RT9263CGX5 RICHTEK [Richtek Technology Corporation], RT9263CGX5 Datasheet - Page 7

• Manufacturer Part Number: RT9263CGX5
• Description: High Efficiency, Low Supply Current, Step-Up DC/DC Converter
• Manufacturer: RICHTEK [Richtek Technology Corporation]

Application Information
Output Voltage Setting
Referring to application circuits Figure 1 to Figure 4 the
output voltage of the switching regulator (V
set with Equation (1).
Feedback Loop Design
Referring to application circuits Figure 1 to Figure 4. The
selection of R1 and R2 based on the trade-off between
quiescent current consumption and interference immunity
is stated below:
For applications without standby or suspend modes, lower
values of R1, and R2 are preferred. For applications
concerning the current consumption in standby or
suspend modes, the higher values of R1, and R2 are
needed. Such
sensitive to any interference, which require careful layout
and avoid any interference, e.g. probing to FB pins.
DS9263-09 March 2007
Follow Equation (1)
Higher R reduces the quiescent current (Path current
= 1.25V/R2), however resistors beyond 5MW are not
recommended.
Lower R gives better noise immunity, and is less
sensitive to interference, layout parasitics, FB node
leakage, and improper probing to FB pins.
A proper value of feed forward capacitor parallel with
R1 on Figure 1 to Figure 4 can improve the noise
immunity of the feedback loops, especially in an
improper layout. An empirical suggestion is around
100pF ~ 1nF for feedback resistors of MΩ, and 10nF ~
0.1μF for feedback resistors of tens to hundreds KΩ.
V
OUT1
= (1+
R2
R1
“
high impedance feedback loops
) 1.25V
×
OUT1
) can be
Preliminary
”
are
(1)
Layout Guide
A full GND plane without gap break.
V
for C2 to Pin2 and Pin5.
V
to L1 inductor, when V
Minimized FB node copper area and keep far away from
noise sources.
Minimized parasitic capacitance connecting to LX and
EXT nodes, which may cause additional switching loss.
OUT1
IN
PRECAUTION 1: Improper probing to FB pin will
cause fluctuation at V
and system chips because V
rise to an over-rated level due to unexpected
interference or parasitics being added to FB pin.
PRECAUTION 2: Disconnecting R1 or short circuit
across R2 may also cause similar IC damage as
described in precaution 1.
PRECAUTION 3: When large R values were used
in feedback loops, any leakage in FB node may
also cause V
damage. To be especially highlight here is when
the air moisture frozen and re-melt on the circuit
board may cause several mA leakage between IC
or component pins. So, when large R values are
used in feedback loops, post coating, or some
other moisture-preventing processes are
recommended.
to GND noise bypass
to GND noise bypass
Q
+
_
Prober Parasitics
OUT1
voltage fluctuation, and IC
IN
OUT1
is not an idea voltage source.
−
Add a 100μF capacitor close
. It may damage RT9263
−
Short and wide connection
OUT1
V
OUT1
R1
R2
may drastically
RT9263
www.richtek.com
FB Pin
7