LTC4210 LINER [Linear Technology], LTC4210 Datasheet - Page 18

• Manufacturer Part Number: LTC4210
• Description: Dual Supply Hot Swap Controller for Advanced Mezzanine Card
• Manufacturer: LINER [Linear Technology]

LTC4223-1/LTC4223-2
PCB Layout Considerations
For proper operation of the LTC4223’s circuit breaker,
Kelvin-connection to the sense resistor is strongly rec-
ommended. The PCB layout should be balanced and
symmetrical to minimize wiring errors. In addition, the
PCB layout for the sense resistor and the power MOSFET
should include good thermal management techniques for
optimal device power dissipation. A recommended PCB
layout for the 12V sense resistor and the power MOSFET
is illustrated in Figure 12.
In applications where load current exceeds 10A, wide
PCB traces are recommended to minimize resistance
and temperature rise. The suggested trace width for 1
oz copper foil is 0.03” for each ampere of DC current to
keep PCB trace resistance, voltage drop and temperature
rise to a minimum. Note that the sheet resistance of 1 oz
copper foil is approximately 0.5mΩ/square, and voltage
drops due to trace resistance add up quickly in high cur-
rent applications.
In most applications, it will be necessary to use plated-
through via to make circuit connections from component
layers to power and ground layers internal to the PCB. For
1 oz copper foil plating, a general rule is 1A of DC current
per via. Consult your PCB fabrication facility for design
rules pertaining to other plating thicknesses.
It is important to place the V
close as possible between V
voltage suppressors Z1 and Z2 are also placed between
the supply inputs and ground using short wide traces.
Design Example
As a design example, consider the AMC Hot Swap ap-
plication shown earlier in Figure 1 with the power supply
requirements given in Table 2.
APPLICATIONS INFORMATION
18
Figure 11. RC Network for V
AUXIN
51Ω
R2
CC
CC
and GND. The transient
bypass capacitor C2 as
C2
330nF
CC
Filtering
422312 F11
V
CC
0.03" PER AMPERE
The fi rst step is to select the appropriate value of R
for the 12V supply. Calculating R
the maximum load current and the lower limit for the
circuit breaker threshold, ΔV
If a 1% tolerance is assumed for the 6mΩ sense resistor,
the minimum and maximum circuit breaker trip current is
calculated as follows:
Table 2. AMC Power Supply Requirements
Table 3. MicroTCA Power Supply Requirements
TRACK WIDTH W:
ON 1OZ Cu FOIL
SUPPLY VOLTAGE
SUPPLY VOLTAGE
Figure 12. Recommended Layout for Power MOSFET, Sense
12V
R
GND
SENSE
IN
CURRENT FLOW
*ADDITIONAL DETAILS OMITTED FOR CLARITY, DRAWING NOT TO SCALE!
3.3V
3.3V
TO LOAD
Z1
12V
12V
W
W
Resistor and GATE Components on 12V Rail
AUX
AUX
=
Δ
R1
C1
V
RESISTOR
SENSE CB MIN
SENSE
I
LOAD MAX
(
1
2
8
(
MAXIMUM LOAD
MAXIMUM LOAD
LTC4223CGN*
)(
CURRENT
CURRENT
150mA
150mA
)
7.4A
7.6A
12V
SENSE(CB)(MIN)
)
GATE
=
CURRENT FLOW
16
15
TO SOURCE
SENSE
47 5
7 4A A
R
R3
POWER PAK
G
.
.
SO-8
mV
C
value is based on
G
MAXIMUM LOAD
MAXIMUM LOAD
•
•
CAPACITANCE
= 6 Ω
CAPACITANCE
.
CURRENT FLOW
1600μF
m
800μF
150μF
150μF
TO LOAD
VIA TO
GND PLANE
VIA TO
GND PLANE
W
SENSE
422312f
12V
GND
422312 F12
OUT