: ALL DIMENSIONS ARE 0.010 INCHES UNLESS OTHERWISE LABELED. ORDERING INFORMATION MSK5043 H G LEAD FORM OPTION BLANK=STRAIGHT; G=GULL WING SCREENING BLANK= INDUSTRIAL; E = EXTENDED RELIABILITY H= MIL-PRF-38534 CLASS H GENERAL PART NUMBER 6 Rev. A 2/06 MECHANICAL SPECIFICATIONS CONTINUED ESD Triangle indicates Pin 1. Weight=15 Grams Typical NOTE: ALL DIMENSIONS ARE 0.010 INCHES UNLESS OTHERWISE LABELED. ORDERING INFORMATION MSK5043 H LEAD FORM OPTION BLANK=STRAIGHT; G=GULL WING SCREENING BLANK= INDUSTRIAL; E = EXTENDED RELIABILITY H= MIL-PRF-38534 CLASS H GENERAL PART NUMBER M.S. Kennedy Corp. 4707 Dey Road, Liverpool, New York 13088 Phone (315) 701-6751 FAX (315) 701-6752 www.mskennedy.com The information contained herein is believed to be accurate at the time of printing. MSK reserves the right to make changes to its products or specifications without notice, however, and assumes no liability for the use of its products. Please visit our website for the most recent revision of this datasheet. Contact MSK for MIL-PRF-38534 qualification status. 7 Rev. A 2/06 |
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