Si9143DB
Vishay Siliconix
Si9143 High-Performance Processor Controller Demo Board
FEATURES
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Voltage Mode Control
Synchronous Buck Converter
Short Circuit Current Limiting
Over-Voltage Protection
Output Current to 15 A
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Power Good Signal
+5 V or +12 V Input
Switching Frequency = 200 kHz
Output Voltage Adjustable 1.8 V to 3.5 V
DESCRIPTION
The Si9143 is a voltage-mode, synchronous buck controller
designed for point-of-use dc-to-dc conversion in
high-performance servers and desktop computers. High
efficiency at full load is accomplished by driving high- and
low-side n-channel MOSFETS. The input voltage range has
been designed for 4.75 V to 13.2 V to allow use of either 5 V or
12 V. This demo board is capable of handling 15 A of
continuous output current. And the output voltage can be set
easily to the desired value (from 1.8 V to 3.5 V in 0.1 V
increments) by adjusting the five voltage identification pins on
the connector. Table 1 shows the logic settings for various
output voltages.
The Si9143 is designed to provide automatic true current
sharing between parallel power supplies. To use this function,
all the Si9143s have to be synchronized by tying their SYNC
pins and all the PWM pins together. These two pins are left
open on the demo board.
The Bill-of-Materials (Table 2) and Demo Board Schematic are
attached to this document. Refer to Table 1 for different voltage
settings.
ORDERING INFORMATION
Part Number Si9143DB
TEST SETUP AND OPERATION
1. The Si9143 Demo Board requires an input power source
and a load. The input power source may be either +5 V or
+12 V. If +5 V is used as an input, be sure it is capable of
sourcing at least 15 A; if +12 V is used as an input, be sure
it is capable of sourcing at least 8 A. An electronic load is
recommended for the load; be sure that it is capable of
sinking 60W, and that it will operate with an input voltage as
low as 1.5 V. Also required for the demonstration described
here are an oscilloscope, two DVMs, and two ammeters.
2. There is a 40-pin connector socket availabe on board,
which is mechanically compatible with Intel’s VRM Header
8, revision 3.0. If no connector will be used, input/output
power can be connected at separate pins on the demo
board. Connections between the load and demo board and
the electronic load should be made with heavy gauge wire
(AWG #14 or larger) and should be as short as possible. For
a specific output voltage set point, certain voltage
identification pins (VIDx) need to be grounded.
3. Attach the first DVM to the input of the Si9143 demo board.
The attachments should be made as close as possible to
Document Number: 70895
30-Jan-98
the board, NOT at the power supply. Attach the second
DVM to the output of the demo board. Again, the
attachments should be made as close as possible to the
board, NOT at the electronic load. In particular, do not rely
on the built-in meters of the power supply and the electronic
load for voltage measurements, because of the voltage
dropped along the connection wires. Set input voltage and
load current to zero before powering up.
4. Put an oscilloscope ground to the output ground. Then
connect Ch1 probe to pin 21 (DH), Ch2 probe to pin 17 (DL),
and Ch3 probe to pin 20 (Lx) of Si9143. Set the scope scale
to 5 V/div. for all channels. At 6-V input voltage and
2.8-V/1-A output, the resulting waveform will appear
approximately as shown in Figure 1.
5. Basic Operation: After powering up the power source,
slowly increase the voltage until the DVM at the input reads
5 V. Adjust the load current within the operating range and
observe the regulation of output voltage. Voltage/current
data at the input and output can be recorded to calculate the
efficiency of the demo board.
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