LTC3770 Datasheet, PDF (22/24 Pages) Linear Technology – Synchronous Controller with Margining, Tracking and PLL

LTC3770
APPLICATIO S I FOR ATIO
When laying out a printed circuit board, without a ground
plane, use the following checklist to ensure proper opera-
tion of the controller.
• Segregate the signal and power grounds. All small
signal components should return to the SGND pin at
one point which is then tied to the PGND pin close to the
source of M2.
• Place M2 as close to the controller as possible, keeping
the PGND, BG and SW traces short.
• Connect the input capacitor(s) C_IN close to the power
MOSFETs. This capacitor carries the MOSFET AC
current.
• Keep the high dV/dt SW, BOOST and TG nodes away
from sensitive small-signal nodes.
• Connect the INTV_CC decoupling capacitor C_VCC closely
to the INTV_CC and PGND pins.
• Connect the top driver boost capacitor C_B closely to the
BOOST and SW pins.
• Connect the V_IN pin decoupling capacitor C_F closely to
the V_IN and PGND pins.
PACKAGE DESCRIPTIO
7.8 – 8.2
G Package
28-Lead Plastic SSOP (5.3mm)
(Reference LTC DWG # 05-08-1640)
1.25 ±0.12
9.90 – 10.50*
(.390 – .413)
28 27 26 25 24 23 22 21 20 19 18 17 16 15
5.3 – 5.7
7.40 – 8.20
(.291 – .323)
0.42 ±0.03
RECOMMENDED SOLDER PAD LAYOUT
5.00 – 5.60**
(.197 – .221)
0.65 BSC
1 2 3 4 5 6 7 8 9 10 11 12 13 14
2.0
(.079)
MAX
0° – 8°
0.09 – 0.25
(.0035 – .010)
0.55 – 0.95
(.022 – .037)
NOTE:
1. CONTROLLING DIMENSION: MILLIMETERS
2.
DIMENSIONS
ARE
IN
MILLIMETERS
(INCHES)
3. DRAWING NOT TO SCALE
*DIMENSIONS DO NOT INCLUDE MOLD FLASH. MOLD FLASH
SHALL NOT EXCEED .152mm (.006") PER SIDE
**DIMENSIONS DO NOT INCLUDE INTERLEAD FLASH. INTERLEAD
FLASH SHALL NOT EXCEED .254mm (.010") PER SIDE
0.65
(.0256)
BSC
0.22 – 0.38
(.009 – .015)
TYP
0.05
(.002)
MIN
G28 SSOP 0204
3770f
22