sp6651a Exar Corporation, sp6651a Datasheet - Page 12

• Manufacturer Part Number: sp6651a
• Description: High Efficiency 800ma Synchronous Buck Regulator
• Manufacturer: Exar Corporation

Note: Components highlighted in bold are those used on the SP6651A Evaluation Board.
Table 2 Component Selection
Output Voltage Program
The output voltage is programmed by the external
divider, as shown in the typical application circuit
on page 1. First pick a value for R
than 300K. Too large a value of R
AC voltage seen by the loop comparator since the
internal FB pin capacitance can form a low pass
filter with R
R
R
Output Voltage Ripple Frequency
An important consideration in a power supply
application is the frequency value of the output
ripple. Given the control technique of the
SP6651A (as described in the operations sec-
tion), the frequency of the output ripple will
vary when in light to moderate load in the
discontinuous or PFM mode. For moderate to
heavy loads greater than about 100mA inductor
Date: 5/25/04
Capacitance
Inductance
F
F
(µH)
(µF)
6.8
6.8
6.8
6.8
= (
10
10
10
10
22
22
47
47
with a given R
V
OUT
0.8V
Sumida CDRH5D28-100
TDK RLF5018T-100MR94
Coilcraft DO1608C-103
Coilcraft LPO6013-103
Sumida CDRH5D28-6R8
TDK RLF5018T-6R8M1R1
Coilcraft DO1608C-682
Coilcraft LPO6013-103
TDK C3216X5R0J226M
SANYO 6APA22M
TDK C3225X5R0J46M
SANYO 6TPA47M
F
Manufacturer/Part No.
Manufacturer/Part No.
in parallel with R
- 1 ) • R
I
I
and output voltage is:
SP6651A High Efficiency 800mA Synchronous Buck Regulator
I
. The formula for
Ω (max)
I
0.002
0.040
0.002
0.040
I
ESR
that is no larger
Series R Ω
will reduce the
CAPACITORS - SURFACE MOUNT
0.048
0.056
0.160
0.300
0.081
0.130
0.200
0.47
INDUCTORS SURFACE MOUNT
RippleCurrent
(A) @ 45°C
3.00
1.90
4.00
1.90
I
SAT
1.30
0.94
1.10
0.70
1.12
1.10
1.20
0.60
(A)
Capacitor Specification
12
LxW(mm) Ht. (mm)
Inductor Specification
3.2 x 1.6
7.3 x 4.3
3.2 x 1.6
6.0 x 3.2
APPLICATION INFORMATION: Continued
LxW(mm)
5.7 x 5.5
5.6 x 5.2
6.6 x 4.5
6.0 x 5.4
4.7 x 4.5
5.6 x 5.2
6.6 x 4.5
6.0 x 5.4
current ripple, (for the typical 10µH inductor
application on 100mA is half the 200mA induc-
tor current ripple), the output ripple frequency
will be fairly constant. From the operations
section, this maximum loop frequency in con-
tinuous conduction mode is:
F
Data for loop frequency, as measured from
output voltage ripple frequency, can be found in
the typical performance curves.
Layout Considerations
Proper layout of the power and control circuits is
necessary in a switching power supply to obtain
good output regulation with stability and a mini-
mum of output noise. The SP6651A application
circuit can be made very small and reside close to
the IC for best performance and solution size, as
long as some layout techniques are taken into
consideration. To avoid excessive interference
LP
Size
≈
Size
1.6
2.0
1.6
2.8
Ht. (mm)
K
3.0
2.0
2.9
1.3
3.0
2.0
2.9
1.3
1
ON
Voltage
(V)
6.3
6.3
6.3
6.3
*
Shielded Ferrite Core
Shielded Ferrite Core
Unshielded Ferrite Core coilcraft.com
Unshielded Ferrite Core coilcraft.com
Shielded Ferrite Core
Shielded Ferrite Core
Unshielded Ferrite Core coilcraft.com
Unshielded Ferrite Core coilcraft.com
V
Inductor Type
V
OUT
IN
Capacitor Type
X5R Ceramic
POSCAP
X5R Ceramic
POSCAP
© Copyright 2004 Sipex Corporation
*
(
V
IN
- V
sumida.com
tdk.com
sumida.com
tdk.com
tdk.com
sanyovideo.com
tdk.com
sanyovideo.com
OUT
Manufacturer
Manufacturer
Website
Website
)