LTC4010 datasheet(21/24 Pages) LINER

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LTC4010

4010fb

1. Input capacitors should be placed as close as possible

to switching FET supply and ground connections with

the shortest copper traces possible. The switching

FETs must be on the same layer of copper as the input

capacitors. Vias should not be used to make these

connections.

2. Place the LTC4010 close to the switching FET gate

terminals, keeping the connecting traces short to

produce clean drive signals. This rule also applies to IC

supply and ground pins that connect to the switching

FET source pins. The IC can be placed on the opposite

side of the PCB from the switching FETs.

3. Place the inductor input as close as possible to the

drain of the switching FETs. Minimize the surface area

of the switch node. Make the trace width the minimum

needed to support the programmed charge current.

Use no copper fills or pours. Avoid running the con-

nection on multiple copper layers in parallel. Minimize

capacitance from the switch node to any other trace

or plane.

4. Place the charge current sense resistor immediately

adjacent to the inductor output, and orient it such

that current sense traces to the LTC4010 are not long.

These feedback traces need to be run together as a

single pair with the smallest spacing possible on any

given layer on which they are routed. Locate any filter

component on these traces next to the LTC4010, and

not at the sense resistor location.

5. Place output capacitors next to the sense resisitor

output and ground.

applicaTions inForMaTion

6. Output capacitor ground connections must feed into

the same copper that connects to the input capacitor

ground before tying back into system ground.

7. Connection of switching ground to system ground,

or any 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. RouteanaloggroundasatracetiedbacktotheLTC4010

GND pin before connecting to any other ground. Avoid

usingthesystemgroundplane.AusefulCADtechnique

is to make analog ground a separate ground net and

use a 0Ω resistor to connect analog ground to system

ground.

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

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

applying this rule.

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. Copper planes

on multiple layers can also be used in parallel. This

helps with thermal management and lowers trace in-

ductance, which further improves EMI performance.

12. For best current programming accuracy, provide a

Kelvin connection from RSENSE to SENSE and BAT.

See Figure 13 for an example.

13. It is important to minimize parasitic capacitance on the

TIMER, SENSE and BAT pins. The traces connecting

these pins to their respective resistors should be as

short as possible.

Figure 12. High Speed Switching Path

4010 F12

VBAT

VIN

HIGH

FREQUENCY

CIRCULATING

PATH

BAT

SWITCH NODE

CIN

SWITCHING GROUND

COUT

Figure 13. Kelvin Sensing of Charge Current

SENSE

4010 F13

DIRECTION OF CHARGING CURRENT

RSENSE

BAT

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