LTC4100 datasheet(22/24 Pages) LINER

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LTC4100

sn4100 4100is

APPLICATIO S I FOR ATIO

1. Input capacitors need to be placed as close as possible

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.

2. The control IC needs to be close to the switching FET’s

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.

3. Place inductor input as close as possible to switching

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.

4. Place the output current sense resistor right next to

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.

5. Place output capacitors next to the sense resistor

output and ground.

6. Output capacitor ground connections need to feed

into same copper that connects to the input capacitor

ground before tying back into system ground.

Interfacing with a Selector

The LTC4100 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 infor-

mation.

Electronic Loads

The LTC4100 is designed to work with a real battery.

Electronic loads will create instability within the LTC4100

preventing accurate programming currents and voltages.

Consult LTC applications department for more informa-

tion.

TO CSP AND BAT

4100 F14

DIRECTION OF CHARGING CURRENT

RSENSE

Figure 12. Kelvin Sensing of Charging Current

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