SP6652 Datasheet, PDF (9/16 Pages) Sipex Corporation – 1A, High Efficiency, High Frequency Current Mode PWM Buck Regulator

APPLICATIONS INFORMATION
Manufacturers/ Website
TDK/www.tdk.com
TDK/www.tdk.com
TDK/www.tdk.com
Murata/www.murata.com
Murata/www.murata.com
Murata/www.murata.com
Part Number
C1005X5R0J105M
C1608X5R0J475K
C2012X5R0J106M
GRM155R60J105KE19B
GRM188R60J475KE19
GRM21BR60J106KE19L
Capacitance/
Voltage
1uF/6.3V
4.7uF/6.3V
10uF/6.3V
1uF/6.3V
4.7uF/6.3V
10uF/6.3V
Capacitor
Size/Type/Thickness
0402/X5R/0.5mm
0603/X5R/0.9mm
0805/X5R/1.35mm
0402/X5R/0.55mm
0603/X5R/0.9mm
0805/X5R/1.35mm
ESR at
100KHz
0.03
0.02
0.02
0.03
0.02
0.02
Table 1. Capacitor Selection
Note: Component highlighted in bold is used on the SP6652EB Evaluation Board.
The range of typical inductor values and sizes are shown here in Table 2.
Manufacturers/ Website
Coilcraft/ www.coilcraft
Coilcraft/ www.coilcraft
Sumida/ www.sumida.com
Sumida/ www.sumida.com
Wurth Elektronik/ www.we-online.de
Wurth Elektronik/ www.we-online.de
Table 2. Inductor Selection
Part Number
Inductance/ Isat
Rating
Inductor
Length/Width/Thickness
DCR Max
ohms
MSS5131-332MX
MSS5131-332MX
CDRH3D28-3R3
CDRH3D28-4R7
WE-TPC #744042003
WE-TPC #744042004
3.3uH/1.6A
4.7uH/1.4A
3.3uH/2.0A
4.7uH/1.65A
3.3uH/1.8A
4.7uH/1.65A
5.1x5.1x3.1mm
5.1x5.1x3.1mm
4.0x4.0x3.0mm
4.0x4.0x3.0mm
4.8/4.8/1.8mm
4.8/4.8/1.8mm
0.032
0.045
0.058
0.071
0.065
0.082
Note: Component highlighted in bold is used on the SP6652EB Evaluation Board.
The output voltage can be set using the
formula:
VOUT = VFB*(1 + RF/RI)
Where VFB = 0.8V typically, and for no-load
Ton is kept within 200nsec Minimum:
Ton(min) = VOUT/(VIN *Freq).
Compensation Component Selection
For simplicity in compensation with ce-
ramic output capacitors, the SP6652 uses
current mode PWM control, so all that is
needed for stability is a series RZ and CC
at the COMP pin to compensate the error
amplifier. To see the actual SP6652 re-
sponse with frequency, in figure 3 we have
taken a bode plot of gain and frequency re-
sponse of the SP6652 circuit with 3.3Vout.
Looking first at the SP6652 Modulator Gain
at low frequency you see a constant gain
of about 26dB and the first pole or -3dB
point at about 4 kHz, where the slope of
the gain curve becomes about -20dB/de-
cade. At high frequency on the SP6652
Modulator Gain curve one can see the
modulator curve slope increase down-
SP6652 Bode Plot .
60
180
50
At 0dB Loop Gain
150
Fo = 80kHz
40
Loop Phase = 50deg
120
30
90
20
60
pole1 -3dB
10
at 4kHz
30
0
0
-10
-20dB/dec
-30
-20
-60
-30
3.3Vout
-90
-40
Rz = 4K Ω
-120
-50
Cc = 10nF
-150
-60
-180
100
1000
10000
100000 1000000
Log
SP6652 Loop Gain
Frequency (Hz)
SP6652 Modulator Gain
SP6652 Loop Phase
SP6652 Modulator Phase
Figure 3. SP6652 Gain and Frequency
Response 3.3V output voltage
ward for a high frequency pole at about
150KHz, which is widely separated in
frequency from the low frequency 4kHz
pole, so that the SP6652 can be compen-
sated by a zero at the low frequency pole
where the gain slope is only -20dB/decade.
The gain for the error amplifier is the cross-
Oct10-07 RevJ
SP6652 1A, High Efficiency, Current Mode PWM Buck Regulator

© 2007 Sipex Corporation