FAN5092 View Datasheet(PDF) - Fairchild Semiconductor
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Description
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FAN5092
Fairchild Semiconductor
FAN5092 Datasheet PDF : 4 Pages
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APPLICATION BULLETIN
AB-28
An integrated version of the opto-coupler (H11A817A) and
secondary voltage reference (RC431A) is also available
(FOD2712).
In the following sections we dive into some details of the
conversion from 12V and 5V down to final electronic load
voltage.
FAN5092 Two-Phase Interleaved
Buck Converter
The FAN5092 step-down (buck) converter is ideal for data
communications applications. This IC is a two-phase inter-
leaved buck converter switching up to 1MHz per phase. The
application diagram illustrates conversion from 12Vdown to
3.3V in a 12V-only input voltage source environment. The
chip integrates the controller and the drivers on a single die.
The high frequency of operation is enabled by:
• The monolithic approach of integrating controller and
drivers on board
• A fast proprietary “leading edge valley control”
architecture with 100ns of response time
• The strongest drivers in the industry at 1 Ω of source and
sink impedance for both high and low side driver of each
phase
Such combination of features, together with loss-less current
sensing via RDSON sense, allows for a very efficient delivery
of power with very small passive components leading to new
record levels of power density.
The application diagram of the IC is shown in Fig 8 for a
3.3V, 30A load. Optimum companions of the FAN5092 are
the Fairchild discrete DMOS FDB6035AL for high side pass
transistors Q1,2 and FDB6676S for low side synchronous
rectification transistors Q2,4.
Two FAN5092 can be paralleled by means of doubling the
above application and connecting together two pins (pin 26
and pin 15). This will allow handling of loads up to 120A.
+12V
L1 (Optional)
+12V
CIN
+12V
D3=8.2V
D1
D2
+12V
+12V
C4
D3
C5
R5
Q1
L2
R6
Q2
C2
A
ENABLE/SS
C1
PWRGD
R1
+5V
1 2 3 4 5 6 7 8 9 10 11 12 13 14
U1
FAN5092
28 27 26 25 24 23 22 21 20 19 18 17 16 15
R2 R3
+12V
R4 C3
+12V
R7
Q3
R8
Q4
X
L3
30A
3.3V
COUT
R16
R17
Fig. 8. FAN5092 Application Circuit
REV. 1.0.0
3
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