FAN3278 Fairchild Semiconductor, FAN3278 Datasheet - Page 12

• Manufacturer Part Number: FAN3278
• Description: The FAN3278 dual 1
• Manufacturer: Fairchild Semiconductor

© 2010 Fairchild Semiconductor Corporation
FAN3278 • Rev. 1.0.0
The SOIC-8 package has a junction-to-board thermal
characterization parameter of 
application, the localized temperature around the device
is a function of the layout and construction of the PCB
along with airflow across the surfaces. To ensure
reliable operation, the maximum junction temperature of
the device must not exceed the absolute maximum
rating of 150°C; with 80% derating, T
to 120°C. Rearranging Equation 4 determines the board
temperature
temperature below 120°C:
Differences between FAN3278 and FAN3268
FAN3278 and FAN3268 are pin-compatible to each other and are designed to drive one P-Channel and one
N-channel MOSFET in applications such as battery-powered compact fan / pump DC motor drives. However, there
are key differences, highlighted in Table 1.
Table 1. Differences between FAN3278 and FAN3268
Gate Drive Regulator
Minimum Operating
T
T
Output Gate Drive
B
B
OUTB Gate Drive
Current Strength
=T
=120°C – 0.308W • 43°C/W=107°C
Supply Voltage
Architecture
J
- P
Voltage
Startup
TOTAL
required
• 
JB
to
maintain
JB
27V Operating Maximum
30V Absolute Maximum
Yes, since the maximum operating V
be as high as 27V, the gate voltage to the
external MOSFETs is limited to about 13V.
The optimum operating range is 8V to 27V.
After the IC turns on at about 3.8V, the
output tracks V
voltage rail of about 11~13V. Below 8V of
V
and (b) with limited gate drive voltage until
it reaches around 8V.
The IC starts operating approximately at
3.8V which acts as a loose UVLO
threshold. It incorporates a “smart startup”
feature where the outputs are held OFF
before the IC starts operating.
Standard MOS-based output structure with
gate drive clamp.
Optimized for P-channel: The turn-OFF
(1.5 A) is stronger than turn-ON (1.0A).
=43°C/W. In a system
DD
, the FAN3278 operates, but (a) slower
J
would be limited
the
junction
DD
FAN3278
up to the regulated
(8)
(9)
12
Test Circuit
Figure 20. Quasi-Static I
DD
can
18V Operating Maximum
20V Absolute Maximum
No gate drive regulator is needed. The
gate drive voltage is V
FAN3268 switches rail-to-rail.
4.1V is the UVLO turn-off voltage
which is the minimum operating
voltage.
Has the tight UVLO threshold of 4.5V
on / 4.1V off. Incorporates “smart
startup” (outputs held OFF before IC is
fully operational at the UVLO
threshold).
Compound MillerDrive™ architecture
in the final output stage to provide a
more efficient gate drive current during
the Miller plateau stage of the turn-
on/turn-off switching transition.
P-channel turn-ON (2.4A) is stronger
than turn-OFF (1.6A).
OUT
FAN3268
/ V
OUT
DD
Test Circuit
and the
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