SP6654 Datasheet, PDF (13/17 Pages) Sipex Corporation – High Efficiency 800mA Synchronous Buck Regulator Ideal for portable designs powered with Li Ion battery

APPLICATION INFORMATION
INDUCTORS SURFACE MOUNT
Inductor Specification
Inductance
(µH)
Manufacturer/Part No.
10
Sumida CDRH5D28-100
Series R Ω
0.048
I_SAT (A)
1.30
Size
LxW(mm) Ht. (mm)
Inductor Type
5.7 x 5.5
3.0 Shielded Ferrite Core
Manufacturer
Website
sumida.com
10
TDK RLF5018T-100MR94
0.056
0.94 5.6 x 5.2
2.0 Shielded Ferrite Core tdk.com
10
Coilcraft DO1608C-103
0.160
1.10 6.6 x 4.5
2.9 Unshielded Ferrite Core coilcraft.com
10
Coilcraft LPO6013-103
0.300
0.70 6.0 x 5.4
1.3 Unshielded Ferrite Core coilcraft.com
6.8 Sumida CDRH5D28-6R8
0.081
1.12 4.7 x 4.5
3.0 Shielded Ferrite Core sumida.com
6.8 TDK RLF5018T-6R8M1R1
0.47
1.10 5.6 x 5.2
2.0 Shielded Ferrite Core tdk.com
6.8 Coilcraft DO1608C-682
0.130
1.20 6.6 x 4.5
2.9 Unshielded Ferrite Core coilcraft.com
6.8 Coilcraft LPO6013-103
0.200
0.60 6.0 x 5.4
1.3
CAPACITORS - SURFACE MOUNT
Capacitor Specification
Unshielded Ferrite Core coilcraft.com
Capacitance Manufacturer/Part No.
(µF)
22
TDK C3216X5R0J226M
ESR RippleCurrent
Size
Ω (max) (A) @ 45°C LxW(mm) Ht. (mm)
0.002
3.00
3.2 x 1.6 1.6
Voltage
(V)
6.3
Capacitor Type
Manufacturer
Website
X5R Ceramic tdk.com
22
SANYO 6APA22M
0.040
1.90
7.3 x 4.3 2.0
6.3 POSCAP
sanyovideo.com
47
TDK C3225X5R0J46M
0.002
4.00
3.2 x 1.6 1.6
6.3 X5R Ceramic tdk.com
47
SANYO 6TPA47M
0.040
1.90
6.0 x 3.2 2.8
6.3 POSCAP
sanyovideo.com
Note: Components highlighted in bold are those used on the SP6654 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_I that is no larger
than 300K. Too large a value of R_I will reduce the
AC voltage seen by the loop comparator since the
internal FB pin capacitance can form a low pass
filter with R_F in parallel with R_I. The formula for
R_F with a given R_I and output voltage is:
R_F = ( ^VOUT - 1 ) • R_I
0.8V
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 SP6654
(as described in the operations section), 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 current ripple, (for
the typical 10µH inductor application on 100mA
is half the 200mA inductor current ripple), the
output ripple frequency will be fairly constant.
From the operations section, this maximum loop
frequency in continuous conduction mode is:
F_LP ≈
1 _* V_{OUT * (VIN - VOUT)}
K_ON
V_IN
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 SP6654 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
between the SP6654 high frequency converter and
Date: 2/1/05
SP6654 High Efficiency 800mA Synchronous Buck Regulator
13
© Copyright 2005 Sipex Corporation