TS3300 Datasheet, PDF (12/14 Pages) Touchstone Semiconductor Inc – 0.6-4.5VIN, 1.8-5.25VOUT, 3.5-uA, Low Input Voltage, High-Efficiency Boost + LDO

TS3300
The LDO was designed to operate in conjunction with
the boost regulator where the output of the boost
regulator is connected to the input to the linear
regulator. The LDO can provide an output voltage
based on the resistor divider circuit as shown in
Figure 3 or the output voltage can be set to the input
voltage where the internal switch/FET is fully
enhanced. Table 1 summarizes the settings for pins
REG EN and SW EN. Figure 4 shows the
configuration where the internal switch/FET is fully
enhanced (SW EN =high, REG EN = low) so the
boost output is equal to the LDO output. The LDO
can be shutdown by connecting the REF FB pin to
BO when SW EN = low and REG EN = high.
SW EN REG EN CONDITION FUNCTION
low
high
Connect
REG EN pin
to BO pin
Connect
REG FB pin
to BO pin
LDO Normal
Operation
LDO
Shutdown
high
low
Connect
SW EN pin
to BO pin
Internal FET
Hard-on
Table 1. LDO REG EN and SW EN Settings
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
Inductors
Supplier
Website
Coilcraft www.coilcraft.com
Murata www.murata.com
Sumida www.sumida.com
Capacitors
Taiyo
Yuden
www.t-yuden.com
Murata www.murata.com
AVX
www.avxcorp.com
TDK
www.component.tdk.com
Table 2. Inductor and Capacitor
Manufactures
Page 12
shows how the inductor peak current varies with load
current with a LPS4018-103ML inductor from
Coilcraft.
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 dielectric are recommended.
For the LDO, a low ESR ceramic input and output
capacitor of at least 10μF is recommended to be
placed as close as possible to the REG OUT pin.
Refer to Table 2 for a list of inductor and capacitor
manufacturers.
Buck-Boost Function
The TS3300 can act as a buck-boost device. For
instance, if two 1.5V alkaline cells are used to power
the TS3300, the boost output voltage (V_BO) can be
set to 5V and the LDO output voltage (V_REGOUT) can
be set to 2.5V. The output voltage for the boost
regulator and the LDO can be set according to Figure
2 and 3, respectively.
Boost Input Anti-Crush^TM Feature
The TS3300 includes an anti-crush^TM feature to
prevent the collapse of the input voltage to the boost
regulator when the input is a weak (high impedance)
source. If the input voltage drops below a determined
voltage threshold (settable by a resistor divider), the
boost regulator switching cycles are paused,
effectively limiting the minimum input voltage.
Anti-crush^TM is useful in applications where a buffer
capacitor at the boost’s output can service burst
loads, and the input source exhibits substantial
source impedance (such as with an old battery, or at
cold temperatures).
To set the anti-crush^TM voltage, a feedback pin
(BI FB) in conjunction with a voltage divider circuit
can be implemented as shown in Figure 7. The
feedback pin voltage is 392mV. It is recommended to
use large resistor values to minimize additional
current draw at the input.
TS3300DS r1p0
RTFDS