MP1583 MPS, MP1583 Datasheet - Page 6

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

Where V
is the input voltage, f
frequency of the LC filter, f
frequency. In the case of tanatalum or low-
ESR
dominates the impedance at the switching
frequency, and so the output ripple is
calculated as:
Where V
the inductor ripple current, and R
equivalent series resistance of the output
capacitors.
Output Rectifier Diode
The output rectifier diode supplies the current
to the inductor when the high-side switch is off.
To reduce losses due to the diode forward
voltage and recovery times, use a Schottky
rectifier.
Tables 3 provides the Schottky rectifier part
numbers based on the maximum input voltage
and current rating.
Table 3: Schottky Rectifier Selection Guide
Table 4 lists some rectifier manufacturers.
Table 4: Schottky Diode Manufacturers
MP1583 Rev 2.0_06/30/04
Monolithic Power Systems
V
(Max)
15V
20V
26V
#
1
2
3
4
5
6
IN
Vendor
Diodes, Inc.
Fairchild Semiconductor
General Semiconductor
International Rectifier
On Semiconductor
Pan Jit International
electrolytic
2A Load Current
Part
Number
30BQ15
B220
SK23
SR22
20BQ030
B230
SK23
SR23
SS23
RIPPLE
RIPPLE
V
is the output voltage ripple, ∆I is
is the output ripple voltage, V
RIPPLE
Vendor
4
1
6
6
4
1
6
3, 6
2, 3
~= ∆I * R
capacitors,
LC
Web Site
www.diodes.com
www.fairchildsemi.com
www.gensemi.com
www.irf.com
www.onsemi.com
www.panjit.com.tw
SW
3A Load Current
Part
Number
B320
SK33
SS32
B330
B340L
MBRD330
SK33
SS33
is the resonant
ESR
is the switching
the
ESR
Vendor
1
1, 6
3
1
1
4, 5
1, 6
2, 3
is the
www.monolithicpower.com
ESR
IN
Choose a rectifier who’s maximum reverse
voltage rating is greater than the maximum
input voltage, and who’s current rating is
greater than the maximum load current.
Compensation
The system stability is controlled through the
COMP pin. COMP is the output of the internal
transconductance error amplifier.
capacitor-resistor combination sets a pole-zero
combination to control the characteristics of
the control system.
The DC loop gain is:
Where:
•
•
•
•
•
The system has 2 poles of importance, one is
due to the compensation capacitor (C3), and
the other is due to the output capacitor (C2).
These are:
Where P1 is the first pole, and G
error amplifier transconductance (800µS).
and
V
1.222V
V
voltage
A
voltage gain, 400 V/V
G
output current divided by the voltage at
COMP), 3.8 A/V
R
where I
A
FB
OUT
VEA
LOAD
CS
VDC
is the current sense gain, (roughly the
is the transconductance error amplifier
is the feedback threshold voltage,
= (V
is the desired output regulation
is the load resistance (V
f
OUT
P1
f
P2
FB
= G
is the output load current)
= 1 / (2π*R
Step Down Converter
/ V
MEA
OUT
/ (2π*A
) * A
LOAD
VEA
VEA
* G
*C2)
MP1583
*C3)
CS
* R
3A, 23V
MEA
OUT
A series
LOAD
is the
/ I
OUT
6