MIL-PRF-38534 AND 38535 CERTIFIED FACILITY
M.S.KENNEDY CORP.
HIGH EFFICIENCY,
8 AMP ADJUSTABLE
SURFACE MOUNT
SWITCHING REGULATOR
5043
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
DESCRIPTION:
The MSK5043 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 MSK5043 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 MSK5043 down to an absolute minimum.
EQUIVALENT SCHEMATIC
TYPICAL APPLICATIONS
PIN-OUT INFORMATION
Step-down Switching Regulator
Microprocessor Power Source
High Efficiency Low Voltage
Subsystem Power Supply
1
2
3
4
5
6
7
1
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
8548-94 Rev. C 5/14
8
ABSOLUTE MAXIMUM RATINGS
Input Voltage
Enable Voltage
Output Current
Sense Pin Voltage
Thermal Resistance
(Each MOSFET)
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-0.3V, +36V
-0.3V, +36V
8.5 Amps
-0.3V, +7V
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TST
TLD
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Storage Temperature Range
Lead Temperature Range
(10 Seconds)
Case Operating Temperature
MSK5043
MSK5043H
Junction Temperature
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TC
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6.5°C/W
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TJ
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9
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-65°C to +150°C
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300°C
-40°C to +85°C
-55°C to +125°C
+150°C
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ELECTRICAL SPECIFICATIONS
Parameter
Group A
Test Conditions 1
Output Current
Load Regulation
Max.
1,2,3
4.75
-
30
4.75
-
30
V
1
1.2
-
5.5
1.2
-
5.5
V
Within SOA
1
8.0
8.5
-
8.0
8.5
-
A
VIN=6.6V
1
-
1.5
2.0
-
1.5
2.5
%
Oscillator Frequency 2
7
Max.
2,3
-
-
3.0
-
-
%
1,2,3
-
0.9
1.5
-
0.9
2.0
%
Internal IOUT≥2.5A
-
270
300
330
270
300
330
KHz
High
1,2,3
2.0
-
-
2.0
-
-
V
Enable Input Current 2
Cton Current 2
2A≤IOUT≤5.5A
Low
1,2,3
-
-
0.5
-
-
0.5
V
VEN =VIN
1
-
0.5
2.0
-
0.5
2.0
μA
V EN =0V
1
-
0.2
2.0
-
0.2
2.0
μA
1
-
2.0
2.5
-
2.0
2.5
mA
VEN=0V
Current Limit Threshold 2
Efficiency
Typ.
VOUT=3.3V IOUT=4A 5.0V≤VIN≤20V
Enable Input Voltage 2
Disabled Quiescent Current 2
VIN=7.0V
Min.
-
VOUT=3.3V
Line Regulation
Units
Typ.
IOUT=2.5A
2
MSK5043
Min.
Input Supply Range 2
Output Voltage Range
MSK5043H
Subgroup
VIN=30V
Positive
1
80
100
120
75
100
125
mV
Negative
1
-50
-100
-160
-45
-100
-165
mV
Source
1
2.5
4.0
6.5
2.5
4.0
6.5
μA
Fault Sink
1
2.0
-
-
2.0
-
-
mA
VIN=5.0V
IOUT=2.5A
VOUT=1.5V
-
-
83
-
-
83
-
%
VIN=5.0V
IOUT=2.5A
VOUT=2.5V
-
-
88
-
-
88
-
%
VIN=5.0V
IOUT=2.5A
VOUT=3.3V
-
-
90
-
-
90
-
%
-
-
92
-
-
92
-
%
VIN=7.0V IOUT=2.5A VOUT=5V
NOTES:
1
2
3
4
5
6
VIN=ENABLE=5V, 5mV≤(sense high-sense low)≤75mV, IL=0A, COUT=3x330μF + 1μF ceramic, CIN=6x10μF, CTON=0.01μF 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 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=+25°C
Subgroup 2
TA=TC=+125°C
Subgroup 3
TA=TC=-55°C
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.
9 Internal solder reflow temperature is 180°C, do not exceed.
2
8548-94 Rev. C 5/14
APPLICATION NOTES
CURRENT LIMITING:
INPUT CAPACITOR SELECTION:
The MSK5043 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.
The MSK5043 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 MSK5043. Select the bulk input filter
capacitor according to input ripple-current 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
power-up 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:
SOFT START/Cton:
OUTPUT CAPACITOR SELECTION:
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 4μA 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 10μS.
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:
IRMS = ILOAD X √VOUT(VIN-VOUT)
VIN
CF > 2.5V(1 + VOUT/VIN(MIN))
VOUT x RSENSE x f
RESR < RSENSE x VOUT
2.5V
ENABLE FUNCTION:
The MSK5043 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.
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/(2πfC)). 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:
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)=ILOAD² x RDS x DUTY
+ VIN x ILOAD x f x
VIN x CRSS+20ns
IGATE
Pd (lower FET)=ILOAD² x RDS x (1-DUTY)
DUTY= (VOUT+VQ2)
(VIN-VQ1)
Where: VQ1 or VQ2 (on state voltage drop)=ILOAD x RDS
CRSS=94pF
RDS=0.035Ω MAX at 25°C
IGATE=1A
RDS=0.080Ω MAX at 150°C
VNOISE(p-p)= 0.02 x RESR + 0.0003 x 3.3μH x [1/VOUT + 1/(VIN-VOUT)]
RSENSE
(RSENSE)² x C
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
8548-94 Rev. C 5/14
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 MSK5043 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 20KΩ 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 MSK5043 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 MSK5043 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
LOAD
DESCRIPTION
0
X
DEVICE DISABLED
1
LOW <10%
PULSE SKIPPING MODE DISCONTINUOUS INDUCTOR CURRENT
1
MED <30%
PULSE SKIPPING MODE CONTINUOUS INDUCTOR CURRENT
1
HIGH >30%
CONSTANT FREQ. PWM MODE CONTINUOUS INDUCTOR CURRENT
TYPICAL 2.5V APPLICATION CIRCUIT
4
8548-94 Rev. C 5/14
TYPICAL PERFORMANCE CURVES
5
8548-94 Rev. C 5/14
MECHANICAL SPECIFICATIONS
ESD TRIANGLE INDICATES PIN 1
WEIGHT=15 GRAMS TYPICAL
ALL DIMENSIONS ARE SPECIFIED IN INCHES
ORDERING INFORMATION
MSK5043 H G
LEAD FORM OPTION
BLANK= STRAIGHT; G=GULL WING
SCREENING
BLANK= INDUSTRIAL; H= MIL-PRF-38534 CLASS H
GENERAL PART NUMBER
6
8548-94 Rev. C 5/14
MECHANICAL SPECIFICATIONS
ESD TRIANGLE INDICATES PIN 1
WEIGHT=15 GRAMS TYPICAL
ALL DIMENSIONS ARE SPECIFIED IN INCHES
ORDERING INFORMATION
MSK5043 H
LEAD FORM OPTION
BLANK= STRAIGHT; G=GULL WING
SCREENING
BLANK= INDUSTRIAL; H= MIL-PRF-38534 CLASS H
GENERAL PART NUMBER
7
8548-94 Rev. C 5/14
REVISION HISTORY
M.S. Kennedy Corp.
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.
8
8548-94 Rev. C 5/14