Datasheet
I
CIN(RMS)
= 12A
0.5 x 0.5 = 6A
D =
V
OUT
V
IN
I
CIN(RMS)
= I
OUT
D(1 - D)
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Bill of Materials (BOM)
6 Bill of Materials (BOM)
The Bill of Materials is shown below, including the manufacturer and part number.
Table 2. Bill of Materials
Quantity ID Description Vendor Part Number
1 AC INJ Header, TH, 100mil, 2x1, Gold plated, 230 mil Samtec Inc. TSW-102-07-G-S
above insulator
1 C1 CAP, CERM, 1 uF, 10V, +/-10%, X7R, 0603 MuRata GRM188R71A105KA61D
6 C3, C4, C5, C6, C7, C8 CAP, CERM, 100 uF, 6.3V, +/-20%, X5R, 1206 MuRata GRM31CR60J107ME39L
1 C9 CAP, CERM, 0.1 uF, 50V, +/-10%, X7R, 0603 TDK C1608X7R1H104K
1 C
C1
CAP, CERM, 1800pF, 50V, +/-5%, C0G/NP0, MuRata C1608C0G1H182J
0603
1 C
C2
CAP, CERM, 56pF, 50V, +/-5%, C0G/NP0, MuRata GRM1885C1H560JA01D
0603
1 C
C3
CAP, CERM, 820 pF, 50V, +/-5%, C0G/NP0, MuRata GRM1885C1H821JA01D
0603
1 C
SS
CAP, CERM, 0.033 uF, 16V, +/-10%, X7R, MuRata GRM188R71C333KA01D
0603
4 GND_FI, GND_FO, Standard Banana Jack, Uninsulated, 15A Johnson 108-0740-001
VIN_F, VOUT_F Components
1 L1 Inductor, Shielded Drum Core, Powdered Iron, Vishay-Dale IHLP4040DZERR56M01
560nH, 27.5A, 0.0018 ohm, SMD
1 R1 RES, 1.0 ohm, 5%, 0.1W, 0603 Vishay-Dale CRCW06031R00JNEA
1 R
AC
RES, 49.9 ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW060349R9FKEA
1 R
C1
RES, 11.0k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW060311K0FKEA
1 R
C2
RES, 165 ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW0603165RFKEA
3 R
FB1
, R
FB2
, R
PG
RES, 10 kohm, 1%, 0.1W, 0603 Vishay-Dale CRCW060310K0JKEA
1 R
ADJ
RES, 95.3k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW060395K3FKEA
1 SH-J1 Shunt, 100mil, Gold plated, Black Samtec Inc. SNT-100-BK-G
1 U1 12A Buck DC/DC Converter Texas LM21212-2
Instruments
7 Component Selection
This section provides a walk-through of the design process of the LM21212-2 evaluation board. Unless
otherwise indicated, all equations assume units of amps (A) for current, farads (F) for capacitance, henries
(H) for inductance, and volts (V) for voltages.
7.1 Input Capacitors: C1, C2, C3
The required RMS current rating of the input capacitor for a buck regulator can be estimated by
Equation 1:
(1)
The variable D refers to the duty cycle, and can be approximated by:
(2)
From this equation, it follows that the maximum I
CIN(RMS)
requirement will occur at a full 12A load current
with the system operating at 50% duty cycle. Under this condition, the maximum I
CIN(RMS)
is given by:
(3)
Ceramic capacitors feature a very large I
RMS
rating in a small footprint, making a ceramic capacitor ideal
for this application.
7
SNVA480A–May 2011–Revised May 2013 AN-2140 LM21212-2 Evaluation Board
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