T6309B Taiwan Memory Technology, T6309B Datasheet - Page 8

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

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4. Using a Logic Signal
The LED current can be controlled in discrete
steps with a logic signal as shown in the
figure below. When the NMOS is off, R1 set
the minimum current. When the NMOS is on,
R2 sets the LED current increment value.
Start-Up and Inrush Current
The T6309B has no internal soft start circuit
included to achieve minimum start-up delay.
All inductive step-up converters have higher
inrush current during start-up. The inrush
current for T6309B is about 200mA. If soft-
start is required, a recommended external
TM Technology Inc. reserves the right
to change products or specifications without notice.
Logic
Signal
Signal
PW M
0.1nF
10K
CH
TE
R2
100K
R2
T6309B
T6309B
FB
FB
25K
R1
25 Ohm
R
R
1
S
P. 8
circuit is shown in the below figure.
Output Voltage Selection
Referring to Fig. 3, select an output voltage
for
FB to a resistive divider between the output
and GND. The V
V
Higher R1,R2 values reduce quiescent current,
but give bad noise immunity. To keep stable
feedback loop operation and better noise
immunity, select (R1+R2) value less than
1MOhm.
Inductor Selection
The T6309B is designed to work well with a
10uH inductor in most applications. Low
inductance values supply higher output
current, but also increase the ripple and
reduce efficiency. Higher inductor values
reduce ripple and improve efficiency, but also
limit output current. Choose a low DC-
resistance inductor, usually less than 1 Ohm
to minimize loss. It is necessary to choose an
inductor with saturation current greater than
the peak current that the inductor will
OUT
T6309B-A
T6309B
= (1+R1/R2) x 0.4V
GND
FB
(0.4V reference) by connecting
OUT
D1
D2
Publication Date: SEP. 2005
can be set as:
4.7K
2.2nF
T6309B
1K
Revision: A
R
S