LTC2925CUF Linear Technology, LTC2925CUF Datasheet - Page 20

• Manufacturer Part Number: LTC2925CUF
• Description: IC POWER SUPPLY CONTROLLER 24QFN
• Manufacturer: Linear Technology

Specifications of LTC2925CUF

• Applications: Power Supply Controller
• Voltage - Supply: 2.9 V ~ 5.5 V
• Current - Supply: 1.5mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 24-QFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Voltage - Input: -

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 feed-
back node of the slave supply in series with the FBx pin
of the LTC2925.
This resistor must not exceed:
20
R
SERIES
=
1 6
.
I
V V
MAX
–
FB
=
⎛
⎝ ⎜
1 6
V
.
TRACK WIDTH W:
FB
ON 1 OZ COPPER
V
0.03" PER AMP
Figure 22. Making PCB Connections to the Sense Resistor
–
1
⎞
⎠ ⎟
(
R
V
FA
CC
CURRENT FLOW
LTC2925
Figure 21. Layout Considerations
||
0.1μF
TO LOAD
R
F
B B
GND
FB1
)
W
IRC-TT SENSE RESISTOR
MINIMIZE
SENSEP
LENGTH
TRACE
LR251201R010F
OR EQUIVALENT
0.01Ω, 1%, 1W
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.
TO
R
SERIES
TO
SENSEN
R
2925 F21
FA
FB
DC/DC
CURRENT FLOW
R
FB
OUT
TO LOAD
2925 F22
2925fc