MP1580HS-LF Monolithic Power Systems (MPS), MP1580HS-LF Datasheet - Page 5

• Manufacturer Part Number: MP1580HS-LF
• Description: Switching Converters, Regulators & Controllers 2A 380kHz Step-Down Converter
• Manufacturer: Monolithic Power Systems (MPS)

Specifications of MP1580HS-LF

• Rohs: yes
• Output Voltage: 21 V
• Output Current: 2 A
• Input Voltage: 4.75 V to 25 V
• Switching Frequency: 380 kHz
• Operating Temperature Range: - 40 C to + 125 C
• Mounting Style: SMD/SMT
• Package / Case: SOIC-8

APPLICATION INFORMATION
COMPONENT SELECTION
Sync Pin Operation
The SYNC pin driving waveform should be a
square wave with a rise time less than 20ns.
The Minimum High voltage level is 2.7V and the
Low level is less than 0.8V. The frequency of
the external sync signal needs to be greater
than 445KHz.
A rising edge on the SYNC pin forces a reset of
the oscillator. The upper transistor M1 is
switched off immediately if it is not already off.
250ns later M1 turns on connecting SW to V
Setting the Output Voltage
The output voltage is set using a resistive
voltage divider from the output to FB (see
Figure 3). The voltage divider divides the output
voltage down by the ratio:
Where V
the output voltage.
Thus the output voltage is:
R2 can be as high as 100kΩ, but a typical value
is 10kΩ. Using this value, R1 is determined by:
For example, for a 3.3V output voltage, R2 is
10kΩ and R1 is 17kΩ.
Inductor
The inductor is required to supply constant
current to the output load while being driven by
the switched input voltage. A larger value
inductor results in less ripple current that in turn
results in lower output ripple voltage.
However, the larger value inductor has a larger
physical size, higher series resistance and/or
lower saturation current. Choose an inductor
that does not saturate under the worst-case
load conditions.
MP1580 Rev. 3.0
10/10/2007
FB
is the feedback voltage and V
R
TM
1
V
≅
OUT
V
FB
. 8
18
=
=
. 1
V
×
222
MPS Proprietary Information. Unauthorized Photocopy and Duplication Prohibited.
OUT
(
V
OUT
×
R
1
R
R
+
1
−
2
R
+
R
. 1
2
R
2
222
2
)
© 2007 MPS. All Rights Reserved.
www.MonolithicPower.com
OUT
IN
.
is
MP1580 – 2A, 380KHz STEP-DOWN CONVERTER
A good rule for determining the inductance is to
allow the peak-to-peak ripple current in the
inductor to be approximately 30% of the
maximum load current. Also, make sure that the
peak inductor current (the load current plus half
the peak-to-peak inductor ripple current) is
below the 2.4A minimum current limit.
The inductance value can be calculated by the
equation:
Where V
frequency and ΔI is the peak-to-peak inductor
ripple current. Table 1 lists a number of suitable
inductors from various manufacturers.
Sumida
CDRH5D28 Shielded Ferrite
CDRH5D28 Shielded Ferrite
CDRH6D28 Shielded Ferrite
CDRH104R Shielded Ferrite
Toko
Coilcraft
Vendor/
DO3308
DO3316
CDH74
Type A
D53LC
D104C
D10FL
Model
CR75
D75C
Table 1—Inductor Selection Guide
IN
is the input voltage, f is the oscillator
L
Shielded Ferrite
Shielded Ferrite
Shielded Ferrite
=
Open
Open
Open
Open
Open
Core
Type
V
OUT
×
Material
(
Ferrite
Ferrite
Ferrite
Ferrite
Ferrite
Core
V
V
IN
IN
−
×
V
f
×
OUT
10.1
10.0
Δ
7.0
7.3
5.5
5.5
6.7
5.0
7.6
9.7
9.4
9.4
W
I
Dimensions
)
Package
(mm)
10.0
10.0
11.5
13.0
13.0
7.8
7.6
8.0
5.7
5.7
6.7
5.0
L
5.5
5.2
5.5
5.5
3.0
3.0
3.0
5.1
4.3
4.0
3.0
5.1
H
5