LTC4100 Linear Technology, LTC4100 Datasheet - Page 21

• Manufacturer Part Number: LTC4100
• Description: Smart Battery Charger Controller
• Manufacturer: Linear Technology

APPLICATIO S I FOR ATIO
Protecting SMBus Inputs
The SMBus inputs, SCL and SDA, are exposed to uncon-
trolled transient signals whenever a battery is connected
to the system. If the battery contains a static charge, the
SMBus inputs are subjected to transients which can cause
damage after repeated exposure. Also, if the battery’s
positive terminal makes contact to the connector before
the negative terminal, the SMBus inputs can be forced
below ground with the full battery potential, causing a
potential for latch-up in any of the devices connected to the
SMBus inputs. Therefore it is good design practice to
protect the SMBus inputs as shown in Figure 10.
Figure 10. Recommended SMBus Transient Protection
CONNECTOR
TO BATTERY
U
V
U
DD
TO SYSTEM
W
4100 F13
U
PCB Layout Considerations
For maximum efficiency, the switch node rise and fall
times should be minimized. To prevent magnetic and
electrical field radiation and high frequency resonant prob-
lems, proper layout of the components connected to the IC
is essential. (See Figure 11.) Here is a PCB layout priority
list for proper layout. Layout the PCB using this specific
order.
V
IN
C2
Figure 11. High Speed Switching Path
CIRCULATING
FREQUENCY
SWITCH NODE
PATH
HIGH
L1
D1
LTC4100
C4
sn4100 4100is
21
BAT
4100 F15
V
BAT