LM2642 Reference Design - Sychronous Buck Triple Output Converter: 18-21V Input, 2.5V @ 0.9A; 3.3V @ 1.75A; 1.5V @ 3.7A Outputs

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Design Specifications

Inputs	Outputs #1	Outputs #2	Outputs #3
VinMin=18	Vout1=2.5	Vout2=3.3	Vout3=1.5
VinMax=21	Iout1=0.9	Iout2=1.75	Iout3=3.7

Design Resources

LM2642 Reference Design

Additional Resources

•	LM2642 Product Folder

Bill Of Materials

Part	Manufacturer	Part#	Attributes
C10	TDK	C3216X7R1E105	1u F
C11	Vishay	VJ0603Y101KXAAT	100p F
C12	TDK	C3216X7R1E105	1u F
C13	Nichicon	F930J226MAA	22u F
C14	Nichicon	F930J226MAA	22u F
C15	OPEN	OPEN
C16	Vishay	VJ0603Y103KXAAT	10n F
C17	Vishay	VJ0603Y103KXAAT	10n F
C18	Vishay	VJ0603Y471KXAAT	470p F
C19	TDK	C3216X7R1E225	4.7u F
C20	Vishay	VJ0603Y104KXAAT	0.1u F
C21	Vishay	VJ0603Y104KXAAT	0.1u F
C22	Vishay	VJ0603Y104KXAAT	0.1u F
C23	Sanyo	6MV1500WG	1500u F
C24	TDK	C2012X7R1C105	1u F
C25	Vishay	VJ0603Y105KXAAT	0.01u F
C26	Vishay	VJ0603Y103KXAAT	0.01u F
C27	OPEN	OPEN
C28	Vishay	VJ0603Y103KXAAT	1n F
C29	TDK	C2012X7R1C105	1u F
C30	TDK	C3216X7R1E105	1u F
C31	Sanyo	6MV1500WG	1500u F, 0.019 Ohms
C32	TDK	C3216X5R0J476	47u F
D10	Vishay	BAW56	1.25 V
L10	Coilcraft	DO3308P-153ML
L11	Coilcraft	DO3316H-332ML
M10	Vishay	SI3424DV
M11	Vishay	SI3424DV
M12	Vishay	SI4412ADY
M13	Vishay	SI3424DV
R10	Dale	CRCW06034R70FRT6	4.7 Ohms
R11	Dale	CRCW06031000FRT6	100 Ohms
R12	Dale	CRCW06031002FRT6	10k Ohms
R14	Dale	CRCW06031102FRT6	11k Ohms
R15	Dale	CRCW06032002FRT6	20k Ohms
R16	Dale	CRCW06032002FRT6	20k Ohms
R17	Dale	CRCW06031002FRT6	10k Ohms
R18	Dale	CRCW06034R70FRT6	4.7 Ohms
R19	Dale	CRCW06033322FRT6	33.2k Ohms
R20	Dale	CRCW06031002FRT6	10k Ohms
R21	Dale	CRCW06031692FRT6	16.9k Ohms
R22	Vishay	WSL0805 0.033 1%	0.033 Ohms
R23	Dale	CRCW06034221FRT6	4.22k Ohms
U1	National Semiconductor	LM2642
U2	National Semiconductor	LP3872

Design Description

This is an LM2642 high efficiency three output step-down regulator.

Note that the MOSFETs M10, M11, M12, and M13 in the schematic correspond to Q10, Q11, Q12, and Q13 in the PCB layout respectively. Also, U2 in the schematic (the LP3872) is represented as U10 in the PCB layout.

Schematic

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Example Schematic Showing Connection for all Components.

Layout

Board's Bottom View

Board's Top View