B340L MPS [Monolithic Power Systems], B340L Datasheet - Page 6

• Manufacturer Part Number: B340L
• Description: 2A, 32V, 330KHz Step-Down Converter
• Manufacturer: MPS [Monolithic Power Systems]

The input capacitor value should be greater
than 10µF. The capacitor can be electrolytic,
tantalum or ceramic. However, since it absorbs
the input switching current it requires an
adequate ripple current rating. Its RMS current
rating should be greater than approximately 1/2
of the DC load current.
For insuring stable operation C1 should be
placed as close to the IC as possible.
Alternately, a smaller high quality ceramic
0.1µF capacitor may be placed closer to the IC
and a larger capacitor placed farther away. If
using this technique, it is recommended that the
larger capacitor be a tantalum or electrolytic
type. All ceramic capacitors should be placed
close to the MP1591.
Output Capacitor (C5)
The output capacitor is required to maintain the
DC output voltage. Low ESR capacitors are
preferred to keep the output voltage ripple low.
The characteristics of the output capacitor also
affect the stability of the regulation control
system.
electrolytic capacitors are recommended. In the
case of ceramic capacitors, the impedance at
the switching frequency is dominated by the
capacitance, and so the output voltage ripple is
mostly independent of the ESR. The output
voltage ripple is estimated to be:
Where V
the resonant frequency of the LC filter, f
switching frequency.
In the case of tantalum or low-ESR electrolytic
capacitors, the ESR dominates the impedance
at the switching frequency, and so the output
ripple is calculated as:
Where V
R
output capacitors.
MP1591 Rev. 2.3
9/27/2006
ESR
is the equivalent series resistance of the
RIPPLE
RIPPLE
Ceramic,
V
RIPPLE
is the output ripple voltage, f
V
is the output voltage ripple and
RIPPLE
≅
1
4 .
tantalum
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
≅
×
∆
V
I
IN
×
R
×
ESR
⎛
⎜
⎜
⎝
f
f
SW
LC
or
⎞
⎟
⎟
⎠
2
low
© 2006 MPS. All Rights Reserved.
SW
www.MonolithicPower.com
is the
ESR
LC
MP1591 – 2A, 32V, 330KHz STEP-DOWN CONVERTER
is
Output Rectifier Diode (D1)
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.
Table 2 provides some recommended Schottky
rectifiers based on the maximum input voltage
and current rating.
Table 3 lists manufacturer’s websites.
Choose a rectifier whose maximum reverse
voltage rating is greater than the maximum
input voltage, and whose current rating is
greater than the maximum load current.
#
1
2
3
4
5
6
(Max)
15V
20V
30V
34V
V
IN
Vendor
Diodes, Inc.
Fairchild Semiconductor
General Semiconductor
International Rectifier
On Semiconductor
Pan Jit International
Table 3—Schottky Diode Manufacturers
Table 2—Diode Selection Guide
MBRS240L
20BQ030
Number
21DQ04
30BQ15
2A Load Current
SR22
SR23
SK23
SK23
SS23
SK24
SS24
B220
B230
Part
Vendor
3, 6
2, 3
2, 3
4
1
6
6
4
1
6
4
5
6
Web Site
www.diodes.com
www.fairchildsemi.com
www.gensemi.com
www.irf.com
www.onsemi.com
www.panjit.com.tw
MBRD330
MBRS340
Number
3A Load Current
B340L
B340L
SK33
SS32
SK33
SS33
SK34
SS34
B320
B330
Part
Vendor
1, 6
4, 5
1, 6
2, 3
1, 6
2, 3
1
3
1
1
1
4
6