WEBENCH® Tools/LM25088: 12V 10A out 18V in not working

Hi David,

Can you please share the actual design schematic and BOM used for the board you are measuring with? Is it possible for you to check if the input supply's max current limit is sufficient? For this design, a max value of input current (which will happen at lowest Vin) can be around 7A. Please make sure there is some additional room for variations and see if that helps regulate the output voltage. At input voltages > 18V, the input current requirement will be lower than 7A. Also, with lower output load values, you will need lower input current than 7A.

Regards,
Amod

1	5	C1, C22, C23, C24, C25	CAP CER 4.7UF 50V X7R 1206	Murata	GRM31CR71H475KA12L
2	1	C2	CAP CER 0.1UF 25V X7R 0603	Kemet	C0603C104K3RACTU
3	1	C4	CAP CER 820PF 50V X7R 0603	Kemet	C0603C821K5RACTU
4	4	C5, C13, C16, C18	CAP CER 10000PF 50V X7R 0603	Kemet	C0603C103J5RACTU
5	1	C6	CAP CER 22nF 25V X7R 0603	Kemet	C0603C223K3RACTU
6	1	C7	CAP CER 2.7nF 50V NP0 0603	Murata	GRM1885C1H272JA01J
7	1	C8	CAP CER 22PF 25V NP0 0603	Kemet	C0603C220K3GACTU
8	2	C9, C10	CAP ALUM POLY 180UF 20% 16V SMD	Panasonic	16SVPE180M
9	3	C11, C14, C17	CAP CER 0.1UF 50V X7R 0603	TDK	C1608X7R1H104K
10	2	C19, C20	CAP ALUM 330UF 20% 50V SMD	Panasonic	EEE-FT1H331AP
11	1	C21	CAP CER 2.2UF 16V X5R 0603	Murata	GRM188R61C225KE15D
12	1	D1	DIODE SCHOTTKY 45V 16A D2PAK	ON	MBRB1645T4G
13	1	F1	FUSE BRD MNT 8A 32VAC 63VDC 1206	Schurter	3413.0327.22
14	1	FB1	FERRITE BEAD 100 OHM 3312 1LN	Laird	HI3312X101R-10
15	1	L1	FIXED IND 12UH 19A 4.3 MOHM SMD	Wurth	74435581200
16	1	L2	CMC 10A 2LN 170 OHM TH	Laird	CM2545X171B-10
17	1	P1	CONN HEADER VERT 2POS .156 TIN	TE	640445-2
18	1	P2	Header, 6-Pin	TE Connectivity AMP Connectors	640445-6
19	1	Q1	MOSFET N-CH 60V 20A TSDSON-8	Infineon	BSZ100N06LS3 G
20	1	Q3	MOSFET N-CH 60V 100A LFPAK	NXP	BUK9Y6R0-60E,115
21	1	R1	RES SMD 49.9K OHM 1% 1/8W 0805	Vishay	CRCW080549K9FKEA
22	1	R2	RES SMD 5.62K OHM 1% 1/8W 0805	Panasonic	ERJ-6ENF5621V
23	1	R3	RES SMD 200K OHM 1% 1/10W 0603	Vishay	CRCW0603200KFKEA
24	1	R4	RES SMD 26.1K OHM 1% 1/10W 0603	Vishay	CRCW060326K1FKEA
25	1	R5	RES SMD 51.1K OHM 1% 1/10W 0603	Vishay	CRCW060351K1FKEA
26	1	R6	RES SMD 13.7K OHM 1% 1/16W 0402	Yageo	RC0402FR-0713K7L
27	1	R7	RES SMD 1.54K OHM 1% 1/16W 0402	Vishay	CRCW04021K54FKED
28	1	R8	RES SMD 0.007 OHM 1% 1W 1206	Riedon	CSR1206-0R007F1
29	4	R9, R10, R11, R12	Do Not Populate		DNP
30	1	U1	IC REG CTRLR BUCK 16TSSOP	Texas Instruments	LM25088MH-1
31	1	C3	CAP CER 0.47UF 16V X7R 0603	Kemet	C0603C474K4RACTU
32	2	C12, C15	CAP CER 1UF 50V X5R 0603	TDK	C1608X5R1H105K
33	1	D2	DIODE ZENER 9.1V 225MW SOT23-3	ON	MMBZ5239BLT1G
34	1	D3	TVS DIODE 36.8VWM 59.3VC SMB	Vishay	P6SMB43CA-E3/52
35	1	R13	RES SMD 10K OHM 5% 1/10W 0603	Rohm	MCR03ERTJ103
36	1	R14	RES SMD 100 OHM 1% 1/16W 0402	Yageo	RC0402FR-07100RL

For the input voltage, I was using a variable power supply that could output 1 to 36 VDC 10A. 

Hello David,

What is the voltage on the Feedback pin? What is the voltage directly across the top and bottom Feedback resistors?Is the output voltage dropping as you increase the load current? If so, can you tell me before the voltage drops, is the Switching node stable? Are you able to trigger on the square wave ans obtain a periodic scope capture?

If not, I think the first thing we should look at is your layout?

Thanks.

David.

Hello David

When the voltage is bad the voltage at the feedback pin 1s 1.11. it drops to this when the load is about 1.3 Ohms.

Thanks,

David