MP1583 MPS, MP1583 Datasheet - Page 4

• Manufacturer Part Number: MP1583
• Description: Step Down Converter
• Manufacturer: MPS

Figure 2: Functional Block
Functional.Description
The MP1583 is a current-mode step-down
regulator.
4.75V to 23V down to an output voltage as low
as 1.22V, and is able to supply up to 3A of
load current.
The MP1583 uses current-mode control to
regulate the output voltage.
voltage is measured at FB through a resistive
voltage divider and amplified through the
internal error amplifier. The output current of
the
presented
compensates the regulation control system.
The voltage at COMP is compared to the
switch current measured internally to control
the output voltage.
The converter uses an internal n-channel
MOSFET switch to step-down the input voltage
to the regulated output voltage.
MOSFET requires a gate voltage greater than
the input voltage, a boost capacitor connected
between SW and BS drives the gate.
capacitor is internally charged while SW is low.
MP1583 Rev 2.0_06/30/04
Monolithic Power Systems
EN
IN
7
transconductance
2
Comparator
Frequency
Foldback
It regulates input voltages from
at
Regulators
Internal
2.285/2.495V
COMP
0.7V
Comparator
0.7V
Shutdown
error
where
5
42/380KHz
Comparator
Oscillator
FB
Lockout
1uA
1.22V
amplifier
The output
a
Since the
Compensation
network
gm= 800uA/Volt
Error Amplifier
Slope
CLK
www.monolithicpower.com
The
is
Σ
6
COMP
Amplifier
Current
Sense
An internal 10Ω switch from SW to GND is
used to insure that SW is pulled to GND when
SW is low to fully charge the BS.capacitor.
Application Information
Setting the Output Voltage
The output voltage is set using a resistive
voltage divider from the output voltage to FB
(see Figure 3). The voltage divider divides the
output voltage down by the ratio:
Thus the output voltage is:
R2 can be as high as 100KΩ, but a typical
value is 10KΩ.
determined by:
For example, for a 3.3V output voltage, R2 is
10KΩ, and R1 is 17KΩ.
Comparator
Current
8
SS
100K
R1 ~= 8.18 * (V
V
V
OUT
FB
5V
R
S
1.8V
= V
= 1.222 * (R1 + R2) / R2
Step Down Converter
Q
Q
OUT
Using that value, R1 is
* R2 / (R1 + R2)
OUT
– 1.222) (KΩ)
MP1583
3A, 23V
M1
M2
3
4
1
BS
SW
GND
4