KA5H0365 Fairchild, KA5H0365 Datasheet - Page 4

• Manufacturer Part Number: KA5H0365
• Description: Power Conversion for the Data Communications Market
• Manufacturer: Fairchild

AB-28
FAN5236 Dual Synchronous Buck
Converter
The FAN5236 PWM controller (Fig. 9) provides high
efficiency and regulation for two output voltages adjustable
in the range from 0.9V to 5.5V. Synchronous rectification
and hysteretic operation at light loads contribute to a high
efficiency over a wide range of loads. The hysteretic mode
of operation can be disabled separately on each PWM
converter if PWM mode is desired for all load levels. Again
high efficiency is obtained by using MOSFET’s RDSON for
current sensing. Out-of-phase operation with 180-degree
phase shift reduces input current ripple.
4
+5
ILIM2/
REF2
ILIM1
DDR
VCC
FB
Fig. 9. FAN5236 Block Diagram
FAN5236
PWM1
PWM2
5µA
1mA
7.5V
2.5R
1R
Q1
Q2
Q3
Q4
L
L
5 to 24V
OUT1
OUT2
Fig. 10. KA5H0365 converter architecture
+
–
Voffset
sense
Thermal
VOUT1
VOUT2
= 2.5V
= 1.8V
+
–
???
OSC
????
C
C
OUT1
OUT2
ck
32V
S
R
POR
VCC
Q
RC1585/7 Linear Regulators
In some cases if the input to output voltage difference is sen-
sibly less than the output voltage it make sense to use linear
regulators. In Fig.6 Fairchild’s RC1587, 3A and RC1585, 5A
linear regulators are showcased.
KA5H0365 Offline Converter
The high level of simplicity of the AC/DC converter in Fig. 6
is possible thanks the multi-chip approach to integration of
the this controller family (Fig. 10). The TO220 package
houses two dies, a controller die and a high voltage MOS-
FET die on board. Here again power hungry discrete current
sense resistors are avoided, in this case by means of a ratioed
sense-fet technique on board of the discrete element.
For more details and a complete bill of materials please refer
to the FAN5092, FAN5236, RC1585, RC1587 and FOD2712
data sheets available on the Fairchild web site.
For KA5H0365 please refer to the data sheet as well as to
FPS Application Notes for SMPS design available on the
Fairchild web site.
Conclusion
The merging of data, voice and video blurs the line between
computing and communications. The smart loads of either
application draw from the same advanced, high-density sub-
micron low voltage CMOS technologies and require similar
solutions for distributed power conversion. Fairchild exper-
tise in power conversion for computing and communications
offers proven solutions to the merging converged data com-
munications market.
POR
R
S
UVLO
Q
sense
Control IC
Volt
Ref
Sense
FET
APPLICATION BULLETIN
DRAIN
GND
7/18/02