AN701 Datasheet, PDF (1/19 Pages) Vishay Siliconix – reduce the size of energy storage components

AN701
Vishay Siliconix
Designing High-Frequency DC-to-DC Converters
With the Si9114A Switchmode Controller
INTRODUCTION
Vishay Siliconix’s Si9100 monolithic switchmode PWM
controller established the standard for low-power, high-
efficiency dc-to-dc converters. This versatile device integrates
a number of useful features, including a power MOSFET,
high-voltage start circuitry, and low power consumption. The
Si9114A controller pushes the limits for high-frequency power
conversion by further reducing delay times and adding
additional features. As a result, dc-to-dc converters can be
designed for frequencies up to 1 MHz with simple PWM
topologies instead of the complex resonant ones.
The Si9114A uses constant frequency current mode control.
By increasing the conversion frequency, power supply
designers will be able to:
S reduce the size of energy storage components
S increase reliability by using ceramic capacitors
S produce an all-surface-mount assembly solution
S lower system costs
S simplify the implementation of a distributed power
architecture.
Traditionally, distributed power has been regarded as costly
and impractical to implement due to the high cost of local
power conversion and the perceived complexity of resonant
power supplies. But these decision criteria are now being
changed by the availability of small-outline control ICs,
LITTLE FOOTr MOSFETs, ceramic capacitors, and new
magnetic components.
4
NI
3
V_REF
7
SS
14
V_CC
1
+V_IN
FB
COMP
5
6
Error
Amplifier
–
+
Ref
Gen
CURRENT SENSE
13
2V
+––
+
4.6 V
+
20 mA
–
1.25 V
–V_IN
SYNC
10
R_OSC C_OSC
8
9
B2
Enable
OSC
Out
OSC
R
Q
S
Substrate
V_CC
20 mA
12 _DRIVER
OUTPUT
11
–V_IN
S
Q
R
2
SHUTDOWN
–
+
–
Undervoltage
–
0.2 V
+
Lockout
+
9.2 V
Document Number: 70575
16-Jan-01
Figure 1 Si9114A Block Diagram
www.vishay.com
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