ZA3020 Datasheet, PDF (6/10 Pages) List of Unclassifed Manufacturers – 2A STEP DOWN PWM SWITCH MODE DC DC REGULATORS

ZA3020
2A Step-Down, PWM, Switch-Mode
DC-DC Regulators
Applications Information Continued
Table 2: Diode Selection Guide
V_IN (Max)
15V
20V
1A Diodes
10BQ15
1N5817
B120
SS12
1N5818
30V
B130
MBRS130
SS13
2A Diodes
30BQ15
B220
SK23
SR22
20BQ030
B230
SK23
SR23
SS23
Table 3: Schottky Diode Manufacturers
Vendor
Diodes, Inc.
Fairchild Semiconductor
General Semiconductor
International Rectifier
On Semiconductor
Pan Jit International
Web Site
www.diodes.com
www.fairchildsemi.com
www.gensemi.com
www.irf.com
www.onsemi.com
www.panjit.com.tw
Inductor – L1
Optimal inductor selection involves trade-offs in
electrical value, current rating and mechanical
sizing.
Table 4 lists the recommended minimum inductor
values for common output voltage values. Table 5
Selection guide lists inductors by manufacturer,
electrical value, maximum output current, DC
resistance, core type, core material and
mechanical sizing.
The Maximum current rating of the inductor should
be above the peak operating current:
I_PEAK = I_LOAD + (V_OUT)(V_IN-V_OUT)
2(L)(F)(V_IN)
Example: V_IN=12V V_OUT=3.3V, L=15µH, I_LOAD=1.2A
I_PEAK = 1.6 + (3.3)(12-3.3)
2(15u)(380KHz)(12)
I_PEAK = 1.809A
Using Table 5 select a 15µH inductor with a Max
I_DC rating of > 1.809A.
Output Capacitor - C2
The selection of the output capacitor is the most
critical component of a switching regulator. Its
electrical value and equivalent series resistance
(ESR) directly affect:
• System stability
• Loop compensation components R3
and C3
• Output ripple voltage
Moreover C2 is frequently the most expensive
component of a switching regulator.
Figures 3 and 4 along with Table 4 are schematics
for two C2 components that have low ESR value.
Table IV. Recommended components for standard output voltages
V_OUT
1.22V
1.5V
1.8V
2.5V
3.3V
5.0V
R2
0ȍ
2.32Kȍ
4.75Kȍ
10.5Kȍ
16.9Kȍ
30.9Kȍ
L1 minimum
6.8µH
6.8µH
10µH
10µH
15µH
22µH
ZA3020 Rev. 3.5 2003-04-22
www.vimicro.com
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