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Co

Lx

Rs(DCR)

+

Cx

Rx

CSP

CSN

Inductor

Rc1

Rc2

R

NTC

LAYOUT CONSIDERATIONS

Inductor

CSP

R

C

H-FET

L-FET

SW

Cout

V5SW

R1

R2

VFB

CSN

Vout

TPS51221

SLVS786 – NOVEMBER 2007

Figure 48. Inductor DCR Current Sensing With Temperature Compensation

Certain points must be considered before starting a PCB layout work using the TPS51221.

Placement

• Place RC filters for CSP1 and CSP2 close to the IC pins.

• Place bypass capacitors for VREG5, VREG3 and VREF2 close to the IC pins.

• Place frequency-setting resistor close to the IC pin.

• Place the compensation circuits for COMP1 and COMP2 close to the IC pins.

• Place the voltage setting resistors close to the IC pins.

Routing (sensitive analog portion)

• Use separate traces for: (see Figure 49)

–

Output voltage sensing from current sensing (negative-side)

–

Output voltage sensing from V5SW input (when Vout=5V)

–

Current sensing (positive-side) from switch-node

Figure 49. Sensing Trace Routings

• Use Kelvin sensing traces from the solder pads of the current sensing device (inductor or resistor) to current

28

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Product Folder Link(s): TPS51221