TM
MP1411 – 2A, 18V, 380KHz STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS
(continued)
V
IN
= 12V, T
A
= +25°C, unless otherwise noted.
Parameter
Maximum Duty Cycle
Minimum On Time
EN Shutdown Threshold
Enable Pull Up Current
EN UVLO Threshold Rising
EN UVLO Threshold Hysteresis
Supply Current (Shutdown)
Supply Current (Quiescent)
Thermal Shutdown
Note:
4) Slope compensation changes current limit above 40% duty cycle.
Symbol Condition
D
MAX
V
FB
= 0.8V
t
ON
I
CC
> 100µA
V
EN
= 0V
V
EN
Rising
V
EN
≤
0.4V
V
EN
≥
3V
Min
0.7
2.37
Typ
90
100
1.0
1.0
2.50
210
23
1.1
160
Max
1.3
2.62
36
1.3
Units
%
ns
V
µA
V
mV
µA
mA
°C
PIN FUNCTIONS
Pin #
1
2
Name Description
No Connect.
Bootstrap. This capacitor (C5) is needed to drive the power switch’s gate above the supply
voltage. It is connected between the SW and BS pins to form a floating supply across the
power switch driver. The voltage across C5 is about 5V and is supplied by the internal +5V
supply when the SW pin voltage is low.
NC
No Connect.
IN
Supply Voltage. The MP1411 operates from a +4.75V to +18V unregulated input. C1 is needed
to prevent large voltage spikes from appearing at the input.
SW Switch. This connects the inductor to either IN through M1 or to GND through M2.
GND Ground. This pin is the voltage reference for the regulated output voltage. For this reason care
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.
FB
Feedback. An external resistor divider from the output to GND, tapped to the FB pin, sets the
output voltage. To prevent current limit runaway during a short circuit fault condition the
frequency foldback comparator lowers the oscillator frequency when the FB voltage is below
400mV.
COMP Compensation. This node is the output of the transconductance error amplifier and the input to the
current comparator. Frequency compensation is done at this node by connecting a series R-C to
ground. See the compensation section for exact details.
EN
Enable/UVLO. A voltage greater than 2.62V enables operation. Leave EN unconnected for
automatic startup. An Under Voltage Lockout (UVLO) function can be implemented by 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 700mV.
SS
Soft-Start. Connect SS to an external capacitor to program the soft-start. If unused, leave it
open.
NC
BS
3
4
5
6
7
8
9
10
MP1411 Rev. 1.3
1/22/2010
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