ltc4101 Linear Technology Corporation, ltc4101 Datasheet - Page 26

• Manufacturer Part Number: ltc4101
• Description: Smart Battery Charger Controller
• Manufacturer: Linear Technology Corporation

LTC4101
APPLICATIO S I FOR ATIO
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.
1. Input capacitors need to be placed as close as possible
2. The control IC needs to be close to the switching FET’s
3. Place inductor input as close as possible to switching
26
V
to switching FET’s supply and ground connections.
Shortest copper trace connections possible. These
parts must be on the same layer of copper. Vias must
not be used to make this connection.
gate terminals. Keep the gate drive signals short for a
clean FET drive. This includes IC supply pins that con-
nect to the switching FET source pins. The IC can be
placed on the opposite side of the PCB relative to above.
FET’s output connection. Minimize the surface area of
this trace. Make the trace width the minimum amount
needed to support current—no copper fills or pours.
Avoid running the connection using multiple layers in
parallel. Minimize capacitance from this node to any
other trace or plane.
IN
C2
Figure 11. High Speed Switching Path
CIRCULATING
FREQUENCY
SWITCH NODE
PATH
HIGH
U
U
W
L1
D1
C4
U
BAT
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V
BAT
4. Place the output current sense resistor right next to
5. Place output capacitors next to the sense resistor
6. Output capacitor ground connections need to feed
Interfacing with a Selector
The LTC4101 is designed to be used with a true analog
multiplexer for the SafetySignal sensing path. Some se-
lector ICs from various manufacturers may not implement
this. Consult LTC applications department for more
information.
Electronic Loads
The LTC4101 is designed to work with a real battery.
Electronic loads will create instability within the LTC4101
preventing accurate programming currents and voltages.
Consult LTC applications department for more
information.
the inductor output but oriented such that the IC’s
current sense feedback traces going to resistor are not
long. The feedback traces need to be routed together
as a single pair on the same layer at any given time with
smallest trace spacing possible. Locate any filter
component on these traces next to the IC and not at the
sense resistor location.
output and ground.
into same copper that connects to the input capacitor
ground before tying back into system ground.
Figure 12. Kelvin Sensing of Charging Current
DIRECTION OF CHARGING CURRENT
TO CSP AND BAT
R
SENSE
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