LTC2925CGN(RevD) View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LTC2925CGN
(Rev.:RevD)

Multiple Power Supply Tracking Controller with Power Good Timeout

Linear Technology 

LTC2925

Applications Information

Layout Considerations

Be sure to place a 0.1µF bypass capacitor as near as pos-

sible to the supply pin of the LTC2925.

To minimize the noise on the slave supplies’ outputs, keep

the traces connecting the FBx pins of the LTC2925 and the

feedback nodes of the slave supplies as short as possible.

In addition, do not route those traces next to signals with

fast transition times. In some circumstances it might be

advantageous to add a resistor near the feedback node of

the slave supply in series with the FBx pin of the LTC2925.

This resistor must not exceed:

( ) RSERIES

=

1.6V – VFB

IMAX

=

1.6V – 1

VFB

RFA|| RFB

This resistor is most effective if there is already a

capacitor at the feedback node of the slave supply (often

a compensation component). Increasing the capacitance

on a slave supply’s feedback node will further improve the

noise immunity, but could affect the stability and transient

response of the supply.

For proper circuit breaker operation, Kelvin-sense PCB

connections between the sense resistor and the LTC2925’s

SENSEP and SENSEN pins are strongly recommended.

The drawing in Figure 22 illustrates the correct way of

making connections between the LTC2925 and the sense

resistor. PCB layout should be balanced and symmetrical to

minimize wiring errors. In addition, the PCB layout for the

sense resistor should include good thermal management

techniques for optimal sense resistor power dissipation.

The power rating of the sense resistor should accommodate

steady-state fault current levels so that the component is

not damaged before the circuit breaker trips.

VCC

LTC2925

FB1

GND

0.1µF

RSERIES

MINIMIZE

TRACE

LENGTH

DC/DC

FB OUT

RFA RFB

2925 F21

Figure 21. Layout Considerations

CURRENT FLOW

TO LOAD

IRC-TT SENSE RESISTOR

LR251201R010F

OR EQUIVALENT

0.01Ω, 1%, 1W

CURRENT FLOW

TO LOAD

TRACK WIDTH W:

0.03" PER AMP

W

ON 1 OZ COPPER

2925 F22

TO TO

SENSEP SENSEN

Figure 22. Making PCB Connections to the Sense Resistor

For more information www.linear.com/LTC2925

2925fd

21

Share Link: