TS3300 Datasheet, PDF (9/12 Pages) Touchstone Semiconductor Inc – 0.6-4.5VIN, 1.8-5.25VOUT, 3.5-uA, Low Input Voltage, High-Efficiency Boost + LDO

Boost Only Operation
For Boost Only operation, please refer to Figure 2
which displays the appropriate circuit configuration.
The Anti-Crush feature can be used during Boost
Only operation. During Boost Only operation, a
shutdown (BEN) pin is available to shutdown the
boost regulator. The boost regulator is in shutdown
mode when BEN is HIGH. During shutdown, the
supply current reduces to 0.1µA. For Boost Only
operation, the following pins should be connected to
analog ground, REGIN, REGOUT, REGFB, REGEN,
and SWEN.
How to Set the Boost Output Voltage
The output voltage can be set via a voltage divider
circuit as shown in Figure 3. The output feedback
(BO FB) pin is 505mV. It is recommended to use
large resistor values to minimize additional current
draw at the output. Resistors values less than 8MΩ
are recommended.
Figure 3. Setting the Boost Output Voltage
with a Voltage Divider
Using the following equation to solve for R1 for a
given R2 value, the output voltage can be set:
R1=
V_BO - 0.505
0.505
R2
TS3300
To set a 3V output voltage with R2 = 1.37MΩ, R1 is
calculated to be 6.77MΩ. A 1% standard resistor
value of 6.81MΩ can be selected. This results in an
output voltage of 3.02V.
APPLICATIONS INFORMATION
Inductor Selection
A low ESR, shielded 10μH inductor is recommended
for most applications and provides the best
compromise between efficiency and size. A low loss
ferrite and low dc resistance (DCR) inductor is best
for optimal efficiency. Furthermore, there should exist
at least an 8% margin between the saturation current
of the inductor and the peak inductor current for a
given set of operating conditions. Table 2 provides a
list of inductor manufactures. Refer to the Inductor
Peak Current vs Load Current plot in the “Typical
Performance Characteristics” section. This plot
shows how the inductor peak current varies with load
current with a LPS4018-103ML inductor from
Coilcraft.
Inductors
Supplier
Website
Coilcraft
www.coilcraft.com
Murata
www.murata.com
Sumida
www.sumida.com
Table 2. Inductor Manufactures
Input and Output Capacitor Selection
For the boost regulator, a low ESR ceramic input and
output capacitor of at least 10μF is recommended to
be placed as close as possible to the BI and BO pin.
Output voltage ripple can be reduced by increasing
the value of the output capacitor while providing
improved transient response. Ceramic capacitors
with X5R or X7R dielectric with a minimum voltage
rating of 10V are recommended.
TS3300 Rev. 1.0
Figure 2. Boost Only Circuit Configuration
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