MP1593 – 3A, 28V, 385KHz STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS
(continued)
Refer to Typical Application Schematic on Page 1
Switching
Waveforms
I
L
1A/Div.
100
95
90
Efficiency vs
Load Current
100
Efficiency vs
Load Current
95
90
V
IN
= 5V
V
IN
= 9V
V
IN
= 24V
V
IN
= 12V
EFFICIENCY (%)
EFFICIENCY (%)
V
OUT
10mV/Div.
V
IN
100mV/Div.
V
SW
10V/Div.
85
80
75
70
65
60
55
50
0
500 1000 1500 2000 2500 3000 3500
85
80
75
70
65
60
55
50
0
V
IN
= 24V
V
IN
= 12V
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
LOAD CURRENT (mA)
PIN FUNCTIONS
Pin # Name Description
1
2
High-Side Gate Drive Boost Input. BS supplies the drive for the high-side N-Channel MOSFET
switch. Connect a 10nF or greater capacitor from SW to BS to power the high-side switch.
Power Input. IN supplies power to the IC. Drive IN with a 4.75V to 28V power source. Bypass IN
IN
to GND with a suitably large capacitor to eliminate noise on the input to the IC. See
Input
Capacitor.
Power Switching Output. SW is the switching node that supplies power to the output. Connect
SW 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.
GND Ground. Note: Connect the exposed pad to Pin 4.
Feedback Input. FB senses the output voltage and regulates it. Drive FB with a resistive voltage
FB divider from the output voltage to ground. The feedback threshold is 1.222V. See
Setting the
Output Voltage.
Compensation Node. COMP is used to compensate the regulation control loop. Connect a series
COMP RC network from COMP to GND. In some cases, an additional capacitor from COMP to GND is
required. See
Compensation.
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. An Under-Voltage Lockout (UVLO) function can be implemented by
EN
the addition of a resistor divider from V
IN
to GND. For complete low current shutdown the EN pin
voltage needs to be less than 0.7V. For automatic startup leave EN disconnected.
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 0.1µF capacitor sets the soft-start period to 10ms. To disable the
soft-start feature, leave SS disconnected.
BS
3
4
5
6
7
8
MP1593 Rev. 1.9
9/14/2006
www.MonolithicPower.com
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4
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