FAN5094MTCX Fairchild Semiconductor, FAN5094MTCX Datasheet - Page 19

• Manufacturer Part Number: FAN5094MTCX
• Description: IC CTRLR DC/DC SYNC BUCK 28TSSOP
• Manufacturer: Fairchild Semiconductor

Specifications of FAN5094MTCX

• Applications: Controller, Intel Pentium® IV
• Voltage - Input: 12V
• Number Of Outputs: 1
• Voltage - Output: 1.1 ~ 1.85 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 28-TSSOP
• Output Voltage: 1.85 V
• Output Current: 60 A
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 70 C
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: FAN5094MTCXTR; FAN5094MTCX_NL; FAN5094MTCX_NLTR; FAN5094MTCX_NLTR

PRODUCT SPECIFICATION
voltage of the MOSFET’s body diode. Power capability is
not a criterion for this device, as its dissipation is very small.
Output Filter Capacitors
The output bulk capacitors of a converter help determine its
output ripple voltage and its transient response. It has
already been seen in the section on selecting an inductor that
the ESR helps set the minimum inductance. For most con-
verters, the number of capacitors required is determined by
the transient response and the output ripple voltage, and
these are determined by the ESR and not the capacitance
value. That is, in order to achieve the necessary ESR to meet
the transient and ripple requirements, the capacitance value
required is already very large.
The most commonly used choice for output bulk capacitors
is aluminum electrolytics, because of their low cost and low
ESR. The only type of aluminum capacitor used should be
those that have an ESR rated at 100kHz. Consult Application
Bulletin AB-14 for detailed information on output capacitor
selection.
For higher frequency applications, particularly those running
the FAN5094 oscillator at >1MHz, Oscon or ceramic capaci-
tors may be considered. They have much smaller ESR than
comparable electrolytics, but also much smaller capacitance.
The output capacitance should also include a number of
small value ceramic capacitors placed as close as possible to
the processor; 0.1µF and 0.01µF are recommended values.
Input Filter
The DC-DC converter design may include an input inductor
between the system main supply and the converter input as
shown in Figure 5. This inductor serves to isolate the main
supply from the noise in the switching portion of the DC-DC
converter, and to limit the inrush current into the input capac-
itors during power up. A value of 1.3µH is recommended.
REV. 1.0.2 5/13/02
It is necessary to have some low ESR capacitors at the input
to the converter. These capacitors deliver current when the
high side MOSFET switches on. Because of the interleaving,
the number of such capacitors required is greatly reduced
from that required for a single-phase buck converter. Figure
5 shows 3 x 1000 F, but the exact number required will vary
with the output voltage and current, according to the formula
for the four phase FAN5094, where DC is the duty cycle,
DC = Vout / Vin. Capacitor ripple current rating is a function
of temperature, and so the manufacturer should be contacted
to find out the ripple current rating at the expected opera-
tional temperature. For details on the design of an input filter,
refer to Applications Bulletin AB-16.
Design Considerations and Component
Selection
Additional information on design and component selection
may be found in Fairchild’s Application Note 59.
+12V
I
rms
Figure 5. Input Filter
=
1.3 H
I
-------- - 4DC 16DC
out
4
–
2
1000 F, 16V
Electrolytic
Vin
FAN5094
19