MP1593 – 3A, 28V, 385KHz STEP-DOWN CONVERTER
TYPICAL PERFORMANCE CHARACTERISTICS (continued)
Refer to Typical Application Schematic on Page 1
Switching
Waveforms
Efficiency vs
Load Current
Efficiency vs
Load Current
100
95
90
85
80
75
70
65
60
55
50
100
95
90
85
80
75
70
65
60
55
50
I
V
= 9V
L
IN
V
= 5V
IN
1A/Div.
V
V
= 24V
OUT
IN
V
= 24V
10mV/Div.
IN
= 12V
V
= 12V
IN
V
IN
V
IN
100mV/Div.
V
SW
10V/Div.
0
500 1000 1500 2000 2500 3000 3500
0
500 1000 1500 2000 2500 3000 3500
LOAD CURRENT (mA)
LOAD CURRENT (mA)
MP1593-TPC07
MP1593_TPC08
MP1593_TPC09
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 10nF 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 28V power source. Bypass IN to GND with a suitably large capacitor to
eliminate noise on the input to the IC. See Input Capacitor section.
Power Switching Output. SW is the switching node that supplies power to the output. Connect
3
4
5
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 on backside to Pin 4).
Feedback Input. FB senses the output voltage to regulate that voltage. Drive FB with a resistive
FB voltage divider from the output voltage. The feedback threshold is 1.222V. See Setting the
Output Voltage section.
Compensation Node. COMP is used to compensate the regulation control loop. Connect a series
COMP RC network from COMP to GND to compensate the regulation control loop. In some cases, an
additional capacitor from COMP to GND is required. See Compensation section.
6
7
8
Enable Input. EN is a digital input that turns the regulator on or off. Drive EN high to turn on the
regulator, drive EN low to turn it off. An Under Voltage Lockout (UVLO) function can be
implemented by the addition of a resistor divider from VIN to GND. For complete low current
EN
shutdown its needs to be less than 0.7V. For automatic startup, leave EN unconnected.
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 unconnected.
MP1593 Rev. 1.8
1/6/2006
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4
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