RC5033M データシートの表示（PDF） - Raytheon Company
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RC5033M Datasheet PDF : 16 Pages
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PRODUCT SPECIFICATION
Applications Discussion
VCCP
C5
200µF
C4
0.1µF
+12V
GND
9
8
10
7
11
6
12 RC5033 5
13
4
14
3
15
2
16
1
C1
47pF
C13
4.7µF
R2
12K
+ LM308A
–
+
–
R3
88K
RC5033
DS2
EC10QS02
M1
MTD20N03HDL
L1
C2
1.5µH
1µF
R1
0.012Ω
DS1
MBRB1545CT
VO
C9
330µF
C1
47pF
M2
MTD20N03HDL
VO2
2.9V
65-5033-08
Dual Power Supply Application
In some CPU power applications there may be a need for a
split voltage converter. The circuit in Figure 4 addresses this
need with only minimal component count. The basic
RC5033 non-synchronous DC-DC converter is augmented
with an op-amp, a power MOSFET, and some 1% resistors
to provide a dual power supply with one voltage set to 3.3V
and the other, slaved off of the 3.3V, set to 2.9V. In this con-
figuration, the RC5033 converts the 5V to 3..3V with high
efficiency. By using the op-amp, power FET, and the resis-
tors, a low-dropout linear regulator is realized that can be run
off of the 3.3V. The 2.9V linear regulator has a relatively
high efficiency just due to the fact that the ratio of 2.9V/3.3V
is close to 88%. The power FET is a low Rdson n-channel
MOSFET, and thus it is reasonably inexpensive. The opamp
can be a garden variety, though the input bias current and
output slew rate need to be considered to optimize accuracy
and transient response. The overall efficiency of this power
supply system will very much depend upon the percentage of
power used on each power output. Overall, the efficiency of
this system will be lower than if both supplies were imple-
mented as switchers; however, the added savings of the part
count reduction may more than compensate for the overall
lower efficiency.
Standard Application Circuit
The circuit shown in Figure 1 along with its components and
values has been designed as representative of the typical
application involving the RC5033 for a Pentium™ CPU. Use
of the standard application circuit will deliver the perfor-
mance curves shown under the Typical Operating Character-
istics section of the data sheet. Many users will want to
develop their own DC-DC converter solution that is uniquely
tailored to a specific application requirement. In that case,
the users should review the detailed information in the
Design Procedure and Applications Information section of
the data sheet.
Detailed Description
The RC5033 is a programmable voltage synchronous con-
troller. When designed around the appropriate external com-
ponents, it can be configured to deliver more than 10A of
output current. During heavy loading conditions the RC5033
functions as a current-mode PWM step down regulator.
Under light loading conditions, the regulator functions in the
PFM or pulse skipping mode, thereby increasing its effi-
ciency under light loads.
10
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