FAN5019MTC Fairchild Semiconductor, FAN5019MTC Datasheet - Page 27

• Manufacturer Part Number: FAN5019MTC
• Description: DC/DC Switching Controllers PWM 4 phases contrlr
• Manufacturer: Fairchild Semiconductor

Specifications of FAN5019MTC

• Number Of Outputs: 4
• Input Voltage: 10.2 V to 13.8 V
• Mounting Style: SMD/SMT
• Package / Case: TSSOP-28
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: 0 C

PRODUCT SPECIFICATION
Since the FAN5019 turns off all of the phases (switches
inductors to ground), there is no ripple voltage present
during load release. Thus, you do not have to add headroom
for ripple, allowing your load release V
than V
V
this implies that capacitors can be removed. When removing
capacitors, make sure to check the output ripple voltage as
well to make sure it is still within spec.
Layout and Component Placement
The following guidelines are recommended for optimal
performance of a switching regulator in a PC system.
Key layout issues are illustrated in Figure 11.
REV. 1.0.7 1/5/04
TRAN1
TRAN1
and V
Figure 10. Transient Setting Waveform
Figure 11. Layout Recommendations
by that amount and still be meeting spec. If
TRANREL
are less than the desired final droop,
TRANREL
to be larger
General Recommendations
• For good results, at least a four-layer PCB is
• Whenever high currents must be routed between PCB
• If critical signal lines (including the output voltage sense
• An analog ground plane should be used both around and
• The components around the FAN5019 should be located
• The output capacitors should be connected as close as
Power Circuitry
• The switching power path should be routed on the PCB to
recommended. This should allow the needed versatility
for control circuitry interconnections with optimal
placement, power planes for ground, input, and output
power, and wide interconnection traces in the rest of the
power delivery current paths. Keep in mind that each
square unit of 1 ounce copper trace has a resistance of
~0.53 m at room temperature.
layers, vias should be used liberally to create several
parallel current paths so that the resistance and inductance
introduced by these current paths is minimized and the via
current rating is not exceeded.
lines of the FAN5019) must cross through power circuitry,
it is best if a signal ground plane can be interposed
between those signal lines and the traces of the power
circuitry to serves as a shield to minimize noise injection
into the signals..
under the FAN5019 for ground connections to the
components associated with the controller. This plane
should be tied to the nearest output decoupling capacitor
ground and should not tie to any other power circuitry to
prevent power currents from flowing in it.
close to the controller with short traces. The most
important traces to keep short and away from other traces
are the FB and CSSUM pins.
possible to the load (or connector) that receives the power
(e.g., a microprocessor core). If the load is distributed, the
capacitors should also be distributed, and generally in
proportion to where the load tends to be more dynamic.
encompass the shortest possible length in order to
minimize radiated switching noise energy (i.e., EMI) and
conduction losses in the board. Failure to take proper
precautions often results in EMI problems for the entire
PC system as well as noise related operational problems
in the power converter control circuitry. The switching
power path is the loop formed by the current path through
the input capacitors and the power MOSFETs including
all interconnecting PCB traces and planes. The use of
short and wide interconnection traces is especially critical
in this path for two reasons: it minimizes the inductance in
the switching loop, which can cause high-energy ringing,
and it accommodates the high current demand with
minimal voltage loss. Avoid crossing any signal lines over
the switching power path loop, described below.
FAN5019
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