T6309B Taiwan Memory Technology, T6309B Datasheet - Page 9

• Manufacturer Part Number: T6309B
• Description: Micropower Step-up DC/DC Converter
• Manufacturer: Taiwan Memory Technology

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encounter in the application. Saturation occurs
when the inductor’s magnetic flux density
reaches the maximum level the core can
support and inductance falls. Inductor with
600mA rating or greater would be suitable for
the T6309B.
Capacitor Selection
The input capacitor stabilizes the input
voltage and minimizes the peak current ripple
from the source. The value of the capacitor
depends on the impedance of the input source
used.
Resistance) ceramic capacitor with value of
1uF to 4.7uF would be suitable.
The output capacitor is used to sustain the
output voltage when the internal MOSFET is
switched on and smoothing the ripple voltage.
The larger the output ripple, the larger the line
regulation, which means the LED current
changes if the input voltage changes. Low
ESR capacitor should be used to reduce
output ripple voltage. Use a 4.7uF to 10uF
ceramic output capacitor with about 50mOhm
to 150mOhm ESR to provide stable switching
and good line regulation.
Schottky Diode Selection
DC-DC converters. The most important
parameters which affect the efficiency are the
forward voltage drop, V
recovery time. The forward voltage drop
creates a loss just by having a voltage across
the device while a current flowing through it.
TM Technology Inc. reserves the right
to change products or specifications without notice.
The diode is the largest source of loss in
Small
CH
TE
ESR
( Equivalent
F
, and the reverse
Series
P. 9
The reverse recovery time generates a loss
when the diode is reverse biased, and the
current appears to actually flow backwards
through the diode due to the minority carriers
being swept from the P-N junction. A
Schottky
characteristics is recommended:
Small forward voltage, VF = 0.3 V
Small reverse leakage current, Fast reverse
recovery time/switching speed, Rated current
larger than peak inductor current, Reverse
voltage larger than output voltage.
Layout Considerations
High switching frequencies make PC board
layout a very important part of design. Good
design minimizes excessive EMI on the
feedback paths and voltage gradients in the
ground plane, both of which can result in
instability or regulation errors.
Connect the inductor, input filter capacitor,
and output filter capacitor as close to the
device as possible, and keep their traces short,
direct, and wide to reduce power loss so as to
improve efficiency. Connect their ground pins
at a single common node in a star ground
configuration, or at a full ground plane.
The output capacitor should be placed close to
the
smoothing effect on the output ripple.
In addition, the ground connection for the
sense resistor Rs should be tied directly to the
GND pin and not shared with any other
component. This ensures a clean, noise-free
connection.
output
diode
terminals
Publication Date: SEP. 2005
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T6309B
Revision: A
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