MP1484 – 3A, 18V, 340KHz SYNCHRONOUS RECTIFIED STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameter
Symbol Condition
Min
Typ
2.5
Max
Units
V
EN Lockout Threshold Voltage
EN Lockout Hysterisis
2.2
2.7
210
mV
Input Under Voltage Lockout
Threshold
VIN Rising
3.80
4.05
210
4.40
V
Input Under Voltage Lockout
Threshold Hysteresis
mV
Soft-Start Current
VSS = 0V
6
ȝA
ms
°C
Soft-Start Period
Thermal Shutdown (4)
CSS = 0.1ȝF
15
160
Note:
4) Guaranteed by design, not tested.
PIN FUNCTIONS
Pin # Name Description
High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel MOSFET
switch. Connect a 0.01ȝF or greater capacitor from SW to BS to power the high side switch.
1
2
BS
IN
Power Input. IN supplies the power to the IC, as well as the step-down converter switches.
Drive IN with a 4.75V to 18V power source. See Input Capacitor.
Power Switching Output. SW is the switching node that supplies power to the output. Connect
the output LC filter from SW to the output load. Note that a capacitor is required from SW to
BS to power the high-side switch.
3
4
5
SW
GND Ground (Connect the exposed pad to Pin 4).
Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive
voltage divider connected to it from the output voltage. The feedback threshold is 0.925V. See
FB
Setting the Output Voltage.
Compensation Node. COMP is used to compensate the regulation control loop. Connect a
6
7
8
COMP series RC network from COMP to GND. In some cases, an additional capacitor from COMP to
GND is required. See Compensation Components.
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on
the regulator; low to turn it off. Attach to IN with a 100kȍ pull up resistor for automatic startup.
EN
Soft-Start Control Input. SS controls the soft-start period. Connect a capacitor from SS to GND
SS
to set the soft-start period. A 0.1ȝF capacitor sets the soft-start period to 15ms. To disable the
soft-start feature, leave SS unconnected.
MP1484 Rev. 0.9
10/23/2008
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3
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