TM
MP1580 – 2A, 380KHz STEP-DOWN CONVERTER
ELECTRICAL CHARACTERISTICS (continued)
VIN = 12V, TA = +25°C, unless otherwise noted.
Parameter
Symbol Condition
VFB = 1.0V
Min
Typ
Max
Units
%
Maximum Duty Cycle
90
Minimum Duty Cycle
VFB = 1.5V
0
%
EN Shutdown Threshold Voltage
Enable Pull-Up Current
EN UVLO Threshold Rising
EN UVLO Threshold Hysteresis
Supply Current (Shutdown)
Supply Current (Quiescent)
Thermal Shutdown
ICC > 100µA
VEN = 0V
0.7
1.0
1.46
2.495
210
23
1.3
1.8
2.62
V
1.15
2.37
µA
V
VEN Rising
mV
µA
mA
°C
36
VEN ≤ 0.4V
1.0
1.2
VEN ≥ 2.6V, VFB = 1.4V
160
Note:
4) Derate current limit 0.011A/°C.
PIN FUNCTIONS
Pin #
Name Description
Bootstrap (C5). This capacitor is needed to drive the power switch’s gate above the
supply voltage. It is connected between 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.
1
BS
Supply Voltage. The MP1580 operates from a +4.75V to +25V unregulated input. C1 is
needed to prevent large voltage spikes from appearing at the input.
2
3
IN
SW
Switch. This connects the inductor to either IN through M1 or to GND through M2.
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.
4
GND
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 700mV.
5
FB
Compensation. This node is the output of the transconductance error amplifier and the
6
7
8
COMP 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.
Enable/UVLO. A voltage greater than 2.62V enables operation. For complete low current
shutdown the EN pin voltage needs to be less than 700mV.
EN
Synchronization Input. This pin is used to synchronize the internal oscillator frequency to
SYNC an external source. There is an internal 11kΩ pull down resistor to GND; therefore leave
SYNC unconnected if unused.
MP1580 Rev. 3.0
12/5/2005
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3
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