SRM4010 Microsemi Commercial Components Group, SRM4010 Datasheet - Page 6

• Manufacturer Part Number: SRM4010
• Description: DIODE SYNC POWERMOD 40A SMD
• Manufacturer: Microsemi Commercial Components Group

Specifications of SRM4010

• Applications: Processor
• Operating Temperature: -40°C ~ 80°C
• Package / Case: SMD 1.83mm x 1.43mm
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Mounting Type: -
• Current - Supply: -
• Voltage - Supply: -

Discontinuous/Light Load Operation
The SRM
is also called discontinuous conduction mode. In this mode of
operation, the inductor current goes to zero. During this mode,
there are times when both MOSFETS in the module are OFF.
Discontinuous operation can be at the normal switching
frequency or in the event the converter operates in a skipped
cycle mode.
The module senses a valid turn-on of the primary MOSFET by
the voltage rise on the Catch MOSFET Drain (Pin1). In the case
of light mode operation, there is an extended period where the
primary-side power switch is OFF. During this period of time, the
voltage on the Drain can be ringing. The SRM
module can distinguish between a voltage rise due to the primary
MOSFET being turned ON and ringing. The distinguishing
characteristic between the two cases is the speed of the voltage
rise. A voltage rise driven by the turn on of the primary MOSFET
is fast compared to ringing. The dV/dT threshold for sensing a
valid turn on can be adjusted by changing the bias on the SPD pin
(pin9). Biasing this pin to +5v through a resistor will make the
normal turn on respond to a slower transition. This could be
necessary if a turn on snubber is used to slow the normal turn on
speed. Biasing this pin to the REGOUT through a resistor makes
the controller less sensitive.
Current Mode Control and High Bandwidth
Converters
voltage mode control. The module can tolerate large step changes
in pulse width that can occur in high bandwidth control loops
without having cross conduction of the rectifying MOSFETs.
adequate ramp compensation to prevent cycle by cycle
instabilities where the pulse width is changing between
alternating cycles. This stabilization is accomplished in the
current mode control by adding in a compensating ramp to the
current feedback signal.
In the case of a sudden increase in load or drop in input voltage,
current mode control allows rapid increases in pulse width to
correct for the resulting output change. The Catch MOSFET
drive is momentarily reduced before the end of the next OFF time
when there is a sudden increase in ON time of the primary
Switch. The ON time then recovers to the normal prediction time
over a number of cycles. This technique prevents problems of the
Catch MOSFET being ON when it needs to be OFF, yet
maintains good efficiency in the steady state condition.
For best efficiency, the current mode control should have
Copyright
2004-02-06
TM
4010 is well behaved in light mode operation, which
2000
The SRM
REV. 1
TM
4010 accommodates current mode or
C O L O R A D O D I V I S I O N
800 Hoyt Street, Broomfield, CO. 80020, 303-469-2161, Fax: [phone]
TM
4010 power
Colorado Division
Microsemi
Internal 5V Regulator
The internal regulator is a linear regulator that requires at least
0.8 volts of headroom. The voltage on pin 4 REG
least 5.8 volts at the lowest point of the ripple. To achieve the
required 5.8 volts of input to the regulator, the peak transformer
voltage during either reset or the forward mode needs to be at
least 6.8 volts. If an external load is added to the REG
REG
voltage of 6.8 volts is maintained on pin 4. Externally injected
voltage must be diode isolated to prevent loading of the internal
diodes.
minimum needed to provide proper regulator input voltage,
power can be supplied to the regulator input from an additional
secondary winding through a diode and a series resistor. The peak
voltage fed to the REG
maximum voltage of 20 volts. Voltages this high are undesirable
however since there is a power loss associated with the voltage
drop in the regulator.
Converter Switching Frequency
The converter switching frequency can range from 200 KHz to
400 KHz. From a SRM
limits on the maximum ON time and maximum OFF time. This
is due to internal timing used for prediction. The timing circuitry
will saturate at low frequency if the times exceed the capability
of the timing circuits. At the high frequency end, the same
timing is less accurate
In applications where the peak transformer voltage is below the
40A Synchronous Rectifier Module
OUT
pin, care must be exercised to make sure that a minimum
IN
TM
pin should be below the absolute
4010 module standpoint, there are
SRM
IN
TM
should be at
IN
4010
pin or the
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