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LTC4006

4006fa

Figure 14. Kelvin Sensing of Charging Current

CSP

4006 F14

DIRECTION OF CHARGING CURRENT

RSNS

BAT

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.

General Rules

7. Connection of switching ground to system ground or

internal ground plane should be single point. If the

system has an internal system ground plane, a good

way to do this is to cluster vias into a single star point

to make the connection.

8. Route analog ground as a trace tied back to IC ground

(analog ground pin if present) before connecting to

any other ground. Avoid using the system ground

plane. CAD trick: make analog ground a separate

ground net and use a 0

Ω resistor to tie analog ground

to system ground.

9. A good rule of thumb for via count for a given high

current path is to use 0.5A per via. Be consistent.

10. If possible, place all the parts listed above on the same

PCB layer.

11. Copper fills or pours are good for all power connec-

tions except as noted above in Rule 3. You can also use

copper planes on multiple layers in parallel too—this

helps with thermal management and lower trace in-

ductance improving EMI performance further.

12. For best current programming accuracy provide a

Kelvin connection from RSENSE to CSP and BAT. See

Figure 13 as an example.

It is important to keep the parasitic capacitance on the RT,

CSP and BAT pins to a minimum. The traces connecting

these pins to their respective resistors should be as short

as possible.

APPLICATIO S I FOR ATIO

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