TM
MP2359 – 1.2A, 24V, 1.4MHz STEP-DOWN CONVERTER IN A TSOT23-6
PIN FUNCTIONS
Pin # Name Description
Bootstrap. A capacitor is connected between SW and BS pins to form a floating supply across
BST the power switch driver. This capacitor is needed to drive the power switch’s gate above the
supply voltage.
1
2
Ground. This pin is the voltage reference for the regulated output voltage. For this reason care
GND must be taken in its layout. This node should be placed outside of the D1 to C1 ground path to
prevent switching current spikes from inducing voltage noise into the part.
Feedback. An external resistor divider from the output to GND, tapped to the FB pin sets the
output voltage. To prevent current limit run away during a short circuit fault condition, the
frequency foldback comparator lowers the oscillator frequency when the FB voltage is below
3
FB
250mV.
4
5
6
EN
IN
On/Off Control Input. Pull EN above 1.2V to turn the device on.
Supply Voltage. The MP2359 operates from a +4.5V to +24V unregulated input. C1 is needed
to prevent large voltage spikes from appearing at the input.
SW Switch Output.
TYPICAL PERFORMANCE CHARACTERISTICS
VIN = 12V, VOUT = 3.3V, L = 4.7µH, C1 = 10µF, C2 = 22µF, TA = +25ºC, unless otherwise noted.
Efficiency vs
Load Current
Efficiency vs
Load Current
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
V
IN = 12V
V
IN = 18V
V
IN = 24V
V
IN = 24V
V
OUT = 2.5V
V
OUT = 5V
0.01
0.1
LOAD CURRENT (A)
10
1
0.01
0.1
LOAD CURRENT ( A)
10
1
Switching Frequency vs
Die Temperature
Feedback Voltage vs
Die Temperature
0.820
0.818
0.816
0.814
0.812
0.810
0.808
0.806
0.804
0.802
0.800
1.50
1.48
1.46
1.44
1.42
1.40
1.38
1.36
1.34
1.32
1.30
-50 -25
0
25 50 75
125 150
-50 -25
0
25 50 75
125 150
100
100
DIE TEMPERATURE (OC)
DIE TEMPERATURE (OC)
MP2359 Rev. 1.1
6/23/2006
www.MonolithicPower.com
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3
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