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MP2361DQ-LF-P

P1-P3P4-P6P7-P9P10-P12P13-P14
MP2361 – 2A, 23V, 1.4MHz STEP-DOWN CONVERTER
MP2361 Rev. 1.4 www.MonolithicPower.com 4
9/22/2011 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
ELECTRICAL CHARACTERISTICS
V
IN
= 12V, T
A
= +25°C, unless otherwise noted.
Parameter Symbol Condition Min Typ Max Units
Feedback Voltage V
FB
4.75V ≤ V
IN
≤ 23V
0.892 0.920 0.948 V
Upper Switch On Resistance R
DS(ON)1
0.18 Ω
Lower Switch On Resistance R
DS(ON)2
10 Ω
Upper Switch Leakage V
EN
= 0V; V
SW
= 0V 0 10 μA
Current Limit
(5)
2.8 3.5 A
Current Sense Transconductance
Output Current to Comp Pin Voltage
G
CS
1.95 A/V
Error Amplifier Voltage Gain A
VEA
400 V/V
Error Amplifier Transconductance G
EA
ΔI
C
= ±10μA
630 930 1230 μA/V
Oscillator Frequency f
S
1.4 MHz
Short Circuit Frequency V
FB
= 0V 210 kHz
Soft-Start Pin Equivalent
Output Resistance
9 kΩ
Maximum Duty Cycle D
MAX
V
FB
= 0.8V 70 %
Minimum On Time t
ON
100 ns
EN Shutdown Threshold Voltage V
EN
I
CC
> 100μA 0.7 1.0 1.3 V
Enable Pull Up Current I
EN
V
EN
= 0V 1.0 μA
EN UVLO Threshold Rising V
UVLO
V
EN
Rising 2.37 2.50 2.62 V
EN UVLO Threshold Hysteresis 210 mV
Supply Current (Shutdown)
I
OFF
V
EN
≤ 0.4V
20 36 μA
Supply Current (Quiescent)
I
ON
V
EN
≥ 3V
1.2 1.4 mA
Thermal Shutdown
160
°C
Note:
5) Equivalent output current = 1.5A ≥ 50% Duty Cycle
2.0A ≤ 50% Duty Cycle
Assumes ripple current = 30% of load current.
Slope compensation changes current limit above 40% duty cycle.
MP2361 – 2A, 23V, 1.4MHz STEP-DOWN CONVERTER
MP2361 Rev. 1.4 www.MonolithicPower.com 5
9/22/2011 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
PIN FUNCTIONS
QFN and
MSOP
Pin #
SOIC
Pin #
Name
Description
1 NC No Connect.
2 1 BS
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.
3 NC No Connect.
4 2 IN
Supply Voltage. The MP2361 operates from a +4.75V to +23V unregulated
input. C1 is needed to prevent large voltage spikes from appearing at the input.
5 3 SW Switch. This connects the inductor to either IN through M1 or to GND through M2.
6 4 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.
7 5 FB
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 400mV.
8 6 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.
9 7 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 it’s the EN pin voltage needs to be less than
700mV.
10 8 SS
Soft-Start Pin. Connect SS to an external capacitor to program the soft-start. If
unused, leave it open.
MP2361 – 2A, 23V, 1.4MHz STEP-DOWN CONVERTER
MP2361 Rev. 1.4 www.MonolithicPower.com 6
9/22/2011 MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
© 2011 MPS. All Rights Reserved.
OPERATION
The MP2361 is a current mode regulator. That
is, the COMP pin voltage is proportional to the
peak inductor current. At the beginning of a
cycle: the upper transistor M1 is off; the lower
transistor M2 is on (see Figure 1); the COMP
pin voltage is higher than the current sense
amplifier output; and the current comparator’s
output is low. The rising edge of the 1.4MHz
CLK signal sets the RS Flip-Flop. Its output
turns off M2 and turns on M1 thus connecting
the SW pin and inductor to the input supply.
The increasing inductor current is sensed and
amplified by the Current Sense Amplifier. Ramp
compensation is summed to Current Sense
Amplifier output and compared to the Error
Amplifier output by the Current Comparator.
When the Current Sense Amplifier plus Slope
Compensation signal exceeds the COMP pin
voltage, the RS Flip-Flop is reset and the
MP2361 reverts to its initial M1 off, M2 on state.
If the Current Sense Amplifier plus Slope
Compensation signal does not exceed the
COMP voltage, then the falling edge of the CLK
resets the Flip-Flop.
The output of the Error Amplifier integrates the
voltage difference between the feedback and
the 0.92V bandgap reference. The polarity is
such that the FB pin voltage lower than 0.92V
increases the COMP pin voltage. Since the
COMP pin voltage is proportional to the peak
inductor current an increase in its voltage
increases current delivered to the output. The
lower 10Ω switch ensures that the bootstrap
capacitor voltage is charged during light load
conditions. External Schottky Diode D1 carries
the inductor current when M1 is off.
MP2361_BD01
LOCKOUT
COMPARATOR
ERROR
AMPLIFIER
FREQUENCY
FOLDBACK
COMPARATOR
INTERNAL
REGULATORS
1.8V
SLOPE
COMP
5V
CLK
CURRENT
COMPARATOR
CURRENT
SENSE
AMPLIFIER
SHUTDOWN
COMPARATOR
COMP
8
IN
4
EN
9
GND
6
OSCILLATOR
210KHz/
1.4MHz
S
R
Q
SW
5
BS
2
5V
+
Q
0.7V
+
+
2.29V/
2.50V
+
0.92V
0.4V
+
+
FB
7
--
--
--
--
--
--
SS
10
Figure 1—Functional Block Diagram
P1-P3P4-P6P7-P9P10-P12P13-P14

MP2361DQ-LF-P

Mfr. #:
Buy MP2361DQ-LF-P
Manufacturer:
Monolithic Power Systems (MPS)
Description:
Switching Voltage Regulators 2A 23V 1.45MHz Step-Down Converter
Lifecycle:
New from this manufacturer.
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