sc1155csw.tr Semtech Corporation, sc1155csw.tr Datasheet - Page 16

• Manufacturer Part Number: sc1155csw.tr
• Description: Programmable Synchronous Dc/dc Hysteretic Controller With Vrm 9.0 Vid Range
• Manufacturer: Semtech Corporation

PRELIMINARY - August 7, 2000
MATERIALS LIST
Layout guidelines
1. Locate R8 and C5 close to pins 6 and 7.
2. Locate C6 close to pins 5 and 7.
3. Components connected to IOUT, DROOP, OCP, VHYST, VREFB, VSENSE, and SOFTST should be refer-
enced to AGND.
4. The bypass capacitors C10 and C15 should be placed close to the IC and referenced to DRVGND.
5. Locate bootstrap capacitor C13 close to the IC.
6. Place bypass capacitor C14 close to Drain of the top FET and Source of the bottom FET to be effective.
7. Route HISENSE and LOSENSE close to each other to minimize induced differential mode noise.
8. Bypass a high frequency disturbance with ceramic capacitor at the point where HISENSE is connected to Vin.
9. Input bulk capacitors should placed as close as possible to the power FETs because of the very high ripple cur-
rent flow in this pass.
10. If Schottky diode used in parallel with a synchronous (bottom) FET, to achieve a greater efficiency at lower
Vout settings, it needs to be placed next to the aforementioned FET in very close proximity.
11. Since the feedback path relies on the accurate sampling of the output ripple voltage, the best results can be
achieved by connecting the AGND to the ground side of the bulk output capacitors.
12. DRVGND pin should be tight to the main ground plane utilizing very low impedance connection, e.g., multiple
vias.
13. In order to prevent substrate glitching, a small (0.5A) Schottky diode should be placed in close proximity to the
chip with the cathode connected to BOOTLO and anode connected to DRVGND.
© 2000 SEMTECH CORP.
Quantity
1
6
3
7
2
6
2
1
1
1
1
1
2
1
2
1
1
1
1
3
1
1
1
C5
C1-C4, C8, C11
C17-C19
C6,C7,C9,C12,C16,C20, C27
C13,C14
C21-C26
C10,C15
D1
L1
L2
Q1
Q2
RA,RB
R1
R2,R4
R3
R5
R6
R7
R8,R9,R10
R11
R12
U1
Reference
PROGRAMMABLE SYNCHRONOUS
DC/DC HYSTERETIC CONTROLLER
WITH VRM 9.0 VID RANGE
0.001µF
0.01µF
150µF, 16V (TPS)
0.1µF
0.33µF
150µF, 4V, (PosCap)
2.2µF, 16V
MBRD1035
1µH, DO5022P-102
1.5µH, DO5022P-152HC
IRL3103NS, D2PAK
IRL2203NS, D2PAK
0
2K
1K
2.7K
100
20K
150
10K
2.2
3.9
SC1155, SO-28
Part/Description
AVX
Sanyo
MOT
Coilcraft
Coilcraft
Int. Rect.
Int. Rect.
SEMTECH
Vendor
SC1155
Notes
16